Carbohydrate Binding to VO³⁺. Sugar Vanadate Esters Incorporating l-Amino Acid Schiff Bases as Coligands

Abstract

The glycosides methyl-2,6-dimethoxy-beta-D-galactopyranoside (beta-D-H(2)Me(3)GP), methyl-4,6-dimethoxy-alpha-D-mannopyranoside (alpha-D-H(2)Me(3)MP), and methyl-5-methoxy-beta-D-ribofuranoside (beta-D-H(2)Me(2)RF) have been synthesized, and their reaction with VO(L-Asal)(OMe)(OHMe) in dichloromethane has afforded esters of the type VO(beta-D-HMe(3)GP)(L-Asal), VO(alpha-D-HMe(3)MP)(L-Asal), and VO(beta-D-HMe(2)RF)(L-Asal) as dark-colored solids (red in solution). Here, L-Asal(2)(-) is the deprotonated salicylaldimine of L-alanine (A = a), L-valine (A = v), and L-phenylalanine (A = p). The X-ray structures of VO(beta-D-HMe(3)GP)(L-vsal).H(2)O and VO(alpha-D-HMe(3)MP)(L-psal).H(2)O have revealed five-membered (O,O)-chelation by monoionized carbohydrates, the undissociated hydroxyl group lying trans to the oxo oxygen atom. In the carbohydrate frame, the alkoxidic oxygen atom is axial in the former ester and equatorial in the latter. The V-O(alkoxidic) and V-O(alcoholic) distances are, respectively, approximately 1.80 and approximately 2.30 Å. The ONO coordinating tridentate salicylaldimine ligand is folded (by approximately 35 degrees ) along a C-N bond. The chiral configuration of the metal site corresponds exclusively to the endo disposition of the V=O and the amino acid C-R (R = Me, CHMe(2), CH(2)Ph) bonds. In VO(beta-D-HMe(3)GP)(L-vsal).H(2)O two ester molecules constitute the asymmetric unit and these along with the two water molecules form a macrocyclic supramolecule (diameter, approximately 6.1 Å) held by hydrogen bonds involving alcohol and an OMe function as well as water (O.O distance, 2.59-2.86 Å). On the other hand, in VO(alpha-D-HMe(3)MP)(L-psal).H(2)O the water molecule bridges two symmetry-related ester molecules via alkoxide.water and alcohol.water hydrogen bonds forming an infinite chain structure (O.O lengths, 2.65 and 2.85 Å). The molecular structures observed in the solid state are preserved in solution ((1)H and (51)V NMR). No isomerization is detectable either at the metal site or at the anomeric carbon atom, and the V-O(alkoxidic) and V-O(alcoholic) sites and the metal-carbohydrate binding remain in tact. The VO(beta-D-HMe(2)RF)(L-Asal) species did not afford single crystals but NMR results are consistent with (O,O)-chelation by the ribose fragment, the alkoxidic carbon being C3. Crystal data are as follows. VO(beta-D-HMe(3)GP)(L-vsal).H(2)O: chemical formula, C(21)H(32)NO(11)V; crystal system, orthorhombic; space group, P2(1)2(1)2(1); a = 13.146(7) Å, b = 15.142(5) Å, c = 25.631(9) Å; Z = 8. VO(alpha-D-HMe(3)MP)(L-psal).H(2)O: chemical formula, C(25)H(32)NO(11)V; crystal system, monoclinic; space group, P2(1); a = 13.645(4) Å, b = 7.022(2) Å, c = 15.500(4) Å; beta = 113.98(2) degrees; Z = 2.

Fifteen years of dancing with vanadium

“…Many different classes of vanadium(V) alkoxides now exist, and the reader is referred to the Cambridge Crystallographic Data Centre [1,[3][4][5][10][11][12][13][14]16,17,[86][87][88][89][90]. The Rosenthal group [91,92] has recently reported an interesting example of this type of chemistry.…”

Thirty years through vanadium chemistry

“…As mentioned above, other researchers made also relevant contributions in this same field, such as Fujita [105], Rehder [110,111,130,131], Casella [132], Chakravorty [112,113,[133][134][135], and others [136][137][138], in some cases reporting peculiar characteristics of the compounds or catalytic activity.…”

Two galactomannan preparations from seeds from Mimosa scabrella (bracatinga): Complexation with oxovanadium(IV/V) and cytotoxicity on HeLa cells

“…Therefore, in the present work, pure complexes were obtained from different preparations of the same polymer, which presented stability in a range of temperature interesting in terms of biological studies. In addition, it is also interesting to characterize the interaction between the oxovanadium (VO 3+ ) ion with polysaccharides, since the complexation among monosaccharide derivatives and oxovanadium (VO 3+ ) ion has already been described [65].…”