Synthesis,spectroscopic studies,and X-ray crystallographic analysis of the organophosphorus carbohydrate: methyl 4,6-O-benzylidene-3-deoxy-3-C-diphenylphosphinyl-α-D-altropyranoside

The synthesis and molecular structure determination of an organophosphorus carbohydrate are reported. In the solid state the molecules of methyl 4,6-O-benzylidene-3-deoxy-3-C-diphenyl-phosphinyl--D-altropyranoside are linked together by intermolecular hydrogen bonding involving the oxygen attached to phosphorus and the hydroxy group. The five-valent phosphorus atom is in a distorted tetrahedral environment. The chiral molecules crystallize in the monoclinic space groupP2₁ withZ+2. Results from¹ H.¹³C and³¹P NMR investigations together with IR data are presented.     

Synthesis and absolute configuration of (+) α-hydroxymethyltyrosine by X-ray analysis of its N-benzoyl derivative

-Hydroxymethyltyrosine has been synthesized by a route involving-hydroxymethylation. Dextrorotatory N-benzoyl--hydroxymethyltyrosine4 crystallizes in space group P2₁2₁2₁ with cell parameters:a=13.2266(9),b=16.1099(9),c=7.4475(5) Å,V=15.86.9(2) ų,Z=4. The structure was solved by direct methods and refined toR=0.047 andR _w =0.066 with 1549 independent and 956 reflections. The absolute configuration of 1 was determined asR by the application of Hamilton test and by the estimation of the Bijvoet coefficientB. Just as in N-benzoyl--methylcysteine (Wieczorek et al., 1989), the-amino acid residue adopts the C⁵ ring conformation similar to the fully extended form. The two side chains also adopt an extended conformation around the C atom.     

α-Hydroxymethylaspartic acid: Synthesis and absolute configuration by X-ray analysis of its derivative (+)-4-benzoylamino-4-carboxy-γ-butyrolactone

(+)-4-Benzoylamino-4-carboxy--butyrolactone was synthesized, and its structure solved by direct methods and refined toR=0.033. The molecule adopts a skew conformation with a C7-N1-C8-C12 torsion angle of 59.6(2)°. The lactone ring has an envelope conformation, with the C(8) atom deflected from the ring plane. The absolute configuration of (+)-benzylami-no-4-carboxy--butyrolactone5 was assigned asR by the application of Hamilton's test to the unique diffraction data, and confirmed by the estimation of the Bijvoet coefficientB fromhkl and diffraction data. This result proves theR configuration for (+) enantiomer of the parent-hydroxymethylaspartic acid.     

Synthesis and structure determination of 3α-triphenylstannyl-cholest-5-ene

3-Triphenylstannylcholest-5-ene (1) has been synthesised and its molecular structure has been determined by single crystal X-ray diffraction. Refinement in the triclinic space groupP1 witha=7.805(6),b=7.862(5),c=32.351(10)Å, =90.87(8), =94.77(8) and =101.15(4)^o converged atR=0.063. One of the two crystallographically independent molecules in the unit cell has a patially disordered side chain. The bond lengths and valency angles about tin indicate some steric hindrance due to the proximity of one of the phenyl rings with the B ring of the steroid nucleus.     

Crystal Structure and Synthesis of 17α-Acetoxy-pregn-4,6-diene-3,20-dione

Abstract  

17α-Acetoxy-pregn-4,6-diene-3,20-dione (1), C₂₃H₃₀O₄, was synthesized from the commercially available 17α-acetoxyprogesterone. X-ray diffraction analysis of (1) demonstrated that it consists of four rings, three six-membered rings (A, B and C) and one-five-membered ring (D). A, B, C and D rings occur in an envelope; half chair and chair; and half chair conformations, respectively. The crystal of 17α-acetoxy-pregn-4,6-diene-3,20-dione is in orthorhombic crystal system with space group P2₁2₁2₁, lattice constants: a = 10.843(1), b = 11.744(1), c = 15.815(2)?, V = 2013.9(4)?³, Dx = 1.222 g/cm³ and Z = 4. The molecules in the crystal are stabilized by C–H···O interactions and van der Waals forces.     

