Stereoselective synthesis of plant growth-prompting steroids, brassinolide, castasterone, typhasterol, and their 28-nor analogues

Abstract

Plant growth-promoting steroids, brassinolide (1a), (22R,23R,24S)-2α,3α,22,23-tetrahydroxy-B-homo-7-oxa-5α-ergostan-6-one, castasterone (2a), (22R,23R,24S)-2α,3α,22,23-tetrahydroxy-5α-ergo-stan-6-one, 28-norbrassinolide (1b), (22R,23R)-2α,3α,22,23-tetrahydroxy-B-homo-7-oxa-5α-chole-stan-6-one, brassinone (2b), (22R,23R)-2α,3α,22,23-tetrahydroxy-5α-cholestan-6-one, and typh-asterol (2c), (22R,23R,24S)-3α,22,23-trihydroxy-5α.-ergostan-6-one, have been stereoselectively synthesized. These steroids show very strong biological activities in three different kinds of bioassays.