Orde Q. Munro

Pyrano-isoflavones with erectile-dysfunction activity from Eriosema kraussianum

Five pyrano-isoflavones have been isolated from the rootstock of Eriosema kraussianum N. E. Br (Papilionaceae). Spectral data and single crystal X-ray analyses were used for structural elucidation. The most active of the compounds had an activity of 75% of that found in Viagra in the erectile dysfunction test on rabbit penile smooth muscle.

Stereostructure and anti-inflammatory activity of three diastereomers of ocobullenone from Ocotea bullata

A novel diastereomer of ocobullenone. designated as sibyllenone, was isolated from the stem bark of mature Ocotea bullata in the course of a search for anti-inflammatory compounds from this plant. The stereostructure was established by X-ray crystallography and corroborated by NOESY analysis. Ocobullenone, obtained previously, was re-isolated and crystallised successfully for X-ray analysis, thus making possible an accurate spatial comparison of ocobullenone, iso-ocobullenone and the new stereoisomer. Tested pharmacologically for cyclooxygenase-1 and 2, and 5-lipoxygenase inhibition, sibyllenone was the only compound from O. bullata which showed good inhibitory activity towards 5-lipoxygenase.

Transformation of naturally-occurring 1,9-trans-9,5-cis sweroside to all trans sweroside during acetylation of sweroside aglycone

From the rootstock of Scabiosa columbria L. loganin and sweroside were isolated. Sweroside showed moderate antibacterial activity. Pure sweroside was converted to the sweroside aglycone 1-acetoxy derivative (DABCO/Ac2O) after hydrolysis of the glucose unit. X-ray crystallography of the monoacetate showed unambiguously that it had been transformed to a new seco-iridoid having the novel trans diaxial configuration for the protons on C-1, C-9 and C-5. The mechanism for the rearrangement is discussed.

Complementary hydrogen bonding in a new tridentate Schiff base ligand: X-ray, DFT and solution NMR studies

The X-ray crystal structure of a novel mono(pyrrole)-containing tridentate Schiff base ligand, N-[(1E)-1H-pyrrol-2-ylmethylene]benzene-1,2-diamine (3), shows unexpected hydrogen bond complementarity between neighbouring pairs of molecules in the solid state (monoclinic space group C2). The supramolecular structure is best described as a hinged dimer in which the dihedral angle between the two ligand planes measures 65(1)° and is stabilized by a pair of hydrogen bonds involving the pyrrole N–H proton on one molecule and the N atom of the aryl amino group on the neighbouring molecule. The experimental H(pyrrole)⋯N(amine) H-bond distances are equivalent at 2.40(2) A. The 1H NMR spectrum of 3 in CDCl3 shows concentration-dependent features that are consistent with endergonic dimerization by intermolecular hydrogen bonding at higher concentrations [KD = 0.89(16) M−1 at 25 °C]. DFT calculations at the B3LYP/6-31G** level of theory correctly predict the main geometrical features of the dimer, which has slightly inequivalent H(pyrrole)⋯N(amine) distances of 2.31 and 2.33 A in the calculated structure. The DFT-calculated dimer shows some conformational differences from the X-ray structure that primarily reflect the fact that the individual molecules of 3 in the in vacuo model are twisted about the CN–CC torsion angle involving the imine group and adjacent phenyl ring (C5–N2–C6–C7) by 4–8° more than is the case for the experimental structure. These conformational differences reflect the role that crystal packing plays in fine-tuning the supramolecular structure of 3.

Stereostructure, conformation and reactivity of P- and a-gardiol from Burchellia bubalina

Abstract From the leaves of Burchellia bubalina (Rubiaceae) pure P- and a-gardiol have been isolated, the latter in crystalline form for the first time. X-ray analysis of P-gardiol establishes its relative configuration. Treatment of the tosyl derivative of P-gardiol with base affords a crystalline elimination product amenable to X-ray analysis. Evidence is presented for the partial conversion of a-gardiol to the epimeric P-gardiol at room temperature. Molecular dynamic studies at 1000 K on the two gardiols provide useful conformational information. In the case of P-gardiol, the analysis shows interesting correlations between conformations adopted at 1000 K and those present in the crystalline state at room temperature.

