Malika Ibrahim-Ouali

Recent advances in azasteroids chemistry

Modified steroids have attracted a great deal of attention these last years. Their preparation is a stimulating challenge to the organic chemist, often demanding development of new and generally useful reactions. Moreover, the biological properties of modified steroids have proved to be of interest. The recent development in the partial and total syntheses of azasteroids is herein described.

Recent advances in oxasteroids chemistry.

The continuous interest in the field of oxasteroids mainly arises from the fascinating aspects associated with their peculiar stereochemical features and their promising and sometimes unexpected biological activities. The recent development in the partial and total syntheses of oxasteroids are herein described.

Recent advances in thiasteroids chemistry.

Since it has been proven these last years that the introduction of a heteroatom in the steroidal moiety could have a biological impact, there has been progress in the field of thiasteroids. The recent development in the partial and total syntheses of thiasteroids are herein described.

First total synthesis of 11-oxa steroids

Abstract The first total synthesis of 11-oxa steroids was achieved via an intramolecular Diels–Alder cycloaddition of orthoquinodimethane as the key-step.

First [2+2]-cycloaddition of a 3,4-didehydropyridine and a ketene dialkyl acetal

Abstract The 3- or 4-halopyridines and a ketene dialkyl acetal were shown to permit the synthesis of pyrido[ b ]cyclobutene derivatives. This finding constitutes the first published report of cycloadditions involving an olefin and a 3,4-pyridyne partner. The reaction is totally regioselective and the structure of the cycloadduct is determined unambiguously by NMR experiments.

Efficient Synthesis of New Steroids Possessing an Aromatic A‐Ring with a 2‐Hydroxy or a 2‐Fluoro Substituent

5-Fluoro-1-iodobenzocyclobutene (7) and 5-tert-butoxy-1-iodobenzocyclobutene (8) have been used for the synthesis of the title compounds. This strategy involves the use of an intramolecular Diels−Alder cycloaddition of o-xylylenes as the key step. We have shown that the introduction of a tert-butyl ether as a protecting group at the beginning of the synthesis, in place of the methyl ether used previously, is a judicious choice by which to obtain steroids possessing an aromatic A-ring with a 2-OH substituent. Finally, the vinyl groups of the synthesized fluoro and hydroxy steroids have been oxidized by the Wacker process in good yields. An X-ray crystal structure of the fluoro steroid 14b, the trans-anti-trans ring configuration of which matches those in natural products, is reported.

Synthesis of pentacyclic steroids

Due to their high profile biological activity, the steroids are among the most important secondary metabolites. A review of literature on the synthesis of pentacyclic steroids is presented.

Reinvestigation relative to the regioselectivity of the aryne cycloaddition. Synthesis of the tricyclo[6.2.0.02,5]-1,5,7-triene-3,10-dione

Abstract A rapid and total synthesis of a tricyclo[6.2.0.0]deca-1,5,7-triene-3,10-dione 7b is described. Its synthesis involves the [2+2] cycloaddition of a benzyne to 2-methylene-1,3-dioxepane followed by hydrolysis to the corresponding ketone. This reaction is totally regioselective and the real structure of the molecule is given thanks notably to the X-ray crystal structure of the intermediate benzo-bis-cyclobutene.

Diels–Alder route to steroids and associated structures

The Diels-Alder reaction continues to dominate the developments in steroid synthesis. A review of literature on the Diels-Alder route to steroids is presented.

First total synthesis of (±)-3-aza-11-oxa-1,3,5(10)-trieno steroids

We set out to describe a new and versatile method for preparing 3-aza-11-oxa-1,3,5(10)-trieno steroids via an intramolecular Diels-Alder cycloaddition of o-quinodimethanes as the key step. The characteristic 1H and 13C NMR spectroscopic features of the synthesized compounds are reported.