1. (2R,3R)-3-O-Benzoyl-N-benzyl-tartramide
Izabela D Madura, Janusz Zachara, Urszula Bernaś, Halina Hajmowicz, Ludwik Synoradzki Acta Crystallogr Sect E Struct Rep Online. 2012 Jun 1;68(Pt 6):o1891-2. doi: 10.1107/S1600536812022933. Epub 2012 May 26.
The title compound, C(18)H(17)NO(6) [systematic name: (2R,3R)-4-benzyl-amino-2-benzo-yloxy-3-hy-droxy-4-oxobutanoic acid], is the first structurally characterized unsymmetrical monoamide-monoacyl tartaric acid derivative. The mol-ecule shows a staggered conformation around the tartramide Csp(3)-Csp(3) bond with trans-oriented carboxyl and amide groups. The mol-ecular conformation is stabilized by an intra-molecular N-H⋯O hydrogen bond. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds between the carboxyl and amide carbonyl groups, forming translational chains along [001]. Further O-H⋯O and N-H⋯O hydrogen bonds as well as weaker C-H⋯O and C-H⋯π inter-molecular inter-actions extend the supra-molecular assembly into a double-layer structure parallel to (100). There are no directional inter-actions between the double layers.
2. (4S,5S)-2,2-Dimethyl-1,3-dioxolane-4,5-dicarbo-nitrile
Alan H Haines, David L Hughes Acta Crystallogr Sect E Struct Rep Online. 2013 Jun 15;69(Pt 7):o1104. doi: 10.1107/S1600536813015973. eCollection 2013.
The title compound, C7H8N2O2, formed by dehydration of the corresponding dicarboxamide, crystallizes as rectangular prisms. The mol-ecules have a C 2 axis of symmetry through the C atom bearing the methyl groups and the mid-point of the ring C-C bond, and the 1,3-dioxolane ring adopts the extreme twist conformation of the two possible with this symmetry. This brings the two nitrile groups nearest to a linear arrangement when the mol-ecule is viewed along the ring C-C bond. The correct absolute configuration of the mol-ecule was defined by that of the original starting material, (2R,3R)-tartaric acid. The packing is largely controlled by a number of C-H⋯N interactions.
3. (2 R,3 R)-1,4-Dioxa-spiro-[4.4]nonane-2,3-di-carb-oxy-lic and (2 R,3 R)-1,4-dioxa-spiro-[4.5]decane-2,3-di-carb-oxy-lic acids
Mikhail E Minyaev, Dmitrii M Roitershtein, Alexey A Vinogradov, Ivan V Ananyev, Ilya E Nifant'ev Acta Crystallogr E Crystallogr Commun. 2018 Jul 6;74(Pt 8):1058-1062. doi: 10.1107/S2056989018009593. eCollection 2018 Aug 1.
The title compounds, C9H12O6 and C10H14O6, were formed by careful hydrolysis of the corresponding diethyl esters. Their single crystals were grown from an ethyl acetate/hexane mixture. Crystals of both compounds have monoclinic (P21) symmetry with a single mol-ecule in the asymmetric unit. Both crystal structures are very similar and display four -CO-OH⋯O=C(OH)- hydrogen bonds, forming a two-dimensional double-layered framework.
