4 ',x-seco and 4 ',x-4 ',5 '-diseco C-nucleosides from 2-hydrazino-(3H)thieno[2,3-d]pyrimidin-4-ones

Cyclization of 2-hydrazino-5,6-dimethyl-3H-thieno[2,3-d]pyrimidin-4-one (1) with acetic acid gave 3,6,7-trimethyl-1,2,4-triazolo[3,4-a]thieno[2,3-d] p yrimidin-5-one (5) whose Dimroth rearrangement gave 2,6,7-trimethyl-1,2,4-t riazolo[3,4-a]thieno[2,3-d]pyrimidin-5-one (11). Alternatively, 5 was obtai ned from the dehydrogenative cyclization of acetaldehyde 5,6-dimethyl-4-3H- oxo-thieno[2,3-d]pyrimidin-2-yl hydrazone (7). Reaction of 1 and 2 with a n umber of sugars gave the respective hydrazones 19 and 20. Those of the D-gl ucose exist in the cyclic pyranosyl structure in addition to minor amounts of the acyclic structure. Dehydrogenative cyclization of the sugar hydrazon es gave the respective fused tricyclic compounds 25 and 26.