Structure, absolute configuration, and conformation of the antimalarial drug artesunate

The crystal and molecular structure of the antimalarial compound artesunate has been determined by direct methods. Crystals are orthorhombic, P2₁2₁2₁, a = 9.8371(12), b = 10.517(2), c = 18.7594(5) Å, Z = 4, D _c = 1.316 mg/mL. The molecule is comprised of a fused ring system containing a six-membered ring C which includes an oxygen bridge and a peroxy bridge. The 9-atom oxygen–carbon chain from O(5)—C(12)... to ... O(2)—C(6) displays a striking sequence of short, long, short, long ... bonds while these distances are all within the ranges of a normal single bond or partial double bond. It is proposed that this pattern is caused by the delocalization of the lone pair electrons on the oxygen atoms. The ring C has a distorted boat conformation and the C—O—O—C torsion angle is 46.3(2)°. Rings A and D have ideal chair conformations. Ring junctions A/B and A/D are cis junctions, B/D and C/D are trans. Packing of the molecules is stabilized by one strong hydrogen bond involving the hydroxyl group on the ester linkage and the oxygen atom of the lactone ring.     

Crystal structure and conformation of the antimalarial drug 5,7-methoxy-8-(3-methyl-1-buten-3-ol)-coumarin

The crystal and molecular structure of the antimalarial compound 5,7-methoxy-8-(3-methyl-1-buten-3-ol)-coumarin, C₁₆H₁₈O₅, M _r = 290.3 Da, has been determined from X-ray diffraction data. The material crystallizes in the monoclinic space group P2₁/c with 4 molecules per unit cell of dimensions a = 8.9044(9), b = 17.623(1), c = 10.175(1) Å, = 113.97(1)°, crystal density D _c = 1.322 g/cm³. The structure was determined using direct methods and refined by full-matrix least squares to a conventional R index of 0.066 for 2416 measured reflections and 206 parameters.The coumarin ring system is almost planar with the methoxy C atoms rotated slightly out of the coumarin mean plane. Apart from the terminal CH₃ groups C(12) and C(13), which are 1.184(3) Å above and –1.315(3) Å below the plane, the 3-methyl-1-buten-3-ol substituent is planar (rms deviation 0.009 Å) making an angle of 6.31(7)° with the phenyl ring. One intermolecular hydrogen bond is present in the crystal structure between O(5)–HO(5) and the symmetry related O(2) oxygen, generated by the symmetry operation (x, 1/2 – y, –1/2 + z).     

Structure,absolute configuration,and conformation of a fused complex cyclic carbohydrate from a cameroon plant extract (CAMT2)

The crystal and molecular structure of the natural product C₂₉H₃₈O₉, an extract from a Cameroonian plant, has been determined by direct methods. Crystals are orthorhombic, P2₁2₁2₁,a=24.571(4),b=16.398(3),c=13.778(4) Å,Z-8,D _c=1.270 mg/m³. The final R-factor for 2892 reflections withI>2(I) is 0.0531. The two molecules forming the asymmetric unit have very similar molecular geometry. each molecule comprising a nucleus of six fused rings B to G: where B=pyranyl, C=pyranyl, D=furanyl, E=cyclohexene, F=pyranyl, G=cyclohexyl. Ring B also has a furanyl side-group (ring A). The ring conformations in both molecules are: A (1/2-chair/envelope); B(envelope); C(envelope); D(1/2-chair); E(1/2-chair); F(envelope); G(chair). In the cyclohexene ring E the substitution pattern is 2-hydroxy 3-methyl 5-dimethyl. The two molecules in the asymmetric unit are linked by two OH...O hydrogen bonds to form the crystal structure.     

Crystal structure,conformation, and absolute configuration of (−)-menthyl-p-bromophenylglyoxylate

The crystal and molecular structure of (—)-menthyl-p-bromophenylglyoxylate has been studied by x-ray diffraction techniques using diffractometer data. Crystals of this compound are triclinic:a= 10.152(3),b=19.661(3),c = 9.220(3) Å, α = 92.45(2), β = 102.74(4), γ = 93.11(4) °, andZ = 4. The structure was refined by least squares toR = 0.064. All 88 hydrogen atoms were determined from electron density difference maps. The significant structural features are the following: (i) the four molecules are conformationally different from one another; (ii) the two > C=O groups of the glyoxylate are twisted with respect to each other across the central C-C bond by angles ranging from 92 ° to 111 °; (iii) the phenyl group is coplanar with the proximal > C=O group; and (iv) all four molecules exhibit a conformation in which the axial hydrogens on the cyclohexane rings eclipse the closer keto oxygen. The absolute configuration was determined by the anomalous dispersion method and is (1R, 3R, 4S).     

