A new caged firefly luciferin (luciferin) with a thiochromone S,S-dioxide (TSSDO) as a photolabile protecting group was synthesized. Photodeprotection of the caged compound proceeded smoothly under photoirradiation at 365 nm in aqueous solution. The bioluminescence of the regenerated luciferin after uncaging was detected using a typical luciferin-luciferase reaction. These results indicated that TSSDO could be an attractive chemical tool for regulating biological phenomena. (C) 2014 Elsevier Ltd. All rights reserved.