4-Formylphenyl 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-?–glucopyranoside is a pyranoside that is a potent inhibitor of the enzyme glycosidase. It is used to study the interactions between enzymes and substrates. The crystal structure of 4FFAP has been determined using X-ray diffraction data. This compound has a six membered ring with two acetamido groups and one carbonyl group attached to the same carbon atom in the ring. 4FFAP interacts with other molecules through hydrogen bonding and van der Waals forces.