Derivate der zucker-thioacetale : XXXIX. Mitteilung. Isopropyliden-verbindungen der D-xylose-thioacetale

Abstract

When D-xylose dimethyl dithioacetal was condensed with acetone in the presence of copper sulphate and sulphuric acid the 2,3:4,5-di- O-isopropylidene derivative was obtained. When copper sulphate or zinc chloride was used as catalyst, a mixture of the 3,4- O-, 4,5- O-, 2,3:4,5-di- O-, and 2,3:4,5-di- O-isopropylidene derivatives was formed. The components of the mixture were isolated by crystallisation and chromatography on alumina. The 2,3:4,5-di- O-isopropylidene derivative was partially hydrolysed to 2,3- O-isopropylidene- D-xylose dimethyl dithioacetal. The 4,5- O-isopropylidene derivative rearranged into the 3,4-isomer by treatment for 1 h with zinc chloride in acetone. Extension of the reaction time to 24 h gave the 2,3,4,5-di- O-isopropylidene derivative in addition to the latter compound. Treatment of the 3,4- O-isopropylidene derivative with zinc chloride in acetone gave 2,3:4,5-di- O-isopropylidene- D-xylose dimethyl dithioacetal. The structures of the above derivatives were established by the application of oxidation with lead tetra-acetate and methylation. Derivatives of the 3,4- O-isopropylidene compound were obtained.