Structure and absolute configuration of enhydrin bromohydrin

X-ray study of enhydrin bromohydrin, C₂₃H₂₉BrO₁₀, reveals that the crystal has space groupP2₁2₁2₁ with cell parametersa =10.08,b = 26.97, andc = 8.94 Å. There are four molecules in the unit cell. The structure was solved by direct methods, with three-dimensional CuK diffractometer data to = 75 °, and refined by block-diagonal least squares to anR index of 11.4% for 2254 reflections. The molecule is a germacronolide sesquiterpene having acis sterochemistry at the C(1), C(10) double bond and atrans configuration at the epoxide ring, C(4)-O-C(5). The absolute configuration established on the basis of the anomalous scattering of CuK. radiation by the bromine atom shows that the asymmetric atoms have the 4R, 5R, 6S, 7S, 8S, 9S, 20S, and 22S configurations.     

Crystal structure,absolute configuration and stereochemistry of nupharidine hydrobromide

An X-ray diffraction study of nupharidine hydrobromide has been carried out in order to obtain an unequivocal solution to the question of the N-oxide configuration. Nupharidine hydrobromide (C₁₅H₂₄BrNO₂) crystals are orthorhombic, space groupP2₁2₁2₁ withz = 4. The unit cell constants at 22 ± 3 ° area = 13·419(2),b = 13·668(4),c = 8·731(2) Å (CuK₁, = 1·54051 Å). Three-dimensional intensity data, to the limit 2 = 145 ° for CuK₁, were measured on a GE XRD-490 automatic diffractometer equipped with Ni-Co balanced filters for monochromatization. The crystal structure was solved by the heavy-atom method and refined by least squares to anR of 0·06 for 1960 reflections.X-ray analysis clearly established that (a) the quinolizidine N-oxide system is built of twocis-fused chairs, (b) the methyl and the furan substituents occupy the equatorial position and (c) the absolute configuration indicated by the chemical methods is in agreement with the X-ray work. The stereochemical aspects of the Polonovski elimination reaction in the conversion of (+) nupharidine to ⁶-dehydrodeoxynupharidine has been studied in the light of these X-ray results.     

Structure and absolute configuration of 9-desoxy-9-chloroquinine,C20H23N2OCl

The title compound crystallizes in the orthorhombic space groupp2₁2₁2₁a=8.674(1),b=8.944(1),c=23.255(4) Å,Z=4. The structure was solved by direct methods, and refined by full-matrix least squares toR=0.047 for 1472 observed reflections. Determination of the absolute configuration [S at C(9)] enabled a discrepancy in the literature concerning the stereochemical outcome of the reaction between SOCl₂ and quinine to be resolved.     

Structure and absolute configuration of 10-chloro-10-sulfinylcamphor,C10H13ClO2S

The structure of the title compound, C₁₀H₁₃ClO₂S, was determined by X-rays:M _r =232.72, monoclinic, space groupP2₁,a=6.4902(6),b=12.022(1),c=14.130(3) Å,=103.11(1)°,V _c =1073.7 ų,Z=4,D _x =1.44 Mg m^–3. MoK radiation (graphite crystal monochromator, =0.71069 Å),(MoK)=4.9 cm^–1,F(000)=342,T=293 K. Final conventionalR-factor=0.035 for 2221 observed reflections and 252 variables. The structure was solved usingDirdif. The absolute configuration of the structure is reported. The two independent molecules differ primarily in the orientation of the sulfine group with respect to the camphor moiety.On leave from the Department of Chemistry, University of Colorado, Boulder, Colorado 80309.     

Crystal structure and conformation of frentizole, [1-(6-methoxy-2-benzothiazolyl)-3-phenylurea, an antiviral agent and an immunosuppressive drug

Crystals of Frentizole (from ethanol/water) are monoclinic, space group P2₁/c, with a = 11.187(4), b = 7.392(2), c = 32.727(6) Å, = 92.77(2)°, Z = 8, D _o = 1.47 g/cm³, and D _c = 1.472 g/cm³. There are two independent molecules in the crystallographic asymmetric unit with very different conformations. In molecule A the urea group is in the plane of the benzothiazole ring (0.9°) whereas in molecule B the dihedral angle between them is 4.4°. The dihedral angle between the planes of the phenyl group and the benzothiazole ring are ±157° and ±12°, respectively, in the two molecules. The molecules are linked by a pair of N–H···N hydrogen bonds involving the urea nitrogen and two other N–H···N bonds involving the urea nitrogen and the nitrogen of the benzothiazole group.     

