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The newly developed methods to carry out diastereo- and enantioselective desymmetrization of cyclic meso-anhydrides are reviewed. The methods could be applied to generate optically active intermediates to synthesize biologically active natural products.

A novel method for determination of the monosaccharide anhydrides (MAs) levoglucosan, mannosan, and galactosan in atmospheric aerosols has been developed. The method is based on solvent extraction of aerosol filter samples and chemical analysis performed with high-performance liquid chromatography (HPLC) combined with time-of-flight high-resolution mass spectrometry. The MAs were separated on two series connected 2.1 mm x 150 mm reversed-phase HPLC columns and identified by negative electrospray ionization mass spectrometry using the m/z 113, 129, and 161 as monitoring ions. The limit of quantification (LOQ) at S/N 10 ranges between 20 and 40 pg for the three isomers. The LOQ can easily be improved. Samples from Elverum (urban background) and Oslo (urban) in Norway were used in validation experiments. Tetrahydrofuran was found to be the most efficient extraction solvent. The choice of solvent is of crucial importance to minimize adsorption to the glassware. Interactions between the MAs and active sites on the quartz filter surface are observed.

A mechanistic study of the Staudinger ligation with a focus on factors that affect reaction kinetics and on the identification of intermediates is discussed. The structure of an intermediate that accumulates under anhydrous conditions was identified.

The denominator D resulting from the CR-CCSD(T) calculations correlates with the degree of diradical character of the system of interest. The CCSD(T) approach often regarded as the gold standard of electronic structure theory favored pathways through diradical structures.

The recombinant form of human carbonic anhydrase-II is utilized as the enzyme source and benzenesulfonamide and its derivatives as inhibitors. The steady-state kinetics revealed that the attachment of iminodiacetate (IDA)-Cu(super 2+) to benzenesulfonamide enhanced its binding affinity for hCA-II by about 40-fold.

Difructose anhydride III (DFAIII), a nondigestible disaccharide, promotes intestinal calcium absorption. Exercise-induced mechanical stimuli are essential for bone growth. In the present study, we examined the effects of consuming DFAIII and voluntary running exercise on calcium absorption and bone characteristics using male Sprague-Dawley rats (4 wk old). The study was designed in a 2 x 2 factorial arrangement with two conditions (sedentary or exercised) and two diets [AIN-93G diet with or without DFAIII (30 g/kg diet)]. Both consuming DFAIII and running exercise increased net calcium absorption, and the effects of DFAIII and exercise were additive. Both consuming DFAIII and exercise also increased femoral variables such as calcium content and total bone mineral density (BMD); however, only consuming DFAIII increased bone strength in the femur. Conversely, running exercise augmented tibial calcium content, total BMD and bone strength, but consuming DFAIII did not. We conclude that consuming DFAIII and running exercise additively enhance calcium absorption and differentially stimulate femoral and tibial BMD and mechanical properties in rats. KEY WORDS: * difructose anhydride III * voluntary running exercise * calcium absorption * bone * rats

The synthesis of a nonadride (+)-byssochlamic acid, from the ascomycete byssochlamys fulva is described.

A study concerning the diastereoselective synthesis of beta-thiomannopyranosides is presented. The formation of the intermediate alpha-mannosyl triflate is described.

Issues concerning the formation mechanism of tropospheric formic acid anhydride are discussed. It is concluded that the mechanism involving single O2 seems to be the most favourable one in atmospheric conditions.

A study concerning the synthesis of peri-hydroxy aromatic compounds is presented. Experiments include base-induced [4+2] cycloaddition of homophthalic anhydrides with alpha-sulfinyl-substituted enolizable enone derivatives.

Research has been conducted on the intermolecular anhydride formation reaction between acetate and acetate phenyl ester by means of ab initio quantum mechanical and molecular dynamics method. Results indicate correlation of calculated reaction activation energies with experimental values.

