A boron-containing estrogen mimic.

A prototype of a new class of 2,3,1-benzodiazaborine-based estrogen mimics is described. 1,2-Dihydro-1,6-dihydroxy-2-(2-methoxy-6-pyridyl)-2,3,1-benzodiazabor ine, (6), was obtained as a crystalline monohydrate (C13H12BN3O3.H2O) after regioselective BBr3-mediated O-demethylation of the condensation product formed from 2-formyl-4-methoxybenzeneboronic acid and 2-hydrazino-6-methoxypyridine. As intended by design, the solid-state structure of (6) features an intramolecular hydrogen-bond association between the donor B--OH group and the acceptor pyridine ring N, a connection which constitutes an additional 'virtual' six-membered ring, thereby providing for an overall topography closely matching that of a tetracyclic steroid. Specifically, prototype (6) can be viewed as a boron-containing mimic of the O17-methyl ether derivatives of dihydroequilenin or estradiol.