Carnosol. Crystal structure,absolute configuration,and spectroscopic properties of a diterpene

The structure and absolute configuration of naturally occurring Carnosol have been investigated by X-ray analyses. Crystal data are: orthorhombic P2₁2₁2;a=15.762(1),b=13.755(1),c=7.7747(7) Å,Z=4,V=1688.2 ų, andR=0.031 (2569 reflections). The absolute configuration is established at a significance level better than 0.995 according to HamiltonsR-factor test and is in accordance with that predicted experimentally by chemically means. Correlation of the solid-state IR pattern of the regions sensitive to hydrogen bonding (CO and OH stretching bands) with the X-ray crystal structure is excellent and shows, that even weak inter- and intramolecular hydrogen bonds may be unambiguously identified by IR spectroscopy. The variable-temperature nuclear magnetic resonance studies (NMR) show that the twinning of the signals from the isopropyl methyl protons cannot be due to hindered rotation but can be ascribed magnetic nonequivalence induced by the chiral centers.     

Single Crystal Growth,Structure and Physical Property of LiCoO2 and LiNiO2

Abstract

Single crystals of LiCoO₂ and LiNiO₂ have been successfully grown for the first time by a flux method. A single-crystal X-ray diffraction study confirmed trigonal symmetry, and their lattice parameters were a = 2.8161(5) Å and c = 14.0536(5) Å for LiCoO₂, and a = 2.8899(13) Å and c = 14.1938(17) Å for LiNiO₂, respectively. The cation distribution in Li_0.92Ni_1.08O₂ was determined to be (Li_0.74Ni_0.26)_3a[Li_0.18Ni_0.82]_3bO₂ with a final R value of 2.7% by a single-crystal X-ray structure analysis. LiCoO₂ proved to show a semiconducting behavior below room temperature by an in-plane electrical resistivity measurement using the single crystal specimen.     

Crystal Structure of N2,N2-Dimethylacetamidinium N,N-Dimethylcarbamate

The title compound crystallizes in the monoclinic space group P2 1 /c with four formula units in a unit cell of dimensions a = 10.814(2), b = 8.400(2), c = 11.398(4) A, β = 110.86(2)°, V = 967.5(5) A³. The crystal structure is characterized by almost exactly planar [Me₂NC(NH₂)Me]⁺cations and [O₂CNMe₂ ]^- anions which are approximately perpendicular oriented to one another. The amidine N¹—C and N²—C bond lengths are significantly different (1.341(7) and 1.292(7) A, respectively) but the C—O distances of the carbamate anion are equal within experimental error (1.263(6) and 1.256(6) A). An essential feature of the crystal structure are N—H —O hydrogen bonds between cations and anions.     

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.     

Structure, characterization, and EPR of a novel Cu(II) compound with 4-aminopyrimidine. A compound with a very high lattice symmetry

The new copper(II) coordination compound [Cu(4apm)₄(CF₃SO₃)₂](H₂O)^8/3, (in which 4apm = 4-amino-pyrimidine) is studied. This compound is investigated in detail by spectroscopy, EPR, and X-ray crystal structure analysis. The compound crystallizes in the rare cubic spacegroup Im-3m with a,b, and c = 16.823(2) Å, Z = 6. The copper(II) atom has an elongated octahedral geometry, of which the basal plane is formed by four nitrogen atoms of four monodentate ligands with a Cu–N distance of 2.010(4) Å, while the apical positions are occupied by oxygen atoms of the triflate anion with a Cu–O distance of 2.606(5) Å.     

Structure, thermal behavior, and IR investigation of a new organic sulfate

[1-(2-ammoniumethyl) piperazinium] sulfate denoted PIPS has a monoclinic unit cell. The parameters are: a = 6.6521(3), b = 7.8756(5), c = 19.197(1) Å, = 94.43(1)° and the space group is P2₁/n. The preparation, thermal analysis, and IR spectrometric investigation are described. The PIPS structure exhibits a complex three-dimensional network of H-bonds connecting all its components.     