Synthesis,spectroscopic studies,and x-ray crystallographic analysis of the organotin carbohydrate: 1,2∶3,4-di-O-isopropylidene-6-O-triphenylstannylmethyl-α-D-galactopyranose

The title organotin carbohydrate, C₃₁H₃₆O₆Sn, has been synthesized and its molecular structure has been determined in solution and in the solid state. NMR, infrared, mass and X-ray crystallographic techniques were used. The chiral molecules crystallize in the monoclinic space group P2₁ withZ=2. The triphenyltin and carbohydrate moieties are linked by a trans methylene-oxygen-methylene arrangement. The pyranosyl ring adopts a twist-boat conformation and the isopropylidene rings adopt different (half-chair and envelope) forms. Solution and solid-state conformations are similar as only three ¹³C shift values are greater than 2ppm; the ¹¹⁹Sn value is 12 ppm.     

X-ray structure determination of cyclobutane photodimers from (Z)-α, β-diarylacrylonitriles

Irradiation of(Z)-, -diarylacrylonitriles (1) ArCH=C(CN)Ar (a: Ar=2-thienyl, Ar=Ph;b: Ar=p-MeC₆H₄, Ar=Ph) in the solid state gives cyclobutane dimers (2) in good yield. The mass spectra of the dimers, where no fragments derived from dimers with equal groups on adjacent carbons are present, suggest a truxillic structure (head to tail dimerization). X-Ray determinations confirm a centrosymmetric arrangement with a D_2d symmetry of the cyclobutane ring and a puckering constant=24.0° for (2a) significantly higher than that of (2b) (=19.2°).     

Synthesis, X-ray and neutron diffraction and Mössbauer studies of SrFeOx crystals

Tetragonal single crystals of the nonstoichiometric strontium ferrate with the lattice parameters a = 3.8525(3) and c = 3.8781 (3) Å have been synthesized for the first time by the method of floating-zone melting in the SrFeO_x system. The neutron diffraction patterns of the crystals showed weak additional reflections indicating the formation of the superstructure with double spacing along the [hh0] direction. The Mössbauer spectra of the crystals were obtained and measured in the temperature range 80–300 K. It was established that below the temperature T _N = 232(1) K, the crystals are in the magnetically ordered state with 3/5 of iron ions being in the trivalent state and all the remaining iron ions in the tetravalent state. This leads to the crystal composition SrFeO_2.71. The electric resistivity of the crystals equal to 100 ω cm at room temperature drastically decreases at temperatures exceeding 470 K.     

Synthesis,extended Hückel molecular orbital calculations,and X-ray diffraction structure of the pentamethylcyclopentadienylruthenium complex Cp*Ru(NO)(2,3-quinoxalinediolate)

The reaction between Cp^*Ru(NO)Cl₂ and the heterocyclic compound 2,3-quinoxalinediol in the presence of methanolic KOH leads to the formation of the new piano-stool compound Cp^*Ru(NO)(2,3-quinoxalinediolate) (1). Product isolation and characterization by solution spectroscopic methods (¹H and¹³C NMR and IR) are described. The solid-state structure of Cp^*Ru(NO)(2,3-quinoxalinediolate) confirms the replacement of each chloride ligand in Cp^*Ru(NO)Cl₂ by an oxygen group of the 2,3-quinoxalinediol ligand. Cp^*Ru(NO)(2,3-quinoxalinediolate) crystallizes in the orthorhombic space group Pbca, a=14.846(1) Å,b=12.718(1) Å,c=18.255(2) Å,V=3446.7(5) ų,Z=8,d _calc=1.643 g·cm^–3;R=0.0364,R _w=0.0393 for 1245 observed reflections withI>3(I). The observed Ru–N–O bond angle of 156.3(7)° in the X-ray structure of1 confirms the nonlinear nature of the nitrosyl linkage. This bend in the nitrosyl moiety away from the quinoxalinediolate ligand presumably results from solid-state packing forces and does not derive from electronic interactions, on the basis of extended Hückel molecular orbital calculations. The MO properties of1 are compared with other Cp^*Ru(NO)-substituted complexes previously synthesized in these laboratories.     

