Enzymatic synthesis of 1-(2-deoxy-β-D-ribofuranosyl) imidazole-4-carboxamide, a simplified DNA building block

Coupling of silylated 4-(5)-imidazolecarboxamide (5) with 1-chloro-2-deoxy-3,5-di-O-p-toluoyl-α-D-erythro-pentofuranose (6) in the presence of SnCl4 in CH3CN or condensation of the sodium salt of 5 with the halogenose 6, afforded a mixture of 1-β-glycosylated 4-(5)-imidazolecarboxamide (11) and the corresponding α anomer (12). Using a crude extract of nucleoside N-deoxyribosyltransferases from Lactobacillus leichmannii only one product was formed, the N-1-β-stereoisomer (2), in a good yield.