Maleimido derivative (MAF) of aniline-formaldehyde (AF) resin was prepared by the reaction of AF with maleic anhydride. The MAF was characterized by elemental analysis, IR spectroscopy and thermogravimetry. A MAF having 3 to 4 maleimido groups was reacted with various grades of furan resin (FR) through Diels-Alder reaction. The resultant polyimides were characterized by IR spectral studies and thermal properties. Both MAF and FR components were polymerized in situ on glass and carbon fiber. The physical, chemical and mechanical properties of the resultant composites have been determined., INTRODUCTION Polyimides are known for their high performance properties. They are prepared by various routes (1), like polycondensation of diamines-teracarboxylic acid, addition polymerization of bismaleimides and Diels-Alder (DA) polymerization of [...]

Research was conducted to examine the conversion of the enantio- and diastereomerically pure amido acid into enantiomerically pure cyclopentane derivatives. The objective was to show how the combination of a Diels-Alder reaction between cyclopentadiene derivatives and maleic anhydride, followed by desymmetrization and ozonolysis can be applied to an enantio- and diastereocontrolled synthesis of highly substituted cyclopentanes. Results reveal that the method provides a versatile and concise approach to the synthesis of enantiomerically pure tetra- and penta-substituted cyclopentanes in which the cyclopentane substituents are syn to one another.

The reaction of N-(mesyloxy)phthalimides with secondary amines was studied. Transformations were performed by one-reactions to optionally provide corresponding 2-ureidobenzamides, 2-ureidobenzoic acids, ethyl 2-ureidobenzoates, or isatoic anhydrides, respectively. A proton transfer mechanism involving the ureido moiety as an internal acid catalyst is suggested. Intermediate 2-ureidobenzoic acids underwent a further transformation to isatoic anhydrides.

A study on acetylcholinesterase was conducted to solve the three-dimensional structures of aged phosphylated Torpedo californica acetylcholinesterase (TcAChE) to understand the forces that oppose reactivation or dephosphylation of the organophosphorus acid anhydride. Further, the experiment also provides structural models for the deacylation tetrahedral intermediate of carboxyl ester hydrolysis. No major structural rearrangement in TcAChE were detected as a result of the aging reaction itself.

A study was conducted to describe a procedure for characterizing acyl adenyl anhydrides and to determine rates of hydrolysis. Spectroscopic studies were carried out on compounds to determine unequivocal structural assignments to possible V-Z reaction products. 1H-nuclear magnetic resonance spectroscopy was used to identify proton chemical shifts from the 6-amino group. In addition, thin layer chromatography analysis was carried out show that palmitoyl-AMP underwent hydrolysis to palmitate.

A study was conducted to prepare oxetanone 1233A, a novel category of natural products, from 3-methylglutaric anhydride. 3-methylglutaric anhydride was synthesized under Heathcock protocol while optical rotations were carried out at 20 degrees C. Results indicated the application of the asymmetric (2+3) cycloaddition of oxazoline N-oxides and the use of complex dipolarophiles in the chemical reactions.

Research was conducted to derive a synthesis for N-carboxy anhydride formally derived from polyhydroxylated alpha-amino acides using non-alpha-amino acid precursors. Results demonstrate that the approach sets the basis for the development of a practical and concise access to simultaneously amino-protected and carboxy-activated forms of polyhydroxylated alpha-amino acids.

A study was conducted to characterize the rearrangement and oxidation structures of N-substituted 2,5-dibromopyrroles after HNO3 treatment. A number of termaleimides were harvested from pyrrole, maleic anhydride and citraconic anhydride. Results indicated that terminal maleimides were canted 37 degrees relative to the central maleimide unit. Findings also suggested a dipolar stabilization between two terminal maleimides.

A study was conducted to characterize palladium-catalyzed unsymmetrical 1,4-functionalizations associated with cyclic 1,3-dienes. The oxidation reaction was carried out in dichloromethane/acetic acid or acetone/acetic acid solvent mixtures during the presence of lithium trifluoroacetate and trifluoroacetic anhyride. Results indicated that the chemoselectivity of the reactions depended on the kinetic stability of intermediate palladium complexes.

Titanium Lewis acid Ti-TADDOLates are used as chiral in the enantioselective isopropyl hemiester formation from cyclic meso-anhydrides through a ring opening reaction. Highly enantioselective isopropyl hemiesters can be generated from a range of structurally diverse anhydrides. The reaction proceeds either by desymmetrization through enantiotopic carbonyl compound differentiation or racemic compound kinetic resolution.

