SYNTHESIS OF THE 2-MONOMETHYL AND 4-MONOMETHYL ETHERS AND THE 4-DEOXY-4-FLUORO DERIVATIVE OF 4-CYANOPHENYL 1,5-DITHIO-BETA-D-XYLOPYRANOSIDEAS POTENTIAL ANTITHROMBOTIC AGENTS

The title glycoside undergoes acetonation with 2-methoxypropene to giv e a 2:1 mixture of the crystalline 2,3- and 3,4-isopropylidene acetals in 94% yield, which upon methylation under controlled conditions foll owed by deacetonation afforded the respective 4- and 2-monomethyl ethe rs. The 2,3-acetal underwent reaction with diethylaminosulfur trifluor ide to introduce fluorine at C-4 with net retention of stereochemistry , but the 3,4-acetal under comparable conditions underwent migration o f the arylthio group to C-2 and fluorination at C-1, with stereochemic al retention at both positions.