Andrzej Konowal

The synthesis of racemic purpurosamine B

Abstract 2,6-Diacetamido-2,3,4,6,7-pentadeoxy- dl - ribo -heptopyranose (2,6-di- N -acetyl- dl -purpurosamine B) was synthesized from 6-acetyl-2-methoxy-5,6-dihydro-2 H -pyran in nine steps. The synthesis confirmed the ribo configuration of the natural sugar.

Four diastereoisomeric methyl esters of 2,4-dimethoxytetrahydropyran-6-carboxylic acid

Abstract Treated with 1% methanolic hydrogen chloride, the butyl ester of 2-methoxy-5,6-dihydro-α-pyran-6-carboxylic acid 2 underwent alcoholysis and added methanol to the double bond to yield stereoisomeric methyl esters of 2,4-dimethoxytetrahydropyran-6-carboxylic acid. Equilibration of the isomers xylo and arabino in 1% methanolic hydrogen chloride gave the diastereoisomeric esters lyxo and ribo, respectively. The configuration of the esters was established by NMR spectroscopy. The degradation of the ester 2 with p -toluenesulphonic acid gave a mixture, from which the following components were isolated and identified: the butyl ester of 5-formylbutadienecarboxylic acid, the mixture of cis and trans isomers of the ester 2 , butyl esters of xylo- and arabino-2,4-dimethoxytetrahydropyran-6-carboxylic acid. The volatile products of the degradation of methyl 4,6-0-benzylidene-2,3-dideoxy-α- D -hex-2-enopyranoside with aqueous acetic acid were investigated and found to contain small quantities of furan. A discussion of results is given.