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 th
e 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. (C) 2001
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