GB968746A - 19-nor-steroid-ketals and process for their manufacture - Google Patents

Abstract

The invention comprises (1) a process for the selective protection of a 3-oxo group in a D 5(10)-3-oxo-19-nor-steroid containing at least one other oxo group by ketalization, wherein the steroid is treated with a lower aliphatic or a monocyclic-aryl-lower aliphatic monohydric or dihydric alcohol in the presence of an acidic agent; and (2) D 5(10)-3, 3-dialkoxy-19-nor-pregnenes and -androstenes, the alkoxy groups each containing at most 5 carbon atoms. The process may be combined with other reaction steps, for example as follows:-a D 5(10)-3,17-dioxo-19-nor-androstene is converted to a D 5(10)-3, 3-dialkoxy-17-oxo-19-nor-androstene, this is reduced to the 17b -ol and the 3-keto group is released, before or after optional esterification. The reduction may be effected with a metal hydrocarbon or halohydrocarbon compound, so that the hydrocarbon or halohydrocarbon group is simultaneously introduced into the 17-position. Other oxo groups present in the products may also be reduced to hydroxyl groups. Acid hydrolysis of the D 5(10)-3-ketals produces either D 5(10)- or D 4(5)-3-oxo-19-norsteroids. Examples are given. D 5(10)-3-oxo-steroids are prepared by reduction of D 1,3,5(10)-3-alkoxy-steroids with alkali metals and liquid ammonia or an amine, the intermediate D 2,5(10)-3-alkoxy-steroids being subjected to mild acid hydrolysis. Alternatively they may be prepared by decarboxylating D 4-3-oxo-steroid-19-acids.