Analogues of the marine immunosuppressant microcolin A: preparation and biological activity.

A series of analogs of the immunosuppressive lipopeptide microcolin A has been prepared and evaluated for in vitro activity in the human and murine two-way mixed lymphocyte reaction. The compounds tested were obtained by semisynthetic modification and chemical degradation of the natural product. The relative potencies of these analogs suggest that the hydroxyproline and 5-methyl-3-pyrrolin-2-one portion of the molecule are important for immunosuppressive activity and that other structural elements may play an ancillary role. Methanolysis of microcolin A also led to a novel immunosuppressive lactone analog.