Minor and Trace Sterols in Marine Invertebrates. 31. Isolation and Structure Elucidation of 23H-Isocalysterol, a Naturally Occurring Cyclopropene. Some Comparative Observation on the Course of Hydrogenolytic Ring Opening of Steroidal Cyclopropenes and Cyclopropanes

Article abstract of DOI:10.1021/ja00388a041

A new naturally occuring cyclopropene, 23H-isocalysterol (2), and a novel steroidal cyclopropane, 23,24-dihydrocalysterol (3), were isolated from the sponge Calyx niceaensis.Structure elucidation was accomplished by both NMR and mass spectroscopic analyses.Catalytic hydrogenation and detailed NMR analysis of the products led to the determination of the absolute configuration of calysterol (1) (28R), 23H-isocalysterol (2) (23R), and 23,24-dihydrocalysterol (3b) (23S,24S,28R).Partial synthesis of several hydrogenolysis products as well as synthetic approach to 23,24-dihydrocalysterol are also reported.