A series of Z-and Boc-protected tripeptide methyl esters ] was prepared using the amino acids glycine, alanine and valine. In both the alanine and the valine series a single glycine unit was introduced and its position inside the tripeptide framework was systematically varied. Reaction of these 16 tripeptide derivatives with the organometallic reagent [Cp 2 TiCH 3 (THF) + ][BPh 4 − ] (13) resulted in the formation of methyl(peptide)titanocene cation complexes that contained the strongly electrophilic [Cp 2 TiCH 3 + ] cation moiety coordinated to a single carboxamide carbonyl oxygen atom. Mostly, the carbonyl oxygen atom of the central amino acid residue was specifically attached to yield the coordination products 5−12(coord 7 ). In a few specific cases, formation of the κO-adduct between the [Cp 2 TiCH 3 + ] cation and the Nterminal amino acid moiety was also observed, especially in the cases of the N-terminal glycine derivatives. In one case