title: Synthesis of 26,27-bisnorcastasterone analogs and analysis of conformation-activity relationship for brassinolide-like activity.
abstract: Three castasterone (CS) derivatives with varied side-chain moieties, 26,27-bisnorcastasterone (20S-bisnorCS), 20-epi-26,27-bisnorcastasterone (20R-bisnorCS), and 21,26,27-trisnorcastasterone (trisnorCS), were synthesized stereoselectively from either stigmasterol or dehydroisoandrosterone. The 50% effective doses (ED50, nmol/plant) in the concentration-response curve for brassinolide-like activity in the rice lamina inclination assay were determined to be 0.020 nmol (pED50 = 10.7) for 20S-bisnorCS, 3.2 nmol (pED50 = 8.5) for 20R-bisnorCS, and 2.0 nmol (pED50 = 8.7) for trisnorCS. An analog containing an ester linkage between the steroid and the side-chain moiety of 20S-bisnorCS was also synthesized and its activity was evaluated to be 3.2 nmol (pED50 = 8.5), being equipotent to 20R-bisnorCS and trisnorCS. The activity of 20S-bisnorCS was 1/40 that of CS. The conformation analysis was conducted using a systematic search, showing that the activity decreases with an increase in the degree of freedom of the side chain of the steroidal skeleton.
authors.affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Shuji
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Bunta
authors.initials: B
authors.lastname: Watanabe
authors.forename: Junko
authors.initials: J
authors.lastname: Otsuki
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nakagawa
authors.forename: Miki
authors.initials: M
authors.lastname: Akamatsu
authors.forename: Hisahi
authors.initials: H
authors.lastname: Miyagawa
mesh_terms: D060406:Brassinosteroids; D002777:Cholestanols / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D008956:Models, Chemical; D012275:Oryza / Q000187:drug effects; D010937:Plant Growth Regulators / Q000138:chemical synthesis / Q000737:chemistry* / Q000502:physiology; D013237:Stereoisomerism; D013260:Steroids, Heterocyclic / Q000737:chemistry* / Q000494:pharmacology; D013329:Structure-Activity Relationship
chemical_list: D060406:Brassinosteroids; D002777:Cholestanols; D010937:Plant Growth Regulators; D013260:Steroids, Heterocyclic; C083545:castasterone; C023623:brassinolide