Synthesis and Structural Analysis of 5-Deoxy-3-O-methyl-5-C-[(R)- and (S)-phenylphosphinothioyl]-α- and β- d -xylopyranoses

Treatment of 5-deoxy-5-iodo-1,2-O-isopropylidene-3-O-methyl-α-d-xylofuranose with ethyl phenylphosphinothioate in the presence of NaH in DMF gave a 1:1 mixture of the 5-deoxy-5-C-[(R)- and (S)-(ethoxy)phenylphosphinothioyl] derivatives. Reduction of these d-xylofuranoses with sodium dihydrobis(2-methoxyethoxy)aluminate, followed by the acid hydrolysis, provided the title compounds, which are the first sugar analogues having a phosphinothioyl group in the hemiacetal ring. These compounds were converted into four, separable 1,2,4-tri-O-acetates, the structures and conformations of which were established by spectroscopy. The corresponding per-O-acetyl-5-deoxy-5-C-[(R)- and (S)-phenylphosphinyl] analogues were also prepared and their previously presented structures were revised. Complete 1H NMR (500-MHz) parameters of these two types of compounds are given for a comparative, structural study.