Structure of a New Schiff Base of Gossypol with Ethyl 4-Amino-1-piperidiiie Carboxylase in the Solid and in the Solution

摘要

Crystals of the Schiff base derivative of gossypol with ethyl 4-amino-l-piperidine carboxylate (GSPC) have been grown and subsequently examined by X-ray diffraction, FT-IR and NMR methods. The crystal space group is P21 with a = 11.869(1) A, b = 13.540(1) A, c = 28.119(1) A, P = 91.22(1)° and Z = 4. In the crystal GSPC exists in the enamine-enamine tautomeric form. The intramolecular N(16)~H(16)…O(2), N(16')-H(16')…O(2') hydrogen bonds assisted by the resonance of the re-electrons in the aromatic system are the strongest. The FT-IR spectral features of the crystals are in agreement with the X-ray data indicating that both parts of the molecule are similarly intramolecular hydrogen-bonded but different intermolecular hydrogen-bonded, although the molecule is symmetrically substituted. The FT-IR as well as ~1H and ~(13)C NMR spectra have shown that in chloroform solution the enamine-enamine tautomeric form is preserved and the whole structure of GSPC becomes more symmetrical.