Benzotriazole reagents for the syntheses of Fmoc-, Boc-, and Alloc-protected amino acids

Stable Fmoc-, Boc-, and Alloc-benzotriazoles react with various amino acids including unprotected serine and glutamic acid, in the presence of triethylamine at 20° as reagents to introduce -amino protecting groups to afford Fmoc-, Boc-, and Alloc-protected amino acids (77-94%) free of dipeptide and tripeptide impurities. Fmoc-, and Alloc-Gly-Gly-OH dipeptides were prepared in 90% yields by N-acylation of glycylglycine with Fmoc- and Alloc-benzotriazoles in the presence of triethylamine. Synthesized N-protected amino acids were greater than 99% pure, analyzed by HPLC.