SECONDARY MOLD METABOLITES .36. ISOLATION AND STRUCTURE ELUCIDATION OF SULCATINE-C, SULCATINE-D AND SULCATINE-E, NOVEL NORSESQUITERPENES FROM LAURILIA-SULCATA, AND 7-EPI-SULCATINE-D

Three novel norsesquiterpenes, sulcatines C-E (5, 6 and 11), have been isolated from still liquid cultures of Laurilia sulcata. Their structures were elucidated by H-1 and C-13 NMR spectroscopic studies, including H-1-C-13 heteronuclear correlation spectra (HETCOR and COLOC), and the relative configurations were established through a series of NOE difference spectra and the magnitude of the H-1-H-1 coupling constants. The absolute configuration of these metabolites was deduced by the application of the exciton chirality method to the pivalate dibenzoate of sulcatine D, compound 9. Sulcatines C and E (5 and 11) were shown to exist in solution as an equilibrating mixture of ring-closed hemiketal (5a and 11b) and ring-opened keto (5c and 11a) forms. By reduction with NaBH4 sulcatine C 5 afforded a separable mixture of sulcatine D 6 and its C-7 epimer 10.