InCl3–CH3CN–H2O: an efficient catalyst-solvent combination for the synthesis of Perlin aldehydes and related compounds. Application in the synthesis of unnatural l-azasugars

InCl3–CH3CN–H2O has been found to be an efficient catalyst-solvent combination for the synthesis of Perlin aldehydes and related compounds. While acetylated glycals afforded the Perlin aldehydes directly with InCl3 and water, benzylated glycals on the other hand provided the hemiacetals under identical condition. The methodology reports a non-mercurial approach to Perlin aldehydes. Noteworthy is that this reaction is more facile as well as highly selective with glycals possessing a hydroxyl as a leaving group than with a benzyloxy group. Extension of this reaction to 2-C-hydroxymethyl glycals resulted in the formation of the corresponding hemiacetals, which were further transformed in to unsaturated azasugars with an exo-methylene group at C-2 position. Glycosidase inhibition studies reveal that these compounds display selectivity in inhibiting glucosidases rather than galactosidases.