Structures of two N-methylated tricyclic quinolones with antimalarial activity

The crystal structures of two N-methylated tricyclic quinolones were determined. 3-amino-6-methoxy-9-methyl-(1H)pyrazolo[3,4-b]-4-quinolone hydrate, C₁₂H₁₂N₄O₂ · H₂O (1) crystallizes in P-1 with a=11.5078(18) ?, b=13.0614(19) ?, c=9.0860(15) ?, α=106.229(4)°, β=108.378(3)°, γ=71.118(3)° and Z=4, while 2,4-diamino-10-methyl-9-methoxypyrimido[4,5-b]-5-quinolone, C₁₃H₁₃N₅O₂ (2) crystallizes in P2₁/n with a=10.6643(17) ?, b=10.1114(17) ?, c=11.3185(18) ?, β=99.351(4)° and Z=4. Both molecules are essentially planar, including the exocyclic groups. 1 and 2 have moderate antimalarial activity which seems to be related to the formation of intramolecular N – H · · · O=C hydrogen bonds; 1 does not form these bonds and has approximately twice the activity of 2. In both crystal structures there are extensive networks of N–H · · · O and N–H · · · N hydrogen bonds, and in 1 the water molecules of solvation form N–H · · · Ow, Ow–H · · · O=C and Ow–H · · · Ow bonds.     

ThePoranthera corymbosa alkaloids,II. Molecular structure and absolute configuration of porantheridine hydrobromide

Crystals of the hydrobromide of the alkaloid designated porantheridine, C₁₅H₂₇NO, isolated from the plantPoranthera corymbosa Brogn. (family Euphorbiacaea), belong to the space groupP2₁2₁2₁, with cell dimensionsa= 10·059,b = 16·704 andc = 9·629 Å. The crystal structure was solved by the heavy-atom method and refined with 624 reflexions to a residual of 0·078. The molecule consists of three six-membered rings fused on to a common central nitrogen atom; one ring contains an oxygen atom with ann-propyl group and a methyl group substituted on the vicinal carbon atoms. The rings have thechair conformation, two being fusedtrans to each other andcis to the third. The absolute configuration was determined using the anomalous scattering power of the bromine atom.     

Growth and Structure of Doped KLN Crystal

KLN, Fe:KLN, Mn:KLN and Cu:KLN crystals were grown by Czochraski method. The structure of crystal was measured by X‐ray diffraction technique. The results indicated that the doped crystals kept the same structural characteristics as the pure KLN crystal, but the lattice constants of Fe:KLN and Mn:KLN crystals became smaller than that of pure KLN crystal, and that values of Cu:KLN crystal became larger than that of pure KLN crystal. This indicated that Fe and Mn cations replaced Nb cation, and Cu cation replace K cation after they entered into the lattice of KLN crystal. The result of ultraviolet‐visible absorption spectra was identified with that of X‐ray diffraction analysis.     

The Crystal and Molecular Structure of tert‐Butoxycarbonyl ‐ α‐aminoisobutyryl ‐ isoleucyl ‐methylester

The crystal structure of the synthetic peptide Boc — Aib — Ile ‐ OMe (C₁₆ H₃ 0 N₂ O₅ ) has been determined from three‐dimensional X — ray diffraction data. The peptide crystallizes in triclinic space group P1 with a = 9.570(9), b = 10.261(7), c = 10.610(2) Å , α = 101.9(0), β = 91.7(0), γ = 98.6(0)° V = 1006.1(12) ų, Z = 2, D_calc = 1.09 Mg m^‐3. The structure was solved by direct methods and refined by full‐matrix least‐squares method to an R value of 0.072 (λ = 1.5418Å). The conformation of Aib residue in molecule A is αL and in molecule B is αR. The Ile residue in molecule A adopts folded conformation, while in molecule B it is in the extended region. The peptide units are trans and show significant deviations from planarity.     

Structure of antitumor agents 2-acetylpyridinethiosemicarbazone hemihydrate and 2-acetylpyridinethiosemicarbazone hydrochloride

The structures of two antitumor agents, 2-acetylpyridinethiosemicarbazone hemihydrate (1), C₁₈H₁₁N₄O_0.5S, colorless,M _r 203.3, monoclinic,P2₁ lc,a=16.713(3),b=9.460(2),c=12.642(2) ?, β=97.60(1)°,V=1981.2(6) ?³,Z=8,R=0.054,R _w =0.085 and 2-acetylpyridinethiosemicarbazone hydrochloride (2), C₁₈H₁₂N₄SCl, yellow,M _r =230.7, monoclinic,P2₁ ln,a=7.676(2),b=7.889(1),c=17.452(4), ?, β=100.96(2)°,V=1037.5(4) ?³ Z=4,R=0.041,R _w =0.076, have been determined. Both compounds exhibit an E configuration(S atomtrans to the N atom of the hydrazine group). Three hydrogen bonds link the two crystallographically independent molecules in a pairwise fashion in the hemihydrate. An intramolecular N−H...Cl bond lends extra conformational stability to the hydrochloride salt.