title: Crystal structure of (4S)-aminoproline: conformational insight into a pH-responsive proline derivative.
abstract: The crystal structure of a (4S)-configured ammoniumproline derivative is presented. The trifluoroacetic acid salt of the acetylated methylester of (4S)-aminoproline (Ac-(4S)Amp-OMe) crystallized as the trans conformer with a C(4)-endo ring pucker. The high-resolution structure shows typical parameters for a transannular H-bond and an n → π* interaction between the adjacent amide and ester groups. The structure corroborates previous findings of solution phase studies on the importance of these two interactions in acidic and neutral aqueous environments for the conformation of this pH-responsive proline derivative.
authors.affiliation: Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 3, CH-8093, Zürich, Switzerland.
authors.forename: Christiane
authors.initials: C
authors.lastname: Siebler
authors.forename: Nils
authors.initials: N
authors.lastname: Trapp
authors.forename: Helma
authors.initials: H
authors.lastname: Wennemers
mesh_terms: D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008968:Molecular Conformation; D011392:Proline / Q000031:analogs & derivatives* / Q000737:chemistry; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry
chemical_list: C467925:aminoproline; D014867:Water; D011392:Proline
keywords: aminoproline; crystal structures; pH responsiveness; peptides; stereoelectronic effects