Multinuclear magnetic resonance, electrospray ionization–mass spectroscopy, and parametric method 5 studies of a new derivative of gossypol with 2‐thiophenecarbohydrazide as well as its complexes with LI⁺, Na⁺, K⁺, RB⁺, and Cs⁺ cations

Abstract

A new derivative of racemic gossypol with 2-thiophenecarbohydrazide (GHHT) and its complexes with monovalent cations have been synthesized and studied by electrospray ionization-mass spectroscopy (ESI-MS), multinuclear nuclear magnetic resonance (NMR), as well as by the Parametric Method 5 (PM5) methods. It is demonstrated that GHHT forms stable complexes of 1:1 stoichiometry with monovalent metal cations. The structures of the complexes are stabilized by three types of intramolecular hydrogen bonds. The spectroscopic methods have provided clear evidence that GHHT and its complexes exist in the DMSO-d6 solution in the N-imine-N-imine tautomeric forms. The structures of the GHHT and its complexes with Li+, Na+, K+, Rb+, and Cs+ cations are visualized and discussed in detail.

Synthesis, crystal structures and antibacterial activity studies of aza-derivatives of phytoalexin from cotton plant – gossypol

“…In the spectrum of GOS the signal of C(7) carbon atom was found at 155.6 ppm in CDCl 3 [54] and at 151.4 ppm in CD 3 CN [55], whereas the signal of C(7) carbon atom in the spectra of 19-27 was in the range 150.1-157.3 ppm ( Table 5). The chemical shift of the C(7) signals of gossypol hydrazones (19)(20)(21)(22)(23)(24)(25)(26)(27), similar to those of GOS, are in the range characteristic of the C-OH carbon atoms of phenols [46,[56][57][58][59]. This result shows clearly that gossypol hydrazones are present in the N-imine-N-imine tautomeric form, which is analogous to the aldehyde-aldehyde form of GOS (Scheme 1).…”

“…This result indicates clearly that the Schiff bases studied occur in the enamineenamine tautomeric form irrespectively of the kind of solvent and substituent they have. The appearance of a singlet at about 10 ppm in all spectra of gossypol hydrazones (19)(20)(21)(22)(23)(24)(25)(26)(27) assigned to the C(11)-H protons is the evidence of formation of a tautomeric form different than that observed for the gossypol Schiff bases, i.e. the Nimine-N-imine form.…”

“…The limited antibacterial activity of gossypol can be probably concerned with the relatively poor ability to form complexes with the monovalent cations such as Na þ or K þ [31]. In our earlier papers we have reported the synthesis and the physicochemical properties of some Schiff bases or hydrazones of gossypol [14,19,32,33]. The complexation of biologically important monovalent metal cations such as Na þ and K þ , by aza-derivatives of gossypol has been proved and described in detail [34,35].…”

“…For this reason the syntheses and tests of gossypol derivatives, in which both aldehyde groups are blocked, are desired to enable their application as drugs. Up to now many gossypol derivatives including its Schiff bases, periacetylated gossylic nitriles, periacetylated gossylic imino-lactones, azo-derivatives, hydrazones, thioderivatives of gossypol have been obtained [13][14][15][16][17][18][19] and tested for their antipsoriatic [20], antimalarial [21], anticancer [22,23], interferon-inducing [24] as well as anti-HIV [25] activity. Earlier studies have shown that the activity of gossypol is rather bacteriostatic than antibacterial [26][27][28] although gossypol structural analogues like hemigossypol, 2,7-dihydroxycadalene, lacinilene and their respective 7-methyl esters have shown very promising antibacterial activity [29,30].…”

X-ray, FT-IR, ESI MS and PM5 studies of Schiff base of gossypol with allylamine and its complexes with alkali metal cations and perchlorate anion

“…Recently, we have studied derivatives of gossypol, which are able to complex the monovalent and divalent metal cations [20][21][22], such as the Schiff base of gossypol with allylamine, described here. The two allyl moieties within this Schiff base can change the complexation ability towards metal cations relative to that of gossypol.…”