3‐(2‐Furyl)‐2‐sulfanylpropenoic Acid as a Chelating Agent for Lead(II) and Diorganonolead(IV) Compounds – Chemical Behaviour and In Vitro Protective Effect against Dimethyllead(IV) Toxicity

Abstract

The reaction of the title acid (H2fspa) with lead(II) acetate and dimethyl‐ or diphenyllead(IV) acetate in alcoholic medium gives the 1:1 complexes [Pb(fspa)] and [PbR2(fspa)] (R = Me, Ph). When the reaction was carried out in the presence of diisopropylamine (Q), the [HQ]2[Pb(fspa)2] and [HQ]2[PbPh2(fspa)2] derivatives formed in low yield. Additionally, the compounds Na[PbMe2(OAc)3], [PbPh2(fspa)(DMSO)] and [PbPh2(fspa)(DMSO)]·DMSO were also isolated as crystalline solids in subsequent crystallization processes. All these compounds were characterized by IR and NMR (1H and 13C) spectroscopy and, in some cases, by X‐ray diffractometry and 207Pb NMR spectroscopy. Pig renal proximal tubule LLC‐PK1 culture cells were used to determine in vitro the nephroprotective effect of H2fspa, [HQ]2[Zn(fspa)2], vitamin B1 and vitamin B6 against PbMe2(NO3)2 toxicity. The beneficial effects of the acid, the zinc(II) complex and/or their combinations with vitamin B1 (thiamine nitrate) are described.

The Chelating Behaviour of 3‐(4‐X‐Phenyl)‐2‐sulfanylpropenoic Acids with the PbII Ion – Relevance of the Lone Electron Pair in the Supramolecular Structures of the 2:1 Complexes

“…This study shows (vide . These values are close to those found previously in similar complexes [13,14,31] and, bearing in mind the effect of the hydrogen bond, [32] fall inside the general range for monodentate carboxylate groups. [33] The lower value found for the F derivative, 188, can be attributed to the presence in the lattice of a stronger hydrogen bond, though the participation of the carboxylate group in some additional interaction cannot be ruled out.…”

“…A septuplet and a doublet at high field in the spectra were assigned to the -C(H) and CH 3 groups of the diisopropylammonium cation, and the very broad signal at δ ≈ 8 ppm was ascribed to the NH 2 + moiety of [HQ] + . As could be expected, in the 13 C NMR spectra of the ligands an important dependence of the position of the C(7) signal on the nature of the para-X atom was observed. In the complexes, the S coordination was confirmed by the large deshielding of C(2) with respect to the corresponding ligands, [13,14,34,39] and the large downfield shift of C(1) provided evidence for the coordination of the carboxylate group.…”

“…The synthesis and characterization of H 2 (CH 3 O-pspa) were described previously. [ 13 6 ]DMSO): δ = 169.9 (C-1), 118.9 (C-2), 125.7 (C-3), 134.0 (C-4), 131.8 (C-5 and C-9), 115.6 (C-6 and C-8), 158.4 (C-7) ppm.…”

“…The NMR signals (see Experimental Section) were assigned by considering previous data for rhodanines, [38] sulfanylpropenoic acids [34,35] and complexes, [13,14,34,39] and on the basis of gradient heteronuclear multiple quantum coherence (gHMQC) and gHMBC experiments when necessary. Freshly prepared solutions of [D 6 ]DMSO were used to record the spectra, but even under these conditions H 2 (Ipspa) evolved very rapidly to give new species (possibly the disulfide), which were not fully characterized.…”

“…H 2 (I-pspa) behaves as a neuroprotective agent because it inhibits calpain, a class of protease located within the cell, in the cytosol. [12] We describe here the solubility and spectroscopic and structural characteristics of the Pb II complexes formed by H 2 (X-pspa) To the best of our knowledge, previous research in this field has been limited to the preparation of the related Pb II complexes with 3-(2-furyl)-2-sulfanylpropenoic acid, [13] 3-(phenyl)-2-sulfanylpropenoic acid [14] and 3-(phenyl)-3-(methyl)-2-sulfanylpropenoic acid. [15] Results and Discussion…”