title: Insights into diastereoisomeric characterization of tetrahydropyridazine amino acid derivatives: crystal structures and gas phase ion chemistry.
abstract: Structural, conformational properties, and gas phase reactivity of two representative diastereoisomeric members of a series of α,α-tetrahydropyridazine amino acid derivatives have been investigated by using X-ray crystallography, tandem mass spectrometry and theoretical calculations. Both diastereoisomers show an unusual screw-boat conformation of the tetrahydropyridazine ring. While protonated molecules mainly decompose in the gas phase by loss of acetamide, the main reactivity of the [M + Na](+) species consists of loss of PhNCO followed by acetamide and it is strictly dependent upon the stereochemistry of the parent compound. The most stable energy minimized structures obtained by theoretical calculations are in full agreement with the experimental data and allowed us to rationalize the gas phase reaction pathways.
authors.affiliation: Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, Via Aldo Moro, 53100 Siena, Italy. gianluca.giorgi@unisi.it
authors.forename: Gianluca
authors.initials: G
authors.lastname: Giorgi
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Favi
authors.forename: Orazio A
authors.initials: OA
authors.lastname: Attanasi
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005740:Gases / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D011724:Pyridazines / Q000737:chemistry*; D011789:Quantum Theory; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry
chemical_list: D000596:Amino Acids; D005740:Gases; D007477:Ions; D011724:Pyridazines