Synthesis of 2-imino-3-[1-(beta-D-ribofuranosyl)oxo]-1H,5H-1,5-benzodiazepine through condensation of O-phenylenediamine with formylisoxazole glycoside

The synthesis of 3-[1-(beta-D-ribofuranosyl)oxo]-1H-1,5-benzodiazepine (3) and 2-imino-3-[1-(beta-D-ribofuranosyl)oxo]-1H,5H-1,5-benzodiazepine (8) is described. The cyclocondensation of enaminone glycoside (1) with o-phenyle nediamine afforded benzodiazepine (2)in 64% yield. The reaction of formylis oxazole (4) with o-phenylenediamine led to three products, iminobenzodiazep ine (5), benzimidazole (6), and enaminone nitrile (7) in 33%, 27%, and 9% y ields, respectively. Removal of the sugar protecting groups in 2 and 5 with aqueous sodium carbonate in methanol gave the deprotected C-nucleosides (3 and 8).