Chemoenzymatic synthesis of Gal(β1-3)Gal(β1-4)Xyl(β)- l-Ser and Gal(β1-3)Gal(β1-4)Xyl(β)-MU by the use of β- d-galactosidase

• Published in: Tetrahedron letters 1996-09, Vol.37 (37), p.6763-6766
• Main Authors: Fukase, Koichi, Yasukochi, Takashi, Suda, Yasuo, Yoshida, Masao, Kusumoto, Shoichi
• Format: Article
• Language: English
• ISSN: 0040-4039; 1873-3581
• DOI: 10.1016/S0040-4039(96)01462-1

The title trisaccharide-serine conjugate 1 constituting the linkage region between glycosaminoglycan and protein in proteoglycan, was synthesized via a trisaccharide p-nitrophenyl (PNP) glycoside prepared by stepwise enzymatic transglycosidation to Xyl-PNP with a β- d-galactosidase. In the second transglycosidation step, partial protection of the disaccharide intermediate, Gal-Xyl-PNP, furnished selective galactosylation at the 3′-position. Cleavage of the PNP group after peracetylation, chemical coupling with serine and final deprotection afforded 1. Fluorescence labeled trisaccharide, Gal(β1-3)Gal(β1-4)Xyl(β)-MU (MU: 4-methylumbelliferyl) ( 2) was also synthesized in a similar way. Gal(β1-3)Gal(β1-4)Xyl(β)- l-Ser ( 1) and Gal(β1-3)Gal(β1-4β)Xyl(β)-MU ( 2) (MU: 4-methylumbelliferyl) were synthesized by a combination of chemical sythesis and enzymatic transglycosidation of p-nitrophenyl β- d-galactopyranoside (Gal-PNP) using a β- d-galactosidase. Regioselective transglycosidation reactions were achieved by partial protection of acceptors.