Synthesis and Plant Growth-promoting Activity of Brassinolide Analogues

Abstract

The analogues of brassinolide, 15, 19-23, 29 and 30, were synthesized via key intermediate 5 from stigmasterol. Compound 15 which has the same functional groups as brassinolide on rings A and B showed one tenth of the activity of brassinolide in the lamina inclination test on rice seedlings. However, other analogues with modified ring A were poorly active, and an analogue with modified ring B, 6-oxa-ketone 30, showed only one hundredth of the activity of its 7-oxa-ketone isomer, 29, suggesting that the 2α, 3α-dihydroxy-7-oxa-6-ketone moiety is one of the requisites for the biological activity.