17 側鎖に官能基をもつステロイド類の合成 : Antheridiol,Brassinolide,Calcidiol lactoneの合成

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Stereoselective syntheses of some biological active steroids having functional groups in their side chain have been investigated. Brassinolide (A), a new plant growth promoter isolated from rape pollen, was synthesized from bisnorcholenic aicd. The 22R-hydroxy-23R, 24R-epoxide (6) was obtained by Sharpless oxidation of cis-allylic alcohol (5). A nitrile group, which was subsequently transformed to methyl group via aldehyde, was introduced at C-24 position by hydrocyanation. The side chain having same stereochemical configuration was thus obtained. After introduction of 6-ketone and 2α, 3α-diol groups, Baeyer-Villiger oxidation gave the lactone 16, which was converted to A, mp 273-278 (decomp). The IR, MS and ^<13>C-n.m.r spectra are in good agreement with those of the natural one. Calcidiol lactone (B), a new metabolite of vitamin D_3, has also synthesized from the 22-aldehyde 2. Reaction with vinylmagnesium bromide afforded the (22R)-22-alcohol 17 predominantly. By the Claisen rearrangement of 17 with orthopropionate gave the 26-ester 18. Iodolactonization of 18 yielded regio- and stereoselctively a single product 19, which was led to the lactone 20. The C-23 configuration of the lactone was determined as R by transformation into 22- and 23-hydroxycholesterols. Introduction of a hydroxyl at C-25 was achieved by oxidation with MoOPH. The hydroxylactone 25 was converted to (23R)-calcidiol lactone. The UV and MS spectra of the synthetic compound were identical with those of the metabolite. The iodolactonization was applied to the stereoselective synthesis of antheridiol (C). The 24-isopropyl-26-ester (32) was transformed to 22,23-epoxy-26-ester (32) via iodolactone 31. The epoxide 32 was converted to the 22-hydroxy-γ-lactone 34, possessing the same stereochemical configuration as that of natural antheridiol.
天然有機化合物討論会の論文
1980-09-10

17 側鎖に官能基をもつステロイド類の合成 : Antheridiol,Brassinolide,Calcidiol lactoneの合成

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