Crystal and molecular structure of voacangine: An alkaloid fromStemmadenia Donnell-Smithii

C₂₂H₂₈N₂O₃,M _r=368.5, orthorhombic, D ₂ ⁴ -P2₁2₁2₁. Unit cell dimensions at 293 K area=8.753(3),b=9.252(2),c=24.422(7) Å,V=1978(1) ų,D _c=1.24 g cm^–3, andZ=4. The structure has been determined from single-crystal data collected with a four-circle diffractometer and refined from 1562 reflections down toR=0.050 andwR=0.055. The structural features determined from chemical and spectroscopic studies are confirmed and extended. The stereochemistry at C(4) and C(18) is 4S and 18S. The indole ring is not planar and the seven-membered nitrogen-containing ring adopts a distorted-chair conformation. The indole and seven-membered rings lie on the same plane with a dihedral angle of 0.7 (1)°, while the C(5)-N(6)-C(19)-C(2) atoms of the central axis of the iso-quinuclidine tricyclic structure is perpendicular to seven-membered ring [dihedral angle is 92.7 (1)°]. The packing in the crystal is entirely due to van der Waals forces.     

Crystal and molecular structure of isovoacangine: An alkaloid from Stemmadenia Donnell-Smithii

C₂₂H₂₈N₂O₃ is monoclinic,P2₁. Unit-cell dimensions at 293 K area=10.023(5),b=6.615(3),c=14.749(6) Å,=91.41(4)°,V=978(1) ų,D _c =1.25 g cm^–3, andZ=2. The structure has been determined from single-crystal data collected with a four-circle diffractometer and refined from 1421 reflections toR=0.057. The structural features determined from chemical and spectroscopic studies are confirmed and extended. The stereochemistry at C(4) and C(18) is 4S and 18S. The indole ring is not planar and the seven-membered nitrogen-containing ring adopts a distorted-chair conformation. The angle between the normals to the planes of the indole and sevenmembered rings is 15.2(1)°, while the C(5)-N(6)-C(19)-C(2) atoms of the central axis of the iso-quinuclidine tricyclic structure is 69.1(1)°. The molecules in the crystal are held together by a hydrogen bond, a C-HO contact, and van der Waals interactions.     

Crystal structure and absolute configuration of the indole alkaloid arborescidine C

The structure and absolute configuration (3R, 17R) of the indole alkaloid arborescidine C were determined by x-ray diffraction. The six-membered ring assumes a half-chair conformation and the seven-membered ring has a twist-like conformation. The crystal packing is characterized by intermolecular hydrogen-bonding between the hydroxyl group and nitrogen atom N4 which leads to the formation of infinite chains of molecules along the a-axis of the crystal. The absolute configurations of two related indole alkaloids, arborescidine B and arborescidine D are inferred from the experimentally determined configuration of arborescidin C molecule. A comparison of the present structure with that of a related indole alkaloid akagerine showed significant conformational and configurational differences. Crystal data: C₁₆H₁₉N₂OBr, orthorhombic, P2₁2₁2, a = 10.3376(8), b = 15.461(4), c = 9.2094(9)Å, V = 1471.9(6)ų, Z = 4, D _calc = 1.510 g cm^–3, = 1.54178Å.     

Structural and spectral studies of N-trans-cinnamylidene-m-toluidine and N-trans-cinnamylidene-m-chloroaniline

N-trans-cinnamylidene-m-toluidine (1) C₁₆H₁₅N, and N-trans-cinnamylidene-m-chloroaniline (2) C₁₅H₁₂NCl form isomorphous crystals which are monoclinic, space group P2_l/c, with unit cell dimensionsa=5.967(2),b=13.793(3),c=15.048(5) Å, =91.97(3)° anda=5.868(2),b=13.788(4),c=15.191(4) Å, =91.87(3)°, respectively. The single-crystal X-ray structure determinations of the title compounds revealtrans structures. Ring (A) C_10–15 and ring (B) C_1–6, are practically planar in both structures with dihedral angels of 61.3(3) and 63.6(2)°, respectively.¹H nmr, u.v. and i.r. spectra are also reported.     

Crystal and molecular structure of 2,3,6,7-tetramethoxy-9-trichloromethyl-10-carboxymethyl-9,10-dihydroanthracene

Cl₃O₆C₂₁H₂₁,M _r =475.75, orthorhombic,P2₁2₁2₁,a=21.895(3),b=12.101(2), andc=8.237(2) Å,V=2182.4(7) ų,D _x =1.45 g cm^–3 forZ=4, (MoK)=0.71069 Å=3.99 cm^–1,F(000) 984, room temperature,R=0.035 for 1877 observed reflections. The molecule exhibits a folded conformation: the dihedral angle between the benzene rings is 28.3(1)°. The central ring is characterized by acis diaxal configuration of hydrogen atoms in the 9, 10 positions, confirming the 13-C NMR results.     

