6-Amino-1,8-dihydroimidazo[4,5-e][1,3]diazepin-4(5H)-one, a ring expanded analogue of guanine

Abstract

The preparation of 6-amino-1,8-dihydroimidazo[4,5-e][1,3]diazepin-4(5H)-one (15), an analogue of guanine which has a seven-membered ring in place of the usual six-membered ring, is described. Cyclization to form the aminodiazepine ring involves reaction of amide and isothiourea groups in a suitably substituted imidazole precursor. The method is also shown to be applicable to the synthesis of an acyclonucleoside derivative (20).