Zur Prins-Reaktion von Lumihecogeninacetat

Transetherification-mediated E-ring opening and stereoselective "Red-Ox" modification of furostan

We have developed a novel E-ring opening method for furostan, and applied it to prepare D-ring modified steroids, which can be used to synthesize cephalostatin analogs.

Norrish-Prins reaction as a key step in the synthesis of 14β-hydroxy-5α (or 5β or Δ(5,6))-pregnane derivatives

Numerous bioactive glycosteroids are characterized by aglycones bearing a 14β-hydroxy pregnane skeleton like boucerin and isoramanone. In general, the syntheses of the latter are achieved by acidic hydrolysis of the corresponding glycosteroids. These aglycones were also obtained by a combined Norrish type I-Prins reaction starting from the corresponding 12-keto-pregnane derivatives. However, for the Norrish-Prins reaction, no reports describe the influence of the A/B ring junction (cis or trans or Δ(5,6) double bond) or the influence of the substitution pattern at position 20. Herein, we describe the use of Norrish type I-Prins reactions to synthesize isoramanone and boucerin derivatives and their A/B cis and trans analogs. The influence of the parameters mentioned above is also presented. These studies showed that the A/B ring junction has little influence on the Norrish type I-Prins reaction but that the substitution pattern at position 20 is important. The presence of a dioxolane group induced not only the formation of the desired 14β-hydroxy pregnane derivatives in the highest yields but also the formation of new spiro derivatives.

Synthesis of Hoodigogenin A, aglycone of natural appetite suppressant glycosteroids extracted from Hoodia gordonii

14β-hydroxy pregnane glycosides extracted from Hoodia gordonii, a succulent plant isolated from Apocynaceae are suggested to have appetite suppressant properties in animals and humans. However, limited reports on biological studies concerning the appetite suppressant properties are available in the open literature. One reason for that is the poor availability of these glycosteroids because H. gordonii is a protected plant and the yield of extraction lies between 0.003% and 0.02%. Starting from 3α,12α-diacetoxy-pregnanone 1, we disclose in this report the synthesis of Hoodigogenin A, the aglycone of the natural 14β-hydroxy pregnane glycosides extracted from H. Gordonii.

Steroid glycosides from Polygonatum prattii

Investigation of the roots of Polygonatum prattii afforded three new steroid glycosides, paratiosides A-C, and three new prosapogenins, pratiosides D1, E1 and F1. The latter three, which were obtained from the enzymatic hydrolysis products of a glycoside mixture, are considered to be the corresponding spirostanol glycosides of their proto-type furostanol ones in the plant. The structures of these compounds were established by chemical and spectral methods. It is noted that pratioside C possessing a 3,27-di-O-sugar chain is the first example to be isolated from a natural source.