Syntheses via diketones

Syntheses via Diketones. The general scheme of the syntheses consists in the preparation of AD fragments containing keto groups 

Treatment of the triketone (553) with strong acids (hydrochloric or polyphosphoric) is accompanied by double cyclization and leads to the tetracyclic ketone (364),the conversion of which into (369) is also 

D-homoestrone have been synthesized from the ketone (559) [442, 614]. Subsequent reduction, hydrolysis, and oxidation have enabled (559) to be converted into the triketone (560), which cyclizes into the da, lOp -ketol (562) during chromatography on Florex. Dehydration and reduction of the 17a-oxo group lead to the 3-oxo-A derivative (563). Isomerization of the latter into D-homoestradiol (564) takes place in low yield when it is boiled with palladized carbon. 

Like its six-membered homolog (553), the triketone (565) undergoes conversion on treatment with benzoic acid and triethylamine into the ACD diketone (566). In this case, however, the reaction takes place considerably more slowly, which is due to the increased strain introduced into the bicyclic system by the five-membered ring. The catalytic hydrogenation of (566) and the cyclization of the mixture of isomers formed (567) led to the methyl ether of -dehydroestrone (402) with an over-all yield of 

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