As part of a search for a substrate for droplet-based microfluidic screening assay of α-N-acetylgalactosaminidases, spectral and physical characteristics of a series of coumarin derivatives were measured. From among these a new coumarin-based fluorophore, Jericho Blue, was selected as having optimal characteristics for our screen. A reliable method for the challenging synthesis of coumarin glycosides of α-GalNAc was then developed and demonstrated with nine examples. The α-GalNAc glycoside of Jericho Blue prepared in this way was shown to function well under screening conditions.