摘要:

The fungusMarasmiusoreadeshas previously been reported to produce the sesquiterpenes marasmone (1), anhydromarasmone (2), isomarasmone (3), and dihydromarasmone (4) when grown in liquid culture. We report herein several other sesquiterpene metabolites of the same skeleton but with differing oxidation patterns. The norsesquiterpenesO-formyloreadone (15a), 3α-hydroxyoreadone (15c), and dehydrooreadone (17b) are also reported. It is suggested that the formyl group in15ais derived biogenetically from C-15 of a precursor sesquiterpene. Oxidation of 1α,15-dihydroxymarasmene (13a), one of the new sesquiterpenes reported, with one equivalent of pyridinium dichromate givesO-formyloreadone (15a) as one of the products. Agrocybin (5), a polyacetylene amide previously isolated from the fungusAgrocybedura, has also been isolated from the cultures ofM.oreades. It is suggested that agrocybin (5) is the phytotoxic compound responsible for the killing of grass caused by the fairy ring mushroom fungus.Keywords: sesquiterpenes, fungal metabolites, drimanes, fairy ring mushroom, agrocybin.

ISSN:0008-4042    

DOI:10.1139/v89-210

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Potassium permanganate in aqueous solutions of surfactant can be used to oxidize aromatic compounds to the corresponding acids. It has been found that oxidation of aromatic alcohols and aldehydes proceeds under mild reaction conditions, while the oxidation of alkylbenzenes requires higher temperatures. The yields are very high and the work-up is simple, which makes oxidation with potassium permanganate a convenient synthetic method.Keywords: surfactant, oxidation, aromatic compounds, catalysis.

ISSN:0008-4042    

DOI:10.1139/v89-211

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Reaction of a phenol with an aldehyde in the presence of phenylboronic acid gives a 1,3,2-benzodioxaborin. The latter could be reduced to the correspondingortho-alkylphenol withtert-butylamine borane in the presence of aluminum chloride. Alternatively, the dioxaborin, when reacted with an alkylthiol or an alcohol in the presence of an acid, gave the correspondingortho-alkylthiomethyl- orortho-alkoxymethylphenol.Keywords: phenol, alkylation,ortho-specific, 1,3,2-benzodioxaborin.

ISSN:0008-4042    

DOI:10.1139/v89-212

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Reaction at room temperature of either 3,4,6-tri-O-acetyl-2-azido-2-deoxy-α- or -β-D-galactopyranosyl chloride with a twofold excess of 4-methylumbelliferone and silver trifluoromethanesulfonate in dichloromethane containing an equimolar amount of.sym-collidine yielded 4-methylumbelliferyl tri-O-acetyl-2-azido-2-deoxy-α-D-galactopyranoside in 33% yield. The β anomer was formed in 20 and 10% yields, respectively. Reduction of the azido group, acetylation followed by de-O-acetylation, provided the desired 4-methylumbelliferyl 2-acetamido-2-deoxy-α- and -β-D-galactopyranosides (N-acetyl-α- and -β-D-galactopyranosaminides). The α-glycoside proved to be an effective substrate for the highly sensitive fluorimetric detection ofN-acetyl-α-D-galactopyranosaminidase activity in human tissues and was used to examine the deficiency of this activity, which is the enzymatic defect in Schindler disease.Keywords: synthesis of 4-methylumbelliferylN-acetyl-α- and -β-D-galactopyranosaminides,N-acetyl-α-D-galactosaminidase deficiency (Schindler disease).

ISSN:0008-4042    

DOI:10.1139/v89-213

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

2-Flurophenyl- and 2,5-bis(fluorophenyl)pyrrolidin-1-oxyls (2and6) were synthesized from the corresponding nitrones1,4, and5with the Grignard reagent prepared from 1-bromo-4-fluorobenzene. The reaction of 2,2,5,5-tetramethyl-3-formyl-3-pyrrolin-1-oxyl (8) with (4-FC6H4)2Cd gave 2,2,5,5-tetramethyl-3-(α-hydroxy-4-fluorobenzyl)-3-pyrrolin-1-oxyl (9), which was oxidized with MnO2to 2,2,5,5-tetramethyl-3-(4-fluorobenzoyl)-3-pyrrolin-1-oxyl (10). The aryl nitroxides2,6, and10were nitrated with concentrated H2SO4/HNO3toortho-fluoronitrophenyl compounds3,7, and11. The fluoro nitro derivatives served as versatile synthons in the nucleophilic replacement of fluorine with OH, NH2, α-amino acid ester, or thiol. The hydroxy nitroaryl compounds16,26, and30were nitrated further to give dinitrophenol derivatives17,27, and31.Keywords: fluorophenyl nitroxides, nitroaryl nitroxides, NMR spectra of nitroxides.

