Resolution of N-Acyl Amino Acids with Optically Active Neutral Amino Acid Amides

A convenient method of chemical resolution of DL-N-acyl amino acids was described. The resolution by using salt of N-acyl derivatives with a certain simple base, especially L-leucin-amide, was discussed. A new agent, L-leucinamide, readily gave L-alanine, L-valine, L-leucine, L-phenylalanine, L-tryptophan and L-methionine from the corresponding DL-N-acyl derivatives. Resolution done with L-tyrosinamide and L-phenylaninamide gave products lower in yield and purity than those resolved with L-leucinamide as resolving agent.     

A Synthesis of Optically Active Key Intermediate for the Synthesis of Optically Active Thromboxanes

An optically active key intermediate, methyl 2, 4-dideoxy-4-C-carboxymethylene-α-d-ribo-hexopyranoside 2′→3 lactone (XII), for the syntheses of optically active Thromboxanes was prepared from d-glucose.     

光学活性叔亮氨酸合成的研究进展

由于叔丁基的特殊结构和性质 ,叔亮氨酸是重要的医药中间体和不对称合成的手性诱导模板。本文综述了近年来光学活性的叔亮氨酸的合成研究及最新进展。     

Chemoenzymatic Preparation of Optically Active Long-Chain 3-Hydroxyalkanoates

The synthesis of optically active 3-hydroxyalkanoates of varying chain length (C_lo, C₁₄ and C₁₈) was investigated using chemoenzymatic methods. While bakers' yeast mediated reduction of 3-oxoalkanoates gave (R)-3-hydroxyalkanoates (e.e. >80%, yield —10%), both enantiomers were obtained by enzymatic resolution of racemic methyl 3-butanoyloxyalkanoates using Geotrichum candidum lipase with moderate to good optical purity (e.e. 32–92%, yield 40–60% for both enantiomers). Lipase-catalysed interesterification, however, was found to proceed with similar enantioselectivity but with slow rate of conversion.     

New Synthesis of Optically Active O-Aryl O-Ethyl Phenylphosphonothionates

The mixed anhydride method was applied to synthesize O-aryl O-ethyl phenylphosphonothionate. The reaction of O, O-diethyl phosphorochloridate with O-ethyl phenylphosphonothioic acid afforded O, O-diethyl phosphoric O-ethyl phenylphosphonothioic anhydride in a good yield. This anhydride was converted to O-aryl O-ethyl phenylphosphonothionates by reacting with the appropriate sodium phenoxide. This esterification occurred without racemization and produced optically pure O-ethyl O-(4-nitrophenyl) phenylphosphonothionate (EPN) and O-(4-cyanophenyl) O-ethyl phenylphosphonothionate (cyanofenphos).     

活性氨基酸农药

介绍了活性氨基酸作为农用杀菌剂,杀虫剂、除草剂以及生长调节剂的结构与应用,它为解决环境保护问题展示了新的前景。     

Synthesis and Antimicrobial Activity of Optically Active trans-Cycloheximide Isomers

Optically active tiraras-cycloheximide isomers such as cycloheximide [(2S,4S,6R,αR)-form (1)], naramycin B[(25,4S,6RαR)-form(4)], and new stereoisomers (2S,4S,6S,αS)-form (8) and (2S,4S,6R,αS)-from (9) were synthesized by an aldol condensation of trans-2,4-dimethyl-l-cyclohexanone (5b), with 4-(2-oxoethyl)-2,6-piperidinedione(6). The antimicrobial activity of trans- cycloheximide isomers (1, 4, 8, and 9) was examined against S. cerevisiae and P. oryzae. The stereoisomers 1 and 4 exhibited marked antimicrobial activity against both microorganisms as compared with their C- α-epimers 8 and 9.     

Asymmetric Synthesis of Optically Active 1,3-Oxathiolane Nucleoside Analogues

Abstract

A ready asymmetric synthesis of 3′-oxa-4′-thionucleosides has been accomplished in three main steps from benzoyloxyethanal. The synthesis is characterized by high overall yield and appreciable enantiomeric excesses. It represents a general synthetic scheme to prepare a wide range of heterosubstituted sulfur-containing nucleoside analogues.     

Double Stereodifferentiation in the Asymmetric Dihydroxylation of Optically Active Olefins

A study of the stereochemical control on the asymmetric dihydroxylation of the double bond of optically active vinyl epoxides and their derivatives (bromo derivatives, azido derivatives, and vinyl aziridines) was carried out and the obtained results are herein reported. The most interesting results were obtained on trans α,β‐unsaturated epoxy esters, which were successfully converted with a diastereomeric ratio >80% into the corresponding diols using either the matched or the mismatched conditions, depending on the ligand used. Unprotected bromo derivatives and unprotected aziridines did not afford significant results, while for the protected bromo derivatives, azido derivatives, and N‐Boc protected aziridines the matched conditions led to a diastereomeric ratio >95%. Chirality 28:387–393, 2016. © 2016 Wiley Periodicals, Inc.     

Chemoenzymatic Synthesis of Optically Active Diacylglycerophospholipid Hydroperoxides Derived from Arachidonic Acid

A new derivative of sulfatide, 2-O-α-l-fucopyranosyl sulfatide, was synthesized. The compound inhibited the binding of HL-60 cells, which express sialyl Lewis X, to P- and L-selectin more than the corresponding non fucosylated compound.     

