Synthesis of (+)-3,7,8-trideoxy-3,7-imino-d-threo-l-galacto-octitol and its inhibition of β-glucosidases

The readily available 2,3:6,7-di-O-sopropylidene-d-glycero-heptono-1,4-lactone [(−)-5] was converted in four synthetic steps into the new iminooctitol (+)-3,7,8-trideoxy-3,7-imino-d-threo-1-galacto-ocitol [(+)-10]. Although the piperidine unit of (+)-10 has the absolute configuration of β-d-galacto-hexopyranosides, this iminoalditol does not inhibit five commercially available β-galactosidases. However, (+)-10 was found to be a good competitive inhibitor of β-glucosidases from almond (K1 = 15 μM) and from Caldocellum saccharolyticum (K1 = 41 μM).