The synthesis of 3‐(β‐D‐ribofuranosyl)imidazo[4,5‐c] pyridazines

Abstract
7‐Chloro‐3‐(β‐D‐2,3,5‐tri‐O‐benzoylribofuranosyl)imidazo[4,5‐c] pyridazine (3), obtained from the condensation of 7‐chloro‐3‐trimethylsilylimidazo[4,5‐c] pyridazine (1) with 2,3,5‐tri‐O‐benzoyl‐D‐ribofuranosyl bromide (2), served as the percursor of 7‐chloro‐ (4), 7‐amino‐ (8), and 7‐mercapto‐3‐(β‐D‐ribofuranosyl)imidazo[4,5‐c] pyridazine (9). 3‐(β‐D‐ribofuranosyl)imidazo[4,5‐c] pyridazine (7) was obtained from 3‐(β‐D‐2,3,5‐tri‐O‐benzoylribofuranosyl)imidazo‐[4,5‐c]pyridazine (6). The site of ribosidation is based upon uv spectral comparisons with model methyl compounds. The assignment of the anomeric configuration is derived from pmr spectral data.