Synthesis of demethylgorgosterol and its stereoisomers.
作者:SUSUMU SATO、AKIRA AKAIWA、YOSHINORI FUJIMOTO、MASAJI ISHIGURO、NOBUO IKEKAWA
DOI:10.1248/cpb.29.406
日期:——
A stereoselective synthesis of demethylgorgosterol (2) is described. Alkylation at the C-22 position of the steroidal 23-aldehyde (5) was achieved by Claisen rearrangement of the piperidine enamine to give the (22S)-22-aldehyde (10a) predominantly. Compound 10a was transformed to the 22-hydroxymethyl-24-aldehyde mesylate (15a). When the mesylate was treated with potassium t-butoxide, the 22, 23-cyclopropyl 24-aldehyde (19a) was obtained in high yield. An isopropyl group was introduced at the C-24 position by means of the Grignard reaction and subsequently the hydroxy group was oxidized to provide the 24-ketone (25a). Wittig reaction of 25a followed by hydroboration and then LiAIH4 reduction of the mesylate gave 2, which was identical with the natural compound in all physical properties. Three other epimers, the (22R, 23R, 24S)-isomer (32), (22S, 23S, 24R)-isomer (34) and (22S, 23S, 24S)-isomer (35), were prepared by the same procedure. These four isomers can be separated by gas-liquid chromatography on a glass capillary column coated with OV-17.
本文介绍了一种立体选择性合成去甲基麦角甾醇(2)的方法。通过哌啶烯胺的克莱森重排,在类固醇 23-醛 (5) 的 C-22 位进行烷基化,主要得到 (22S)-22-醛 (10a)。化合物 10a 转化为 22-羟甲基-24-甲醛甲磺酸盐(15a)。用叔丁醇钾处理甲磺酸盐后,可以高产率得到 22、23-环丙基 24-醛(19a)。通过格氏反应在 C-24 位引入一个异丙基,随后羟基被氧化,得到 24-酮(25a)。对 25a 进行维蒂希反应,然后进行氢硼化反应,最后用 LiAIH4 还原甲磺酸盐,得到了 2,它的所有物理性质都与天然化合物相同。用同样的方法还制备了另外三种外延物,即(22R, 23R, 24S)-异构体(32)、(22S, 23S, 24R)-异构体(34)和(22S, 23S, 24S)-异构体(35)。这四种异构体可在涂有 OV-17 的玻璃毛细管色谱柱上通过气液色谱法分离。