Isolation, Biological Significance, Synthesis, and Cytotoxic Evaluation of New Natural Parathiosteroids A−C and Analogues from the Soft Coral <i>Paragorgia</i> sp.
Three unusual new steroid thioesters, parathiosteroids A-C (1a-3a), were isolated from the 2-propanol extract of the soft coral Paragorgia sp. collected in Madagascar. Their structures, determined by detailed spectroscopic analysis, were confirmed by synthesis and represent the first isolation of natural steroids bearing a C22 thioester in their side chain. These compounds displayed cytotoxicity against