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A short and efficient stereo-specific synthesis of three stereoisomers (two diastereomer and one enantiomer) of Oxalate salt of benzyl (2S,5R)-5-(benzyloxyamino)piperidine-2-carboxylate (8) has been described. Compound 8 is a key intermediate in the synthesis of β-lactamase inhibitors, was synthesized in high diastereomeric excess using chirally pure L-pyroglutamic acid. In this report, we also describe a chiral high performance liquid chromatography (CHPLC) method to separate these isomers. The developed CHPLC method was validated for the accurate determination of the diastereomeric purity of compound 8. [ABSTRACT FROM AUTHOR]

A method of analysis was developed for the simultaneous chemo- and enantioseparation of 2-, 3-, and 4-chloromethcathinones by high-performance liquid chromatography tandem mass-spectrometry. The fast method enables the reliable identification of positional isomers of chloromethcathinones in biological samples. In addition, the same method can be used for the enantioselective quantitative determination of one of these compounds and its major phase-1 metabolites in biological fluids. The developed method was applied to oral fluid samples collected by police during routine random traffic control in Belgium from January to November, 2023. It was found that 3-CMC was more frequently abused compared to 4-CMC. Although some differences were observed between the concentrations of enantiomers in OF, most likely the drugs were abused in the racemic form. No abuse of 2-CMC was detected at the timepoint of sample collection. • Simultaneous separation of CMC positional isomers and their enantiomers. • Method applied to human oral fluid samples. • Identification of major phase-1 metabolites of CMCs. [ABSTRACT FROM AUTHOR]

While not initially a focus or priority, in recent decades, an emphasis has been placed on the activity of individual enantiomers of widely used pesticides. Of particular note are organophosphorus‐based pesticides like fenamiphos and profenofos, as examples. This work explores the enantioselective high‐performance liquid chromatography (HPLC) separations of seven such organophosphorus pesticides (OP's) on the library of immobilized polysaccharide‐based chiral stationary phases (CSPs) with normal phase hexane/alcohol mixtures. Further exploration of the effect of mobile phase strength and temperature on several of the separations was performed using simple factorial design. Equivalent retention of the first eluting enantiomer of several combinations of temperature and mobile phase was compared for peak shape, selectivity, and resolution. Similarly, equivalent selectivity of several combinations of temperature and mobile phase was compared for peak shape, retention of the first eluting enantiomer, and resolution. The results of this study make available several new chiral separations of the OPs included in the work that were not previously documented, including separations on the three most recently commercialized phases, Chiralpak IH, IJ, and IK. Additionally, sufficient understanding was obtained to be able to predict the trade‐off of resolution, analysis time, peak sharpness (and thus improve limit‐of‐detection [LOD]/limit‐of‐quantification [LOQ]), robustness, and convenience of conditions for further application optimization. [ABSTRACT FROM AUTHOR]

The presence of planar chirality of a variety of medium‐sized heterocycles, along with nine‐membered cyclic ketone and its enol ester, was revealed by observation of isolable enantiomers by analytical high‐performance liquid chromatography (HPLC) using a chiral stationary phase with a polysaccharide‐based chiral selector. Several tens of milligrams of enantiomers of the planar‐chiral molecules were successfully separated by preparative‐scale HPLC, leading to the preparation of an enantioenriched sample. This in turn enabled detailed stereochemical studies, including measurement of half‐lives of the optical activity and X‐ray crystallography for elucidation of stereochemistry. [ABSTRACT FROM AUTHOR]

Stereogenic silicon centres in functionalised tetracoordinated organosilanes generally exhibit very high configurational stability under neutral conditions. This stability drops completely when higher coordination states of the silicon centre are reached due to rapid substituent exchange. Herein we describe the synthesis of chiral and neutral pentacoordinate silicon derivatives with high configurational stability. The zwitterionic nature of these air‐ and water‐tolerant species allows for the first time their direct and efficient optical resolution using chiral HPLC techniques. By means of this method, pentacoordinate silicon compounds exhibiting high Si‐inversion have been obtained as single enantiomers. A rationalisation of the enantiomerisation pathways has been also carried out using DFT calculations. [ABSTRACT FROM AUTHOR]

In the present study, an accurate, rapid, and simple chiral HPLC‐UV method with amylose tris(3‐chloro‐5‐methylphenylcarbamate) as stationary phase was developed and applied for enantiomeric determination of six nonsteroidal anti‐inflammatory drugs (NSAIDs) in the commercial pharmaceutical formulations, including (R,S)‐ibuprofen, S‐ibuprofen, (R,S)‐ketoprofen, S‐ketoprofen, S‐naproxen, and (R,S)‐loxoprofen sodium. Experiments on the influence of mobile phase composition, proportion of organic modifier, percentage of acid additives, and column temperature on enantioseparation were conducted to obtain the best separation condition. It was indicated that one mobile phase simply composed of acetonitrile‐water (0.1% formic acid, v/v) at the proportion of 50:50 (v/v) with a flow rate of 0.6 ml/min at 22°C could simultaneously provide the excellent enantiomeric resolutions for all selected NSAIDs, which made the enantioseparation process more applicable and operable. The newly developed method was then applied for determination of NSAID enantiomers in pharmaceutical formulations containing racemic mixtures or single stereoisomers. Calibration curve of each enantiomer at the concentration of 5.0–100 ug/ml showed good linearity with the correlation coefficient above 0.9996. Satisfactory recovery (96.54–101.54%), good intra‐day precision (RSD 0.52–1.46%), and inter‐day precision (RSD 0.13–1.09%) were also obtained. The newly developed method was then applied for determination of NSAID enantiomers in pharmaceutical formulations containing racemic mixtures or single stereoisomers. Quantitative results of the commercial capsules and tablets demonstrated that the difference between the declared and measured values did not exceed 1.52%. [ABSTRACT FROM AUTHOR]

