Functionalization of Glucose at Position C-3 for Transition Metal Coordination: Organo-Rhenium Complexes with Carbohydrate Skeletons

Novel 3-O-[1,2;5,6-di-O-isopropylidene-alpha-D-glucofuranose] and 3-O-[D-glucose] derivatives with an iminodiacetate (N,O,O), a histidinate, and an N-(acetetyl)picolylamine (N,N,O) chelating system for tridentate coordination of the organometallic M(CO)(3)-fragment (M = Tc, Re) have been prepared. The chelates were introduced and assembled through reductive amination starting from 3-O-[1,2;5,6-di-O-isopropylidene-alpha-D-glucofuranose]-acetaldehyde. After deprotection, the pyranose derivatives were reacted with the precursor [NEt(4)](2)[ReBr(3)(CO)(3)] to afford the corresponding organometallic complexes in yields between 54% and 94%. The NMR, MS, and IR analyses corroborated the tridentate coordination of the organometallic metal center exclusively via the synthetic chelates. In the case of the N-(acetyl)picolylamine derivative, the coordinative properties were further confirmed by X-ray structure analysis of the first Re(CO)(3)-D-glucofuranose complex. All glucose complexes unveiled good stability and solubility in organic and aqueous media.