Conformational studies of substituted nitroanilines: geometry of 2-methyl-5-nitroaniline

The title compound (C₇H₈N₂O₂), is monoclinic, space group P2₁/n, witha=9.552(2),b=5.677(2),c=13.586(3)Å, =92.68(2)⁰, andD _x=1.374 g-cm^–3 forZ=4. The refinement converged toR=0.043,wR=0.038. The molecule is approximately planar, with dihedral angles of 3.7(2.1)⁰ between the amino group and the aromatic ring, and 3.2(2)⁰ between the nitro group and the ring. According to the UV spectrum in solution, the molecular geometry indicates weak intramolecular charge transfer. The three-dimensional structure is stabilized by three intermolecular H bonds. A bifurcated one induces the formation of chains along , while the other two link molecules that belong to adjacent chains and are related by an inversion center.     

Structure of 5-methyl-7-methoxy-isoflavone

The structure of 5-methyl-7-methoxy-isoflavone was determined by X-ray diffraction. The compound crystallizes in the monoclinic space group P2₁/c, with cell dimensions of a = 10.321(3) Å; b = 11.290(5) Å; c = 11.979(8) Å; = 107.00(5)°; V = 1334.9(11) ų and D_calc. = 1.325 Mg/m³ for Z = 4. The structure was solved by direct methods and refined to an R value of 0.0409. As expected ring A and ring B in 5-methyl-7-methoxy-isoflavone are coplanar, while ring C is rotated to a dihedral angle of 59.42 (7)°. Intermolecular C–HO hydrogen bonds link molecules related by the screw axis and glide-planes to form a loosely connected layer structure.     

Investigation of 2-(3,4-dimethoxyphenyl)-5,6-dimethoxy-1H-indene by X-ray crystallography and NMR spectroscopy

2-(3,4-Dimethoxyphenyl)-5,6-dimethoxy-1H-indene (obtained by acid treatment of 1,2-bis(3,4-dimethoxyphenyl)-1,3-propanediol) crystallizes in space groupP2₁/c witha=6.836(6),b=28.631(9),c=16.344(6) Å, =95.73(5)°, andZ=8. There are two molecules in the asymmetric unit; the conformations of these molecules exhibit minor differences. In the crystals the double bond in the five-membered ring of the compound is disordered over two positions. The nature of the bonds in the five-membered ring could be ensured by¹H-NMR and¹³C-NMR spectral examinations.     

Structure of 1-ethyl-2-(2′-chloro-4′-nitrostyryl)benzimidazole

The title compound C₁₇H₁₄ClN₃O₂ (et-4-nsbiz) is monoclinic, witha=12.240(2),b=12.144(4),c=10.544(4)Å,=100.09(2)°,V=1543(1)ų,Z=4,D _x =1.411 g cm^–3, (MoK)=0.71073Å,=2.57 cm^–1,F(000)=680,M _r =327.77,T=298K. The structure was solved by heavy atom and Fourier methods and refined toR=0.049 for 1503 unique observed reflections in space groupP2₁/c. Except for the ethyl group, the molecule is almost planar, with a dihedral angle of 9.5(5)° between the benzimidazole and phenyl rings. The dihedral angle between the ethyl group and the benzimidazole ring to which it is attached is 91.5(2)°.     

The structure of (1,2:5, 6η-cyclononatetraene) (η-cyclopentadienyl)cobalt,CoC14H15

The title compound crystallizes in the monoclinic space groupP2₁/a,a=11.50(2),b=7.724(1),c=12.599(3) Å,=102.22(5)°,Z=4. The structure was solved by direct methods and refined by full-matrix least squares toR=0.049 for 1032 observed reflections. The cobalt atom is -bonded to the cyclopentadienyl ring, with a mean Co-C distance of 2.07(1) Å, and also -bonded to the cyclonoatetraene ring at C(2)-C(3) and at C(6)-C(7), with a mean Co-C distance of 2.00(1) Å.     

Structure of (1αH,6βH,7αH,8αH)-1α,10α-epoxy-8β-hydroxy-germacr-2,11(13)-dien-6,12-olide (Incomptine B): A sesquiterpenoid lactone

C₁₅H₁₈O₄ is monoclinic,P2₁. Unit-cell dimensions at 293 K area=15.048(5),b=9.756(3),c=15.815(5)Å,=114.18(2)°,V=2118(1)ų,D _x=1.23 g cm^–3, andZ=6. The structure has been determined from single-crystal data collected with a four-circle diffractometer and refined from 2816 observed reflections toR=0.054. The structural features determined from chemical and spectroscopic studies are confirmed and extended. The incomptine B occurs as three independent molecules with different conformations. The stereochemistry at C(6), C(7), and C(8) is 6S, 7R, and 8R. The 10-membered ring has an approximate C₂ symmetry for the A, B, and C molecules. The -methylene -lactone ring adopts a half-chair conformation for molecule A, and a conformation intermediate between-envelope and half-chair for the B and C molecules, respectively. The structures are stabilized by a three-dimensional network of O-HO hydrogen bonds and several C-HO interactions.     

