Synthesis of a potent aminocyclitol α-mannosidase inhibitor, 1 -(1,2,3,5/4)-5-amino-4-O-methyl-1,2,3,4-cyclopentanetetrol

Demethylthio-, de-S-methyl-, and ethylthio-derivatives of the α-mannosidase inhibitor, mannostatin A, have been synthesized and evaluated for their inhibition of Jack bean α-mannosidase in order to elucidate the roles of the methylthio group. All derivatives had lowered inhibitory potentials. However, a mannostatin A analogue with a methoxyl instead of the methylthio, exhibited about 2-fold enhancement of the activity, indicating an importance for the methyl group rather than the sulfur atom.