Titanium tetrachloride smoothly reacted with a selection of α-amino acids (aaH) in CH₂Cl₂ affording yellow to orange solid coordination compounds, 1a–d, in 70–78% yields. The salts [NHEt₃][TiCl₄(aa)], 2a–b, were obtained from TiCl₄/aaH/NEt₃ (aa = L-phenylalanine, N,N-dimethylphenylalanine), in 60–65% yields. The complex , 3, was isolated from the reaction of L-proline with NbCl₅/NHⁱPr₂, performed in CH₂Cl₂ at room temperature. The X-ray structure of 3 features a bridging (E)-1,2-bis(3,4-dihydro-2H-pyrrol-5-yl)ethene-1,2-diolate ligand, resulting from the unprecedented C–C coupling between two proline units. Unusually stable α-ammonium acyl chlorides were prepared by the reactions of PCl₅/MCl_n (MCl_n = NbCl₅, WCl₆) with L-proline, N,N-dimethylphenylalanine, sarcosine and L-methionine. MX₅ (M = Nb, Ta; X = F, Cl) reacted with L-leucine methylester and L-proline ethylester to give ionic coordination compounds, [MX₄L₂][MX₆] (M = Nb, L = Me₂CHCH₂CH(NH₂)CO₂Me, X = F, 9; Cl, 11a; M = Nb, X = Cl, , 11c; Ta, 11d), in moderate to good yields. [NbCl₅(Me₂CHCH₂CHNH₃CO₂Me)][NbCl₆], 12, was isolated as a co-product of the reaction of NbCl₅ with L-leucine isopropylester, and crystallographically characterized. The reaction of NbCl₅ with L-serine isopropylester afforded NbCl₃(OCH₂CHNHCO₂ⁱPr), 13, in 66% yield. The activation of the ester O–R bond was observed in the reactions of L-leucine methyl ester with NbF₅ and L-proline ethyl ester with MBr₅ (M = Nb, Ta), these reactions proceeding with the release of EtF and EtBr, respectively. All the metal products were characterized by analytical and spectroscopic methods, while DFT calculations were carried out in order to provide insight into the structural and mechanistic aspects.