BACKGROUND: The determination of enantio‐separation, absolute configuration and chiral recognition mechanism of ofloxacin and flumequine was carried out by high‐performance liquid chromatography (HPLC) and modeling studies. The column used was a Chiralcel OD‐H with normal and polar organic mobile phase modes. The exhaustive chiral separation was optimized through various HPLC parameters. RESULTS: The selectivity, separation factors and resolution factors for ofloxacin were 8.2 and 9.4, 1.15 and 2.43 in the normal mobile phase, while these values were 10.5 and 12.0, 1.14 and 2.40 for flumequine in polar organic mobile phase mode, respectively. The thermodynamic parameters were ΔH (−0.137 J mol−1), ΔS (7.35 × 10−4 J mol−1) and ΔG (−0.360 J mol−1 K−1) for ofloxacin, and ΔH (−0.035 J.mol−1), ΔS (21.3 × 10−4 J mol−1) and ΔG (−0.105 J mol−1 K−1) for flumequine, confirming spontaneous chiral separation at all temperatures. The chiral recognition mechanism was established by HPLC and modeling results. The modeling binding affinity were −2.5 kcal mol–1 (R‐enantiomer) and −2.6 kcal mol–1 (S‐enantiomer) for ofloxacin, and −2.30 kcal mol–1 (R‐enantiomer) and −2.40 kcal mol–1 (S‐enantiomer) for flumequine enantiomers. The chiral resolution is controlled by hydrogen bonding, π–π interactions and other forces. CONCLUSION: These methods were applied to monitor ofloxacin and flumequine quinolones in urine samples. Briefly, the developed chiral HPLC methods are effective and may be used to analyze the reported enantiomers in any biological sample. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Series of chiral palladium(II) allyl and cinnamyl complexes bearing a C1‐symmetric N‐heterocyclic carbenes were synthesized from achiral precursors. The chirality of theses complexes results from the formation of the carbene‐palladium bond which restricts the rotation of dissymmetric N‐aryl substituents of the NHC and thus creates an axis of chirality. Chiral HPLC at preparative scale enabled the resolution of racemic complexes and provided a straightforward access to complexes with excellent enantiopurities (>99.5% ee). Enantiopure complexes were studied by crystal X‐ray diffraction and electronic circular dichroism (ECD). Their configuration stabilities were investigated both experimentally and theoretically through the determination of the rotational barrier values. These complexes were tested for the intramolecular α‐arylation of amides, with a moderate chiral induction (up to 54% ee). [ABSTRACT FROM AUTHOR]

Herein, we report a simple and efficient approach to synthesize a functionalized 2,18‐dimethoxy‐5,10,15‐trioxa[9]helicene. It was synthesized from simple phenol building blocks using two subsequent reactions namely oxidative coupling and dehydrative cyclization or palladium mediated cyclization. The molecular integrity of the helical core was determined by single‐crystal X‐ray diffraction and NMR techniques. Its crystal structure showed the spontaneous resolution which was attributed to the conglomerate formation of the same helical isomer via C−H⋅⋅⋅O and π⋅⋅⋅π or H⋅⋅⋅π interactions. Then, it was converted to racemic 2,18‐dihydoxy‐5,10,15‐trioxa[9]helicene. Enantiomers were separated on preparative HPLC with high optical purity (>99 % ee). Based on electronic circular dichroism, the absolute configurations of dextrorotary and levorotatory antipodes were assigned as P and M, respectively. We also studied the absorption, emission and chiroptical behavior of these helical compounds in the solution state. [ABSTRACT FROM AUTHOR]

An efficient first total synthesis of highly polar ulmoside A and (2 R ,3 R)-taxifolin-6- C -β- d -glucopyranoside, useful for the prevention of metabolic disorders, has been described. Key elements of the synthesis include a Sc(OTf)3-catalyzed regio- and stereoselective C -glycosidation on taxifolin in 35% yield with d -glucose and chiral semipreparative reverse-phase high-performance liquid chromatography (HPLC) for the separation of both taxifolins and the diastereomeric mixture of taxifolin-6- C -β- d -glucopyranosides. Correlation of the analytical data of synthetic ulmoside A and its diastereomer with a natural ulmoside A sample confirmed the assigned absolute stereochemistry of the natural products. [ABSTRACT FROM AUTHOR]

A new high‐performance liquid chromatography (HPLC) method for separation and determination of panthenol enantiomers in hair care products was developed. Two types of detectors, low‐wavelength ultraviolet (UV) and polarimetric, were used. Optimized conditions consisted of coupled achiral, amino type, and chiral, amylose tris(3,5‐dimethylphenylcarbamate), stationary phases, mixture of n‐hexane/ethanol (60:40, v/v) as mobile phase under isocratic conditions and flow rate 0.8 cm3 min−1. The effect of column temperature on retention and resolution of enantiomers was studied. The analysis runtime was 10 minutes, and the average retention times for d‐ and l‐panthenol were 7.10 ±0.1 minutes and 8.21 ±0.2 minutes, respectively. The resolution of enantiomers on coupled achiral‐chiral columns was Rs = 2.7. The solid‐phase extraction method was employed for extraction and purification of analytes. The validated method was selective, accurate, and linear (R2 >.998) over the concentration range of 0.001 to 1.0 mg cm−3 for both enantiomeric forms. The limits of detection (LOD) and quantitation (LOQ) of each enantiomer were 0.3 and 1.0 μg cm−3, respectively. The results demonstrated the occurrence of d‐panthenol in hair care products. [ABSTRACT FROM AUTHOR]

• Borrowing hydrogen reaction using the benzylPd(II) system. • Direct use of 2-aminobenzyl alcohol for construction of quinazoline 2. • Self-condensation of in-situ generated 2-aminobenzaldehyde followed by hydrogen transfer. • Both enantiomers are available after chiral separation of 2. We demonstrate the borrowing hydrogen reaction of readily available 2-aminobenzyl alcohol 1 , which is a new synthetic strategy for the construction of ring-fused quinazoline systems. The cascade reaction involves the dehydrogenative oxidation of alcohol 1 to the corresponding aldehyde 3 followed by self-condensation and reduction utilizing the benzyl Pd(II) system. The racemate 2 was successfully separated by chiral HPLC, affording a pair of enantiomers with high purity (>99 % ee) in a 1:1 ratio. The absolute configuration of one enantiomer was established via X-ray crystallography of its heavy atom analog. The structures of the racemate 2 and the pure enantiomer 2a were characterized by single-crystal X-ray analysis. [Display omitted] [ABSTRACT FROM AUTHOR]

The five‐steps synthesis of a hemicryptophane cage combining a benzene‐1,3,5‐tricarboxamide unit and a cyclotriveratrylene (CTV) moiety is described. Chiral high‐performance liquid chromatography (HPLC) was used to resolve the racemic mixture. The absolute configuration of the isolated enantiomers was assigned by comparison of the experimental electronic circular dichroism (ECD) spectra with the calculated ones. X‐ray molecular structures reveal that the capped benzene‐1,3,5‐tricarboxamide unit adopts a structurally chiral conformation in solid state: the chirality of CTV moiety controls the Λ or Δ orientation of the three amides. [ABSTRACT FROM AUTHOR]

