Hydrazinolysis of monosaccharides: a two-step synthesis of chiral pentane-1,2,3-triols from pentoses and observations on the hydrazinolysis of glycoproteins and glycopeptides

1,2-Dideoxyalditols, the corresponding 1-alkenes, and 1-deoxyalditols are formed in various proportions from d-glucose, d-mannose, l-arabinose, and d-xylose by the action of refluxing hydrazine. Sequential hydrazinolysis, catalytic hydrogenation, and chromatography afford a route to 1,2-dideoxyalditols. For example, 1,2-dideoxy-l-erythro-pentitol is formed from l-arabinose in 42% yield, and d-xylose is a source of 1,2-dideoxy-d-threo-pentitol (50%). Under the conditions (anhydrous hydrazine at 100° for 30 h in the absence of air) used by Montreuil for the hydrazinolysis of glycoproteins and glycopeptides, no 1,2-dideoxyalditol was formed; degradation was incomplete, there being some aldose hydrazone present. Under Kochetkov's hydrazinolysis conditions (105° for 10 h with hydrazinium sulphate), less degradation occurred and the product from d-galactose was identified as 1-deoxy-d-tagatose hydrazone.