Solid phase and solution synthesis of NvocLys(CO(CH₂) ₅NH-NBD)OCH₂CN, a trifunctional fluorescent lysine derivative

Herein, we describe a general strategy for the facile synthesis of a multifunctional amino acid derivative bearing both fluorescent and photolabile groups such as the lysine derivative NvocLys(CO(CH₂) ₅NH-NBD)OCH₂CN (1) that can be used as a biophysical tool for studying protein structure. The synthetic strategy involves functionalization of the amine groups while the amino acid is attached to a solid support, followed by esterification of the carboxylic acid in solution. The solid support protects the caboxylic acid, preventing a side reaction associated with the synthesis in solution and obviating the need for chromatographic purification of several intermediates. This synthetic strategy can be used for the preparation of a variety of amino acid derivatives with unusual α-amine and side chain functionalities.