A highly stereoselective synthesis of 1-amino-2,5-anhydro-1-deoxyhexitols via 2-trifluoromethyl-oxazolinium intermediates

A series of 1-amino-2,5-anhydro-1-deoxyalditols, namely derivatives of 1-amino-2,5-anhydro-1-deoxy-D-glucitol, -D-mannitol and -D-talitol was prepared from the corresponding 1-deoxy-1-trifluoroacetamidohexitols by treatment with anhydrous hydrogen fluoride. The reaction was also performed on 1,3-dideoxy-1-trifluoroacetamido-D-ribo-hexitol and 1-deoxy-1-trifluoroacetamido-L-rhamnitol which both gave the expected C-2 inverted anhydrides. The reaction mechanism involves 2-trifluoromethyl-oxazolinium intermediates, which further undergo intramolecular attack of HO-5 at C-2 with inversion of the configuration. The reaction is stereospecific and highly regioselective. The crystal structure of 1-amino-2,5-anhydro-1-deoxy-D-glucitol hydrochloride is presented. (C) 1997 Elsevier Science Ltd.