18-Norpregna-8,11,13-trienes. Part 2. Preparation from 17β-methyl-17α-pregn-13-enes

Abstract

5~-androsta-8,11 ,I 3-trien-3a-yl acetate (6) has been prepared from 9a.11 a-epoxy-l7amethyl-5(3-androstane-3a,l7(3-diol 3-acetate (5) in good yield. An attempt to repeat the aromatisation with the analogous 9a.11 cc-epoxy-5P-pregnane-3a,l7a,20P-triol 3,20-diacetate (1 0) did not give the expected product. However, a number of ring-c-aromatic pregnanes have been successfully prepared from derivatives of 5P-pregnane-3a.11 p.17a, . Attempts to aminate some of these aromatic pregnanes a t the 3-and 20-positions are described.PREVIOUS papers from our laboratories have described the preparation of an 18-norpregna-8,11,13-triene and 18-norandr0sta-8,11,13-trienes.~-~ In continuation of the study to evaluate the biological activities of ringc-aromatic steroids, some other novel syntheses of ringc-aromatic pregnanes have been developed and are described herein.Aromatisation of ring c of a steroid necessitates the removal or migration of the 13p-methyl group. There are a number of examples 2-6 of the concomitant shift of the 13-methyl group of a 17-hydroxy-steroid by way of a Wagner-Meerwein rearrangement to give the 17pmethyl-13-ene. I t seemed that application of this rearrangement to 17a-hydroxypregnanes containing one or two potential double bonds in ring c might lead to an efficient route to ring-c-aromatic pregnanes.

Utility of silver nanoparticles embedded on a covalent organic framework as a highly active catalyst for carboxylative cyclization with CO2: a sustainable route for production of tetronic acids and oxazolidinones

“…8 However, the synthesis of tetronic acids involving various starting materials with multi-step synthetic routes under harsh reaction conditions has been explored previously. [82][83][84][85] T. Yamada et al first reported the synthesis of tetronic acids using CO 2 fixation in conjugate ynone. 86 However, the synthesis of the starting conjugate ynone substrate in this procedure is quite difficult and produces unwanted side products.…”