X-ray and 13C CP MAS investigations of structure of two genistein derivatives

Structural and spectroscopic properties of two distinctly different derivatives of genistein (1), ionic and covalent, engaging the most acidic of its three phenolic functions, have been investigated. Both the 7-O-silyl ether (2), and ammonium salt (3), are stable solids, considered to be useful intermediates for achieving further chemical transformations in a manner securing highly regioselective outcome. It turned out that these two molecules contain genistein structural fragment involved in many intra- and intermolecular hydrogen bonds. In the case of 2, some infinite chains of coupled intra- and intermolecular hydrogen bonds are formed supported by hydrogen bonding to water molecules. In the structure of 3, a helical arrangement of genistein moieties is formed with the cations kept in voids. Single crystal X-ray diffraction shows that the aromatic ring B in both structures is rotated with respect to the AC fused rings of the chromenone moiety by ca. 36degrees (2) and 50degrees (3). Both new compounds crystallise as monohydrates. The number of peaks observed in the solid-state C-13 spectra of 2 and 3 corresponds to the number of magnetically non-equivalent carbons and it is in satisfactory agreement with the X-ray crystal structures of both genistein derivatives. (C) 2004 Elsevier B.V. All rights reserved.