An approach to photolabile, fluorescent protecting groups

The photolabile and fluorescent system 1 was prepared via a convergent route which involved thymidine 3'-functionalized with a proline residue. Photodecomposition of 1 was examined using 360 nm irradiation. Without any additives, 5'-silylated thymidine was not formed, but the N-alpha-deprotected cyclization precursor II accumulated instead. However, in the presence of ethanolamine, 5'-silylated thymidine formed at a rate which increases with the concentration of ethanolamine.