Stereocontrolled Total Synthesis of an Annonacin A-Type Acetogenin: Pseudoannonacin A?

A stereocontrolled first total synthesis of a diastereomer of the presumed mono-tetrahydrofuran type acetogenin annonacin A, starting with enantiomerically pure precursors, is described. The absolute stereochemistry of the C 15 −C 20 segment corresponding to the tetrahydrofuran ring of the natural product was secured by X-ray crystal structure analysis of an advanced intermediate. The synthetic product (a mixture of epimers at C 10 ) had spectroscopic data identical to that of the natural product, but a different optical rotation.