Molecular structures of four triterpenoids. X-ray crystallographic analysis of methyl 2α,3β,23α-triacetoxy-19α-hydroxyurs-12-en-28β-oate

A triterpenoid glycoside has been isolated from the roots of a herb used in traditional Chinese medicine. The molecular structure of this compound and its derivatives have been determined by spectroscopic studies and an X-ray analysis of the 2,3,23-triacetoxy-28-methyl ester of the aglycone. This aglycone belongs to the ursene structure series. The hydroxy group on ring E of these triterpenoids is orientated and the side chains at C(2), C(3), C(4) and C(17) are .,, and orientated, respectively. The C ring, which has a double bond at C(12)=C(13), adopts a sofa conformation.     

Synthesis NMR Characterization and Crystal Structure of Methyl 3α,7α-diacetoxy-12-oxo-13-oxa-C-homo-5β-cholanate

Journal of Chemical Crystallography - The crystal structure and NMR characterization of methyl 3α,7α-diacetoxy-12-oxo-13-oxa-C-homo-5β-cholanate. The title compound which was...     

Expression, purification, crystallization, and preliminary X-ray crystallographic analysis of OXA-17, an extended-spectrum β-lactamase conferring severe antibiotic resistance

OXA-17, an extended-spectrum β-lactamase (ESBL) conferring severe antibiotic resistance, hydrolytically inactivates β-lactam antibiotics, inducing a lack of eradication of pathogenic bacteria by oxyimino β-lactams and not helping hospital infection control. Thus, the enzyme is a potential target for developing antimicrobial agents against pathogens producing ESBLs. OXA-17 was purified and crystallized at 298 K. X-ray diffraction data from OXA-17 crystal have been collected to 1.85 Å resolution using synchrotron radiation. The crystal of OXA-17 belongs to space group P2₁2₁2₁, with unit-cell parameters a = 48.37, b = 101.12, and c = 126.07 Å. Analysis of the packing density shows that the asymmetric unit probably contains two molecules with a solvent content of 54.6%.     

X-ray structure and NMR assignment of 3,3′-dimethylthio-4,4′-diquinolinyl sulfide

The title compound (C₂₀H₁₆N₂S₃) is triclinic, witha=9.494(3)b=9.890(3),c=19.456(5)Å,a=90.26(3)°,°=100.47(3)°, =99.18(3)°,Z=4 and space groupP¯1. The structure was solved by direct methods and refined toR=0.045 for 6076 reflections. There are two nonequivalent molecules in the unit cell. Two pairs of sulfur atoms in ortho-positions remain in very close contact. The S-methyl groups are nearly coplanar to the quinoline moieties and turned to the orthoposition, 2. CP MAS spectrum shows two conformers in the solid state but¹H and¹³C NMR spectra in CDCl₃ solution show rapid equilibrium of the conformers giving rise to average NMR data.Part XX in the series of Azinyl Sulfides.     

