C-24 Stereochemistry of Marine Sterols: (22E)-25,28-Dimethylstigmasta-5,22,28-trien-3 beta-ol and 25,28-Dimethylstigmasta-5,28-dien-3 beta-ol

摘要

The C-24 configurations of (22E)-25,28-dimethylstigmasta-5,22,28-trien-3-beta-ol (1) and 25,28-dimethylstigmasta-5,28-dien-3 beta-ol (2), isolated from the sponge Topsentia ophiraphidites in our previous work, were determined to be both S, through the synthesis of stereodefined (24S)- and (24R)-epimers of 1 and 2 and comparison of the H-1 and C-13 NMR spectroscopic data. In addition, the C-24 configurations of the marine sterols having the same structures as 1 and 2 and their derivatives were also assigned for the first time by NMR comparison.