Steroidal lactones

Conjugate addition of methyl magnesium iodide in the presence of cuprous chloride to the enone (91) leads to the la-methyl product mesterolone (92) Although this is the thermodynamically unfavored axially disposed product, no possibility for isomerization exists in this case, since the ketone is once removed from this center. In an interesting synthesis of an oxa steroid, the enone (91) is first oxidized with lead tetraacetate the carbon at the 2 position is lost, affording the acid aldehyde. Reduction of this intermediate, also shown in the lactol form, with sodium borohydride affords the steroid lactone oxandrolone... 

No appreciable development of betacyanin pigment in the dark was observed in any of the weed seedlings during the course of the experiment. The development of betacyanin in the cotyledons of dark-grown A. retroflexus seedlings is reported to be induced by the plant growth regulator, kinetin (20), but not by brassinolide, a steroidal lactone (21). 

Bufogenins or Bufagins These are nitrogen-free steroidal lactones that are heart toxins found in toad venom. They have no chemical resemblance to bufotenine whatsoever. 

Phenylselenolactonization.1 This reaction has been used to prepare 24,20-steroidal lactones (3a and 3b). Thus reaction of la and lb, prepared in several steps from 3p-methoxy-5-androstene-17-one, with QH5SeCl (2 equiv.) and (1 equiv.) yields directly the unsaturated lactones 2a and 2b which are reduced by diimide to 3a and 3b. 

Withanolides. Withanolides are Cis-steroidal lactones that are isolated from the Solanaceae plant family. Withanolides are characterized by an ergostane-type skeleton, the Cl 7-side chain of which is transformed into a six-member lactone ring. The withanolides and the related crgostancs arc tile only known natural steroids obtained Ifum the same family dial have representatives with both a- and -orientations of the Cl7 side chain. 

The ring-A/B moiety (286) of the naturally occurring C2g steroidal lactone withaferin A has been incorporated into cholestane as outlined in Scheme 14.156 Hydride reduction of the epoxide (280) gave the diol (281) which reacted stereo-specifically with peroxy-acid to yield the a-epoxide (282), and this was in turn converted into the epoxy-enone (283). The yield of (283) based upon the epoxy-dienone (261) is 70%. Ring-opening of the oxide (283) afforded the 5a-alcohol (284) which was dehydrated to the A2,5-diene (285). The A5-bond was then epox-idized stereoselectively and quantitatively to the 5/3-oxide (286). Ring A of this 5/3 -oxide was shown to be in the boat conformation. 

A similar rearrangement was observed for the six-membered unsaturated steroidal lactone 17/i-hydroxy-2-oxaandrost-4-en-3-one which gives the corresponding cyclopropane derivative (mp 195-196°C) in 10.3% yield upon irradiation. ... 

Discovery and Biochemical Studies Withaferin A (WA, 1) is a highly oxygenated steroidal lactone that is found in the medicinal plant Withania somnifera... 

Shohat, B., Kirson, I., Lavie, D. (1978). Immunosuppressive activity of two plant steroidal lactones withaferin A and withanolide E. Biomedicine, 28,... 

Jones reagent [1, 143, after citation of ref. 7] Lavie el al.n treated the steroidal lactone (1) with the Jones reagent expecting to obtain the corresponding enone. Instead they obtained the epoxy diketone (2). The same product was also obtained from the isomeric allylic alcohol (3). Further investigation established that epoxi-dation occurs only if the hydroxy] group is axial, and if the oxidation is slower than... 

Bis-3-methyl-2-butylhorane ( Disiamvlborane ) [1, 57-59. before references]. This was found to be the best reagent for reduction of the steroidal lactone (1) to the corresponding hemiacetal (2).7 No improvement was noted when tri-l-butoxyalum-inum hydride was employed. 

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