摘要:

Erythroandthreo-1,2-diphenyl-2-tert-butylsulfinylethanols5and8were prepared from the condensation of the α-lithio derivative of benzyl-tert-butyl sulfoxide with benzaldehyde. Reaction of5with sulfuryl chloride gave the title compound, (2R*,3S*,4R*,6R*)-3,4-diphenyl-6-(diphenylmethyl)-1,5-dioxa-2-thiane-2-oxide6, the first representative of a new heterocyclic ring system. Similar treatment of8resulted in the formation of7, a stereoisomer of6. This same compound was also obtained by photolysis of6. In both6and7the S=O bond is in an axial orientation.Keywords: sulfuryl chloride, reaction with β-hydroxy sulfoxides; 1,2-diphenyl-tert-butylsulfinylethanol; β-hydroxysulfoxides; β-sultines;N-chlorosuccinimide, reaction with β-hydroxysulfoxides.

ISSN:0008-4042    

DOI:10.1139/v91-029

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The fungusPaecilomycesvariotiiBainier, isolated from larvae ofDendroctonusponderosaHopk. (mountain pine beetle), is antagonistic toOphiostomaclavigerum, the fungus believed responsible for tree mortality caused by blue stain fungi. The metabolites produced byP.variotiiwhen grown in liquid culture have been studied and two new 1H-naphtho[2,3-c]pyran-1-ones related to semi-vioxanthin (4) have been isolated. The structures of these two metabolites, semi-viriditoxin (1) and semi-viriditoxic acid (2), have been determined by chemical and spectroscopic methods.Keywords: fungal metabolites, blue stain disease,Paecilomycesvariotii, semi-viridotoxin, semi-viridotoxic acid.

ISSN:0008-4042    

DOI:10.1139/v91-030

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Photoresponses for various porphyrin films prepared by the electrolytic micelle disruption (EMD) method have been investigated in the indium-tin oxide / porphyrin / I3–, I–/ Pt cell. The EMD film of an n-type porphyrin, 5, 10, 15, 20-tetra(4-pyridyl)porphyrin (T(4-py)P), exhibited a clear optical filtering effect (OFE), while not for the EMD films of p-type porphyrins such as (5, 19, 15, 20-tetraphenylporphyrinato)zinc(II) (ZnTPP). For the EMD-ZnTPP film, the photocurrents at 500–700 nm were remarkably enhanced by increasing the film thickness. These photoelectrochemical properties were explained in terms of the electrolyte-permeability of the EMD films, which were confirmed by the electrochemical measurements and electron microscopic observations. The high conversion efficiency of the EMD-ZnTPP film was explained on the same basis. The difference in the thickness dependence of OFE between T(4-Py)P films prepared by the EMD and physical vapor deposition method was elucidated by the differences in diffusion lengths of excitons and in widths of photoactive layers in the films. In addition, a modified version of the EMD method was described in conjunction with a morphology control of the porphyrin solids.Key words: porphyrin, organic thin film, photoresponse, micelle, electrochemist

ISSN:0008-4042    

DOI:10.1139/v91-901

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Vinylic trifluoromethane sulfonates (triflates) form palladium intermediates that react with pyrimidine nucleosides to produce C-5 alkyl substituted nucleosides after hydrogenation of the vinylic coupling products with hydrogen and Pd/C in methanol. The reaction, which is run under mild conditions, appears to be a general one since both mono- and disubstituted vinylic triflates, as well as the cyclic ones, gave high yields of the corresponding C-5 alkyl-substituted nucleoside. The reaction with allyl triflate requires the use of the 5-chloromercurinucleoside.Keywords: nucleosides, triflates, palladium catalysis

ISSN:0008-4042    

DOI:10.1139/v91-031

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Anabinitiostudy of tropolone was carried out at the 3-21G level, with full optimization of the geometry, and the intramolecular proton transfer in the ground state was analysed. The two equivalentCsstructures can be converted to each other via aC2vsymmetry transition state with a double minimum potential. The splitting of the ground vibrational state generated by proton tunneling was determined by procedures of variable complexity and found to be in the range Δ = 0.1–0.15 cm−1, i.e., clearly smaller than experimental predictions.Keywords: tropolone, intramolecular hydrogen bond, proton transfer,abinitiocalculations, molecular structure.

