16 18-酸素化-C-ノル-D-ホモステロイドの合成

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Compared with normal steroids little success has been noted on the functionalization of 18-methyl group in the field of C-nor-D-homosteroids. In this paper, the successful functionalization of 18-methyl groups of C-nor-D-homosteroids with cis as well as trans C/D ring junction by the intramolecular radical processes will be reported. In all cases, jervine or 11-deoxojervine was chosen as the starting material and transformed via several steps into the nitrogen-free compounds, 17α- or 17β-acetyl-12α-etiojervanes, (X and XII) or 17α-acetyletiojervanes (XVIII and XXVI). These were reduced with NaBH_4 to afford the corresponding 20-ols which were then submitted to the Barton, Hypoiodite and lead tetraacetate reactions. It has been shown that the functionalization of 18-methyl group was possible by the hypoiodite reaction of XVa and the Barton reaction of XXVIIb and afforded 18-oxygenated 12α-etiojervane (XVIa) and 18-oximinoetiojervane (XXX) respectively. (XVIa) may be valuable as a relay compound in transforming jerveratrum alkaloids into fritillaria alkaloids, e.g., verticine and (XXX) would be useful intermediate for C-nor-D-homo-analogue of aldosterone. On the other hand, in hypoiodite and lead tetraacetate reactions of 20-ol (XIXa) derived from (XVIII), it has been observed that the products from β-scission of secondary alkoxyl radical overwhelmingly predominated over hydrogen abstraction. In the course of these studies, some unusual products were obtained. Some aspects of these intriguing variation of the reactions will be discussed.
天然有機化合物討論会の論文
1969-09-01

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