ChemInform Abstract: Chemoenzymatic-Chemical Synthesis of a (2-3)-Sialyl T Threonine Building Block and Its Application to the Synthesis of the N-Terminal Sequence of Leukemia-Associated Leukosialin (CD 43).

Protection of all functional groups of the carbohydrate portion of the chemoenzymatically synthesized sialyl T threonine ester 1 (R=R1 =H, R2 =tBu, Fmoc=9-fluorenylmethoxycarbonyl) and subsequent acidolysis of the tert-butyl ester afforded the building block 2 (R=Ac, R1 =Me, R2 =H). The latter is a useful tool in the solid-phase synthesis of the N-terminal sequence 3 of the leukemia-associated leukosialin.

Cyclodextrin-assisted Glycan Chain Extension on a Protected Glycosyl Amino Acid

By the use of cyclodextrins, we have enhanced the solubility of the protected amino acid glycan Fmoc-Thr(GalNAcα1)-OtBu (1b) up to 100-fold. This improvement enabled us to carry out an enzymatic glycosylation employing a β-galactosidase in combination with an α2,3-sialyltransferase without the aid of organic cosolvents. After optimization of the one-pot reaction, the sialylated core 1 structure Fmoc-Thr[Neu5Ac(α2-3)Gal(β1-3)GalNAcα1]-OtBu (3b) could be obtained with 50% yield.

Chemoenzymatisch-chemische Synthese eines (2-3)-Sialyl-T-Threonin-Bausteins und dessen Einsatz in der Synthese der N-terminalen Sequenz von Leukämie-assoziiertem Leukosialin (CD43)

Chemoenzymatic-Chemical Synthesis of a (2-3)-Sialyl T Threonine Building Block and Its Application to the Synthesis of the N-Terminal Sequence of Leukemia-Associated Leukosialin (CD 43).

Protection of all functional groups of the carbohydrate portion of the chemoenzymatically synthesized sialyl T threonine ester 1 (R=R1 =H, R2 =tBu, Fmoc=9-fluorenylmethoxycarbonyl) and subsequent acidolysis of the tert-butyl ester afforded the building block 2 (R=Ac, R1 =Me, R2 =H). The latter is a useful tool in the solid-phase synthesis of the N-terminal sequence 3 of the leukemia-associated leukosialin.