Precision neutron diffraction structure determination of protein and nucleic acid components. XV. Crystal and molecular structure of the amino acid Lvaline hydrochloride J. Chem. Phys. 60, 4690 (1974); 10.1063/1.1680969 Precision neutron diffraction structure determination of protein and nucleic acid components. XII. A study of hydrogen bonding in the purinepyrimidine base pair 9methyladenine · 1methylthymine J. Chem. Phys. 59, 915 (1973); 10.1063/1.1680114 Precision neutron diffraction structure determination of protein and nucleic acid components. X. A comparison between the crystal and molecular structures of Ltyrosine and Ltyrosine hydrochloride The amino acid salt glycine hydrochloride, H 3 N'·CH,·COOH·CI-, crystallizes in the space group P2 j /c, a = 7.117(2) A, b = 5.234(2) A, C = 13.745(3) A, (3 = 97.25 (1),. The crystal structure has been refined from three-dimensional neutron diffraction data to a final R value based on F' of 0.058. Estimated standard deviations in bond distances and angles are approximately 0.002 A and 0.2°, respectively. There is a network of hydrogen bonds with the chloride ions linking three neighboring glycines to form layers parallel to the ab plane. One ammonium group hydrogen is involved in two weak electrostatic interactions; these interactions join the single layers to form parallel double layers but are probably too weak to be termed hydrogen bonds.

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DL-N-Chloroacetylalanine, C1CH2CONHCH(COOH)(CH3), crystallizes in the monoclinic space group P21/c with unit-cell parameters a=10.807+0.003, b=7-584+0-001, c=9.402+0.002/~ and fl= 108.97 + 0"12 ° at T= 22°C. There are four molecules per unit cell. Intensity data complete to sin 0/2= 0.61 were collected by diffractometer methods using Cu Ks radiation. The structure was deduced by direct methods and subsequently refined by block-diagonal least-squares methods to a weighted index of 0.055. The molecules exists in an extended configuration. The plane defined by the carboxyl group makes an angle of 20.1 ° with respect to the chain of the molecule. Hydrogen bonds link molecules together along the b axis.

The 1 -j3-D-ribofuranosyl derivative 9 of lf/-imidazo[4,5-6jpyrazine (5), a structural analog of the antibiotic nebularine (9-0-D -ribofuranosylpurine), has been prepared by acid-catalyzed fusion of 5 with 1,2,3,5-tetra-0-acetyl-j3-D-ribofuranose and subsequent removal of the acetyl groups. Oxidation of 5 with peracetic acid furnished l/f-imidazo[ 4,5-6 jpyrazine 4(7)-oxide (6). Oxidation of the triacetyl derivative of 9 with m-chloroperoxybenzoic acid, followed by the removal of the protecting groups, provided the inosine analog l-(0-D-ribofuranosyl)imidazo[4,5-6 jpyrazine 4-oxide (11). The site of attachment of the ribosyl moiety in 9 and 11 was substantiated by comparison of their uv spectra with those of the model 1-methylimidazo[4,5-6 jpyrazine (13) and its 4-oxide 15, synthesized by unequivocal routes. The structure of 11 was also confirmed by X-ray crystallography. In the crystal, the nucleoside exists in the anti conformation, the oxygen of the W-oxide function participating in hydrogen bonding with the 2'-hydroxyl group of a neighboring molecule. Compounds 6 and 11 inhibited the in vitro growth of Escherichia coli K12 by 50% at 1 X 10'5 and 6 X 10_6M, respectively. The nebularine analog 9 was inactive. The inhibition of growth was reversed competitively by the natural purines. None of the analogs interfered with the in vitro growth of leukemia L-1210, mammary carcinoma TA-3, and Burkitt's lymphoma cells. In a cell free extract from E. coli, the ribofuranosyl derivative 11 underwent cleavage of its glycosidic bond to furnish the base 6. Imidazopyrazine 4(7)-oxide (6) interfered with the activity of xanthine oxidase from milk, whereas the nucleoside 11 was ineffective.

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