Graphical abstract Highlights • Synthesis of N -alkylated 1-deoxyfuconojirimycins as α-fucosidase inhibitors. • N -Decyl-1-deoxyfuconojirimycin was toxic towards various cancer cells. • Development of homology models for fucosidases from bovine and human origin. Abstract 1,5-Dideoxy-1,5-imino- l -fucitol (1-deoxyfuconojirimycin, DFJ) is an iminosugar that inhibits fucosidases. Herein, N -alkyl DFJs have been synthesised and tested against the α-fucosidases of T. maritima (bacterial origin) and B. taurus (bovine origin). The N -alkyl derivatives were inactive against the bacterial fucosidase, while inhibiting the bovine enzyme. Docking of inhibitors to homology models, generated for the bovine and human fucosidases, was carried out. N -Decyl-DFJ was toxic to cancer cell lines and was more potent than the other N -alkyl DFJs studied. [ABSTRACT FROM AUTHOR]