Stereoselective syntheses of (22R)- and (22S)-22-methyl-1.alpha.,25-dihydroxyvitamin D3: active vitamin D3 analogs with restricted side-chain conformation
作者:Keiko Yamamoto、Jun Takahashi、Kazuhiko Hamano、Sachiko Yamada、Kentaro Yamaguchi、Hector F. DeLuca
DOI:10.1021/jo00061a029
日期:1993.4
(22R)- and (22S)-22-methyl-1alpha,25-dihydroxyvitamin D3 (1b and 1c) were synthesized stereoselectively from 1alpha-hydroxylated C(22)-steroid 2. The two new vitamin D analogs, which have a side chain with restricted flexibility, were designed to allow the study of the stereochemical structure required to bind to the receptor of the active vitamin D3 (VDR). According to force-field calculations, the side chain of (22R)- and (22S)-methylated active vitamin D3 analogs (1b and 1c) adopts with more than 90% of the population gauche(+) and anti conformations, respectively, at the C(17-20-22-23) dihedral angle. Either the (22R)- or (22S)-methylated steroidal side chain was constructed with high stereoselectivity via a kinetically controlled conjugate addition of methylcopper reagent to (22E)- or (22Z)-22-en-24-ones (6 or 7), respectively, as a key step. The ability of the two analogs to bind to VDR was examined and only the (22S)-isomer (1c) showed significant activity. From the results, the side chain conformation best fitted to VDR was suggested to be the anti with respect to the C(17-20-22-23) dihedral angle.
(22R)-和(22S)-22-甲基-1α,25-二羟基维生素D3(1b和1c)是从1α-羟基化的C(22)-甾体2立体选择性合成的。这两种新型维生素D类似物具有柔韧性较低的侧链,设计目的是为了研究与活性维生素D3受体(VDR)结合所需的立体化学结构。根据力场计算,(22R)-和(22S)-甲基化活性维生素D3类似物(1b和1c)的侧链在C(17-20-22-23)二面角下分别有超过90%的构象为gauche(+)和anti构型。通过动力学控制的甲基铜试剂对(22E)-或(22Z)-22-en-24-ones(6或7)的共轭加成,分别以高立体选择性构建了(22R)-或(22S)-甲基化甾体侧链,这是关键的步骤。这两种类似物与VDR的结合能力得到了检测,只有(22S)-异构体(1c)表现出显著的活性。根据实验结果,C(17-20-22-23)二面角下与VDR最佳匹配的侧链构象为anti构型。