Zur Synthese von 5‐(X‐Methyl)ribofuranosyl‐1,2,3‐triazol‐nucleosiden

On the Synthesis of 5‐(X‐Methyl)ribofuranosyl‐1,2,3‐triazole Nucleosides The synthesis of the reactive 5‐(bromomethyl)‐1‐(2′,3′,5′,‐tri‐ O ‐benzoyl‐β‐ D ‐ribofuranosyl)‐1,2,3‐triazole (3) via 1,3‐dipolar cycloaddition of the β‐oxoalkylidenephosphorane 2 to the ribofuranosyl azide 1 under elimination of triphenylphosphane oxide is described. The nucleosides 4a ‐ d are obtained by substitution of the bromide in 3 by N 3 − , SCN − , AcO − and AcS − . With P(OCH 3 ) 3 3 leads in an Arbuzow reaction to the 5‐(dimethoxyphosphorylmethyl)‐1,2,3‐triazole nucleoside 4e . The β‐oxoalkylidenephosphoranes 5a and b react with 1 to form the corresponding 5‐substituted 1,2,3‐triazoles 4f and g , respectively. Removal of the benzoyl groups in 4a, c, e , and g , with CH 3 OH/NH 3 leads to the 1‐β‐ D ‐ribofuranosyl‐1,2,3‐triazoles 6a, c, e , and g . ‐The biological activity of the nucleosides of the typ 6 has been tested.