Enantioselective synthesis of pentacycloanammoxic acid.

A highly effective enantioselective synthesis of pentacycloanammoxic acid (1), an unusual naturally occurring fatty acid from Candidatus Brocadia anammoxidans, has been accomplished. The C20-structure of 1 was assembled with stereocontrol from four building blocks, cyclobutene, 2-cyclopentenone, the chiral silylcyclopentenone 6, and 7-bromoheptanoic acid. Both 1 and its enantiomer are now available in quantities that should facilitate future studies on the mode of biosynthesis which appears to be unprecedented.