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Phyllanthus is a large genus of the Euphorbiaceae family, which has been widely used in traditional medicine. The current study reports the isolation of an unusual C-glycosyl flavonoid, named tenelloside, from Phyllanthus tenellus Roxb., a non-endemic plant present in Canary Islands. The chemical structure of this secondary metabolite was established employing combined spectrometric and spectroscopic techniques, including 1D and 2D NMR experiments and mass spectrometry. The absolute stereochemical configuration was determined via the comparison of experimental and calculated electronic circular dichroism spectra. In our previous work, another C-glycosylated bioactive product was isolated from another Phyllanthus species, suggesting that this class of compounds can be produced in a genus-specific manner in different geographic regions. This work represents another important report for direct future studies on the biological and chemotaxonomic potential of C-glycosylated products of the Phyllanthus genus. [ABSTRACT FROM AUTHOR]

Herein, we report on the synthesis and high-performance liquid chromatography (HPLC) resolution of a new atropisomeric C2-symmetry chiral monomer based on the 3,3′-bithiophene core, which was developed to produce novel, inherently oligomeric chiral electroactive materials. The analytical enantioseparation was optimized using the cellulose-type Chiralpak IB-3 column and a mixture of n-hexane–methanol–dichloromethane 90:5:5 (v/v/v) as the mobile phase. During the scale-up of the enantioseparation analytical conditions to a semipreparative level, remarkable deformations in the HPLC profile, such as peak splitting and plateau zones between enantiomeric peaks, were observed. We demonstrate the effects of sample diluent as they relate to distorted peak profiles, as well as provide experimental solutions to prevent the disturbing phenomenon. The optimized chromatographic conditions were exploited to collect milligram amounts of the enantiopure sample, which was submitted to chiroptical and stereochemical characterization studies. [ABSTRACT FROM AUTHOR]

The kinetic parameters for topomerization around the N-CO bond and enantiomerization around the C-CO bond in N-1-napthoyl fulleropyrrolidine and N-1-naphthoyl pyrrolidine are determined by dynamic NMR. The deltaH(super #) value for topomerization of N-1-napthoyl fulleropyrrolidine is smaller with respect to that of N-1-naphthoyl pyrrolidine by 4.3 kcal mol(super -1) and the value for enantiomerization is greater by 1.4 kcal mol(super -1).

Three new (+)-sparteine-like diamines are prepared for (-)-cytisine and evaluated as sparteine surrogates in the alpha-lithiation rearrangement of cyclooctene oxide and the palladium(II)/diamine catalyzed oxidative kinetic resolution of 1-indanol. The new diamines exhibit opposite enantioselectivity to that observed with (-)-sparteine but increasing the steric hindrance of the N-alkyl group beyond N-Et has a detrimental effect on enantioselectivity.

Research has been conducted on the bis(1-naphthyl) derivative. The synthesis of this derivative and two cognates has been performed via the Suzuki coupling reaction and the results of the study are presented.

High performance liquid chromatography (HPLC) is used in the enantioselective and diastereoselective binding analysis of silica bound macrobicyclic receptors connected by a trans-diaminopyrrolidine linker. The best enantioselection was observed with Leu, Ile and Met, amino acids characterized by similar side chains. It was also observed that DNB derivatives were the most strongly retained enantiomers.

The synthesis and characterization of chiral (4)resorcinarenes are presented. The method involves the Lewis-acid catalyzed cyclization of chiral monomeric amides, derived from the mixed anhydride of cinnamic acid and L- or D-valine. Structural analysis showed that three of the four isomers have flattened-cone, chair and 1,2-alternate conformations.

Hindered naphthyl sulfones exist in asymmetric conformations, resulting in a pair of conformational enantiomers, demonstrating atropisomerism as detected by the variable temperature nuclear magnetic resonance technique. Both the meso and racemic conformers are present in a sulfone with two stereogenic axes. The meso structure is found to be the most stable form when conformational stereoisomers are isolated.

Low temperature chiral HPLC helps separate 10 stereoisomers of 2,6-dimethyl-1,5-bis(2-methyl-2-propylsulfinyl)naphthalene. NMR and on-line circular dichroism detected chiral HPLC help establish the configurational and conformational assignment for these stereoisomers. Absolute configuration of one of the stereoisomers is determined using single crystal X-ray diffraction experiments and circular dichroism relationship uses this absolute configuration to derive the absolute configurations of other stereoisomers.

Diphenyl diselenides and disulfides undergo facile cleavages by indium(I) iodide and the corresponding generated selenate and thiolate anions condense in situ with alkyl or acyl halides present in the reaction mixture. The conclusion states that a one-pot procedure for the synthesis of alkyl phenyl selenides, sulfides (thioethers), selenoesters, and thioesters is developed.

Optically pure enantiomers of the chiral tetrahydroxythiepene derivative 3,6-dihydroxy-4,5-o-isopropylidene-thiepane are obtained using a novel protocol in which a library of all possible stereoisomers of this derivative is synthesized followed by two-step stereoselective chromatography. Configurational and conformational analysis of 3,6-dihydroxy-4,5-o-isopropylidene-thiepane is carried out using vibrational circular dichroism spectroscopy in conjunction with ab initio DFT calculations, which is discussed.

Research has been conducted on 3-nitrobutan-2-one, 3-nitropentan-2-one and 2-nitropentan-3-one. The kinetics of reversible enantiomer interconversion of these compounds has been investigated via dynamic high-resolution gas chromatography using the chiral stationary phase of a beta-cyclodextrin derivative, and the details are reported.

Lactic acid is one of the most important compounds in the field of bio-renewable chemicals. Lactic acid is present in nature but can also be produced by chemical synthesis or by fermentation of biomass. It can be used as raw material for the production of biodegradable and environmentally friendly polymers or copolymers, such as poly lactic acid (PLA). In this work, the equilibrium distribution of monomer and low molecular weight oligomers of lactic acid in aqueous solutions at different overall concentrations of lactic acid (from 0.09 g/g to 0.94 g/g) and temperatures (423 K and 453 K), was investigated. In addition, a kinetic study of monomer and oligomer esterification reactions, of a lactic acid aqueous solution at about 0.09 g/g, was carried out at 423, 433, 443, and 453 K. The values of the kinetic constants were successfully correlated through Arrhenius' law. [ABSTRACT FROM AUTHOR]