Research was conducted to study the motion of a series of ligands characterized by coupled benzenesulfonamide and oligoethylene glycol moieties bound at the active site of human carbonic anhydrase II. Qualitative dynamic information about the motion of the bound ligand was provided through simulation. Results showed that the Gly and Phe groups of the ligands interacted weakly with the protein adjacent to the active site.

A study was conducted to describe the pi-facial diastereoselectivity that influence products based on the Diels-Alder reaction of dienophiles maleic anhydride, bromomaleic anhydride, and N-phenylmaleimide with a distorted hydrocarbon 1,4-diphenyl-benz(a)aceanthrylene. Crystals were determined by the slow evaporation of a supersaturated solution while the topology of the bromomaleic anhydride adduct was obtained by x-ray crystallographic analysis.

A study was conducted to examine the reaction of diisopropylcyanamide with trifluoroacetic anhydride (TFAA). The formation of urea, isourea and triazin derivatives resulting from the reaction was also analyzed in the study. Results indicated that thermolysis at 117 degrees C supported first-order kinetics with the initial products, including trifluoroacetonitrile and diisopropylcarbamic trifluoroacetic mixed anhydride.

Research was conducted to examine the controlled regioselective anilide formation from aspartic and glutamic acid anhydrides. Controlled regioselectivity was performed on aniline with a series of N-protected aspartic and glutamic acid anhydrides through the choice of reaction solvent. The formation of either aspartic acid beta-anilide or glutamic acid gamma-anilide was favored in DMSO while aspartic or glutamic acid alpha-anilides were favored in benzene. Results indicate the efficiency of the method for the formation of glutamic and aspartic acid anilide bonds.

Byline: Friedrich Kreyenmeier (1), E. Schulte (1), Hans-Peter Thier (1) Keywords: Key wordsaFats and oils; Autoxidation; Aldehydes; GC/ECD; Derivatization Abstract: aThis paper describes a novel method for the sensitive determination of the volatile aliphatic aldehydes formed by autoxidation in fats and oils. In a solution of fats, the aldehydes are derivatized to the O-pentafluorobenzyloximes (PFBOs) without any isolation procedure. From the mixture, the lipids are removed by silica gel column chromatography using pentane/dichloromethane (4+1) as the eluant. The eluate is evaporated to dryness and the PFBOs are extracted from the residue with a small volume of acetonitrile. They are separated by capillary column gas chromatography and are determined with high selectivity and sensitivity by using an electron-capture detector. The determination limit was as low as 0.01 mg/kg for hexanal. Analysis of a series of corn oil samples yielded high recoveries for 14 aldehydes added at the 1 mg/kg level, with low relative standard deviations of between 3 and 17%. Author Affiliation: (1) Institute of Food Chemistry, University of Munster, Corrensstrasse 45, D-48149 Munster, Germany, DE Article note: Received: 9 May 1997

Recent hydrocarbon exploration in the Solway Basin has revealed the existence of Lower Carboniferous paralic sediments which contain numerous discrete anhydrite beds. Anhydrite S isotope ratios from the Easton-1 Well are compared with new isotopic data from barite mineralization that occurs along the faulted southern margin of the Northumberland-Solway Basin and published data from the Northern Pennine orefield. Similarities between the [[Delta].sup.34]S of anhydrite and barites from major mines at Haydon Bridge and the Alston district of the Northern Pennine orefield supports a Lower Carboniferous marine sulphate source for mineralization at these sites. Identification of extensive evaporite deposits in the Solway Basin resolves several longstanding problems associated with mineralization in the Northern Pennines including the source of barite sulphate and the origin of hypersaline mineralizing fluids. Keywords: Dinantian, evaporites, Pennines, mineralization, barite.

Three alkanoyl-aroyl anhydrides and three acyl chlorides were reacted with either (N-benzyl)-tributylphosphazene or with (N-benzyl)-triphenylphosphazene in benzene, chloroform and acetonitrile. The results, which were obtained via observation as well as 31P and 1H nuclear magnetic spectroscopy, showed that phosphazenes react similarly with the both classes of aliphatic carboxyl derivatives in general. Differences, however, also arose due to the loss of HCL by intermediates arising from PhCH2COCl.

