Synthesis and ring-opening reactions of 4-chloro-4-deoxy-α-d-galactopyranosyl 3,4-anhydro-1,6-dichloro-1,6-dideoxy-β-d-lyxo-hexulofuranoside

Treatment of 4-chloro-4-deoxy-alpha-D-galactopyranosyl 1,6-dichloro-1,6-dideoxy-beta-D-fructofuranoside (1) with 2.3 mol. equiv. of diethyl azodicarboxylate (DEAD) and 1.3 mol. equiv. of triphenylphosphine (TPP) in toluene gave a mixture of 3,6-anhydro-4-chloro-4-deoxy-alpha-D-galactopyranosyl 3,4-anhydro-1,6-dichloro-1,6-dideoxy-beta-D-lyxo-hexulofuranosi de (2, 55%) and 4-chloro-4-deoxy-alpha-D-galactopyranosyl 3,4-anhydro-1,6-dichloro-1,6-dideoxy-beta-D-lyxo-hexulofuranosi de (3, 35%). Compound 3 was also synthesised from 6-O-tert-butyldiphenylsilyl-4-chloro-4-deoxy-alpha-D-galactopyrano syl 1,6-dichloro-1,6-dideoxy-beta-D-fructofuranoside by epoxidation with DEAD-TPP and removal of the silyl ether group with tetrabutylammonium fluoride. The SN2 reactions of 2,3,6-tri-O-acetyl-4-chloro-4-deoxy-alpha-D-galactopyranosyl 3,4-anhydro-1,6-dichloro-1,6-dideoxy-beta-D-lyxo-hexulofuranosi de (5) with fluoride, chloride, bromide, iodide, and azide ions gave the corresponding 4'-derivatives 10, 12, 14, 18, and 20, respectively. Reduction of 4-chloro-4-deoxy-alpha-D-galactopyranosyl 4-bromo-1,6-dichloro-1,4,6-trideoxy-beta-D-fructofuranoside (15) gave 4-chloro-4-deoxy-alpha-D-galactopyranosyl 1,6-dichloro-1,4,6-trideoxy-beta-D-fructofuranoside (16). A similar reduction of 4-chloro-4-deoxy-alpha-D-galactopyranosyl 4-azido-1,6-dichloro-1,4,6-trideoxy-beta-D-fructofuranoside (21) gave 4-chloro-4-deoxy-alpha-D-galactopyranosyl 4-amino-1,6-dichloro-1,4,6-trideoxy-beta-D-fructofuranoside (22).