Synthesis, characterization and reactivity of carbohydrate platinum(iv) complexes with thioglycoside ligands

Abstract

Reactions of fac-[PtMe3(4,4′-R2bpy)(Me2CO)][BF4] (R = H, 1a; tBu, 1b) and fac-[PtMe3-(OAc-κ2O,O′)(Me2CO)] (2), respectively, with thioglycosides containing thioethyl (ch-SEt) and thioimidate (ch-STaz, Taz = thiazoline-2-yl) anomeric groups led to the formation of the carbohydrate platinum(IV) complexes fac-[PtMe3(4,4′-R2bpy)(ch*)][BF4] (ch* = ch-SEt, 8–14; ch-STaz, 15–23) and fac-[PtMe3(OAc-κ2O,O′)(ch*)] (ch* = ch-SEt, 24–28; ch-STaz = 29–35), respectively. NMR (1H, 13C, 195Pt) spectroscopic investigations and a single-crystal X-ray diffraction analysis of 19 (ch-STaz = 2-thiazolinyl 2,3,4,6-tetra-O-benzoyl-1-thio-β-d-galactopyranose) revealed the S coordination of the ch-SEt glycosides and the N coordination of the ch-STaz glycosides. Furthermore, X-ray structure analyses of the two decomposition products fac-[PtMe3(bpy)(STazH-κS)][BF4] (21a) and 1,6-anhydro-2,3,4-tri-O-benzoyl-β-d-glucopyranose (23a), where a cleavage of the anomeric C–S bond had occurred in both cases, gave rise to the assumption that this decomposition was mediated due to coordination of the thioglycosides to the high electrophilic platinum(IV) atom, in non-strictly dried solutions. Reactions of fac-[PtMe3(Me2CO)3][BF4] (3) with ch-SEt as well as with ch-SPT and ch-Sbpy thioglycosides (PT = 4-(pyridine-2-yl)-thiazole-2-yl; bpy = 2,2′-bipyridine-6-yl), having N,S and N,N heteroaryl anomeric groups, respectively, led to the formation of platinum(IV) complexes of the type fac-[PtMe3(ch*)][BF4] (ch* = ch-SEt, 36–40, ch-SPT 42–44, ch-Sbpy 45, 46). The thioglycosides were found to be coordinated in a tridentate κS,κ2O,O′, κS,κN,κO and κS,κ2N,N′ coordination mode, respectively. Analogous reactions with ch-STaz ligands succeeded for 2-thiazolinyl 2,3,4-tri-O-benzyl-6-O-(2,2′-bipyridine-6-yl)-1-thio-β-d-glucopyranoside (5h) resulting in fac-[PtMe3(ch-STaz)][BF4] (41, ch-STaz = 5h), having a κ3N,N′,N″ coordinated thioglycoside ligand.

A first-principles exploration of the conformational space of sodiated pyranose assisted by neural network potentials

“…Their complexes with metal ions are often found in a variety of biological processes such as cell-cell adhesion, molecular recognition, protein-sugar binding, stabilization of membrane structures, and the transport and storage of metal ions. [1][2][3][4][5][6] The extensive range of functions of the metal ioncarbohydrate complexes in biochemistry are associated with their structural diversity which is related to their conformational flexibilities, hydrogen-bonding networks and multiple binding sites of the metal cations.…”

Discrimination of chiral copper(ii) complexes upon binding of galactonoamidine ligands

“…[12][13][14][15] Further studies reveal formation of carbohydrate platinum(IV) complexes with thioglycoside ligands and their use to switch the selectivity of carbohydrate building blocks. 16,17 More details and additional reports including complex formation between carbohydrates and transition metal or lanthanide ions may be found elsewhere. 11,[18][19][20][21][22][23][24][25][26][27][28][29][30] In this context, we disclose here for the first time a study to evaluate the coordination between a putative transition state analog of the glycoside hydrolysis and metal complexes.…”

Sugar–Metal Ion Interactions: The Complicated Coordination Structures of Cesium Ion with d-Ribose and myo-Inositol

“…The interactions between metal ions and carbohydrates are involved in many important biochemical processes. − It has also been exploited in metal-catalyzed enantioselective synthesis, therapeutic agents, catalysts and diagnostic tracers, etc. − Different saccharides have various coordination modes and some conformations; for example, ax - eq - ax conformations usually are favored for metal ion coordination …”