Structure of 7-methyl-1(2)a,1(6)a,3(4)a-trihomocubane-1(6)a,3(4)a-dione,star-c12h12o2- a case of enantiomeric and rotational disorder

M r = 188.22, monoclinic, P21/n, a = 6.219 (2), b= 10.508 (2), c=7.339 (1)A, t= 107.64 (2) °, V= 457 ,/k 3, Z = 2, D m - - 1.360 (3), D x = 1.366 (2)Mgm -3, ~,(MoKa) = 0.7107/~, #= 0.053 mm -I, F(000) = 200, T= 293 K. Final R = 5.8% for 614 significant reflections. The molecule, which does not possess a centre of symmetry, occupies a crystallographic centre of symmetry because of the statistical enantiomeric and rotational disorder. Latticeenergy calculations, based on van der Waals attractive and repulsive potentials, clearly show minima at the observed disordered positions.

Structure of N-[bis(methylthio)methylene]cinnamamide, C12H13NOS2

M r = 251.34, monoclinic, P21/n, a =14.626 (3), b= 7.144 (1), c= 11.996 (2)\AA \betat=90.03 (2) °, V= 1253.4 (6) \AA 3, Z = 4, Dm= 1.326 (3),Dx=1.331(3)gcm -3, MoKat, \lambda = 0.7107 )\AA , \mu=3.51 cm -3, F(000) = 528.0, T-- 293 K, R -- 3.5% for1455 significant reflections. Of particular interest is an intramolecular attractive interaction between the sulphur and oxygen atoms with an S...O distance of 2.658 (3)\AA, in which the oxygen atom appears to actas a nucleophile.

Cavitation erosion characteristics of poly(methyl methacrylate) in a rotating disk device

Experimental results pertaining to the initiation, dynamics and mechanism of cavitation erosion on poly(methyl methacrylate) specimens tested in a rotating disk device are described in detail. Erosion normally starts at the location nearest to the center of rotation (CR). As the exposure time to cavitation increases, additional erosion areas or sites appear away from the CR and secondary erosion (induced by eroded pits) spreads upstream and merges with the main pit. The microcracks increase in density towards the end of the incubation period and transform into macrocracks in most cases. A study of light optical photographs and scanning electron micrographs of the eroded area shows that material particles are removed from the network of cracks because of crack joining and pits indicate particle debris. Optical degradation (loss of transmittance) is observed to be greater on the back of the specimen than on the front.

Stabilization of the Alleged 'Bishomoaromatic' Bicyclo[3.2.l]octa-2,6-dienyl Anion by Counterion Interactions and by Hyperconjugation

Hyperconjugation and inductive effects, rather than homoaromaticity, are responsible for the stabilization of the title anion in the gas phase; interaction of the double bond with the Li+ gegenion in the endo geometry contributes additionally in solution.

Chemical approach to aspirin hypersensitivity

Rabbits and guinea pigs were immunized with functionalized aspirin-protein conjugates prepared by coupling 5-N-Succinylamino aspirin to BSA and BGG using a water soluble carbodiimide (EDC). Two populations of antibodies, one specific to functionalized aspirin and the other exclusively specific to salicylic acid were detected. These antibodies were fractionated and separated on affinity polymers suitably prepared with 5-N-succinylamino salicylic acid and 5-N-succinylamino-2-ethoxy benzoic acid as the ligands. The isolated and purified antibodies were electrophoretically homogeneous. The physico chemical interactions between the antibodies and the respective haptens were studied by radio-immunoassay, equilibrium dialysis and fluorescence quenching techniques.

Fluorescent labelling of strychnine: A novel approach for recognition of strychnine binding sites on neuronal membrane

trychnine was coupled to fluorescein isothiocyanate to mark strychnine binding sites in spinal cord of rat. Specific binding of strychnine could be demonstrated in synaptosomal fraction. Addition of glycine to the strychninised membrane led to a decrease in fluorescence indicating same receptor loci.

Omega-Hydroxylation of acyclic monoterpene alcohols by rat lung microsomes

Rat lung microsomes were shown to �-hydroxylate acyclic monoterpene alcohols in the presence of NADPH and O2. NADH could neither support hydroxylation efficiently nor did it show synergistic effect. The hydroxylase activity was greater in microsomes prepared from β-naphthoflavone (BNF)-treated rats than from phenobarbital (PB)-treated or control microsomal preparations. Hydroxylation was specific to the C-8 position in geraniol and has a pH optimum of 7.8. The inhibition of the hydroxylase activity by SKF-525A, CO, N-ethylmaleimide, ellipticine, α-naphthoflavone, cyt. Image and p-CMB indicated the involvement of the cyt. P-450 system. However, NaN3 stimulated the hydroxylase activity to a significant level. Rat kidney microsomes were also capable of �-hydroxylating geraniol although the activity was lower than that observed with lungs.

Metabolism of 1,8-Cineole in Rat: Its Effects on Liver and Lung Microsomal Cytochrome P-450 Systems

The monoterpene cyclic ether, cineole (l,8-cineole, I) also known as eucalyptol, is a component of many essential oils and is widely distributed in nature. It is extensively used in pharmaceutical preparations for external application and also as a nasal spray. It was reported earlier that cineole when administered to sheep may be largely oxidized in the system (Scheline 1978). However the mode of metabolism of cineole is not known. Hence the present study was undertaken to investigate the metabolic fate of this ubiquitous terpenoid following its administration to rats by gastric intubation.

