Polydeoxyaminohexopyranosylnucleosides. Synthesis of 1-(2,3,4-Trideoxy-3-nitro-β-D-erythro- and threo-hexopyranosyl)-uracils from Uridine

The first synthesis of nitro-multideoxy-sugar containing nucleosides was achieved. 1-(4,6-O-Benzyiidene-3-deoxy-3-nitro-beta-D-glucopyranosyl)uracil (3) was converted in 75% yield into 1-(4,6-O-benzylidene-2,3-dideoxy-3-nitro-arabinohexopyranosyl)uracil (7) by acetylation followed by NaBH4 reduction in methanol. De-O-benzylidenation with CF3CO2H afforded crystalline 1-(2,3-dideoxy-3-nitro-beta-D-arabinohexopyranosyl)uracil (8) was obtained in 87% yield. Raney Ni reduction of 8 afforded the corresponding 3'-amino-nucleoside 9. Acetylation of 8 followed by NaBH4 treatment afforded an 8.1 mixture from which 1-(2,3,4-trideoxy-3-nitro-beta-D-threohexopyranosyl)-uracil (14) was obtained in pure crystalline form. After Raney Ni reduction of the mixture, 1-(3-amino-2,3,4-trideoxy-beta-D-threohexopyranosyl)uracil (16) and its erythro epimer 21 were isolated. 1-(4,6-O-Benzylidene-2, 3 dideoxy-3-nitro-beta-D-lyxohexopyranosyl)uracil (24) was prepared in 72% yield from 1-(4,6-O-benzylidene-3 -deoxy-3-nitro-beta-D-galactopyranosyl)uracil (4) by acetylation and subsequent reduction with NaBH4. De-O-benzylid-enation of 23 afforded 1-(2,3,4-trideoxy-3-nitro-beta-D-lyxohexopyranosyl)uracil (25) in 83% yield. Schmidt-Rutz reaction of 25 followed by NaBH4 reduction afforded a mixture of three and erythro isomers of 2',3',4'-trideoxy-3'-nitrohexopyranosyluracil, from which pure 16 and 21 were obtained.