A novel synthesis of alpha-D-Galp-(1-->3)-beta-D-Galp-1-O-(CH2)3-NH2, its linkage to activated matrices and absorption of anti-alphaGal xenoantibodies by affinity columns.

Pig organs transplanted into primates are rapidly rejected because of the interaction between Gal alpha(1-->3)Gal epitopes carried by the graft and natural antibodies (anti-alphaGal antibodies) present in the blood of the recipient. This report describes a simplified synthesis of the xenogeneic disaccharide and its linkage to activated gel matrices. The digalactosides alpha-D-Galp-(1-->3)-alpha,beta-D-Galp-OAll were synthesized by the condensation of the trichloroacetimidoyl 2,3,4,6-tetra-O-benzyl-beta-D-galactopyranoside donor with the 3,4-unprotected allyl 2,6-di-O-benzyl-alpha- or beta-D-galactopyranoside acceptor precursor. Deallylation and hydrogenolysis led to the free digalactoside, whereas hydrogenolysis alone resulted in the 1-O-propyl digalactoside. Both products were tested by inhibition ELISA of natural anti-Gal alpha(1-->3)Gal antibodies. The alpha-D-Galp-(1-->3)-beta-D-Galp-OPr was found to be the best inhibitor. Thus, the allyl group of the partially benzylated alpha-D-Galp-(1-->3)-beta-D-Galp-OAll was engineered, via the hydroxy-, the tosyloxy- and the azidopropyl intermediates, into an aminopropyl group amenable to binding to N-hydroxysuccinimide-activated agarose gel matrices in order to obtain specific immunoabsorption columns. Columns made of gel substituted with 5 micromol of disaccharide per milliliter were found efficient for the immunoabsorption of anti-alphaGal antibodies from human plasma.