Ouverture régiospécifique d'un oxirane preparé á partir du d-xylose par des carbanions soufres: Synthèse de c-nucleosides branches

Abstract Two methods using the readily accessible D -xylose have been developed for the synthesis of epoxides 4 and 5 . The oxirane 5 was considered as a good intermediate for the preparation of 3'- C -substituted nucleosides. The crucial step for the synthesis of 32 is the regiospecific opening of the epoxide 5 using two carbanions, derived from either dithiane or bis (phenylthio)methane, followed by desulphurisation leading to 17 . The exclusive opening of the epoxide in 5 was unequivocally established by 13 CNMR spectroscopy.