NEW MATERIAL: The amino acid shown by the formula [X is an-amino protecting group selectively removable without changing alkoxybenzyl; (n) is 1 or 2; (m) is 0 or 1; Z is 1-10C alkyl] and protected by trialkoxybenzyl.

EXAMPLE: The compd. of the formula Fmoc-Asn(Tmob)-OH.

USE: This is the new protecting group for asparagine and glutamine in solid phase peptide synthesis and is useful for bonding amino acid having amide side chains to the reactive group of synthetic resin or unprotected amino group of the final amino acid residue.

PREPARATION: 2,4,6-Trialkoxybenzylamine derivative and N-benzyloxycarbonyl amino acid alpha benzyl ester are condensed to produce a protected intermediate, which is hydrogenated and is then brought to react with protected-OSu(succinoyl) in dioxane/water to obtain the compd. of the formula.