Journal of the American Chemical Society, Vol.129, No.20, 6400-6400, 2007
Total synthesis, assignment of absolute stereochemistry, and structural revision of chlorofusin
The first total synthesis of chlorofusin was accomplished in a convergent fashion. With all four unambiguous diastereomeric model chromophores as references, the absolute stereochemistry of the chlorofusin chromophore was determined and revised to be (4S,8R,9S) by H-1 NMR studies and asymmetric synthesis. This allows the complete structure of natural chlorofusin to be assigned for the first time. Enantioselective copper-mediated oxidation of 4, mild coupling of azaphilone 2 with the free amine-bearing cyclopeptide 3, and a one-pot three-step protocol for the final spiro-aminal formation were successfully achieved with high efficiency to yield the correct stereochemical product 1a.