Structures of cyclootochilone and otochilone,two novel steroidal ketones of the orchids otochilusporecta and otochilusfusca

Cyclootochilone and otochilone, two novel steroidal ketones of the orchids Otochilusporecta were shown to have the structures 1a and 2, respectively, from spectral and chemical evidence, 1a alone has also been obtained from the taxonomically related orchid Otochilusfusca. The significance of these compounds in the biogenetic transformation of lanosterol to steroids and the biogenetic sequence of the origin of 9,19- cyclopropane ring present in some terpenoids and steroids, as well as the mechanism of incorporation of two methyl groups at C-24 of some of these compounds were discussed.