Ex Chiral Pool Synthesis from a Highly Methyl-Branched Wax Ester and Biological Properties of (+)-Capensifuranone.

Unnatural (+)-capensifuranone (+)-2 and its epimer (–)-5-epi-capensifuranone 6 were prepared from enantiopure methyl-branched aldehyde 4, employing cyclisation with 3-bromomethacrylic acid to 4-bromofuranones 5a,b followed by Negishi cross coupling. Compound 4 was obtained from the preen-gland wax-derived ester 3 after ozonolysis and reductive work-up. The configuration of 6 was determined via the X-ray crystal structure analysis of a derivative 10. Compounds (+)-2, 5a,b and 6 showed cytotoxic activity against L-929 mouse fibroblasts, and KB-3-1 HeLa and U-937 lymphoma cells.