Novobiocin II. Die Synthese der 3–O–Carbamoyl‐noviose

The synthesis of 3‐O‐carbamoyl‐noviose, the carbohydrate of the antibiotic novobiocin, is described. Starting with D‐glucose the synthesis comprises a number of steps (1–5) up to the important intermediate 3,5,6‐tri‐O‐benzyl‐2‐O‐methyl‐D‐galactono‐γ‐lactone (5), which was obtained by an intramolecular WALDEN inversion of 3,5,6‐tri‐O‐benzyl‐4‐O‐mesyl‐2‐O‐methyl‐D‐glucono‐N‐methylamide (4). Compound 5 shows the correct steric arrangement of the asymmetric centres with respect to noviose. Successive transformations (6–10) led to the synthesis of noviose and finally (9–14) to methyl 3‐O‐carbamoyl‐α‐novioside, which was identical with the substance obtained by acid catalysed methanolysis of the antibiotic novobiocin.