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The nitrone 4 (4,5-dideoxy-4-hydroxylamino-3,4-O-isopropylidene-L-lyxofuranose) was synthesised from D-ribose and used as key intermediate for the preparation of fucosidase inhibitors. We describe two transformations of 4. Hydrolysis with aqueous sulfur dioxide gave the known potent nanomolar inhibitor 4-amino-4,5-dideoxy-L-lyxofuranose (3). 1,3-Dipolar cycloaddition with enol ethers led to the related 1,2,5,6-tetradeoxy-2,5-imino-L-altroheptonic ester 2a, acid 2b and the corresponding heptitol 2c. The new iminosugars have been evaluated for their inhibitory activity against α-L-fucosidase from bovine kidney. The alcohol 2c turned out to be a potent inhibitor in the same range as the amino-sugar 3 (K(i)=8 vs 10nM).

Pyrrolidine amino-sugars, cyclic iminoalditols as well as linear aminoalditols in 4-amino- l -erythrose and 4-amino-5-deoxy- l -ribose series were synthesised by asymmetric hetero-Diels–Alder reaction followed by chemical transformations. 4-Amino-4-deoxy- l -erythrose and 4-amino-4,5-dideoxy- l -ribose were potent β- d -glucosidase, α- d -mannosidase, α- and β- d -galactosidase inhibitors. We have shown that the ribose derivative was a very potent inhibitor of α- d -mannosidase.