Several fully protected 3,4-O-isopropylidene derivs. of 1,5-anhydro-D-galactitol have been converted into the corresponding 2,6-anhydro-3-deoxy-L-threo-hex-2-enitols through an elimination of acetone promoted by t-BuOk in DMSO, and into the parent compd. (L-2-sorbal) by further hydrolytic removal of methoxyisopropyl (MIP) protecting groups. This method provides an easy access to endocyclic glycals of ketopyranoses, a hitherto completely neglected class of unsatd. sugars that can be useful synthetic intermediates. Their reaction with MCPBA in MeOH, gave, in a regio- and diastereospecific manner, derivatives of methyl alfa-L-tagatopyranoside, from which L-tagatose was obtained by debenzylation and hydrolysis. Structures and conformations of new comounds were confirmed through NMR and computational methods
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