CYANO SUGARS - SYNTHESIS BY OPENING OF AN EPOXIDE RING IN PENTOFURANOSIDES WITH DIETHYLALUMINUM CYANIDE

Reaction of diethylaluminum cyanide (DEAC) with methyl 2,3-anhydroribo furanosides was examined as a potentially useful method for the introd uction of the cyano group at C-2 and C-3 of furanosyl sugars. Thus, tr eatment of methyl 2,3-anhydro-5-O-benzyl-beta-D-ribofuranoside with DE AC provid ed methyl 5-O-benzyl-3-cyano-3-deoxy-beta-D-xylofuranoside ( 2), while similar treatment of methyl 2,3-anhydro-5-O-benzyl-alpha-D-r ibofuranoside gave a mixture of methyl 5-O-benzyl-3-cyano-3-deoxy-alph a-D-xylofuranoside (5) and methyl 5-O-benzyl-2-cyano-2-deoxy-alpha-D-a rabinofurano side (6). Epimerization of 2 at C-3 was readily effected in the presence of base to give methyl 5-O-benzyl-3-cyano-3-deoxy-beta -D-ribofuranoside (9). In contrast, 5 and 6 were resistant were resist ant to base-promoted epimerization. Sequential acetylation and acetoly sis converted the cyano sugars 2 and 9 into the corresponding tri-O-ac etyl derivatives 13, 14 and 15.