TOTAL SYNTHESIS OF THE PROPOSED STRUCTURE OF DOLASTATIN-15

Efficient synthesis of dolastatin 15 (1) was accomplished following a convergent strategy. The pyrrolidinone cycle of 5 was obtained by thermic cyclization of the corresponding Meldrum's adduct 4. The methylation of the enol function was performed under Mitsunobu conditions. On the other hand, the peptide part 10 was elongated by using PyCloP as coupling reagent. The ester linkage between both segments was efficiently performed under conditions we previously described by using a mixed anhydride activation with isopropenyl chlorocarbonate. Final compound 12 was found to exhibit physical properties slightly different from those recently reported by Pettit and co-workers for the natural dolastatin 15 and their synthesis product.