The title compound was prepared starting from the phosphinic dipeptide (I). Deprotection of the tert-butyl ester of (I) under acidic conditions afforded the carboxylic acid (II). This was then coupled with tryptophan amide (III) using EDC and HOBt to produce (IV). Finally, conjugate addition of 2-naphthalenethiol (V) to (IV) in the presence of NaOEt furnished the target thioether.