S. K. Mazumdar

Metal ions-nucleobases interactions: preparation and crystal structures of trichloroadeninium zinc(ii)(form ii) and a similar zinc complex of arprinocid [6-amino-9-(2-chloro-6-fluorobenzyl)purine]

Two zinc complexes—trichloroadeninium zinc(II)(Form 11), C5H6N5Cl3Zn [structure(I)] and a similar complex of Arprinocid, (6-amino-9-(2-chloro-6-fluorobenzyl)purine], C12H10N5FCl4Zn [structure(II)]—have been prepared Structure(I) crystallizes in the space group P21/c with a = 8.223(1)A, b = 6.755(1) A, c = 18.698(3) A, β = 96.10(2)°,and Z = 4. Structure(II) crystallizes in the space group P21/c with a = 8.209(2) A, b = 6.421(8) A, c = 31.794(8) A, β = 90.76(2)°, and Z = 4. Both of these structures were solved by the heavy atom method using diffractometric data and refined to R = 0.028 [structure(I)] and 0.038 [structure(II)]. Zinc with a distorted tetrahedral coordination having three chlorines and N(7) as ligators, protonation of the adenine moiety at N(1), dissymmetry of exocyclic angles at N(7), and an interligand hydrogen bond (“indirect chelation”) involving one of the three chlorines, coordinated to zinc and a proton of the exocylic amino group are the striking features common to both structures. Similar types of indirect chelation as observed in the different complexes of purines have been discussed. The zinc ion deviates from the imidazole plane by 0.412 A in structure(I) and 0.524 A in Structure(II). The imidazol and pyrimidine planes fold about the C(4)-C(5) bond by 2.4° in strctur(I) and 3.8° in structure(II). In structure(I), inversion related molecules are paired through N(9)-H…N(3) hydrogen bonds. N-H…Cl hydrogen bonds and C(8)-H…Cl interactions have been observed in both structures.

Metal-nucleobase interactions: Synthesis and crystal structure of trichlorobis(N6-benzyl adeninium) copper(II) chloride dihydrate

The crystal structure of trichlorobis(N6-benzyl adeninium)copper(II) chloride dihydrate has been investigated to explore the relation among site of protonation, mode/site of coordination, and conformation of the substituent in the adenine system, which is one of the major bases of nucleic acids. Space group: P21/c, a = 10.713(9), b = 21.214(12), c = 13.560(10) A, β = 110.52(6)°, R = 0.0512. Three chloride ions and two benzyl adeninium cations [coordinating through (N9)] complete the trigonal bipyramidal coordination sphere around copper. There are two water molecules of crystallization and a chloride ion, which are not coordinated to the metal, but held in the lattice by the network of hydrogen bonding. The N6 substituent is distal to the imidazole nitrogen as reported for N6 substituted adenines. Both of the adenine moieties are protonated at N(3) in addition to N(7), which is rather unusual and very interesting, whereas under normal situations in adenine, N(1) is the preferred site of protonation. The dihedral angles between the adenine and benzene groups in the ligands are 100.2(2)° and 92.7(2)°, which is close to 90°, as expected for active cytokinins.

Crystal and molecular structure of 6-chloro-3-cyclopentylmethyl-3,4-dihydro-7-sulfamyl-2H-1,2,4-benzothiadiazine-1,1-dioxide

The crystal structure of the title compound, C13H18N3O4S2C1, a sulfa drug, has been determined by X-ray diffraction data using MoKα radiation. The crystals are orthorhombic,Pbca, witha=9.441(4),b=29.633(11),c=12.167(8) Å andZ=8. The structure was solved by the heavy-atom method, and refined by full matrix least-squares to a finalR value of 0.054 with 2062 observed reflections. In the crystal, the molecules are linked by N-H⋯O hydrogen bonds.

Crystal and molecular structure ofp-aminobenzene sulfonacetamide sodium [sulfacetamide sodium] monohydrate

The crystal and molecular structure ofp-aminobenzene sulfonacetamide sodium, C8H9N2NaO3S·H2O, an important substituted sulfa drug, has been determined from diffractometric data using MoKα radiation. The crystals are monoclinic, witha=6.614(2),b=23.788(6),c=7.012(2) Å,β=103.13(2)°, and space groupP21/c. The structure was solved by the heavyatom method, and refined by full-matrix least squares to a finalR value of 0.040 with 1435 unique reflections. In packing, the molecules form dimers through pairs of N-H⋯N and N-H⋯O hydrogen bonds. The molecules are further stabilized by O-H⋯O and O-H⋯N hydrogen bonds.

