General Approach to Anthrapyran Antibiotics Exemplified by the Synthesis of rac-γ-Indomycinone

✍ Scribed by Karsten Krohn; Hoan Trang Tran-Thien; Ishtiaq Ahmed

• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 129 KB
• Volume: 2011
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.201100093

✦ Synopsis

Abstract

A new general route to the anthrapyran antibiotics is presented, which allows the attachment of various branched side chains. A key step is the Baker–Venkataraman rearrangement of the propionate 9 to the diketone 10. Acid‐catalyzed cyclization gives the ethyl‐branched anthrapyranone 11, serving as the starting material for further side‐chain elongation. For example, the ethyl‐substituted anthrapyranones 12a,b,c, the corresponding bromides 13b,c, the phosphonium salts 14b,c, the olefins 22a,c, and the epoxides 23a,c are prepared by starting from 11. A first example demonstrating the potential of this route is the synthesis of the naturally occurring γ‐indomycinone (24b), prepared bycuprate‐mediated opening of the epoxide 23a.