The rapid and simultaneous separation of triacylglycerol (TAG) enantiomers and positional isomers was achieved using chiral high performance liquid chromatography (HPLC). TAGs composed of two fatty acids, which were both saturated (P: palmitic acid or S: stearic acid) and unsaturated (O: oleic acid or L: linoleic acid; e.g., sn-PPO/sn-OPP/sn-POP: 1,2-dipalmitoyl-3-oleoyl-sn-glycerol/1-oleoyl-2,3- dipalmitoyl-sn-glycerol/1,3-dilpalmitoyl-2-oleoylglycerol), were resolved into three peaks using CHIRALPAK IF-3 without recycling on the HPLC system. For example, the mixture of sn-PPO/sn-OPP/sn- POP was resolved in 30 min, although it took 150 min to resolve sn-PPO/sn-OPP using CHIRALCEL ODRH in a previous study using a recycling HPLC system. This novel chiral HPLC method was applicable for the separation of other TAG isomers, including sn-OOP/sn-POO/sn-OPO, sn-PPL/sn-LPP/sn-PLP, sn-LLP/sn-PLL/sn-LPL, sn-SSO/sn-OSS/sn-SOS, sn-OOS/sn-SOO/sn-OSO, sn-SSL/sn-LSS/sn-SLS, and sn-LLS/sn- SLL/sn-LSL. For TAGs composed of three fatty acids containing both saturated and unsaturated fatty acids, the POL isomers were not sufficiently separated but the PSO and SOL isomers were partially separated into several peaks. Their elution order could be estimated by the fragment ions generated in the ion source of the mass spectrometer. However, TAGs consisting of only saturated or unsaturated fatty acids (e.g., sn-PSP/sn-PPS/sn-SPP and sn-OLO/sn-OOL/sn-LOO) were not separated. This novel chiral HPLC method is especially applicable for the analysis of TAG composition of semi-solid fats such as palm oil. [ABSTRACT FROM AUTHOR]

• Coated and immobilized columns were prepared from linear ADMPC and cyclic cADMPC. • Coated cADMPC columns have different chiral separation ability from that of ADMPC. • Separation ability of cADMPC columns resembles that of immobilized ADMPC columns. • Local conformation plays an important role for the chiral separation. Coated-type chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) were prepared from three cyclic amylose tris(3,5-dimethylphenylcarbamate) (cADMPC) samples, of which weight-average molar mass (M w) ranges from 19 to 91 kg mol−1, and from three linear ADMPC samples ranging in M w from 25 to 90 kg mol−1. CSPs made of cADMPC showed appreciably different chiral separation ability comparing with those for ADMPC with a mixed eluent of n -hexane and 2-propanol. Local conformation plays an important role for the chiral separation taking into account that the local helical structure of cADMPC in dilute solution is extended comparing with ADMPC. Immobilized-type CSPs were also prepared from enzymatically synthesized linear and cyclic amylose samples with 3-(triethoxysilyl)propylcarbamate linkers (ADMPCi and cADMPCi) of which M w 's are in the range from 18 to 130 kg mol−1. When we choose quite high linker contents, CSPs of cADMPCi were fairly close to those of ADMPCi. This suggests that local conformations of ADMPCi and cADMPCi are similar in the stationary phase since they are crosslinked to the other polymer chains with multiple points on the polymer chain. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Racemic 3,4-dihydroferroceno[ c ]pyridines were obtained via the Ritter reaction. • MsOH-catalysed reaction of 2-methyl-1-ferrocenylpropan-1-ol with nitriles. • Preparative chiral HPLC resolution of the racemic 3,4-dihydroferroceno[ c ]pyridines. • Assignment of absolute configuration of (R p)- and (S p)-enantiomers by X-ray. Abstract A new approach for the synthesis of functionalized racemic 3,4-dihydroferroceno[ c ]pyridines via the Ritter reaction of 2-methyl-1-ferrocenylpropan-1-ol with nitriles in the presence of methansulfonic acid was developed. The scope and limitations of the reaction were evaluated. Selected racemic 3,4-dihydroferroceno[ c ]pyridines were successfully separated by preparative HPLC on a Chiralcel OD-H column. The absolute configuration of the enantiomers was determined by X-ray crystal structure analysis. [ABSTRACT FROM AUTHOR]

Abstract The enantiomerically pure N- and C-protected derivatives of planar-chiral (3-amino-1,2-dicarba-closo-dodecaboran-1-yl)acetic acid (>99% ee) have first been obtained in good yields via a combination of HPLC separation and synthetic procedures. Assignment of absolute configuration of the carborane fragments has been made based on the X-ray diffraction data of diastereoisomeric derivatives of (S)-amino acids. Graphical abstract Image 1 Highlights • Planar-chiral derivatives of 1,2-dicarba- closo -dodecaborane were obtained in enantiopure form. • Enantiomers of N - and C -protected (3-amino- ortho -carboran-1-yl)acetic acid (>99% ee) were prepared from racemic precursors. • Optical resolution and analysis of enantiomeric composition was performed by chiral HPLC. • Assignment of spatial configuration of ortho -carborane moiety was made using X-ray diffraction. [ABSTRACT FROM AUTHOR]

Highlights • Covalently immobilized chiral selectors. • Chiral selectors immobilized onto superficially porous silica. • Baseline separation of enantiomers in HPLC within 30 s. Abstract Our earlier studies have demonstrated the applicability of polysaccharide-based chiral selectors in combination with superficially porous (or core-shell) silica (SPS) particles for the preparation of highly efficient chiral stationary phases (CSP). In earlier studies, CSPs were prepared by coating (adsorption) of the chiral selector onto the surface of silica. In this study we report for the first time the CSP obtained by covalent immobilization of a chiral selector onto the surface of SPS particles. The applicability of this CSP for the separation of enantiomers in pure methanol and acetonitrile, as well as in n-hexane/2-propanol mobile phases is shown. The effect of the injected sample amount, mobile phase flow rate and detection frequency on separation performance were studied, as well as high efficiency separation of enantiomers with the analysis time less than 30 s was attempted. [ABSTRACT FROM AUTHOR]

Abstract: Herein we present design, synthesis, chiral HPLC resolution, and kinetics of racemization of axially chiral Ni(II) complexes of glycine and di‐(benzyl)glycine Schiff bases. We found that while the ortho‐fluoro derivatives are configurationally unstable, the pure enantiomers of corresponding axially chiral ortho‐chloro‐containing complexes can be isolated by preparative HPLC and show exceptional configurational stability (t1/2 from 4 to 216 centuries) at ambient conditions. Synthetic implications of this discovery for the development of new generation of axially chiral auxiliaries, useful for general asymmetric synthesis of α‐amino acids, are discussed. [ABSTRACT FROM AUTHOR]

