A short and highly stereoselective route to polyhydroxy-perhydroazaazulenes via a C-(d-galacto-pentopyranos-5-yl)isoxazolidine
摘要:
A short and efficient route to enantiomerically pure hexahydroxy- and pentahydroxy-perhydroazaazulenes, ring-homologues of castanospermine, starting from the sole isoxazolidine derivative obtained in the 1,3-dipolar cycloaddition of a D-galactose-derived nitrone and methyl acrylate, is established. The procedure allows both backbone and stereochemical modulation of the products by choice of the starting monosaccharide. Structural assignment was based on crystallographic analysis of the starting isoxazolidine and NMR techniques. The products were tested for inhibitory activity against several glycosidases. (c) 2005 Elsevier Ltd. All rights reserved.
1,3-Dipolar cycloaddition reaction of a d-galactose derived nitrone with allyl alcohol: synthesis of polyhydroxylated perhydroazaazulene alkaloids
摘要:
Diastereofacial intermolecular 1,3-dipolar cycloaddition of D-galactose derived nitrone with allyl alcohol followed by tosylation afforded, in a 1:1 ratio endo- and exo-isooxazolidines 4a and 4b with complete diastereoselectivity at the nitrone carbon. The N-O bond reductive cleavage and S(N)2 displacement afforded the pyrrolidine ring with a galactose appendage that on acetonide cleavage and reductive amino-cyclization afforded pentahydroxylated perhydroazaazulenes 1a and 1b. (C) 2007 Elsevier Ltd. All rights reserved.