The four diastereoisomers of cyclo(-Asp-Val-) were synthesized to compare with a proposed structure of cairomycin A. Their antimicrobial activities were determined against both Gram-positive and Gram-negative bacteria. The physico-chemical properties of the isomers were characterized by mp, 1H NMR, IR, FAB-MS, and solubility in solvents, which were different from those reported for cairomycin A.

Fusarins G1/G2 (1/2) and G3/G4 (3/4), two sets of interesting examples of diastereoisomers with substantially identical NMR data, were discovered from natural products. The reason was discussed and the generally applicable determinant conditions were proposed. The minimum interval for stereoclusters to be entirely segregated was also discussed.

Diaryl ethers carrying carbamoyloxymethyl groups may be desymmetrised enantio- and diastereoselectively by the use of the sec-BuLi-(-)-sparteine complex in diethyl ether. Enantioselective deprotonation of one of the two benzylic positions leads to atropisomeric products with ca. 80:20 e.r.; an electrophilic quench typically provides functionalised atropisomeric diastereoisomers in up to 97:3 d.r.

The racemization of amino acids provides another example how the analytical sciences sit at confluence several disciplines. Over past 60 years a quantity articles has been published on acid in various fields such as anthropology, geology, paleontology, archaeology, history, forensic science, medicine, pharmaceutical analysis and food science. degree postmortem from their L-to D-configuration, f...

The anti-tumour natural product cis-solamin has been shown to occur as a mixture two of tetra-epimeric diastereoisomers 1A and 1B, whereas solamin (6) was isolated as a single diastereoisomer; the biosyntheses of 1A/B and 6 are likely to involve enzyme-mediated cyclohydrations of the bis-epoxide acetogenins anti-diepomuricanin A2 and syn-diepomuricanin A1 respectively, where addition of water o...

Circular dichroism (CD) spectroelectrochemistry is used to determine the extent of singly occupied molecular orbital delocalization in mixed-valence multinuclear complexes, specifically the mixed-valence Ru(II)Ru(III) states of the four diastereoisomers of [(Ru(bpy)(2))(2)(bpt)](3+) [1; bpy = 2,2'-bipyridyl and bpt = 3,5-bis(pyrid-2'-yl)-1,2,4-triazolato anion]. The complex was found to be stab...

Three pairs of glycosidic 8,4'-oxyneolignane diastereoisomers, named isatioxyneolignosides A-F (1-6), were isolated from an aqueous extract of Isatis indigotica roots. Their structures and absolute configurations were elucidated by comprehensive spectroscopic data analysis and enzyme hydrolysis. The validity of ΔδC8-C7 values to distinguish threo and erythro aryl glycerol units and Cotton effec...

A three step route to single diastereoisomers of the vicinal trifluoromethyl motif is described. The route starts from either syn- or anti-alpha,beta-epoxy alcohols and takes a direct approach in that each of the three steps introduces a fluorine atom in a regio- and stereo-specific manner. Starting from either the syn- or the anti-alpha,beta-epoxy alcohol, stereospecific reactions generate two...

Both diastereoisomers of S-tert-butyl-beta-(trifluoromethyl)isocysteine have been synthesized stereoselectively by the sequential reactions of trifluoroacetimidoyl chloride with the lithium enolate of tert-butyl alpha-tert-butylthioacetate, followed by the diastereoselective reduction of the imino group with sodium borohydride in the presence of zinc(II) or di(ethylene glycol) dimethyl ether, a...

Our previously conducted pharmacological screening led as to the discovery of the strong local anesthetic activity of the compound designated as KP-23. Earlier crystallographic studies revealed that the compound KP-23 crystallized in diastereoisomeric form in lowest symmetry. The aim of these comparative investigations was to evaluate anesthetic activity of KP-23 and its R,S-diastereoisomers, w...