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-α-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-α-d-glucofuranose]-acetaldehyde. After deprotection, the pyranose derivatives were
reacted with the precursor [NEt4]2[ReBr3(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.