An efficient total synthesis of calothrixin B

An efficient synthesis of calothrixin B (2) is demonstrated starting from 9H-carbazol-4-ol, having two one-pot reaction sequences as key steps. As a novel observation, DMF–methanol was shown to be a hydride donor for reduction of aldehyde to alcohol. Unexpectedly, nucleophilic substitution of benzyloxy by methoxy group was observed.