First synthesis of a steroid containing an unstable 19-nor-androsta-1,5-dien-3-one system

Mechanisms involved in the maintenance of human pregnancy and initiation of labour are poorly defined. A novel steroid hormone named estradienolone (ED), and having an unusual 19-nor-androsta- 1,5-dien-3-one system, was previously reported. However, ED is scarcely available from urine, placenta and blood of pregnant women. For this reason, we have synthesized ED in order to verify its proposed structure. Although a 1,5-dien-3-one system had already been described for a C19-steroid (androstane) nucleus (no possible aromatization), the synthesis of the 19-nor-analogue is a major challenge because this system is very sensitive to aromatization. We now describe the successful construction and characterization of this unstable system. Starting from nortestosterone, the synthesis of 17 beta-hydroxy-19-nor-androsta-1,5-dien-3-one (1) is based on a protection of the 5,6-double bond, the introduction of the second 1,2-double bond, the careful recovery of the exo double bond and a final regioselective oxidation or reduction. (c) 2006 Elsevier Ltd. All rights reserved.