Total synthesis of pamamycin-607

The macrodiolide antibiotic pamamycin-607 has been synthesized by coupling of the two hydroxy acid constituents using the Yamaguchi method. While the final lactonization with formation of the ester linkage between C(1) and the C(8′) oxygen proceeded with complete C(2) epimerization, the alternative ring closure involving the carboxylic acid of the smaller fragment and the hydroxyl group of the larger fragment yielded the target molecule.