title: Heterocyclic tautomerism: reassignment of two crystal structures of 2-amino-1,3-thiazolidin-4-one derivatives.
abstract: The structures of 5-(2-hydroxyethyl)-2-[(pyridin-2-yl)amino]-1,3-thiazolidin-4-one, C10H11N3O2S, (I), and ethyl 4-[(4-oxo-1,3-thiazolidin-2-yl)amino]benzoate, C12H12N2O3S, (II), which are identical to the entries with refcodes GACXOZ [Váňa et al. (2009). J. Heterocycl. Chem. 46, 635-639] and HEGLUC [Behbehani & Ibrahim (2012). Molecules, 17, 6362-6385], respectively, in the Cambridge Structural Database [Allen (2002). Acta Cryst. B58, 380-388], have been redetermined at 130 K. This structural study shows that both investigated compounds exist in their crystal structures as the tautomer with the carbonyl-imine group in the five-membered heterocyclic ring and an exocyclic amine N atom, rather than the previously reported tautomer with a secondary amide group and an exocyclic imine N atom. The physicochemical and spectroscopic data of the two investigated compounds are the same as those of GACXOZ and HEGLUC, respectively. In the thiazolidin-4-one system of (I), the S and chiral C atoms, along with the hydroxyethyl group, are disordered. The thiazolidin-4-one fragment takes up two alternative locations in the crystal structure, which allows the molecule to adopt R and S configurations. The occupancy factors of the disordered atoms are 0.883 (2) (for the R configuration) and 0.117 (2) (for the S configuration). In (I), the main factor that determines the crystal packing is a system of hydrogen bonds, involving both strong N-H...N and O-H...O and weak C-H...O hydrogen bonds, linking the molecules into a three-dimensional hydrogen-bond network. On the other hand, in (II), the molecules are linked via N-H...O hydrogen bonds into chains.
authors.affiliation: Department of Organic Chemistry, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznań, Poland.
authors.forename: Andrzej K
authors.initials: AK
authors.lastname: Gzella
authors.affiliation: Department of Organic Chemistry, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznań, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Kowiel
authors.affiliation: Department of Organic Chemistry, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznań, Poland.
authors.forename: Aneta
authors.initials: A
authors.lastname: Suseł
authors.affiliation: Department of Pharmaceutical, Organic and Bioorganic Chemistry, Danylo Halytsky Lviv National Medical University, Pekarska 69, Lviv 79010, Ukraine.
authors.forename: Magdalena N
authors.initials: MN
authors.lastname: Wojtyra
authors.affiliation: Department of Pharmaceutical, Organic and Bioorganic Chemistry, Danylo Halytsky Lviv National Medical University, Pekarska 69, Lviv 79010, Ukraine.
authors.forename: Roman
authors.initials: R
authors.lastname: Lesyk
mesh_terms: D062365:Aminobenzoates / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D015394:Molecular Structure; D011725:Pyridines / Q000737:chemistry*; D013844:Thiazoles / Q000737:chemistry*; D053778:Thiazolidines / Q000737:chemistry*
chemical_list: C000592831:2-amino-1,3-thiazolidin-4-one; C000592832:5-(2-hydroxyethyl)-2-((pyridin-2-yl)amino)-1,3-thiazolidin-4-one; D062365:Aminobenzoates; D011725:Pyridines; D013844:Thiazoles; D053778:Thiazolidines; C000592833:ethyl 4-((4-oxo-1,3-thiazolidin-2-yl)amino)benzoate
keywords: 2-amino(imino)-1,3-thiazolidin-4-ones; amine–imine tautomerism; biologically active compounds; crystal structure; heterocyclic tautomerism; hydrogen bonding; medicinal chemistry; pharmaceutical compounds