Scheme 1.

Sequential OPME synthesis of 6-O-sulfo-Le^xβProN₃ (8) from 6-O-sulfo-GlcNAcβProN₃ (7) by OPME β1–4-galactosyl activation and transfer system for the formation of 6-O-sulfo-LacNAcβProN₃ (4) followed by OPME α1–3-fucosyl activation and transfer system for the formation of 6-O-sulfo-Le^xβProN₃ (8). Enzymes and abbreviations: SpGalK, Streptococcus pneumoniae TIGR4 galactokinase;⁴⁴ BLUSP, Bifidobacterium longum UDP-sugar pyrophosphorylase;⁴⁵ PmPpA, Pasteurella multocida inorganic pyrophosphorylase;⁴³ Hp4GalT, Helicobacter pylori β1–4-galactosyltransferase;⁴³ BfFKP, Bacteroides fragilis bifunctional L-fucokinase/GDP-fucose pyrophosphorylase;⁴² and Hp3FT, Helicobacter pylori α1–3-fucosyltransferase.^{39, 41}