SYNTHESIS OF (-CASTANOSPERMINE AND 1-EP ICASTANOSPERMINE FROM D-GLUCOFURANURONO-6,3-LACTONE BY REFORMATSKY REACTION())

Starting from thylsilyl)-1,2-O-isopropylidene-alpha-D-gluco-(2a) or -b eta-L-idofuranurono-6,3-lactone (2b), 7-deoxyoctofuranose derivatives 5a, 5b, 7a and 7b have been synthesized by chain extension at C-6 by R eformatsky reaction followed by reduction with calcium borohydride. Th e respective configuration of the products was determined by transform ation into the known 7,8-dideoxyoctofuranoses 5o, 5p, 7k and 7l. From the mixture of 7a and 7b, formed in a proportion of approximately 4:1, the glycosidase inhibitors (+)-castanospermine (1a) and 1-epicastanos permine (1b) have been prepared in 8 and 9 simple steps, respectively, in overall yields of 33.4 and 9.5%.