Synthesis and biological activity of brassinolide analogues, 26,27-bisnorbrassinolide and its 6-oxo analogue

Synthesis of Five Known Brassinosteroid Analogs from Hyodeoxycholic Acid and Their Activities as Plant-Growth Regulators

“…A large number of reports have shown that the indirect or direct conversion of 3α or 3β-hydroxy steroid in Δ 2 alkenes can take place by following at least three different strategies. The indirect path transforms the alcohol into a good leaving group such as tosylate, which in a subsequent treatment with Li 2 CO 3 /LiBr/DMF in reflux system [25,28,33,34,35] or treatment of mesylate derivatives under the same conditions produces the Δ 2 alkenes [26,36,37,38,39]. On the other hand, an efficient alternative is the direct dehydration of 3α or 3β-hydroxy steroid that is carried out by adsorbing the substrate on silica gel in a reaction catalyzed by copper (II) sulfate [32,40,41,42].…”

Brassinosteroid phytohormones: structure, bioactivity and applications

“…When the 24-substituents of the 22α,23α-brassinosteroids were examined, the order of brassinolide activity is brassinolide (1) > 24-epibrassinolide (6) > 28-homobrassinolide (2) > 24-epi-28-homobrassinolide (171) > dolicholide (3) > 28homodolicolide (4) > 28-norbrassinolide (5), a decreasing order that is also observed in the 6-oxo series in the bean second internode assay (Mandava, 1988) and in the rice lamina inclination assay (Takatsuto et al, 1983a). Introduction of a methyl group at C-25 increases the brassinolide activity ten times, at least in the pairs brassinolide (1)/25-metilbrassinolide (172) and dolichosterone (11)/25-methyldolichosterone (16; Mori and Takeuchi, 1988), while the removal of the methyl groups at C-25, resulting in 26,27-dinorbrassinolide (173) or in 26,27-dinorcastasterone (174) does not affect the brassinolide activity at the rice lamina inclination assay, compared to their parent compounds (Takatsuto et al, 1984).…”

“…Other assays are less frequently employed to evaluate brassinosteroids structure-activity relationships, such as the mung bean epicotyl elongation assay (Gregory and Mandava, 1982), the radish (Takatsuto et al, 1983b(Takatsuto et al, , 1984 and tomato (Takatsuto et al, 1983b) hypocotyl elongation assays, and auxin-induced ethylene production by etiolated mung bean segments (Arteca et al, 1985).…”

Application of [Mo2(OAc)4] for determination of absolute configuration of brassinosteroid vic‐diols by circular dichroism

“…Brassinosteroids (BRs) constitute a novel class of phytohormones showing high growth-promoting activity as well as other multiple effects on the growth and development of plants. [1][2][3] The side chain in naturally occurring BRs carries either a methyl, methylene, ␣-ethyl, ethylidene, methylene, or no substituent at C24, and a vic-glycol moiety at C22 and C23. These vicinal hydroxy groups are mostly of threo configuration, and they may be differentiated from their erythro isomers, e.g., by NMR spectroscopy.…”