Synthesis and reactions of leucrose and its exocyclic glycal.

5-O-alpha-D-Glucopyranosyl-beta-D-fructopyranose (leucrose, 1) was transformed into 3,4-di-O-acetyl-1-O-methanesulfonyl-5-O-(2,3,4-tri-O-acetyl-6-O-methanes ulfonyl-alpha-D-glucopyranosyl)-beta-D-fructopyranosyl bromide (3) and 1,3,4-tri-O-benzoyl-5-O-(2,3,4,6-tetra-O-benzoyl-alpha-D-glucopyranosyl) -beta-D-fructopyranosyl bromide (8), which were converted into derivatives (8 and 9) of 2,6-anhydro-1-deoxy-5-O-alpha-D-glucopyranosyl-D-arabino-hex-1-enitol . Hydrogenation of 8 and 9 gave the corresponding anhydroalditol derivatives. N-Iodosuccinimide-mediated glycosylation of 9 with 1,2,3,4-tetra-O-acetyl-beta-D-glucopyranose gave 1,2,3,4-tetra-O-acetyl-6-O-[3,4-di-O-benzyl-1-deoxy-1-iodo-5-O-(2,3,4,6- tetra-O-benzoyl-alpha-D-glucopyranosyl)-beta-D-fructopyranosyl]- beta-D-glucopyranose (12). Some amino, acetylated, and isopropylidene derivatives of leucrose have been prepared and characterised.