X-ray and NMR studies on the rotational isomerism about the C(5)-C(6) bond of 6-substituted methyl 2,3,4,-tri-O-acetyl-6-X-α-D-glucopyranoside derivatives

The rotamers about the C(5)–C(6) bond of a series of 2,3,4-tri-O-acetyl-6-X--D-glucopyranozide derivatives resulting by substitution at C(6) or O(6) have been studies with¹H-NMR spectroscopy (400 MHz) and X-ray structure analysis. The methyl 2,3,4-tri-O-acetyl-6-O-triphenylmethyl--D-glucopyranoside and the N-(I-O-methyl-2,3,4-tri-O-acetyl--D-glucopyranose-6-yl)-pyridinium nitrate crystallize in the P2₁ space group with =14.940(1),b=11.232(1),c=9.0773(7), and =94.480(7) anda=7.670(1),b=15.384(3),c=9.624(1) and =104.90(1), respectively; the methyl 2,3,4-tri-O-acetyl-6-O-nitro--D-glucopyranoside and methyl 2,3,4-tri-O-acetyl-6-O-deoxy-6-iodo--D-glucopyrano-side crystallize in the P2₁2₁2₁ space group witha=5.630(1),b=14.360(1) andc=22.388(3), anda=5.556(1),b=14.303(6) andc=21.963(6), respectively.     

Synthesis and X-ray structure of 5′-methoxy-2,4,6-trimethyl-2′-nitrosobiphenyl

The synthesis and X-ray crystal structure of 5-methoxy-2,4,6-trimethyl-2-nitrosobiphenyl is reported. The compound (C₁₆H₁₇NO₂) is monoclinic, with a = 11.080(4), b = 16.899(6), c = 15.410(5) Å, = 108.329(5)°, and space group P2₁/n. There are two independent molecules within the crystal. In each of these molecules the two phenyl rings are mutually orthogonal, with interplanar dihedral angles of 85.09 and 89.43° respectively. The nitroso substituents are essentially coplanar with the phenyl ring, with torsional angles of only 3.5 and 2.2°, respectively, while the methoxy groups make angles of 5.2 and 10.0°, respectively, with the phenyl ring.     

Synthesis,infrared and Mössbauer characterization and X-ray crystal structure of 1,10-phenanthrolinium tetrachloromethoxy phenylantimonate(V)

The compound has been characterized by X-ray crystal structure determination, Mössbauer and i.r. spectroscopy. It crystallizes in the monoclinic space groupP2 ₁ /c (No. 14) witha=24.228(4),b=8.335(2),c=23.975(4) Å,=117.83(3)° andZ=8. Least-squares refinement on 3749 observed reflections gave finalR=0.034 (R _w=0.037). The compound is constituted by [(C₆H₅)SbCl₄OMe]^– anions andphenH⁺cations. The coordination polyhedron about Sb is an octahedron (Sb-Cl 2.416(3), Sb-O 1.962(7) and Sb-C 2.138(9) Å). The whole structure is characterized by two short contacts (O(1)N(2) 2.76(1) O(2)N(4) 2.75(1) Å) involving the methoxy oxygens of the two independent anionic units [(C₆H₅)SbCl₄OMe]^– and two nitrogens of the two independent phenanthrolinium moieties.     

Experimental determination of the solid–liquid equilibrium,metastable zone,and nucleation parameters of the flunixin meglumine–ethanol system

Measurements of the metastable zone and solubility for flunixin meglumine–ethanol system were obtained. The solubility was measured within the temperature range from 288.15 to 328.15 K. The mole fraction solubility was correlated satisfactorily with the temperature by the equation: x_eq=2.35×10^?12e^0.07121T. The value of enthalpy of dissolution, enthalpy of fusion and enthalpy of mixing were determined to be 49.04, 64.03 and ?14.99 kJ mol^?1 respectively. The metastable zone width of flunixin meglumine was measured by an electric conductivity method. A comparison of the nucleation temperatures from electric conductivity measurement and from focused beam reflectance measurement (FBRM) shows that both detection techniques give almost the same results for flunixin meglumine. The nucleation parameters of flunixin meglumine in ethanol were determined from the metastable zone data. Over the equilibrium temperature range from 312.28 to 325.55 K, the nucleation rate constant was varied from 0.00001 to 0.00120 #/m² min, whereas the nucleation order was varied from 2.23022 to 3.39299. The obtained high values of nucleation order indicated a high rate of nucleation.