Deuterium and tritium labeling of carbohydrates and glycoconjugates has very wide applicability in the biochemical and biophysical fields. Carbohydrates function as receptors for a variety of hormones and play critical roles in cell recognition and differentiation. Deuterium labeled compounds are frequently utilized in the conformational analysis of oligosaccharides, as well as other glycoconjugates, to alleviate resonance overcrowding in 1 H NMR spectroscopy.
Raney 1 nickel catalyzed 1 H ! 2 H ( 3 H) isotopic exchange is conducted under mild conditions using either ultrasonic or microwave irradiation. The initial and overall rates of isotopic exchange are modulated by the presence of transition metals. Only the Raneynickel 1 type alloys afforded stereospecific C-1 H ! C-2 H isotopic exchange in an ultrasonic or microwave field. Typical supported precious metal catalysts, supported Ni catalysts, singular metal catalysts, or multi-phasic catalysts were ineffective or caused substrate decomposition.
We have explored new digestion conditions for the preparation of highly active Raney nickel catalysts and have developed new protocols for the stereospecific incorporation of 2 H ( 3 H) in a wide variety of glycoconjugates using our facile C-H ! C-D (C-T) exchange reactions. The regioselectivity of isotope incorporation is controlled by the judicious use of modified catalysts, co-solvents, and the isotopic source.
Reactions are easily performed using either a dedicated ultrasound probe, a slightly modified commercial microwave oven, or a dedicated commercial microwave synthesis unit. Research over the past several years is the subject of this attenuated review.