A synthesis of the anomeric spiro-epoxide 15 from D-fructose, in 7-ste
ps in an overall 13% yield, is described. The key intermediate in the
synthesis, -tri-O-benzyl-1-deoxy-1-iodo-beta-D-fructopyranose (14), wa
s prepared from the corresponding methyl (14), was prepared from the c
orresponding methyl fructopyranoside by reaction with the iodine-triph
enylphosphine-imidazole reagent complex, followed by acid hydrolysis.
Ring closure of the iodohydrin 14 was achieved under extremely mild co
nditions on treatment with silver(I) oxide in anhydrous THF. The C-13
NMR spectrum of 15 exhibited a large upfield shift of the resonances a
ssigned to C-1 and C-2, indicative of an oxirane ring involving these
two carbon atoms.