Quality-by-Design approach for enantioselective HPLC method development surpasses Quality-by-Testing in offering the optimal separation conditions with the least number of experiments and in its ability to describe the method's Design Space visually which helps to determine enantiorecognition to a significant extent. Although some schemes exist for enantiomeric separations on Cinchona-based zwitterionic stationary phases, the exact design space and the weights by which each of the chromatographic parameters influences the separation have not yet been statistically studied. In the current work, a screening design followed by a Response Surface Methodology optimization design were adopted for enantioseparation optimization of 3 model drugs namely the acidic Fmoc leucine, the amphoteric tryptophan and the basic salbutamol. The screening design proved that the acid/base additives are of utmost importance for the 3 chiral drugs, and that among 3 different pairs of acids and bases, acetic acid and diethylamine is the couple able to provide acceptable resolution at variable conditions. Visualization of the response surface of the retention factor, separation factor and resolution helped describe accurately the magnitude by which each chromatographic factor (% MeOH, concentration and ratio of acid base modifiers) affects the separation while interacting with other parameters. The global optima compromising highest enantioresolution with the least run time for the 3 chiral model drugs varied extremely, where it was best to set low % methanol with equal ratio of acid-base modifiers for the acidic drug, very high % methanol and 10-fold higher concentration of the acid for the amphoteric drug while 20 folds of the base modifier with moderate %methanol were needed for the basic drug. Considering the selected drugs as models for many series of structurally related compounds, the design space defined and the optimum conditions computed are the key for method development on cinchona-based chiral stationary phases. [ABSTRACT FROM AUTHOR]

The enantiomers of four chiral 3-aryl-substituted-γ-butyrolactones, key intermediates for the preparation of compounds of pharmaceutical interest, were successfully isolated by enantioselective chromatography, employing the Chiralpak AD-H chiral stationary phase. For all compounds the same elution order was observed, as monitored by a full set of chiroptical methods that we employed, namely ORD (optical rotatory dispersion), ECD (electronic circular dichroism, or CD in the UV range), and VCD (vibrational circular dichroism, or CD in the IR range). By density functional theory (DFT) calculations we were able to determine that the first eluted enantiomer has ( S ) absolute configuration in all four cases. We were able to justify the elution order by molecular docking calculations for all four enantiomeric pairs and suitable modeling of the stationary and mobile phases of the employed columns. The optimal performance of the chiroptical spectroscopies and of the DFT calculations allows us to formulate a lactone chirality rule out of the C O stretching region of the VCD spectra. [ABSTRACT FROM AUTHOR]

When polysaccharide-based chiral columns are used in combination with aqueous-organic mobile phases for the separation of enantiomers in high-performance liquid chromatography the separation mode is commonly called “reversed-phase” in analogy to achiral separations. In several earlier and recent studies on neutral and basic chiral analytes it was shown by our and other groups that due to multiple type of interactions involved in selector-selectand binding and enantioselective recognition with polysaccharide derivatives, the above mentioned separation system may not always behave like a reversed-phase system. In the present study additional examples of non-reversed-phase behavior are described for the first time for weak acidic chiral analytes. In addition, the reversal of enantiomer elution order was observed again for the first time for several analytes based on water-content in the mobile phase. [ABSTRACT FROM AUTHOR]

Our earlier studies on the preparation of chiral stationary phases (CSP) based on superficially porous (or core-shell) silica (SPS) particles for the separation of enantiomers in HPLC have provided proof to the advantages of such sorbents. In particular, higher enantioselectivity was observed with the columns packed with superficially porous CSP compared to the columns packed with fully-porous (FP) silica-based CSPs at comparable content of chiral selector (polysaccharide derivative) in CSP. Also, less dependence of plate height on mobile phase flow rate and higher plate numbers and resolution calculated per unit time (i.e. speed of separation) were observed with SPS-based CSPs. Thirty years of CSP development have demonstrated that wide-pore silica has to be used as a support for large molecular weight chiral selectors such as the ones based on polysaccharides. In this study the effect of pore size of the core-shell silica support and of other experimental factors on column performance is demonstrated. Reduced plate heights in the range 1.4–1.5 were obtained, as well as highly effective baseline separations of enantiomers were observed with analysis times of less than 15 s. [ABSTRACT FROM AUTHOR]

The chiral HPLC separation parameters of a series of fourteen β-blockers previously performed on four polysaccharide-based chiral stationary phases (CSPs) was evaluated through computational techniques, using a set of 340 molecular descriptors (MD), calculated with the Molecular Operating Environment (MOE) software. Several semi-empirical mathematical models were built and refined by PLS, O2PLS multivariate data analysis and by PLS-Tree® clustering, correlating chromatographic data with the descriptors. The resulting models revealed the importance of certain analyze descriptors shaping chromatographic behaviour of the studied enantiomers. The chiral selector backbone as well as the presence of halogen atom(s) in the structure of the used stationary phase appears to exert an influence on the type of descriptors that significantly contribute either positively or negatively on the prediction power of the developed models. The influence of additive on the predictive power of models was also briefly analysed. This QSPR study generated models with a good predictive power. However, these results could be substantially improved in the future by including the descriptors for the chiral selectors and additives in the model and by performing docking studies. [ABSTRACT FROM AUTHOR]

MP 3950 is an active metabolite of mosapride which exhibits high 5-HT 4 receptor agonistic effect. The present paper describes an enantioselective chiral HPLC method for separation and quantification of MP 3950 enantiomers in rat plasma. The plasma samples were prepared by liquid–liquid extraction with ethyl acetate and the baseline chromatographic separation was achieved on a Chiralcel OJ-H column with a mobile phase consisting n -hexane/ethanol/methanol/diethylamine (85:5:10:0.4, v/v/v/v) at the flow rate of 1.0 mL/min. The ultraviolet detection was performed at 276 nm. The calibration curve was linear in the range from 0.100 to 5.00 μg/mL with the lower limit of quantification of 0.100 μg/mL for each enantiomer. The intra- and inter-day precisions were not more than 14.7%. The accuracy was from −6.4% to 14.0%. The validated method was successfully applied to chiral inversion and stereoselective pharmacokinetic study in rats after oral administration of MP 3950 racemate. The results indicated that no stereochemical inversion was occurred in rats. And the plasma concentrations and area under plasma concentration-time curve of ( S )-MP 3950 were all significantly higher than those of ( R )-MP 3950 in both male and female rats, which indicated that the disposition of MP 3950 in rats might be stereoselective. [ABSTRACT FROM AUTHOR]