Resolution of DL-Glutamic Acid with Optically Active Neutral Amino Acid Amides

DL-Glutamic acid has been resolved into optically active forms as the diastereoisomeric salt of optically active neutral amino acid amides, and the salt is easily converted to the sodium salt of the active forms. By resolution with L-tyrosinamide and L-leucinamide, sodium L-glutamate was obtained in 65 and 80 per cent yield respectively. Attempts to extend this method to resolution of DL-glutamic acid using L-phenylalaninamide as resolving agent resulted in poor yield of less pure D-glutamic acid.

By the infrared spectroscopy and X-ray diffraction analysis it has been confirmed that the diastereoisomeric salts of L-leucinamide or L-tyrosinamide with L- or D-glutamic acid compose a combined salt structure in solid state, whereas L-phenylalaninamide with L- or D-glutamic acid does not compose a characteristic diastereoisomeric salt but rather the mechanical mixture of L-phenylalaninamide and L- or D-glutamate anion in solid state.

In the previous study¹⁾, it was reported that L-leucinamide forms the characteristic diastereoisomeric salts with racemic N-acyl mono amino acids, most of which are fairly resolved into their antipodes.     

Microbial Production of Optically Active 1,3-Butanediol from 4-Hydroxy-2-butanone

The effect of insulin on polypeptide chain elongation was examined in soleus muscles isolated from 18 hour-fasted mice. Treatment with insulin for 1 hour increased the elongation rate, which was estimated by the half-transit time. This suggests that insulin stimulated protein synthesis by modifying the elongation rate in addition to the initiation rate.     

Synthesis and Insecticidal Activity of Some New Optically Active Phenylphosphonothiolates and Thionates

The four sesquiterpenes shizukanolide (1), dehydro-shizukanolide (2), glechomanolid (3) and isofuranodiene (4) were isolated from Chloranthus japonicus Sieb. (Hitori-shizuka in Japanese, Chloranthaceae). Their absolute structures have been established on the basis of their physical and chemical properties. Dehydro-shizukanolide showed moderate antifungal activity.     

Stereoselective Synthesis of Optically Active Dictyopterenes A and B and Their Geometrical Isomers

Optically active dictyopterenes A and B and their geometrical isomers were stereoselectively synthesized by condensation of acrolein with carboethoxymethyl dimethylsulfonium bromide and by the Wittig reaction between (+)-2-vinylcyclopropylcarbaldehyde, which was derived from partially resolved (+)-(1,S, 2R)-2-vinylcyclopropanecarboxylic acid, and phosphonium salts in liquid-solid two-phase systems using crown ethers.     

Stereoselective Model Synthesis of the Optically Active Olivil Type of Lignan from D-Xylose

The olivil type of lignan, (2S,3R,4R)-4-benzyl-4- hydroxy-3-hydroxymethyl-2-(3,4-methylenedioxyphenyl)tetrahydrofuran, was stereoselectively synthesized from D-xylose.     

Stereoselective Synthesis of the Optically Active Samin Type of Lignan from L-Glutamic Acid

The optically active samin type of lignan, (1R,2S,5R, 6S)-6-(2-methoxy-4,5-methylenedioxyphenyl)-3,7-dioxabicyclo[3.3.0]octan-2-ol, was stereoselectively synthesized from L-glutamic acid via (2R,3R)-2-[(1S and R)- 1-[(tert-butyldimethylsilyl)oxy]-1-(2-methoxy-4,5-methylenedioxyphenyl)methyl]-3-[(tert-butyldiphenylsilyl)oxy]methyl-1,4-butanediol.     

Preparation of Optically Active Allothreonine by Separating from a Diastereoisomeric Mixture with Threonine

A simple procedure is described to obtain D- and L-allothreonine (D- and L-aThr). A mixture of N-acetyl-D-allothreonine (Ac-D-aThr) and N-acetyl-L-threonine (Ac-L-Thr) was converted to a mixture of their ammonium salts and then treated with ethanol to precipitate ammonium N-acetyl-L-threoninate (Ac-L-Thr·NH₃) as the less-soluble diastereoisomeric salt. After separating Ac-L-Thr·NH₃ by filtration, Ac-D-aThr obtained from the filtrate was hydrolyzed in hydrochloric acid to give D-aThr of 80% de, recrystallized from water to give D-aThr of >99% de. L-aThr was obtained from a mixture of the ammonium salts of Ac-L-aThr and Ac-D-Thr in a similar manner.     

Preparation of Optically Active 2-Aminobutanoic Acid via Optical Resolution by Replacing Crystallization

An attempt was made to use a simple procedure to obtain (R)- and (S)-2-aminobutanoic acids [(R)- and (S)-1] which are non-proteinogenic α-amino acids and are useful as chiral reagents in asymmetric syntheses. Compound (RS)-1 p-toluenesulfonate [(RS)-2], which is known to exist as a conglomerate, was optically resolved by replacing crystallization with (R)- and (S)-methionine p-toluenesulfonate [(R)- and (S)-3] as optically active co-solutes. When (S)-3 was employed as the co-solute, (R)-2 was preferentially crystallized from a supersaturated solution of (RS)-2 in 1-propanol, as was (S)-2 in the presence of (R)-3. (R)- and (S)-2 recrystallized from 1-propanol were treated with triethylamine in methanol to give (R)- and (S)-1 in optically pure forms.     

Novel Synthesis of Optically Active Bishomotyrosine Derivatives Using the Friedel-Crafts Reaction in Triflic Acid

We report here a novel synthesis of optically active bishomotyrosine. The bishomotyrosine skeleton was constructed by using a Friedel-Crafts reaction between phenol and optically active N-Tfa-Glu(Cl)-OMe in triflic acid under the mild condition. Reduction and subsequent deprotection then afforded bishomotyrosine derivatives without any loss of optical purity.