Novobiocin III. Die Glykosidsynthese des Novobiocins

The glycosidation of 4‐benzyloxy‐7‐hydroxy‐8‐methyl‐cumarin (2) with 2,3‐0‐carbonyl‐β‐noviosyl chloride (1) leading to the α‐glycoside (3) is described. This intermediate is transformed successively : (a) by hydrogenolysis (4), (b) introduction of an amine function (5) (6), (c) acylation with 4‐acetoxy‐3‐(isopent‐2′‐enyl)‐benzoyl chloride (10), (d) ammonolysis of 10, into a mixture of novobiocin (11) and isonovo‐biocin (12), of which novobiocin was obtained by fractional crystallisation.