Skip to main content
. Author manuscript; available in PMC: 2018 Dec 15.
Published in final edited form as: J Org Chem. 2017 Nov 22;82(24):13152–13160. doi: 10.1021/acs.joc.7b02167

Scheme 4. Chemoenzymatic Synthesis of Disialyl T-Antigen DSTa (6).

Scheme 4

Reagents and conditions: (a) i) Phthalic anhydride, NaOH (1 M); ii) Ac2O, pyridine; iii) EtSH, BF3·Et2O, CH2Cl2, 44% in three steps; (b) i) N2H4·H2O, MeOH; ii) Ac2O, MeOH, 93% in two steps; (c) Gal, ATP, MgCl2 (20 mM), Tris-HCl buffer (pH 6.8), EcGalK, BiGalHexNAcP, 37 °C; (d) Neu5Ac, CTP, MgCl2 (20 mM), Tris-HCl buffer (pH 8.5), NmCSS, Pd2,6ST, 37 °C; (e) NBS, acetone, H2O. Enzymes used: EcGalK, Escherichia coli galactokinase; BiGalHexNAcP, Bifidobacterium infantis D-galactosyl-β1–3-N-acetyl-D-hexosamine phosphorylase; NmCSS, Neisseria meningitidis CMP-sialic acid synthetase; Pd2,6ST, Photobacterium damselae α2–6-sialyltransferase.