The oxidation of alpha-hydroxy beta-lactams gives alpha-keto beta-lactams intermediates that undergo Baeyer-Villiger rearrangement to form threonine- and azathreonine N-carboxy anhydrides. The one-pot oxidation-Baeyer-Villiger reaction occurs only in the presence of 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) and sodium hypochlorite. Rearrangement of the alpha-keto beta-lactams produces alpha-amino acid N-carboxy anhydrides (NACs) which readily form the dipeptides. TEMPO effectively catalyzes the cycloexpansion of alpha-hydroxy beta-lactams.

The carbon skeletons of Chaetomellic anhydrides A and B are generated using the procedure derived from the synthesis of malonic esters. The resulting succinic-type anhydrides are then converted to maleic anhydrides by reacting with Et3N and TMSOTf in benzene under reflux. The intermediates are then treated with tetra-n-butylammonium bromide in dry methylene chloride and then added with bromine to yield Chaetomellic anhydride A. Anhydride B is obtained by a similar reaction but with NBS as oxidant.

The relationship between the probability of pretransition state conformers and the rate of intramolecular reactions of dicarboxylate monoesters was investigated. To this end, the MM3(92) free energies of the ground state conformers of the dicarboxylic acid monoesters were derived to approximate the probability of the nucleophile and electrophile becoming close neighbors in a near-attack conformation. Subsequently, it was shown that rate constants of such intramolecular reactions are based on the distribution of ground state conformations.

The base-induced dimerization of tert-butyloxycarbonyl-protected N-carboxy-alpha-amino acid derivatives is studied. The reaction, which affords 3,5-dialkyl-2,4-dioxo-1-pyrrolidine diones, may be prevented through the proper combination of base and solvent during peptide synthesis. It may also be stereochemically regulated to obtain enantiomeric mixtures of the Z and E isomers.

An imidazolium ion is appropriately positioned in the oxyanion hole to catalyze spontaneous enzyme dephosphonylation, thus conferring a novel organophosphorus (OP) acid anhydride hydrolase activity upon butyrylcholinesterase (BuChE). This was the conclusion reached after the modeling of BuChE and identification of several locations near the active site Ser O(gamma) where catalysis may occur. A number of residues predicted to be near the active site and the oxyanion hole of human BuChE for mutation to His (G115H, G117H, Q119H and G121H) were selected and analyzed. One mutant, BuChE G117H, was found to be an active cholinesterase that also catalyzes hydrolysis of the OP nerve agents GB (sarin) and VX.

Palladium-catalyzed hydroxycarbonylation of benzoic anhydrides in the presence of alkali results in the formation of benzoic acid. Benzoic anhydride is synthesized by carbonylation of (Ph3P)2Pd2Ph2(mu-OH)2 in the presence of PhI. Benzoic acid and hydroxo complexes are used to prepare L2Pd2Ph2(mu-PhCOO)2.

Two different products in an overall yield of about 80% are obtained by the I2-catalyzed photooxidative cyclization of 1,4-phenylene bis(phenylmaleic anhydride) (PPMA). The primary product is found to be the (5)helicene-5,6,9,10-tetracarboxylic 5,6:9,10dianhydride (HLDA). The other products produced include the isomeric dibenz(ah)-anthracene-5,6,12,13-tetracarboxylic 5,6:12,13-dianhydride (DBAA).

A novel method was developed to synthesize alpha-amino acid N-carboxy anhydrides (NCA), which were optically active, and their corresponding alpha-amino acid derivatives. The synthesis involved a Baeyer-Villiger rearrangement subsequent to alpha-hydroxy beta-lactam oxidation to the correlating alpha-keto beta-lactams. This reaction methodology facilitated the preparation of various NCAs from non-amino acid precursors.

Mechanistic studies of the reactions of acetic anhydrides with primary and secondary amines in terms of pH-yield reveal the presence of a base-enhanced hydrolysis in direct nucleophilic attack. The studies analyze the yield of N-substituted acetamides as pH functions. The amine hydrolyzes the anhydride, using a base as catalyst.