The first ever report on the preparation of chiral stationary phases (CSP) based on superficially porous silica (SPS) particles for the separation of enantiomers in HPLC demonstrated clear advantages of such materials. Higher enantioselectivity at the comparable content of a chiral selector, limited dependence of plate height on the mobile phase flow rate and higher plate numbers and resolution calculated per unit time (i.e. higher speed of separation) were observed with columns made with superficially porous CSP in comparison to columns made with fully-porous silica-based CSP. However, later studies reported diverging conclusions. In this report further evidences are described supporting the findings of our first study about the superior performance of polysaccharide-based chiral selectors in combination with SPS when compared to traditional CSPs based on fully porous silica (FPS) particles. [ABSTRACT FROM AUTHOR]

In our previous work we identified the presence of meso -zeaxanthin [(3R,3′S)-zeaxanthin] in trout flesh and skin ( Nolan et al., 2014 ), but were not able to quantify this carotenoid with the method used at that time. In the present study, we developed a protocol that allows for the quantification of lutein and the three stereoisomers of zeaxanthin [(3R,3′R)-zeaxanthin, meso -zeaxanthin and (3S,3′S)-zeaxanthin] in fish flesh. We tested this protocol in two species of farmed trout ( Oncorhynchus mykiss and Salmo Trutta ), and we detected and quantified these carotenoids. The concentrations of each carotenoid detected (ranging from 1.18 ± 0.68 ng g −1 flesh for meso -zeaxanthin to 38.72 ± 15.87 ng g −1 flesh for lutein) were highly comparable for the two fish species tested. In conclusion, we report, for the first time, the concentrations of zeaxanthin stereoisomers (including meso -zeaxanthin) and lutein in trout flesh. This work adds further to the knowledge on the presence of these carotenoids in the human food chain. [ABSTRACT FROM AUTHOR]

The chiral separation of enantiomeric couples of three potential A3 adenosine receptor antagonists: ( R/S)-N-(6-(1-phenylethoxy)-2-(propylthio)pyrimidin-4-yl)acetamide ( 1), ( R/S)-N-(2-(1-phenylethylthio)-6-propoxypyrimidin-4-yl)acetamide ( 2), and ( R/S)-N-(2-(benzylthio)-6-sec-butoxypyrimidin-4-yl)acetamide ( 3) was achieved by high-performance (HPLC). Three types of chiroptical spectroscopies, namely, optical rotatory dispersion (ORD), electronic circular dichroism (ECD), and vibrational circular dichroism (VCD), were applied to enantiomeric compounds. Through comparison with Density Functional Theory (DFT) calculations, encompassing extensive conformational analysis, full assignment of the absolute configuration (AC) for the three sets of compounds was obtained. Chirality 28:434-440, 2016. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Stereoselective analytical HPLC separations have been developed for a series of biologically active chiral 2-pyrazolines (1-22) to be used in monitoring their resolution reactions or to custom semipreparative HPLC separations prior to biological assessment of both enantiomers. Polysaccharide-based chiral stationary phases (CSPs), namely, Lux amylose-2 and cellulose-2, have been used. Both normal (n-hexane/ethanol) and polar organic (ethanol, methanol, acetonitrile, or mixtures thereof) elution modes were very beneficial for the achievement of baseline separations. The impact of various chemical moieties embedded in the structures of 2-pyrazolines1-22and the adopted stationary phases on chiral recognition has been investigated. A case of reversed order of elution following alterations in either stationary phase or elution mode has been observed. Our findings recommend that normal elution mode can be used for optimizing semipreparative HPLC methods whereas polar organic mobile phases (such as acetonitrile and ethanol) are more suited to stereoselective reactions monitoring, routine quality control work, or for pharmacological and toxicological assays. These results settle the implementation of polysaccharide-based CSPs using different elution modes and declare the practicality of such CSPs in stereoselective HPLC. [ABSTRACT FROM PUBLISHER]

A P -helical quinoline oligoamide foldamer was grafted on silica and applied as an HPLC stationary phase for chiral separation. The P -handedness of the quinoline oligoamide foldamer was induced by a (1 S )-camphanyl group, which was introduced at the N-terminus of a tetrameric quinoline oligoamide foldamer (Cmp-Q 4 ). To immobilize the foldamer on porous silica particles, a trimethoxysilyl group was introduced at the opposing end of the foldamer. Elemental analysis indicated that the amount of foldamer on the silica surface was 0.57 μmol/m 2 . Circular dichroism and vibrational CD spectra of Cmp-Q 4 and Cmp-Q 4 -immobilized silica (Sil-Q 4 -Cmp) suggested that the helical structure of Cmp-Q 4 was altered on the silica surface whilst retaining a chiral structure. The chiral recognition ability of Sil-Q 4 -Cmp was evaluated with various aromatic enantiomers. Sil-Q 4 -Cmp showed enantio-selectivity for axially chiral molecules (e.g., α Trigger’s base = 1.26 and α Binaphthol = 1.07). Sil-Q 4 -Cmp showed remarkable recognition of helical octameric quinoline oligoamides with isobutoxy and triethylene glycol side chains ( α = 10.35 and 14.98, respectively). In contrast, an (1 S )-camphanyl group-immobilized porous silica showed no chiral recognition for any enantiomers tested in this study. To elucidate the chiral separation mechanism of Sil-Q 4 -Cmp, thermodynamic parameters were calculated using van’t Hoff plots. HPLC results and thermodynamic parameters suggested that the chiral recognition of Sil-Q 4 -Cmp is based on the helical structure of Cmp-Q 4 and other thermally dependent interactions such as hydrophobic effects associated with aromatic stacking. This work represents the first known application of aromatic foldamers in chiral separation. [ABSTRACT FROM AUTHOR]

