Synthesis of 5,6-Dideoxy-5-phenylphosphinyl-l-galactopyranoses. The P-in-Ring Sugar Analogs of l-Fucose

Abstract

Abstract 1,2-O-Isopropylidene-3-O-methyl-6-O-tosyl-β-d-arabino-hexofuranos-5-ulose (9a) and its 3-O-benzyl congener (9b) were prepared from 1,2:5,6-di-O-isopropylidene-β-d-altrofuranose in 4 steps. Addition of methyl phenylphosphinate to 9a and 9b in the presence of DBU, followed by reduction with Raney Ni, afforded (5R and 5S)-5,6-dideoxy-1,2-O-isopropylidene-5-[(methoxy)phenylphosphinyl]-3-O-methyl-β-d-arabino-hexofuranose(11a) and 3-O-benzyl congener (11b), respectively. The latter compound (11b) was debenzylated to 3-O-unsubstituted hexofuranose 11d. By reduction with sodium dihydrobis(2-methoxyethoxy)aluminate, followed by acid hydrolysis, these key intermediates 11a, 11b, and 11d provided the title l-fucoses 13 (together with a minor proportion of d-altropyranoses 14) having as phenylphosphinylidene group in place of the ring oxygen. Compounds 13 and 14 were converted into per-O-acetyl derivatives for structural and conformational analysis by spectroscopy.