Synthesis of new iso- C-nucleoside analogues from 2-(methyl 2- O-benzyl-4,6- O-benzylidene-3-deoxy-α- d-altropyranosid-3-yl)ethanal

[Display omitted] Treatment of 2-(methyl 2- O-benzyl-4,6- O-benzylidene-3-deoxy-α- d-altropyranosid-3-yl)ethanal with malononitrile, cyanoacetamide and 2-cyano- N-(4-methoxyphenyl)acetamide, respectively, in the presence of aluminium oxide yielded 2-cyano-4-(methyl 2- O-benzyl-4,6- O-benzylidene-3-deoxy-α- d-altropyranosid-3-yl)crotonic acid derivatives. Cyclization with sulfur and triethylamine was performed to synthesize the 2-amino-5-(methyl 2- O-benzyl-4,6- O-benzylidene-3-deoxy-α- d-altropyranosid-3-yl)thiophene-3-carbonic acid derivatives, which were treated with triethyl orthoformate/ammonia and triethyl orthoformate, respectively, to furnish 6-(methyl 2- O-benzyl-4,6- O-benzylidene-3-deoxy-α- d-altropyranosid-3-yl)thieno[2.3- d]pyrimidine derivatives. Deprotection in two steps afforded 2-amino-5-(1,6-anhydro-3-deoxy-β- d-altropyranos-3-yl)thiophene-3-carbonitrile and 6-(1,6-anhydro-3-deoxy-β- d-altropyranos-3-yl)thieno[2.3- d]pyrimidine derivatives, respectively.