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The first total synthesis of a spongipyran macrolide, altohyrtin C (spongistatin 2; see picture below), has been realized. The spongipyrans derived from marine sponges are among the most potent cytotoxic compounds yet isolated, and exhibit subnanomolar activities against a variety of human cancer cell lines. While the structures proposed for the independently isolated altohyrtins and spongistatins are largely homologous, they differ significantly with regard to internal stereochemical relationships. This discrepancy has been resolved by the total synthesis, which verifies the altohyrtin structural assignment and establishes the identity of altohyrtin C and the independently isolated spongistatin 2.
Evans et al. (1997) studied this question.