Spectroscopic studies and PM5 semiempirical calculations of new Schiff bases of gossypol with amino derivatives of crown ethers

摘要

Two Schiff's bases of racemic gossypol with amino derivatives of crown ethers were synthesised and studied by FT-IR and H-1 NMR spectroscopy, while their structures were calculated by the PM5 semiempirical method. These studied Schiff's bases exist in the solid state and in solutions as enamine forms. In the solid state the interactions between OH groups in the 6, 6' positions and oxygen atoms of the crowns are dependent on the crown size whereas in solutions they are not. These interactions are very well evidenced in the FT-IR and H-1 NMR spectra. In the H-1 NMR spectra the existence of two enantiomers of the Schiff's bases are well visible. The structures of the Schiff's bases and the strength of the hydrogen bonds within these structures are discussed. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 34]