Facile synthesis toward the construction of an activity probe library for glycosidases

Chemical probes that selectively label the glycoside hydrolase (GH) subfamilies have proven to be a powerful tool in GH-related research. We have previously demonstrated the design and synthesis of an activity probe for beta-glucosidase adopting a cassette-like design in a model study. Herein we report an improved synthetic route using (4-hydroxyphenyl)acetic acid 2-cyanoethyl ester as the precursor for the latent trapping device. Parallel syntheses were performed for the preparation of a library based on the structure of a key intermediate. The recognition head of this library covers a series of six sugars, including alpha- and beta-d-Glc, alpha- and beta-d-Gal, alpha-d-Man, and alpha-l-Fuc. Each member in this versatile intermediate library could serve as the building block in constructing an activity probe for GHs. As demonstrated in this study, three probes that have the 1,2-cis configuration were thus prepared for the first time to target alpha-d-glucosidase, alpha-d-galactosidase, and alpha-l-fucosidase, respectively.