ISSN:0008-4042    

DOI:10.1139/v91-032

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A series of 22 phenyl substituted derivatives of 2-phenyl-1,1′,3,3′-tetramethylguanidine were used as bases in the proton transfer reaction from bis(4-nitrophenyl)cyanomethane in acetonitrile solvent. Brønsted and Hammett type relationships are examined for this family of closely related substrates. The Brønsted relationship constructed from the pKavalues determined in acetonitrile shows β = 0.55 ± 0.03. The best fit of the Hammett relationship, with special values forp-NO2andp-CN groups, gives the reaction constant ρ = −1.39 ± 0.1. The kinetic isotope effect,kH/kD, increases from 9.6 to 12.4 at 25 °C with decreasing base strength, i.e., when the reaction becomes more thermoneutral.Keywords: tetramethylguanidine, proton transfer, deuterium isotope effects.

ISSN:0008-4042    

DOI:10.1139/v91-033

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

α-Methoxycarbamate12, synthetic precursor of the 2,6-disubstituted alkaloids ofSedumacre, was obtained in high yield from 2-phenacylpiperidine5; the key step of the synthesis rests on the anodic methoxylation, which allows the functionalization of carbon 6. Nucleophilic substitution of the methoxy group by an acetonyl chain leads, after the required transformations, to sedinone23. Bromomethoxylation of the enecarbamate19followed by dehydrohalogenation and nucleophilic substitution of the methoxy group leads to sedacrine33. In both cases, the nucleophilic substitution of the methoxy group leads to acis2,6-disubstituted piperidine derivative.Keywords: synthesis, piperidine alkaloids, anodic methoxylation

ISSN:0008-4042    

DOI:10.1139/v91-034

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The structure of the O-antigen ofActinobacilluspleuropneumoniaeserotype 12 was determined by 1D and 2D NMR spectroscopic methods, methylation analysis, and partial hydrolytic degradation. The O-polysaccharide was shown to consist of a trisaccharide repeating unit having the structureKeywords:Actinobacilluspleuropneumoniae, lipopolysaccharide, polysaccharide, antigen.

ISSN:0008-4042    

DOI:10.1139/v91-035

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The reactivity of the radical cations of methyl 2,2-diphenylcyclohexyl ether (7), 6,6-diphenyl-1,4-dioxaspiro[4.5]decane (8), methylcis- andtrans-2-phenylcyclohexyl ether (9cisandtrans), and 6-phenyl-1,4-dioxaspiro[4.5]decane (10), generated by photosensitized (electron transfer) irradiation, has been studied. Solutions of the ethers and acetals in acetonitrile–methanol (3:1), with 1,4-dicyanobenzene (2) serving as the electron acceptor, were irradiated with a medium-pressure mercury vapour lamp through Pyrex. The diphenyl derivatives7and8were reactive;7gave 6,6-diphenylhexanal dimethyl acetal (11) and8gave 2-methoxy-2-(5,5-diphenylpentyl)-1,3-dioxolane (12). These are the products expected from the intermediate 1,6-radical cation, formed upon carbon–carbon bond cleavage of the cyclic radical cation. The monophenyl derivatives9cisandtransand10were stable under these irradiation conditions. The mechanism for the carbon–carbon bond cleavage and for thecis–transisomerization is discussed. An explanation, based upon conformation, is offered for the lack of reactivity of9and10. Molecular mechanics (MM2) calculations were used to determine the preferred conformation of9cisandtrans, and10.Keywords: photosensitization, electron transfer, radical cation, carbon–carbon bond cleavage, conformation.

ISSN:0008-4042    

DOI:10.1139/v91-036

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The condensation ofN,N′-bis(1-cyano-1-methylethyl)-N,N′-dihydroxymethanediamine and mesitylboronic acid gives 4,6-bis(1-cyano-1-methylethyl)-2-mesityl-1,3-dioxa-4,6-diaza-2-boracyclohexane in good yield. Crystals of the latter compound are orthorhombic,a = 15.825(1),b = 17.958(1),c = 14.014(1) Ǻ,Z = 8, space groupPbca. The structure was solved by direct methods and was refined by full-matrix least-squares procedures toR = 0.037 andRw = 0.051 for 2844 reflections with1 ≥ 3σ(I). The molecule has a six-membered cycloboronate structure featuring the first structurally characterized BONCNO ring. The ring was found to have aC-envelope conformation in the solid state. Bond lengths include: O—B(sp2) = 1.356(2) and 1.370(2), and C(aryl)—B = 1.560(2) Ǻ.Keywords: organoboron compound, boron compound, crystal structur

ISSN:0008-4042    

DOI:10.1139/v91-037

出版商:NRC Research Press    

年代:1991

数据来源: NRC