New coumarin-based chiral thiourea sensor 1 was found to be an enantioselective fluorescent chemosensor for N-Boc-protected proline. The chiralsensor shows lower background fluorescence, and higher fluorescence enhancement with 18 nm blue shifts. Job plot analysis result indicates that sensor 1 can form a 1 : 1 stoichiometric complex and it could be used as a fluorescencesensor for the determination