Preparation and properties of the halogenoalkyl compounds [(η5-C5H5)(CO)2(PPhiMe3−i)Mo{(CH2)nX}] (n=3, 4; i=0–3; X=Br, I) and [{η5-C5(CH3)5}(CO)3Mo{(CH2)nX}] (n=3, 4; X=Br, I) and the crystal structures of [(η5-C5H5)(CO)3W{(CH2)5I}], [(η5-C5H5)(CO)3W{(CH2)3Br}] and [(η5-C5H5)(CO)2(PPh3)Mo{(CH2)3I}]

Abstract The compounds [Cp(CO)2(PPhiMe3−i)Mo{(CH2)nBr}] (Cp=η5-C5H5, n=3, 4; i=0–3) and [Cp*(CO)3Mo{(CH2)nBr}] (Cp*=η5-C5(CH3)5, n=3, 4) were prepared in medium to high yield by the reaction of the corresponding anion ([Cp(CO)2(PPhiMe3−i)Mo]− or [Cp*(CO)3Mo]−) with Br(CH2)nBr. The bromoalkyl compounds were subsequently reacted with NaI to give the corresponding iodoalkyl compounds [Cp(CO)2(PPhiMe3−i)Mo{(CH2)nI}] (n=3, 4; i=0–3) and [Cp*(CO)3Mo{(CH2)nI}] (n=3, 4). The iodoalkyl compounds can also be prepared by the reaction of the corresponding anion and α,ω-diiodoalkane in much lower yields. These compounds have been fully characterised and their properties are discussed. The crystal and molecular structure of [Cp(CO)2(PPh3)Mo{(CH2)3I}] is reported. The compound forms crystals in the monoclinic space group P21/n, with a Mo–C bond length of 2.40 A and a C–I bond length of 2.13 A. The compounds [Cp(CO)3W{(CH2)nX}] (X=Br, I; n=3–6) were also prepared in high yield and the crystal structures of [Cp(CO)3W{(CH2)5I}] and [Cp(CO)3W{(CH2)3Br}] are reported. The former compound forms orthorhombic crystals in the space group P21nb and the latter forms triclinic crystals in the space group P 1 . Both have W–C bond lengths of 2.35 A. The C–I bond length is 2.12 A; the C–Br bond length is 1.94 A.

The isothiocyanate complex of triphenylborane forms an unusual coordination polymer with [K(18-crown-6)](+), both in the solid state and in solution.

The title salt, (1,4,7,10,13,16-hexaoxacyclooctadecane-kappa(6)O)[(isothiocyanato)triphenylborato-kappaS]potassium(I), [K(C(19)H(15)BNS)(C(12)H(24)O(6))] or [K(SCNBPh(3))(18-crown-6)], where 18-crown-6 is 1,4,7,10,13,16-hexaoxacyclooctadecane and [SCNBPh(3)](-) is the (isothiocyanato)triphenylborate anion, exhibits a supramolecular structure that is best described as a helical coordination polymer or molecular screw. This unusual supramolecular structure is based on a framework in which the SCN(-) ion bridges the chelated K(+) ion and the B atom of BPh(3) in a micro(2) fashion. The X-ray crystal structure of the title salt has been determined at 100 (1) and 293 (2) K. The K(+) ion exhibits axial ligation by the S atom of the [SCNBPh(3)](-) anion, with a K-S distance of 3.2617 (17) A (100 K). The trans-axial ligand is an unexpected eta(2)-bound C=C bond of a phenyl group (meta- and para-C atoms) that belongs to the BPh(3) moiety of a neighboring molecule. The K-C bond distances span the range 3.099 (3)-3.310 (3) A (100 K) and are apparently retained in CDCl(3) solution (as evidenced by (13)C NMR spectroscopy). By virtue of the latter interaction, the supramolecular structure is a helical coordination polymer, with the helix axis parallel to the b axis of the unit cell. IR spectroscopy and semi-empirical molecular orbital (AM1) calculations have been used to investigate further the electronic structure of the [SCNBPh(3)](-) ion.

