The invention aims at providing novel compounds useful as primer in producing mucin-type glycopeptides which are useful in a wide field including materials for biochemical research, drugs, and food and the production of which was difficult in the prior art; and a process for the production of glycopeptides by using the primers. The aim is attained by providing novel glycopeptide derivatives (represented by the general formula (I)) which each bear an aldehyde or ketone group at the end and each contain an amino acid residue cleavable with a protease; and an easy and simple process for the production of glycopeptides by using the derivative as the primer.