The structure of a tetrabromotetrahydrodibenzocyclooctene

5, 6, 11, 12-Tetrabromo-5, 6, 11, 12-tetrahydrodibenzo[a, e]cyclooctene, C₁₆H₁₂Br₄, crystallizes in monoclinic space group P2₁/c witha=8.6917(7),b=15.135(2),c=12.892(2) Å, =101.836(8)°, V=1660.0(7) ų,Z=4. The structure was refined toR=0.058 for 3137 observed reflections. The molecule has approximate C₂ symmetry, with the eight-membered ring adopting the twist-boat conformation. The planes of the two phenyl rings form a dihedral angle of 117.3(2)°, C–Br distances range 1.965(5)–1.981(5) Å.     

Molecular structure of the 3-oxide of N-benzyl-3,6-dithiacyclohexene-1,2-dicarboximide

Crystals of the title compound (C₁₃H₁₁,NO₃S₂) are orthorhombic: space groupPbca,a=23.030(3),b=12.897(2),c=8.695(1). The structure was solved by direct methods and refined by full-matrix least-squares procedures to giveR=0.073 andR _w =0.071 for 1303 intensities above 3(I). The 3,6-dithiacyclohexene ring has a deformed half-chair conformation with the axial configuration of the S(3)=O bond. Oxidation of the S(3) atom brings about different lengths of analogous intraring bonds [S(3)-C(2)=1.756(7) and S(6)-C(1)=1.710(7) Å] and angles [C(4)-S(3)-C(2)=95.5(3)° and C(1)-S(6)-C(5)=98.7(3)°]. The structure contains a shortened SO intermolecular contact of 3.053(5) Å.     

Crystal structure of pyrazole derivatives. IV. 5-chloro-4-chlorosulfonyl-3-methyl-1-phenylpyrazole

The title compound crystallizes in space groupP2 ₁/a witha=17.063(1),b=13.208(1),c=21.260(2) Å, =99.51(1)°,V=4726(1) ų,Z=16, there are four independent molecules in the asymmetric unit. The phenyl and pyrazole rings are planar, to within experimental accuracy, making different dihedral angles in the independent molecules: 42.2(1), 129.5(1), 52.5(1), and 46.2(1)°.     

Studies of substituted quinoxaline-di-N-oxides. Part 1. Crystal structure and molecular conformation of 2-[N-(2-hydroxyethyl)carboxamide]-3-methylquinoxaline 1,4-dioxide

A single crystal X-ray investigation of the yellow 2-[N-(2-hydroxyethyl) carboxamide]-3-methylquinoxaline 1,4-dioxide, a commercially available growth promoter used in agricultural stock farming, shows that the molecule is planar. The dihedral angle between the benzene and heterocyclic rings is 0.5°. The N(1)-O(1) and N(2)-O(2) distances are: 1.286(1) and 1.304(1) Å. The C(1)-C(2) bond of the pyrazine ring is not lengthened by substitution at the C(1) and C(2) atoms and is 1.421(2) Å. The atoms O(1) and O(2) deviate by 0.036(2) and 0.123(2) Å from the least-squares plane through the heterocyclic ring. The deviation of the C(12) atom is –0.012(2) Å. The plane through the atoms C(1), C(9), N(3), and O(3) makes an angle of 100.5(2)° with the heterocyclic ring plane. Intermolecular hydrogen bonds O(4)-HO(4)O(3) between the hydroxyl and carbonyl groups generated alternating, antiparalled chains extending in thea direction. The crystals are triclinic,P¯1 (No. 2), witha=7.469(2),b=8.111(2),c=10.357(3) Å,=80.11(2),=88.90(2), =67.73(2)°, andV=571.3(2) ų. The structure was solved by direct phase determination guided by negative quartets and refined by full-matrix least squares to anR value of 0.041 for 2159 observed reflections.Commercially known asOlaquindox.     