Positive association between binding of peptides and self-attachment is observed in neurophysin, an allosteric protein. A serine or threonine hydroxyl unit undergoes succinylation and reveals a fall in the peptide affinity due to the interaction between neurophysin and succinic anhydride. The interaction between acetimidated protein and (14C)succinic anhydride determines the residue involved. Affinity chromatography is used to isolate the impassive and passive constituents. The important residue is recognized as Ser-56 by subjecting the two constituents to performic acid oxidation and tryptic and Asp-N mapping preceding automated Edman degradation.

A study was made on the chiroptical spectra of a number of optically active 1,2-cyclopropanedicarboxylic anhydrides and imides using MNDO calculations of the optimized molecular geometries and crystal structures. The results indicated that the CD spectra of the compounds have an unusual solvent dependence probably due to the cyclopropane ring contribution to the Cotton effect. Slight distortions of the molecular skeleton can have significant effects on the chiroptical spectra of anhydrides and imides.

Tricyclic anhydrides and imides were synthesizedand their circular dichroism spectra were analyzed. Molecular geometry was analyzed using semiempirical MNDO calculations. Circular dichroism data the source of molecule chirality to be the substituent at the C-2 position. The succinic anhydride and imide molecular fragments were not planar and the five-membered rings were slightly twisted. There were small distortions in the planarity of the chromophores. Chromophore twisting was affected by solvation. Overall results showed that these tricyclic structures were not rigid.

Mechanistic studies of the reaction of the various seleninic anhydrides and hexamethyldisilazane has suggested strong evidence for new and interesting Se-O and Si-N bonds in double metatheses. The first metathesis process permits the formation of a new class of heterocyclic molecules containing Se-N formation, followed by the second stage of the metatheses process leadin to the products. A new class of of ligand coupling process has been identified and whose full sythetic potential is yet to be explored.

A study was done on photochemically initiated bond cleavage reactions in mixed anhydrides. High regioselectivity was found upon irradiation from compounds with no alpha-hydrogens which is the basis of the relative C-O bond dissociating energies. In addition the reaction can be quenched by intramolecular electron transfer. Compounds containing alpha-hydrogen atoms possess a faster Norris type II reaction than the corresponding C-O cleavage reactions resulting in poor regioselectivity.

The desymmetrization reactions of 3-substituted glutaricanhydrides with 1-(1'-naphthyl)ethanol provide insights into the enantiodifferentiating ability of the 3-substituent. The results, which show diastereomeric ratios of 40:1, 16:1, 14:1, 8:1, 7:1 and 1:3 for the series TBDMSO, Me, Et, Ph, i-Pr and t-Bu, suggest a counterintuitive inverse relation between steric bulk and prochiral recognition behavior. A proposed mechanism for this involves the kinetic differences between the reactions of enantiomericN-acylpyridinium zwitterions with the chiral alcohol.

A Raman spectra investigation of L-beta-phenyllactyl-p-dimethylaminobenzoate (BPLDAB) reaction with crystals of carboxypeptidase A (CPA) was undertaken to prove the formationof an anhydride intermediate in CPA catalysis. Raman spectra showed bands above1700 cm-1 which can be assigned to an acid anhydride. Hydrolysis products of BPLDAB added to CPA yielded similar bands, revealing the reversibility of acid anhydride formation. Addition of a competitive inhibitor suppresses the intensity of the bands in both directions, suggesting that these bands originate from the enzyme active site.

A revised methodology for lactones acquired through the reduction of hydroxy anhydride or acetoxy anhydride using maleic anhydride is presented through an experiment. Standard 1D and 2D nuclear magnetic resonance (NMR) spectroscopic analysis is used. NMR at 500 MHz reveal errors in the structure attribution caused by the assignment of a (dddd) centered at delta 2.56 and appears as a multiplet.

The Schwartz reagent (Cp2ZrHCl)n promotes the ring opening of lactones and anhydrides. The bis lactone, 1,6-dioxaspiro(4.4)nonane-2,7-dione, under the treatment of the reagent changes to the trizirconated linear derivative and the oxide, (Cp2ZrCl)2O. The treatment of succinic anhydride with (Cp2ZrHCl)n leads to the scission of C-O bonds and the formation of two zirconium oxides. With excess of chlorodiphenylphosphine the two zirconium oxides are converted to diphosphinite and to phosphine-phosphine oxide.