The hexacarbonyl(ethyne)dicobalt unit: An androgen tag

The interaction of estrogens and androgens with their corresponding receptors is known to play an important role in cancers of the breast and prostate. This paper reports the synthesis, characterization, and biochemical properties of a novel organometallic complex derived from 17α-ethynyltestosterone, namely hexacarbonyl{μ[(20,21-η:20,21-η])-(17α)-17- hydroxypregn-4-en-20-yn-3-one}dicobalt ([Co₂(CO)₆(17α-ethynyltestosterone)]). The crystal and molecular structure of this compound was determined by single-crystal X-ray diffraction: it crystallizes in the monoclinic space group with a = 24.6600(18) Å, b = 12.9188(10) Å, c = 26.3573(19) Å, β = 108.651(2)°, and Z = 12. A biochemical study showed that the compound is still recognized by the androgen receptor even when the relative binding affinity (RBA) is quite low (0.5%). This finding can be explained by the recently published 3D structure of the androgen receptor that shows that its binding site cannot accommodate a bulky substituent at the 17α position of the steroid.