Carborane Derivatives with Estrogenic Properties

This complex was prepared from 1,12-dicarba-closo-dodecaborane, 15. The coupling of the C-copper derivative of 15 with 4-methoxyiodobenzene gave the mono-C-arylated compound 16, which was then converted to the C-methoxy-carbonyl derivative 17 by reaction of the lithiate of 16 with methyl chloroformate. 

This carborane cage has also been used to prepare complex 19 which, with its dimethylamino chain, identical to that of hydroxytamoxifen, acts as an efficient antiestrogen [68], while complex 20, based on the structure of (Z)-tamoxifen [70] and thus without an O H group, has no affinity whatsoever for the estradiol receptor [71]. 

The in vivo results show that these estrogenic carboranes are capable of specific interaction with the estrogen receptors. However, the reason their therapeutic use is limited seems to be the low level of estradiol receptors present in the cells of target tissues. In fact, taking into accoimt the receptor/cell density, which is of the order of lO -lO, the maximum amoimt of atoms that could be introduced 

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