Shozo Yamada

Synthetic studies on virginiamycin M2: functionalization at the 2-methyl group of 4-t-butoxycarbonyl-2-methyl-1,3-oxazole

Abstract Substitution reactions of 2-bromomethyl-4-t-butoxycarbonyl-1,3-oxazole ( 6 ) with several anions (C−, S−, O−, and I−) were performed to yield the desired products 7 a ∼ 7 k .

Synthetic studies on virginiamycin m2: a useful model experiment for construction of the 1,3-oxazole moiety

Abstract A useful acylating procedure at the methyl group of 4- t -butoxycarbonyl-2-methyl-1,3-oxazole ( 3 ) is described. Some curious reactions of 4- t -butoxycarbonyl-2-methyl-5-trimethyl-silyl-1,3-oxazole ( 7 ) are also reported.

Use of chiral 1,3-oxazolidine-2-thiones in the diastereoselective synthesis of aldols

A useful diastereoselective synthesis of aldols using chiral 3-acyl-1,3-oxazlidine-2-thiones, (1), (4), (7), and (9), is reported and its application to the synthesis of a chiral azetidinone (11) is described.

Investigation of new chiral 1,3-oxazolidine-2-thiones: analytical separation and optical resolution of racemic carboxylic acids and amino acids

New chiral five-membered heterocycles, (4S)-(4) and (4R)-4-ethyl-1,3-oxazolidine-2-thione (5), (4S)-4-isopropyl-1,3-oxazolidine-2-thione (6), and (4R,5S)-4-methyl-5-phenyl-1,3-oxazolidine-2-thione [(4R,5S)-MPOT](7) have been developed. Among these heterocycles, (4R,5S)-MPOT (7) proved to be an excellent chiral reagent for analytical and efficient separation of racemic products from transformations of chiral carboxylic acids and amino acids.

Synthesis of novel 5- and 6-substituted 3-arylidene-1,4-oxathiin-2(3H)-ones

The reactions of α-acetylthio-β-arylacrylic acids (2a–c) with α-halogeno ketones (3a–f), α-halogeno-β-keto esters (7a–b), and α-halogenopyruvate (9) afforded the corresponding novel 3-arylidene-1,4-oxathiin-2(3H)-ones [(4a–d), (8a–f), and (10a), respectively] having 5- and/or 6-substituents. The β-aryl-α-thioacrylic acids (1a–d) were treated with α-halogeno ketones (3a–f), (7a–b), and (9) to give the corresponding β-aryl-α-alkylthioacrylic acids (5a–d), (11a–f), and (12a–c), which were converted into the respective 3-arylidene-1,4-oxathiin-2(3H)-ones (4a–g), (8a–f), and (10a–c) by intramolecular cyclization when treated with thionyl chloride–dimethylformamide. The sulphur atom of the 1,4-oxathiin-2(3H)-ones (4d), (4g), and (8a) was smoothly oxidized with m-chloroperbenzoic acid to give the corresponding S-oxides (13a–c) in good yields.