A C3 symmetric (R)-phenylglycinol N-1,3,5-benzenetricarboxylic acid-derived chiral stationary phase (CSP) and three C2 symmetric (R)-phenylglycinol CSPs were newly synthesized using o-, m-, and p-phthaloyl dichlorides. © 2016 Wiley Periodicals, Inc. These CSPs were used to compare the resolution of 25 chiral samples using a previously reported 3,5-dinitrobenzoyl (R)-phenylglycinol-derived CSP. Even though all CSPs have the same chiral moiety, the C3 symmetric CSP showed the best resolution. Chirality 28:186-191, 2016.© 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Enantiomerization of allylic trifluoromethyl sulfoxides occurs spontaneously at room temperature through the corresponding allylic trifluoromethanesulfenates via a [2,3]-sigmatropic . Dynamic high-performance (HPLC) analysis revealed the stereodynamics of these sulfoxides ranging from chromatographic resolution to peak coalescence at temperatures between 5 and 53 °C. The rate constant of enantiomerization and activation parameters were determined and compared with Density Functional Theory (DFT) calculations. Chirality 28:136-142, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The methods for the separation of racemic compounds [( RS)-1-bromo-3-chloro-2-propanol, ( RS)-1-bromo-3-chloropropan-2-yl acetate] into the corresponding enantiomers were tried to develop in high performance liquid chromatography in a single injection mode. In the case of HPLC, both the reversed (Phenomenex Lux 5u cellulose-1, Lux 5u cellulose-2, Lux 5u amylose-1) and normal phase (Chiralcel OJH, ODH, ADH) chiral columns were used for this purpose. HPLC methods could not resolute the desired enantiomers. However, phenoxy derivatives of ( RS)-1-bromo-3-chloro-2-propanol and ( RS)-1-bromo-3-chloro- propan-2-yl acetate were separated by normal phase (ODH) column using a mobile phase consisting of n-hexane and isopropanol (80: 20) at a flow rate of 0.5 mL/min (25°C) and detected at 254 nm. The method was validated for linearity, range, accuracy and precision. The developed method was applied for monitoring the progress of lipase catalyzed enantioselective synthesis of ( S)-1-bromo-3-chloropropan-2-yl acetate from ( RS)-1-bromo-3-chloro-2-propanol. All the analytes were synthesized chemically. [ABSTRACT FROM AUTHOR]

• The enantioseparation of HPR and HPP was investigated using CE and HPLC-MS/MS. • Cyclodextrin-modified CE experiments provided excellent enantioseparation. • Chiral HPLC-MS/MS was superior to CE for the analysis of plant samples. • A validated, quantitative HPLC-MS/MS method was developed. • The amino acid content of various Fabaceae plant samples was determined. Non-protein amino acids are important metabolites of the Fabaceae family, possessing valuable biological effects in addition to their toxic properties. We have previously identified two non-protein amino acids homoproline and homopipecolic acid in Ononis species for the first time, and herein the study was extended to investigate further Fabaceae species (O. spinosa, O. arvensis, M. sativa, A. vulneraria) with medicinal, food or cosmetic uses. As the enantiomers of these beta amino acids can carry different activity or toxicity, our aim was to develop a chiral separation method for homoproline and homopipecolic acid enantiomers and apply it to plant samples. For this purpose, dansylated derivatives were prepared and a cyclodextrin-modified capillary electrophoresis in addition to a chiral HPLC method were developed. Although baseline separation was achieved by CE applying mono-(6- N -pyrrolidine-6-deoxy)-β-CD, mono-(6- N -piperidine-6-deoxy)-β-CD or sulfated-gamma-cyclodextrin at pH 6.0, the HPLC method was found to be more suitable for the analysis of the plant samples. Both homoproline and homopipecolic acid were confirmed in plant samples as racemates. The quantitative determination of homoproline and homopipecolic acid in several Fabaceae species were also aimed. Since these molecules can be found in the plants as esters, sample preparation was optimized to liberate the target molecules. Several SPE methods were tested for sample purification and a HPLC-MS/MS method using C8 stationary phase was developed and validated. The presence of homoproline and homopipecolic acid could be confirmed in all species ranging from 1 µg/g through 500 µg/g homopipecolic acid and 6 µg/g to 60 µg/g homoproline and significant changes could be observed between species, geographical origins, and botanical parts. Generally O. spinosa root samples were found to be the richest sources of the two amino acids, but a high variance could be observed between species. [ABSTRACT FROM AUTHOR]

• A method was established for analysis of enantiomeric impurities in S -profen durgs. • Hydrogen-bonding, hydrophobic interactions, π-π stacking were involved in separation. • The calculated BE resluts could expalin the differece in enantiomer elution roder. • Thermodynamic study showed that the enantioseparation was entropy-driven. A rapid reversed-phase high performance liquid chromatographic (HPLC) methodology for chiral separation of three profen compounds has been developed and then applied to enantiomeric impurity testing of their corresponding enantiopure drugs. The assay is specific, allowing quantitation of the enantiomeric impurities at levels of 0.0078%, 0.0105%, and 0.0416% relative to S -ibuprofen, S -naproxen, and S -ketoprofen, respectively. In order to gain a better insight into the chiral recognition mechanisms of chiral profens on an FLM Chiral NQ(2)-RH column, molecular docking studies were carried out using AutoDock 4.0 software. It was found that hydrogen bonding, hydrophobic interactions, and π-π stacking were all involved in stereoselective interactions, and the calculated binding energy (BE) obtained reflected the binding strength of each enantiomer interacting with a chiral selector. The higher the BE value, the harder it was to elute the corresponding enantiomer, which also accorded with the enantiomer elution order observed in the actual enantiomeric separation. Additionally, thermodynamic analysis revealed that the enantioseparation process at 15–40°C was driven mainly by entropic contributions. The methodology was further validated according to the International Council for Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guideline Q2 (R1) and proved to be sensitive, linear, precise, and accurate for determining R -profen impurities in three commercially available single-enantiomer S -profen drugs. As expected, in the case of products acquired in actual pharmacies, the levels of all of the monitored impurities were found to be lower than the allowable impurity limits. [ABSTRACT FROM AUTHOR]

A long-neglected recycling high performance liquid chromatography (R-HPLC) strategy was adopted to improve the enantioseparation efficiency in this work. Taking intractable isoxazolidine mixtures as the example, two different R-HPLC methods including single-column and twin-column based strategy were applied to improve the enantioseparation efficiency. Under the optimized conditions, these two methods present distinct separation results: the conceptually simple and commonly used single-column based R-HPLC led to severe peak broadening and degraded separation efficiency; on the contrary, the enantioseparation was significantly improved by adopting the relatively complicated twin-column strategy. This observed difference might be mainly attributed to less peak spreading and sample mixing of the latter, as a result of avoiding redirecting the effluent back to LC pump. [ABSTRACT FROM AUTHOR]

Polysaccharide-based chiral stationary phases (CSPs) or chiral packing materials (CPMs) have been frequently employed for analyzing and separating various enantiomers by high-performance liquid chromatography (HPLC). The polysaccharide derivatives dissolved in a solvent are usually coated on silica gel to be used as CSPs. This means that some solvents, which can swell or dissolve the derivatives, cannot be used as the eluents in HPLC. In this review, various immobilization methods of the polysaccharide derivatives are described. The immobilization often reduces the chiral recognition ability compared to that of the corresponding coated-type CSPs. This problem can be overcome by the versatility of eluent selection for the immobilized CSPs. Enantioseparations of various racemates on the immobilized commercial columns using the non-standard eluents are briefly summarized. [ABSTRACT FROM AUTHOR]

