A reaction scheme illustrating the chemoenzymatic synthesis of the αGal epitope, p-aminophenyl 3-O-β-D-galactopyranosyl-α-D-galactopyranoside (22) is shown in FIG. 3. p-Nitrophenyl 3-O-α-D-galactopyranosyl-α-D-galactopyranoside (compound 21) was prepared enzymatically as described by Nilsson (Tetrahedron Lett. (1997) 38:133-136). A mixture of p-nitrophenyl 3-O-β-galactopyranosyl-α-D-galactopyranoside (70 mg, 0.15 mmol) and 10 mg Pd/C (10%) in methanol (4 mL) was stirred under hydrogen at room temperature overnight. The reaction mixture was then filtered through Celite and the filtrate was concentrated in vacuo to give (50 mg) as a yellowish solid: 1H NMR (CD3OD): δ 6.87 (t, 2 H), 6.57 (d, 2 H), 5.21 (d, 1 H), 4.98 (d, 1 H), 4.2-4.1 (m, 2 H), 4.1-3.8 (m, 3 H), 3.8-3.7 (m, 3 H), 3.7-3.5 (m,4 H); 13C NMR (CD3OD): δ 143.8, 120.1, 117.9, 115.4, 101.2, 97.6, 78.3, 77.0, 72.6, 71.5, 71.4, 70.3, 68.7, 67.4, 63.2, 62.6; MS (ESI): m/e (M+Na+) Calcd. for C18H27NO11Na: 456.2, obsd: 456.2.