ISSN:0008-4042    

DOI:10.1139/v89-214

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Phosphorane ylids react readily with succinic anhydrides to give enol-lactones. With highly substituted succinic anhydrides, condensations occur at the less substituted carbonyl group, suggesting that the reaction is sterically controlled. This, however, is not the case in monosubstituted anhydrides where effects other than steric become dominant. Condensation of phosphorane1awith methoxysuccinic anhydride occurs selectively at the carbonyl group adjacent to the substituent. Stabilization of the transition state through complexation between the oxygen atom of the substituent and an electron-deficient phosphorus of the ylid is proposed.Keywords: cyclic anhydrides, Wittig reaction, regioselectivity, stabilized ylid.

ISSN:0008-4042    

DOI:10.1139/v89-215

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Studies on the specific adsorption of succinate and maleate anions at polycrystalline gold electrode from solutions at constant cationic strength are reported. The adsorption has been studied by differential capacity – potential measurements. The adsorption can be described by one-constant virial isotherm. The basic parameters of this isotherm are determined. Our experimental results are partly interpreted with the help of the results of the adsorption of dicarboxylic anions on the (210) and (311) faces of gold.Keywords: electrochemistry, adsorption, double layer, gold electrode, dicarboxylic ions.

ISSN:0008-4042    

DOI:10.1139/v89-216

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Spectrophotometric studies on the reaction between diiodine and the title ligand in ratios ranging from 1:1 to 1:20 in CHCl3have shown the formation of a 1:1 charge-transfer complex. A general computer program has been used to refine the equilibrium constant and the extinction coefficients simultaneously. In the solid state a 1:2 (donor to acceptor) complex has been isolated and an X-ray structure analysis of the compound indicated that the crystals are monoclinic, space group C2/cwitha = 16.317(4),b = 13.912(3),c = 12.879(3) Å, β = 111.24(2)°,Z = 4.The molecular structure shows that two sulphur-thioamide atoms of the ligand act as donor with respect to two diiodine molecules. The structural data of the organic molecule of the complex and those of the free molecule are very similar.Keywords: diiodine, thioamides, charge-transfer, structure, equilibrium-constants.

ISSN:0008-4042    

DOI:10.1139/v89-217

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The ultraviolet spectrum of aqueous domoic acid solutions has an intense absorption band, whose λmaxshifts from 240.0 ± 0.3 nm at pH 1.3 to 244.7 ± 0.3 nm at pH 12.3. At the same time, its ϵmaxincreases from 24250 to 26700 L mol−1cm−1. At pH 7 λmaxis 242.8 ± 0.3 nm and ϵmaxis 26035 ± 200 L mol−1 cm−1Analysis of the variation of λmaxand ϵmaxwith pH allowed us to estimate the values of these quantities for each of the five stages of protonation of domoic acid and to verify the pKvalues reported by Takemoto and Daigo.Keywords: ultraviolet spectrum, pKvalues, protonation, domoic acid.

ISSN:0008-4042    

DOI:10.1139/v89-218

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The rate constants for detritiation from the C(2) position of 1-methyl[2-3H]histidine have been determined in a series of aqueous buffers at 85 °C. The resulting sigmoidal rate–pH profile was indicative of a mechanism involving hydroxide ion attack on the N(3)-protonated (4) and the amino-protonated (5) forms of 1-methylhistidine, and dissection of the kinetic data allowed the extraction of the second-order rate constants for the two pathways,kandk′. The unusually large value ofk′for a species not protonated at N(3) of the imidazole ring suggested the involvement of a kinetically equivalent zwitterionic form of the substrate (7). Comparison of the rate constantkwith values determined previously for closely related substrates, such as histidine, 1-methylimidazole, and imidazole, led to the use of FMO theory to explain the effect of the various structural changes, e.g., the effect of methylation and a positively charged side chain onkandk′. The addition of MeHgNO3resulted in a decrease in the pseudo-first-order rate constant for detritiation. The rate retardation was discussed in terms of two mechanisms (Schemes 2 and 3). Analysis of the data in terms of the various metal-ion-coordinated species present under the experimental conditions showed that the reactivity of the protonated substrate greatly exceeds that of the metal-coordinated species. The difference in the catalytic ability of H+vs. MeHg+is discussed in terms of the extent of positive charge developed on the ligating heteroatom in the ylide (carbenoid) reaction intermediate.Keywords: methylmercury, 1-methylhistidine, isotopic exchange, proton transfer, metal ion catalysis.

ISSN:0008-4042    

DOI:10.1139/v89-219

出版商:NRC Research Press    

年代:1989

数据来源: NRC