Regioselective carbon-chain extension at 5'-position of nucleosides and 2-or 3-position of methyl 4, 6-Ο-benzylidene-D-hexopyranosides are described.
Ο
2-Methyluridine,
N3-methyluridine, 4-triazoyl-1- (β-D-ribofuranosyl) -2 (1
H) -pyrimidinone, and
N1,
N6, 2', 3'-Ο-tetrabenzoyladenosine reacted with 2, 6-di-t-butyl-4-nitrophenol, diethyl azodicarboxylate, and triphenylphosphine to give the corresponding 4- (nucleoside-5'-
aci-nitro) -2, 6-di-
t-butylcyclohexa-2, 5-dienones (
aci-nitroester of nucleosides) without any detectable formation of products derived from the reaction at the 2'-and/or 3'-hydroxyl groups. The reaction of
aci-nitroesters with stabilized Wittig reagents afforded carbon-chain extended nucleosides having 5'-6'-double bond. When the sequence of the reactions was carried out in one-pot procedure, the yields of 5-
eno-furanosyl-pyrimidines and-purines were markedly increased.
Methyl 2, 3-anhydro-4, 6-Ο-benzylidene-α-D-allopyranoside and-gulopyranoside reacted with allylic Grignard reagents giving the corresponding 2-deoxy-2-propenyl-α-D-hexopyranosides, while methyl 2, 3-anhydro-4, 6-Ο-benzylidene-α-D-mannopyranoside afforded 3-deoxy-3-propenyl-altropyranosides. The regioselectivity could be explained by diaxial opening of fixed epoxide ring. The reaction of 4, 6-Ο-benzylidene-1, 2-dideoxy-3-Ο-mesyl-D-
ribo-hex-1-enopyranose and-
xylo-hex-1-enopyranose with alkylmagnesium halides resulted in the formation of 1-C-and/or 3-C-substituted enopyranoses. On the other hand, allylic Grignard reagents selectively attack the 1-position of the 3-Ο-mesyl-glycals from β-side to afford 1-C-prop-2-enyl-β-D-hex-2-enitols.
View full abstract