Disclosed are new small molecules having a 4-methylpyrrrolo[1,2-a]pyrimidine-8-carboxamide core structure and the uses thereof for modulating glucocerebrosidase activity. Also disclosed are pharmaceutical compositions comprising the small molecules which may be administered in methods of treating diseases or disorders associated with glucocerebrosidase activity, including neurological diseases and disorders such as Gaucher's disease and Parkinson's disease. The small molecules may contain a fluorophore or may be conjugated to a fluorophore in order to prepare a fluorescent probe for use in high throughput screening methods to identify new modulators of glucocerebrosidase activity via fluorescence polarization.