Leonardo Puccioni

Double reductive amination of l-arabino-hexos-5-uloses: A diastereoselective approach to 1-deoxy-d-galactostatin derivatives☆

Abstract The double reductive amination of l - arabino -hexos-5-ulose with benzhydrylamine and NaBH 3 CN takes place in a diastereospecific manner giving in moderate chemical yield (36 %) the galactosidase inhibitor 1-deoxy- d -galactostatin. The aminocyclization of 2,6- di -O- benzyl- l -arabino- hexos-5-ulose is more complicated giving results dependent from the type of amine: with ammonia or methylamine a mixture of C-5 epimeric 1-deoxyazapyranoses ( d -galacto l -altro ratio ≈ 4:1 ) is obtained in 45–65% combined yield, while with benzhydrylamine substantial amounts of an acyclic 1-deoxy-1-benzydrylamino-hexitol (10 % yield) is isolated together with the expected 1-deoxy-azasugars of the d - galacto and l - altro series.

Stereoselective Synthesis of 4-O-(2-Acetamido-2-Deoxy-β-D-Talopyranosyl)-D-Glucose Derivatives from Lactose

ABSTRACT The 6-O-trityl derivative of 2,3:5,6:3′,4′-O-isopropylidenelactose dimethyl acetal (1) was converted through an oxidation/oximation/reduction sequence involving the free 2-OH group of the D-galactose moiety into the protected disaccharide 5 in up to 75% yield. The complete deprotection of 5 produced the disaccharide 4-O-(2-acetamido-2-deoxy-β-D-talopyranosyl)-D-glucose (7a). The oxime LiAlH4 reduction step produced some unexpected side-products, the most abundant of which, the dimethyl acetal 9, deriving from cleavage of the D-glucose moiety, was formed only when the reaction was conducted in refluxing THF, but not when Et2O was used as the solvent.