Synthesis of a castasterone/ponasterone hybrid compound and evaluation of its molting hormone-like activity

Abstract

Castasterone/ponasterone hybrid compound, (20R)-2α,3α,20, 22-tetrahydroxy-5α-cholestan-6-one, was newly synthesized from the corresponding α-alkoxystannane, in which the α-hydroxy group was protected with a benzyloxymethyl ether, and 6,6-ethylenedioxy-2α,3α-isopropylidenedioxy-5α-pregnan-20-one. The inhibition of the incorporation of [3H]ponasterone A into two insect cell lines was examined, and the concentrations of this hybrid compound required to give 50% inhibition were determined to be 0.29 μM and 0.89 μM for Kc and Sf-9 cells, respectively. This hybrid compound was 10 times more potent than ecdysone, but 100-200 times less potent than ponasterone A. The potency of this compound was equivalent to inokosterone against Sf-9 cells. The molting hormonal effect of this compound was also evaluated in the cultured integument system of the rice stem borer Chilo suppressalis for the induction of chitin synthesis, and the 50% effective concentration was determined to be about 10 μM, equipotent to ecdysone.