A process for the preparation of ω-alkoxycarbonylamino-α-aminoacids and α,ω orthogonally diprotected diaminoacids from α,ω-diaminoacids using 1- alkoxycarbonylbenzotriazoles as protecting agents is disclosed. In an alternative embodiment, carbamoylating agents in the presence of benzotriazoles are used instead of 1-alkoxycarbonylbenzotriazoles. This reaction is preferably applied to the preparation of ε- alkoxycarbonyllysines from lysine. A process for the preparation of t-butoxycarbonylbenzotriazoles and novel complexes of ω-alkoxycarbonylamino-α-aminoacids with benzotriazoles are also disclosed.