ABSTRACT Residual stereoisomers result whenever closed subsets of appropriately substituted interconverting isomers (the residual stereoisomers) are generated from a full set of stereoisomers under the operation of a favored stereomerization mechanism. In the case of the three-bladed propellers, differentiation of the edges of the blades and strict correlation in the motion of the rings are the prerequisites for the existence of residual stereoisomers. In these systems, the two-ring flip mechanism is the lowest energy process. It does not interconvert all possible conformational stereoisomers generated by helicity and the three-blade-hub rotors. In the case of C3 symmetric systems, two noninterconverting subgroups (the residual stereoisomers) are generated, each one constituted of quickly interconverting diastereoisomers. A series of tris-aryl phosphanes, structurally designed for existing as residual enantiomers or diastereoisomers, bearing substituents differing in size and electronic properties on the aryl rings, were synthesized and characterized. The configurational stability of residual phosphanes, evaluated by dynamic 1H- and 31P-NMR analysis and by dynamic high-performance (HPLC), was found 10 kcal mol-1 lower than that shown by the corresponding phosphane-oxides. In accordance with the calculations, an unexpectedly low barrier for phosphorus pyramidal was invoked as responsible for the scarce configurational stability of the residual tris-arylphosphanes. Chirality 26:601-606, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Normal phase chiral HPLC methods are presented for the enantiomeric separation of 30 biaryl atropisomers including 18 new compounds recently produced via a novel synthetic approach. Three new cyclofructan based chiral stationary phases were evaluated. Separations were achieved for all but six analytes and the LARIHC™ CF6-P alone provided 15 baseline separations. Effects of polar modifiers and temperature effects also were studied. Apparent thermodynamic parameters were determined by van't Hoff plots. Preparative scale methods were developed and employed resulting in the first ever isolation of these novel atropisomers in their pure enantiomeric form. Insights into the mechanism of retention and chiral discrimination are presented. [ABSTRACT FROM AUTHOR]

A simple, inexpensive, and efficient preconcentration and cleanup three-phase hollow fiber liquid-phase microextraction method (HF-LPME) was developed for the extraction of the anti-inflammatory ketoprofen (KTP) from human and rat plasma and HPLC enantioseparation of its enantiomers using vancomycin as a chiral mobile-phase additive with an achiral C8 column. The effects of different parameters influencing the efficiency of extraction were optimized for aqueous samples. Under optimized conditions, KTP enantiomers were extracted from 0.5 mL of plasma diluted to 5 mL with salinated and acidified deionized water (pH = 2) with 25 μL of alkalinized acceptor phase (pH = 11) during 30 min at room temperature. The mean recoveries of (−)-( R)- and (+)-( S)-KTP were 72.8% and 70.9%, respectively. The quantification limit was 20 ng/mL with linear response over the 20-2000 ng/mL concentration range for both enantiomers. Assay precision was studied within-day and between-day using 100 ng/mL KTP solutions. For both KTP enantiomers, relative standard deviations were lower than 12%. The proposed microextraction method was applied for the extraction of KTP enantiomers from human and rat plasma samples after oral administration of pure (±)-KTP in 4 mg/kg dosage for rats and 50 mg dosage for humans to assess the enantiospecific bioavailability of KTP enantiomers in their plasma. In vivo inversion studies revealed that the bioavailability of S-KTP is higher than that of the R enantiomers in rat, but they are similar in human plasma. The developed method showed that HF-LPME is a promising technique for sample preparation for the analyses of chiral drugs in biological samples. [ABSTRACT FROM AUTHOR]

ABSTRACT With the aim to define a combined computational/chromatographic empirical approach useful for the high-performance (HPLC) method development of new chiral compounds, 36 racemic aromatic compounds with different chemical structures were used as test probes on four polysaccharide-based chiral stationary phases (CSPs) of the Lux series, namely Lux Cellulose-1, Lux Cellulose-2, Lux Cellulose-4, and Lux Amylose-2, using classical n-hexane/2-propanol mixtures as mobile phase. Electrostatic potential surfaces (EPSs) determined using Density Functional Theory (DFT) calculations were used to derive size, shape, and electronic properties of each analyte. Then a comparative HPLC screening was carried out in order to evaluate the impact of substituents, shapes, and electronic properties of the analytes on the chromatographic behavior as the column changes. The four CSPs showed good complementary recognition ability. The elution sequence was determined in 30 cases out of 36. The success rate to afford baseline separations (Rs ≥ 1.5) was estimated: 29 compounds out of 36 showed baseline enantioseparation on at least one of the four selected CSPs. The combined computational-chromatographic screening furnished useful collective structure-chromatographic behavior relationships and a map of the chiral discrimination abilities of the considered CSPs towards the analytes. On this basis, the chromatographic behavior of new analytes on a set of polysaccharide-based CSPs can be mapped through the qualitative correlation of chromatographic parameters ( k, α, Rs) to computed molecular properties of the analytes. Chirality 25:709-718, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

An accurate, simple and reproducible high-performance liquid chromatographic (HPLC) method has been developed and validated for the direct separation of individual enantiomers of Abacavir sulfate, a nucleoside reverse transcriptase inhibitor for the treatment of HIV, in pharmaceutical bulk drugs. The enantiomers were resolved by normal phase chromatography, on Chiralpak IA column by using a mobile phase with selective composition of Hexane-Ethanol-Methanol-Diethylamine (DEA) (600:250:150:0.1; v/v/v/v). Diethylamine, the mobile phase additive played a very significant role in improving the chromatographic resolution and also in enhancing chromatographic efficiency, with in 20.0 min runtime. Baseline separation of the enantiomers of Abacavir was obtained with a resolution greater than 4. The developed method was extensively validated and proved its suitability and robustness. The developed method was found to be selective in the presence of its degradation products, generated from forced decomposition studies. The standard curves for the two enantiomers were linear (r > 0.999) in the concentration range from 0.06 μg/mL (LOQ) to 2.0 μg/mL for an analyte concentration of 0.5 mg/mL for each enantiomer. The percentage recovery of (R)-Abacavir was ranged from 99.3 to 100.6 in bulk drug samples of Abacavir. The limit of detection and limit of quantitation for (R)-Abacavir were 0.02 μg/mL and 0.06 μg/mL respectively. The intra-day precision (%RSD) results were 2.5 and 2.4, while the inter-day precision results were 3.8 and 2.6 calculated for area response of (R) and (S)-Abacavir, respectively. Abacavir sample solution stability and mobile-phase stability were studied for 48 h and found to be stable during the period. The validated method yielded good results of selectivity, linearity, precision, accuracy and robustness, and was also able to resolve the enantiomers from the USP listed impurities of Abacavir sulfate. [ABSTRACT FROM AUTHOR]

