Syntheses via BCD intermediates with a six-membered ring

Syntheses via BCD Intermediates with a Six-Mem-bered Ring D. Several total syntheses of steroid compounds use BCD fragments with a six-membered ring D as intermediates. 

An alternative method of synthesis comprises ozonolysis of the acetate (255) and reaction of the enol lactone obtained (258) with the Grignard derivative from 5-chloro-2-methyl-l-pentene. The allylation of compound (259) led to a mixture of Cio epimers in a ratio of 2 1. The epimer present in largest amount had the natural lOp -configuration, as was shown by its conversion into the 3,16-diketone (257) [845]. 

Synthesis of the tricyclic homolog (253 R =Me) was carried out from the corresponding methoxytetralone (184 R =Me) by a method similar to that described previously [846]. The methoxycarbonylation and methylation of the initial tetralone led to compound (252), from which the methyl ketone (250 R = Me) was obtained by decarboxylation. Its condensation with acrylonitrile led to the cyanoketone (251), and hydrolysis and methylation of the latter gave the keto ester (254), the conversion of which into the corresponding methyl ketone and cyclization enabled the tricycle BCD fragment (253 R = Me) to be obtained. In this example, the formation of ring A was not studied. 

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