Total Synthesis of rac‐γ‐Indomycinone by Baker–Venkataraman Rearrangement

The total synthesis of racemic γ‐indomycinone (rac‐3) was achieved by Baker–Venkataraman rearrangement of ester 11 to the diketone 12, acid‐catalyzed cyclization to the anthrapyranone 13, followed by methyl ether cleavage and acetylation to 16, selective bromination of the branched side chain with simultaneous SN1‐type hydroxy substitution to 23 and transesterification to rac‐3. The corresponding γ‐indomycinone 11‐methyl ether (rac‐20) was prepared in a similar reaction sequence.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)