Highlights: [•] 21 chiral isochromene derivatives were separated for the first time by chromatography. [•] Separation data and structural features of 35 chiral isochromenes were analyzed. [•] Principal component analysis was used for the study. [•] Some structural features increase retention while others enhance chiral resolution. [ABSTRACT FROM AUTHOR]

ABSTRACT A simple, sensitive, and robust normal-phase isocratic HPLC-UV method was developed and validated for the enantiomeric separation of rasagiline mesylate and its ( S)-enantiomer. The rasagiline and its ( S)-enantiomer were resolved on a Chiralcel-OJ-H (4-methylbenzoate cellulose coated on silica) column using a mobile phase consisting of n-hexane:isopropyl alcohol:ethanol:diethyl amine (96:2:2:0.01) at a flow rate of 1.0 ml/min. The column temperature was maintained at 27 °C and elution was monitored at 215 nm. The resolution ( Rs) between the enantiomers was found to be more than 2.0. The limit of detection and the limit of quantification of the ( S)-enantiomer were found to be 0.35 and 1.05 µg/ml, respectively. The developed method was validated as per ICH guidelines with respect to linearity, limit of detection and quantification, accuracy, precision, and robustness-and satisfactory results were obtained. The sample solution and mobile phase were found to be stable up to 48 h. The method is useful for routine evaluation of the quality of rasagiline mesylate in bulk drug-manufacturing units. Chirality 25:324-327, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: HPLC methods (LC–MS/APCI and chiral HPLC) were used for the identification of astaxanthin derivatives from the red snow alga Chlamydomonas nivalis collected in Austrian Alps, Slovak High Tatra Mountains and Bulgarian Pirin. We observed a striking difference in the composition of astaxanthin optical isomers in C. nivalis collected in geographically distinct regions. Furthermore, algae from the Pirin Mountains differed in the dominance of astaxanthin diglucoside diesters, suggesting an alternative strategy to enhance cell viability at low temperatures. [Copyright &y& Elsevier]

Abstract: Chemical examination of aerial parts of Dracocephalum heterophyllum resulted in isolation of phenolic alkaloids, including two flavonoidal alkaloids, drahebephins A and B, one imidazole alkaloid with a phenolic substituent, drahebenine, together with 15 other known compounds. Their structures were established by extensive spectroscopic data analyses. Due to the stereogenic center in the pyrrolidin-2-one ring, the flavonoidal alkaloids are chiral, although they were isolated as racemates. The enantiomers were separated by HPLC using a chiral phase and stereochemically characterized by circular dichroism (CD) spectroscopy. The structure of compound drahebenine was established by X-ray crystallography. [Copyright &y& Elsevier]

Abstract: This article reports comparative high-performance liquid chromatographic separations of enantiomers with chiral stationary phases (CSPs) prepared by coating cellulose tris(4-chloro-3-methylphenylcarbamate) on totally porous and on core–shell type silica of comparable particle diameter. Several interesting observations were made: (1) the selectivity of separation was higher on core–shell type CSP compared to totally porous CSP at comparable content of chiral selector (polysaccharide derivative); (2) much flatter dependence of plate height on the mobile phase flow rate was observed for columns packet with CSP prepared with core–shell silica compared to the ones packed with CSPs prepared with totally porous particles; (3) at low mobile phase flow rates core–shell CSP provided lower resolving ability compared to a commercially available CSP having four times higher content of chiral selector along with higher retention of chiral analytes. However, at high flow rates core–shell type CSP performed similarly or better than the commercial column in regards of plate count (N) and peak resolution (R s) per column length and within a given total analysis time. The advantage of CSP prepared with core–shell silica is obvious from the viewpoint of plate numbers and resolution calculated per unit time (i.e. speed of analysis). [Copyright &y& Elsevier]

Abstract: A methyl-branched heptadecanol was found in the pheromone gland extract of a female lichen moth, Miltochrista calamina (Arctiidae, Lithosiinae). GC–MS analyses of the alcohol and a hydrocarbon derived from it by subsequent treatments with methanesulfonyl chloride and LiAlD4 in microscale reactions indicated 5-methylheptadecan-7-ol (1) as one possible structure. The four stereoisomers of 1 in a ratio of 4:4:1:1 were prepared from (S)-β-citronellol with 60% ee, and were separated by a combination of achiral and chiral HPLC columns. The absolute configuration of each isomer was determined by the comparison with the chromatographic behaviors of other samples synthesized by a different scheme, which applied the Jacobsen hydrolytic kinetic resolution of racemic 1,2-epoxydodecane to fix the configuration of the 7-hydroxy group. Only the (5R,7R)-isomer attracted male moths; thus, we concluded that M. calamina females secrete (5R,7R)-1 as a sex pheromone, indicating a new chemical class of lepidopteran female sex pheromones. [Copyright &y& Elsevier]

Abstract: All the enantiomers of methoxydihydrosanguinarine (MS), ethoxydihydrosanguinarine (ES) and iso-propoxydihydrosanguinarine (PS) were separated by chiral HPLC. They were further identified by comparing the retention times of authentic standards as well as LC–MS. Interestingly, the approximately same conversion rates for the formation MS from ES or PS and the slower conversion of MS in isopropanol compared to ethanol demonstrated two step mechanism in the reaction of alkoxysanguinarine in alcohols, which is composed of the initial formation of sanguinarine as a planar intermediate and the addition of alcohol to intermediate as possible rate limiting step. Thus, sanguinarine has a pivotal role in the chemical behavior of alkoxysanguinarine in alcoholic solvents. Such possible variation of the structure of sanguinarine may be the source of its diverse biological activities. [Copyright &y& Elsevier]

Abstract: In this paper the elution order reversal of enantiomers of fluorenylmethoxycarbonyl- or FMOC-isoleucine is described depending on the separation temperature and composition of the mobile phase when using the polysaccharide-based chiral column Lux Cellulose-1 in HPLC with normal-phase eluent. Reversal of the enantiomer elution order (EEO) in HPLC depending on the column temperature and content of the polar modifier in the mobile phase has been reported before in the literature. However, EEO reversal by changing the content of acidic modifier in the mobile phase seems to be described for the first time in the present work. [Copyright &y& Elsevier]