Crystal and molecular structure of sarcosine

The crystal structure of sarcosine in pure form has been determined at low temperature (135 K). The crystals are othorhombic, space group P2(1)2(1)2(1) with unit cell dimensions a = 6.687(2) A, b = 7.899(3) A, c = 8.607(3) A. On the basis of 988 reflections with intensities larger than 3 sigma (I) the structure was refined to a conventional R-factor of 0.034 to give e.s.d. in bond lengths of 0.002 A and 0.2 degrees in angles. The molecule is extended and exists in the zwitterionic form. There is a small deviation from planarity in the alpha-amino acid group as well as in the main chain.

Crystal structures and pharmacological activity of calcium channel antagonists: 2,6-dimethyl-3,5-dicarbomethoxy-4-(unsubstituted, 2-methyl-, 4-methyl-, 3-nitro-, 4-nitro-, and 2,4-dinitrophenyl)-1,4-dihydropyridine

The molecular structures of 2,6-dimethyl-3,5-dicarbomethoxy-4-phenyl-1,4-dihydropyridine and the 3-methyl-, 4-methyl-, 3-nitro-, 4-nitro-, and 2,4-dinitrophenyl derivatives were determined by X-ray diffraction methods. The dihydropyridine ring in each of the compounds exists in a boat-type conformation. However, the degree of ring puckering varies among the compounds. The observed ring distortions were found to be influenced to a great extent by the position of the substituent in the 4-phenyl ring and the conformation about the interring bond. The distortion at the apical nitrogen of the dihydropyridine ring was found to be linearly related to that at the apical tetrahedral carbon. A correlation was observed between the pharmacological activities of this class of calcium channel antagonists, determined by their ability to inhibit the Ca2+-dependent muscarinic mechanical responses of guinea pig ileal longitudinal smooth muscle, and the magnitude of the 1,4-dihydropyridine ring puckering; the more active compounds exhibited the smallest degree of ring distortion from planarity.

The crystal and molecular structure of (2-Hydroxyphenyl) alanine (o-Tyrosine)

The crystal structure of D,L-(2-hydroxyphenyl)-alanine has been determined by X-ray methods using 1971 observed reflections. The crystals are monoclinic, space group P2-1, with four molecules in the unit cell of dimensions a=6.32-5 A; b=26.48-9 A; c=5.36-7 A, and beta=98.1-8 degrees. The structure was solved by direct methods and refined to a conventional R-factor of 0.048; estimated standard deviations in bond lengths not involving hydrogen are 0.002-0.004 A and in angles 0.1-0.2 degrees. Bond lengths and angles are in accordance with those found in tyrosine. Owing to an intra-molecular hydrogen bond between the ammonium group and the ring hydroxyl oxygen atom, however, the conformational angles differ from those found in several other phenylalanine derivatives. There are non-crystallographic centres of symmetry between pairs of enantiomeric molecules.