Ismail Kiran

The Stereochemistry of Epoxidation of Steroidal 4,6-Dienes

The epoxidation of some androsta-4,6-dienes with m-chloroperbenzoic acid has been shown to give the 4β,5β;6α,7α-diepoxides, the stereochemistry can be rationalized in terms of the directing effect of one epoxide on the facial selectivity of the second epoxidation.

The effect of a 4-formyl and hydroxymethyl substituent on steroid biotransformations by Mucor plumbeus

Although steroids possessing a 4-formyl substituent undergo reduction on incubation with Mucor plumbeus, they do not appear to be substrates for efficient microbiological hydroxylation by this organism indicating that the structural requirements for these two enzyme systems are different.

The microbiological hydroxylation of 17-chloroandrosta-4,16-dien-3-one by Cephalosporium aphidicola

17-Chloroandrosta-4,16-dien-3-one is hydroxylated at C-6β, C-11α and C-15β by the fungus Cephalosporium aphidicola.

An alternative preparation of steroidal Δ4-3,6-diones

The oxidation of readily available steroidal 3-chloro-3,5-dienes with chromic acid is shown to give the corresponding 4-ene-3,6-diones.

The preparation and crystal structure of 16-acetylandrosta-4,16-dien-3-one

Dehydroisoandrosterone was formylated at C-16 by a Vilsmeier reaction and by condensation with methyl formate. The product of the latter reaction was converted to 16-acetylandrosta-4,16-dien-3-one and its X-ray crystal structure was determined.

The Preparation of Furano-steroid Analogues of Demethoxyviridin

The syntheses of a C-4:C-6 furano-steroid by the base-catalysed cyclization of 6α-acetoxyandrost-4-ene-3,17-dione and of a C-4:C-6 tetrahydrofuran by the cyclization of 3β,6β-dihydroxy-4β-hydroxymethylandrostan-17-one, are described.

The preparation of 21,21-dimethylprogesterone †

The kinetically controlled alkylation of pregnenolone acetate has been used to prepare the 21,21-dimethyl analogue which was then converted into 21,21-dimethylprogesterone.

The Westphalen rearrangement of a tricyclic steroid

A tricyclic steroidal des-ring D-androstane derived from the Koster-Logemann ketone has been shown to undergo a backbone Westphalen rearrangement. The structures of the products have been established by X-ray crystallography.

The Tetracyanoethylene Catalysed Methanolysis of Androstane 2,3-Epoxides

Unlike other acidic systems, the tetracyanoethylene catalysed methanolysis of androstane 2,3-epoxides proceeds normally without giving products arising from the transannular participation of a 5α,6α-epoxide, a 5α-hydroxy group or a 5(6)-ene.

The Transannular Effect of One Androstane Epoxide on the Stereochemistry of a Second Epoxidation

The transannular directing effect of a 2α,3α-, 2β,3β- and 5α,6α-epoxide on the epoxidation of a 5-ene and a 2-ene, respectively, is shown to increase the proportion of epoxidation of the anti face of the alkene when compared to the unsubstituted 2- and 5-androstenes.