Facile solid-phase synthesis of an antifreeze glycoprotein

The antifreeze glycoproteins (AFGPs) 1 are composed of a repeating tripepti de unit (Ala-Thr-Ala) in which the threonine residue is glycosylated with t he disaccharide beta -D-Gal-(1-->3)-alpha -D-GalNAc. A new procedure for sy nthesizing AFGPs using Fmoc-(Ac-4-beta -D-Gal-(1-->3)-benzylidene-alpha -D- GalNAc)Thr-OH (10) as a building block has been developed. Total synthesis of the AFGPs (n = 4, 8) in overall yields of 61 % and 33 %, respectively, h as demonstrated the usefulness of the method. The synthetic AFGPs 1 (n = 4, 8) showed a similar conformation to the native AFGPs in their circular dic hroism spectra.