Novel 13β- and 13α-D-homo steroids: 17a-carboxamido-D-homoestra-1,3,5(10),17-tetraene derivatives via palladium-catalyzed aminocarbonylations.

17a-Methoxycarbonyl- and 17a-carboxamido-D-homoestra-1,3,5(10),17-tetraene derivatives were synthesized by palladium-catalyzed carbonylation reactions of the corresponding 17a-iodo-D-homoestra-1,3,5(10),17-tetraene derivatives using methanol and various amines as O- and N-nucleophiles, respectively. Both the natural (13β) and the epi (13α) series of compounds were isolated. The 17a-iodo-17-ene functionalities in the two 13-epimer series differ in reactivity. While the aminocarbonylations were practically complete in the 13β series in reasonable reaction time under mild conditions and high isolated yields were achieved, the corresponding 13α-17a-iodo-17-ene substrate has shown decreased reactivity resulting in moderate to low yields. However, under high carbon monoxide pressure (40 bar) excellent yields can be obtained even in the 13α series. The aminocarbonylation was completely chemoselective in both series, i.e., the corresponding 17a-carboxamido-17-ene derivatives were formed exclusively.