Stereocontrolled syntheses of carbocyclic C-nucleosides and related compounds

Carbocyclic 9-deazapurine nucleosides (1-4), a spiranic pyrimidone carbocyc lic compound (5), and an unusual carbocyclic isonucleoside (6) were prepare d as enantiomerically pure compounds via the key intermediates 10 and 21 fr om 1,4-gamma -ribonolactone. The key intermediate 10 was prepared by stereo selective reduction with Bu3SnH and then converted to carbocyclic C-ribonuc leosides 1, 3, and 4. 2 ' ,3 ' -Didehydro-2 ' ,3 ' -dideoxycarbocyclic 9-de azainosine (2) was prepared from a 2 ' ,3 ' -dimesylate 17 by treatment wit h Li2Te followed by an acidic deprotection. The key bicyclic intermediate 2 1 was prepared from a diol 20 by an intramolecular cyclization using CHI3-P h3P-imidazole and converted to the spiranic compound and an olefinic nucleo side 6 by the construction of the heterocyclic moiety followed by deprotect ion.