Synthesis and Structural Analysis of 5-Deoxy-5-[(R)- and (S)-methylphosphinyl]-α,β- d -manno- and - l -gulopyranoses

Methyl 5,6-dideoxy-2,3-O-isopropylidene-6-nitro-α-d-lyxo-hex-5-enofuranoside (10) was prepared from d-mannose in 7 steps. Addition of methyl methylphosphinate to 10, followed by the catalytic hydrogenation and diazotization, afforded methyl 5-deoxy-2,3-O-isopropylidene-5-[(methoxy)methylphosphinyl]-α-d-lyxo-hexofuranoside, which was then converted into 6-O-triphenylmethyl and 6-O-tetrahydropyranyl derivatives (14, 15). By reduction with sodium dihydrobis(2-methoxyethoxy)aluminate, followed by acid hydrolysis, both 14 and 15 provided the d-mannopyranoses (together with a minor proportion of l-gulopyranoses) having a methylphosphinylidene group in place of the ring oxygen. These were converted into 1,2,3,4,6-penta-O-acetyl derivatives, whose structures and conformations were established by spectroscopy.