The Origin of Regioselectivity in a-Cleavage Reactions of Cyclopropenethiones: Potential Role of Pseudo-Jahn-Teller Effect in Substituted Cyclopropenyl Systems

Arylalkylcyclopropenethiones undergo highly regioselective photochemical a-cleavage via thioketene carbene intermediates, giving rise to products derived from the less stabilized carbene. UHF MIND0/3 calculations provide an insight into this unexpected regioselectivity. The nx* triplet of cyclopropenethione is calculated to have a highly unsymmetrical geometry with an elongated C-C bond, a delocalized thiaaUyl fragment, and a pyramidal radicaloid carbon (which eventually becomes the carbene center). From this molecular electronic structure, aryl group stabilization is expected to be more effective at the thiaallyl group rather than at the pyramidal radical center. Thus, the stability of the substituted triplet thione rather than that of the thioketene carbene determines the preferred regiochemistry of cleavage. The unusual structure of the cyclopropenethione triplet is suggested to be related to one of the Jahn-Teller distorted forms of the cyclopropenyl radical. An alternative symmetrical structure is adopted by the corresponding triplet of cyclopropenone, partly accounting for its differing photobehavior. A similar structural dichotomy is demonstrated for the corresponding radical anions as well.

Photodimerization of coumarin in aqueous and micellar media

The photochemical and photophysical processes of many organic compounds are a function of the environment in which they are present. In this connection we have chosen to investigate the environmental perturbations on the photodimerization of coumarin,l and the results of our study in aqueous and micellar media are presented in this paper. Coumarin has historically been the subject of intense photochemical and spectroscopic interest, mainly as a consequence of its importance in biological systems. Coumarin has been chosen for our investigation as its fascinating photochemical behavior has been fairly well explored,2 and therefore the environmental influence, which is the subject of our concern, would be easily understandable.

The ethyl, 1- and 2-propyl, and other simple alky carbanions do not exist

A combination of experimental data and theoretical calculations has been used to estimate the electron affinities of simple primary, secondary, and tertiary alkyl radicals and the proton affinities of the corresponding anions. With the exception of cyclopropyl, such carbanionsâ are indicated to be unstable towards loss of an electron and are not expected to exist as long-lived species in the gas phase.

Mechanism of oxidation of α,β-unsaturated thiones by singlet oxygen

Photo-oxidation of α,β-unsaturated thiones yields the corresponding ketones as the only product. Studies carried out on three systems, namely thioketones, α,β-unsaturated thiones and thioketenes, have revealed that there exists a similarity in their mechanism of oxidation. It has been suggested that the thiocarbonyl chromophore is the site of attack by singlet oxygen in α,β-unsaturated thiones and that the adjacent C-C double bond is inert under these conditions. Absence of sulphine during the oxidation of α,β-unsaturated thiones is attributed to the electronic factors operating on the zwitterionic/diradical intermediate. While α,β-unsaturated ketones are poorly reactive, α,β-unsaturated thiones are highly reactive toward singlet oxygen.

Cycloaddition of arynes with oxazoles1 : A convenient synthesis of variously substituted polycyclic hydrocarbons

Substituted polycyclic ethers and hydrocarbons are synthesised by the cycloaddition reaction of arynes with oxazoles.

Side Chain Structure Determines Unique Physiologic and Therapeutic Properties of norUrsodeoxycholic Acid in Mdr2(-/-) Mice

24-norursodeoxycholic acid (norUDCA), a side chain-modified ursodeoxycholic acid derivative, has dramatic therapeutic effects in experimental cholestasis and may be a promising agent for the treatment of cholestatic liver diseases. We aimed to better understand the physiologic and therapeutic properties of norUDCA and to test if they are related to its side chain length and/or relative resistance to amidation. For this purpose, Mdr2-/- mice, a model for sclerosing cholangitis, received either a standard diet or a norUDCA-, tauro norursodeoxycholic acid (tauro- norUDCA)-, or di norursodeoxycholic acid (di norUDCA)-enriched diet. Bile composition, serum biochemistry, liver histology, fibrosis, and expression of key detoxification and transport systems were investigated. Direct choleretic effects were addressed in isolated bile duct units. The role of Cftr for norUDCA-induced choleresis was explored in Cftr-/- mice. norUDCA had pharmacologic features that were not shared by its derivatives, including the increase in hepatic and serum bile acid levels and a strong stimulation of biliary HCO3- -output. norUDCA directly stimulated fluid secretion in isolated bile duct units in a HCO3- -dependent fashion to a higher extent than the other bile acids. Notably, the norUDCA significantly stimulated HCO 3- -output also in Cftr-/- mice. In Mdr2-/- mice, cholangitis and fibrosis strongly improved with norUDCA, remained unchanged with tauro- norUDCA, and worsened with di norUDCA. Expression of Mrp4, Cyp2b10, and Sult2a1 was increased by norUDCA and di norUDCA, but was unaffected by tauro- norUDCA. Conclusion:The relative resistance of norUDCA to amidation may explain its unique physiologic and pharmacologic properties. These include the ability to undergo cholehepatic shunting and to directly stimulate cholangiocyte secretion, both resulting in a HCO3- -rich hypercholeresis that protects the liver from cholestatic injury.