9-Benzyl-7-[(E)-2-butenyl]-2,3-dihydro-6-hydroxy-1,3-dimethylpyrimido[2,1-f]purine-4,8(1H,9H)-dione

The two independent molecules of C 21 H 23 N 5 O 3 in the asymmetric unit of the title compound possess similar conformations. In each molecule, an almost planar purine ring is fused to a reduced pyrimidine ring. The dihedral angles between the fused-ring plane and phenyl-ring plane of the molecules are different [115.5(2)° for molecule (1) and 68.0 (1)° for molecule (2)]. The O14...O13 distances of 2.478 (5) A for molecule (1) and 2.467 (5) A for molecule (2) indicate the presence of intramolecular hydrogen bonding.

Crystal structure of a nucleoside analog : 1-(R)-[6-(R)-hydroxymethyl-1,4-dioxan-2-yl] uracil

The title compound (C9H12N2O5,Mr=228.2) crystallizes in the trigonal space groupP31,21 witha=b=9.438(3) andc=19.775(3) Å,V=1525.5 Å3,Dx=1.490 gm cm−3,Z=6,μ=0.12 mm−1,F(000)=720.0,T=293 K. The structure was solved by direct methods and refined by full-matrix least-squares calculations to anR value of 0.044 on 843 unique observed reflections. The dioxane ring adopts a chair conformation. The crystal structure is stabilized by N-H⋯O hydrogen bonds and C-H⋯O close contacts.

Crystal and molecular structure of 4-(N,N-dimethylamino) benzaldehyde thiosemicarbazone

Abstract4-(N,N-Dimethylamino)benzaldehyde thiosemicarbazone, C10H14N4S, has been prepared. The crystal structure has been determined from X-ray diffractometer data byMultan 78. The crystals are triclinic:P¯1,a=8.532(1),b=9.391(1),c=15.592(4) Å,α=73.81(2),β=79.59(2), γ=82.85(2)°,Z=4, finalR=0.033 for 2198 observed reflections. Atomic charge densities have been calculated by the CNDO/2 method. The S and hydrazinic N atoms in both molecules in the asymmetric unit are in thetrans configuration. The crystal structure is stabilized by N-H⋯S hydrogen bonds. The net negative charge on the hydrazinic N atom, calculated by the CNDO/2 method, is decreased as compared to those in some 4-phenylthiosemicarbazide derivatives.

Crystal and molecular structure of 4-aminoacetyl-N-p-nitrophenylsulfanilamide

The crystal and molecular structure of 4-aminoacetyl-N-p-nitrophenylsulfanilamide (C14H13N3O5S), a derivative of sulfonamide, has been determined from X-ray diffraction data using Cu-Kα radiation. The compound crystallised in the monoclinic space groupP21/c, witha=12.258(9),b=7.339(5),c=16.359(9) Å,β=98.84(4)°. The structure was solved by direct methods and refined by full-matrix least-squares to a finalR value of 0.047 with 2487 unique reflections. In packing, the molecules are found to be stabilised by N-H⋯ O hydrogen bonds.

3'-deoxy-2',3'-difluorothymidine, a nucleoside analogue

The title compound, 1-(2,3-dideoxy-2,3-difluoro-β-d-ribopentofuranosyl)thymine, C10H12F2N2O4, consists of an almost planar heterocyclic base moiety oriented anti with respect to a puckered sugar moiety. The sugar pucker is 2T3 and the N-glycosidic torsion angle is −119.6 (2)°. The conformation of the O5′ atom is +sc and the molecules are held together by a network of N—H⋯O and O—H⋯O hydrogen bonds.

Determination and correlation of heavy atom positions in the derivatives used in the X-ray analysis of ribonuclease A at 2.5 Å resolution

The analysis of four heavy atom derivatives of ribonuclease A is described leading to isomorphous phasing at 2.5 Å resolution. Differences in the characteristics of the derivatives are discussed with respect to the determination of their heavy atom parameters and the correlation of sites between derivatives to produce a self consistent set. The criteria used to ensure consistency are described. In the final phase analysis using refined heavy atom parameters the least squaresR factors of the derivatives were .124, .143, .101, and .067 respectively, and the mean figure of merit for the 3444 observed reflexions was 0.66.