Crystal and molecular structure of 4-(3-indolyl)butyric acid-picric acid 2/2 π complex

The title compound, IBA-PIC, is 2C₁₂H₁₃NO₂·2C₆H₃N₃O₇, triclinic,P¯1,a=7.137(1),b=15.355(4),c=18.282(5) Å,=79.72(2),=79.85(2), =76.87(2)°. The structure was solved by direct methods and refined by least-squares techniques to anR factor of 0.068 for 3395 observed reflections. The IBA-PIC complex occurs as two independent molecules with different conformations. The crystallographic evidence for a prominent overlapping between the phenyl and indole rings corroborates earlier conclusions from UV spectroscopy. Molecules of both IBA and picric acid lie approximately parallel to (100) in layers and -bonding interactions across the 3.55 Å spacing. The angles between the indole ring and carboxyl-group planes are 82.9 and 86.9° for the A and B molecules, respectively.     

Crystal and molecular structure of: 5-(1-oxoethyl)-1-methyl-2-(5-bromo-6-methoxy-2-naphthyl)-6-oxabicyclo[3.2.1]octan-7-one and 5-(1-oxoethyl)-1-methyl-2-(5-bromo-6-methoxy-2-naphthyl)-6-oxabicyclo[3.2.1]octane

X-ray crystallographic studies of the two title compounds have shown that the molecules crystallize in the same triclinic space group, , with very similar cell dimensions. For C₂₁H₂₁BrO₄,a=12.056(5),b=13.206(5),c=7.595(3)Å, =90.38(3), =106.07(3) and =124.42(3)° and for C₂₁H₂₃BrO₃,a=12.076(6),b=13.090(5),c=7.490(3)Å, =92.65(5), =104.90(5) and =124.55(5)°. Both compounds possess the oxabicyclo[3.2.1]octane bridged ring system and differ only at the carbon to the ring oxygen where the Csp³ in the ether is replaced by Csp²=O in the lactone. Both cyclohexane rings adopt distorted chair conformations and the lactone and ether rings approximate closely to the envelope conformation. The bromine substituent at C(4) results in distortion of the naphthalene ring. Both molecules pack with the naphthalene rings parallel to each other with interplanar spacings of 3.71 Å in the ether and 3.66Å in the lactone.     

Structure of 2-{2-[3-methyl-3-(2,4,6-trimethylphenyl) cyclobutyl]-2-oxoethyl}isoindole-1,3-dione

2-{2-[3-Methyl-3-(2,4,6-trimethylphenyl)cyclobutyl]-2-oxoethyl}isoindole-1,3-dione (C₂₄ H₂₅NO₃) was synthesized, and its crystal structure was determined by X-ray crystallographic techniques. The compound crystallizes in the triclinic space group P-1, with unit cell parameters: a = 14.109(9) Å, b = 14.130(8) Å, c = 12.152(6) Å, = 105.62(5)°, = 113.75(4)°, = 98.78(5)°, V = 2039.8(19) ų, D _c= 1.223 g/cm³, and Z = 4. The crystal structure has two crystallographically independent molecules, I and II. These molecules are held together by weak intermolecular C—H···O interactions, forming a continuous chain. The dihedral angles between the N-substituted phthalimide moiety and cyclobutane ring in molecules I and II are 60.37(14) and 68.18(18)°, respectively.     

Crystal structure of orellanine hydrate

Orellanine hydrate crystallizes in the monoclinic space groupC2/c with unit cell parametersa=11.516(1) Å,b=8.573(1) Å,c=11.167(2) Å,=110.92(1)°. The finalR andR _w equal 0.041 and 0.046, respectively. The water molecule in the hydrate binds bothN-oxide oxygens of the orellanine molecule by hydrogen bonds, thus fixing the conformation. The hydrate so formed occupies a special position on a twofold axis which passes through the midpoint of the C2-C2 bond distance and the OW atom. Both of the hydroxy-groups participate also in intermolecular hydrogen bonds. As a consequence of the rigid hydrogen bonded network, the dihedral angle between these two pyridil rings of the orellanine molecule is equal to 90.20(5)°.     

Crystal and molecular structure of 1-oxo-3-propoxyazepino[7,6-b]quinoxaline,C15H13N3O2

Crystals of 1-oxo-3-propoxyazepino[7,6-b]quinoxaline, C₁₅H₁₃N₃O₂, are tri-clinic:a=7.289(2),b=14.414(5),c=6.797(2) Å,a=83.56(3),=68.73(3), =86.58(4)°,Z=2, space groupP¯1. The crystal and molecular structure have been determined from X-ray diffractometer data by direct methods, and refined by least-squares methods toR=0.047 (R _w =0.024) for 908 observed reflections. The puckering of the seven-membered ring corresponds to a distorted boat, with bow and stern angles of 44.5 and 24.9° respectively. An extensive conjugation within the molecule includes the three condensed rings and the two attached oxygen atoms, with the only exception being the C(1)-C(11a) bond. Bond distances and angles are comparable with those in the literature and are discussed. Close molecular packing is afforded by layers of molecules parallel to the (010) plane.