[Fe(TPP)(4-MePip)(2)]: an axially compressed bis(secondary amine) complex of an iron(II) porphyrin.

The low-spin iron(II) ion of bis(4-methylpiperidine)(5,10,15,20-tetraphenylporphyrinato)iron(II), [Fe(TPP)(4-MePip)(2)], where TPP is 5,10,15,20-tetraphenylporphyrinate (C(44)H(28)N(4)) and 4-MePip is 4-methylpiperidine (C(6)H(13)N), is located at a center of inversion, and there is one molecule in the triclinic unit cell. The axial 4-MePip ligands adopt a chair conformation and the alpha-C atoms are oriented at angles of 21.2 (2) and 32.8 (2) degrees relative to the closest porphyrin N atoms. The equatorial Fe-N(TPP) distances are 1.998 (2) and 1.990 (2) A, while the axial Fe-N distance is 2.107 (2) A. The relatively short axial coordination distance reflects compression of the molecule along its principal axis by intermolecular non-bonded interactions.

3-Methyl-1H-quinoxalin-2-one

In the crystal structure of the title compound, C9H7N2O, one-dimensional chains of planarmolecules are interlocked at a dihedral angle of about 30° and display weak aromatic interactions, consistent with π–π stacking. The distance between quinoxaline rings in two neighbouring planes is 3.972 (6) A. Within a chain, molecular dimers, which are held together by a pair of strong intermolecular N—H⋯O hydrogen-bonding interactions at a distance of 2.792 (4) A, are linked by weak ditopic hydrogen-bonding interactions C—H⋯N at a distance of 3.560 (6) A.

Hydrogen bonding and crystal packing favor a nonplanar Co(III) porphyrin conformation and unusually weak axial ligation in [Co(TPP)(benzylamine)2](SCN): A crystallographic and density functional theory investigation

The single crystal X-ray structure of [Co(TPP)(BzNH2)2](SCN), compound 2, where TPP = 5,10,15,20-tetraphenylporphyrin dianion and BzNH2 = benzylamine, reveals that the SCN- ion is hydrogen-bonded to one of the coordinated amino group hydrogen atoms via its sulfur atom. Furthermore, the N–H⋯SCN interaction is balanced by a stronger N–H⋯NCS hydrogen bonding interaction for the trans BzNH2 ligand as a result of the multiple hydrogen bond accepting character of the thiocyanate ion. Analysis of the crystal packing shows that these two hydrogen bonds play a major role in fixing unusual orientations for the axial ligands relative to the porphyrin ring in this system. This, in turn, leads to the formation of a nonplanar porphyrin core conformation that is a mixture of ruffle- and saddle-type distortions. The intricate hydrogen bonding between the cations and anions in 2 results in an unusually long mean Co–Namine coordination distance of 2.033(4) A, some 0.05 A longer than previously observed for other bis(primary amine) complexes of Co(III) porphyrins with comparable porphyrin ligands. Density functional theory (DFT) calculations at the B3LYP/LACVP* level of theory have been used to gauge the perturbation of the electronic structure of the [Co(TPP)(BzNH2)2]+ cation caused by the N–H⋯SCN and N–H⋯NCS hydrogen-bonded SCN- ions. The calculations show that partial mixing of the anion MOs with those of the porphyrin cation lead to changes in the electron populations of the 3d orbitals of up to 0.42 e as well as more nearly tetragonal electronic symmetry for the Co(III) ion as a result of adjustments of the relative energies of the MOs with predominantly 3d character.