Chemical and biotransformation of Gelomulide F: a rare diterpene lactone

Chemical and biotransformations of a rare diterpene lactone, Gelomulide F (1), from the cytotoxic extract of leaves of Suregada multiflora were studied. Fermentation of compound 1 with Sachromyces cerevisiae transformed it to Gelomulide D (2) and E (3), whereas its treatment with 2N KOH yielded Gelomulide D (2). In addition, a novel compound (4) was obtained by its diastereo and chemoselective reduction with NaBH4 . All of these compounds were characterized on the basis of extensive ^1 H-NMR, ^13 C-NMR, 2D NMR, and mass spectral analyses.