Recent developments in corticoid synthesis.

Abstract

In an attempt to improve the industrial manufacture of corticoids starting from desoxycholic acid, two major tasks had to be accomplished: (1) selective transposition of a 12 alpha-oxygen function to the 11-position. (2) Degradation of the side chain by three carbon atoms. The most convenient solution to the first problem included protection of the 3 alpha-hydroxyl, then dehydrating the 12 alpha-alcohol via its mesylate, and treatment of the resulting delta 11-12-alkene with PDC and iodine, to obtain the 12 alpha-iodo-11-ketone in very high yield. After reductive dehalogenation and saponification, the resulting acid proved to be suitable for solving our second problem. Oxidative decarboxylation with lead tetraacetate leads to an olefin, the double bond of which could be shifted along the side chain to produce the corresponding delta 20-22-isomer. Ozonolytic cleavage of the C--C double bond in this position made the 20-ketone 19 readily accessible. The latter plays a key role in the production of various corticoid drugs, since most of them are derived from this very compound, e.g. cortisol.