Abstract
Bromoacetylation of methyl 2,4-di-O-benzoyl-3-deoxy-3-fluoro-.beta.-D-galactopyranoside, followed by the cleavage of the methoxy group from the resulting 6-O-bromoacetyl derivative 2 with 1,1-dichloromethyl methyl ether gave 2,4-di-O-benzoyl-6-O-bromoacetyl-3-deoxy-3-fluoro-.alpha.-D-galactopyranosyl chloride (3). Reaction of 3 with methyl 2,3,4-tri-O-benzoyl-.beta.-D-galactopyranoside promoted by silver trifluoromethanesulfonate afforded methyl O-(2,4-di-O-benzoyl-6-O-bromoacetyl-3-deoxy-3-fluoro-.beta.-D-galacto-pyranosyl)-(1 .fwdarw. 6)-2,3,4-tri-O-benzoyl-.beta.-D-galactopyranoside (5). O-Debromoacetylation of 5 with thiourea gave the disaccharide nucleophile 6 which was condensed with 2,3,4,6-tetra-O-benzoyl-.alpha.-D-galactopyranosyl bromide to afford the expected .beta.-(trans)-linked trisaccharide derivative 7. Debenzoylation of 7 gave the methyl .beta.-glycoside 8 of the (1 .fwdarw. 6)-linked D-galactotriose having the HO-3 of the internal residue replaced by a fluorine atom. Compound 8 was used to further delineate the subsites in the combining area of the monoclonal anti-(1 .fwdarw. 6)-.beta.-D-galactan-specific immunoglobulin IgA J539.

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