摘要:

Wessely oxidation ofo-(3-alkenyl) phenols (5) with lead tetraacetate gives 6-acetoxy-6-(3-alkenyl)-2,4-cyclohexadien-1-ones (6), which undergo intramolecular Diels–Alder reactions to give isotwistene (hexahydro-1,5-methanoindene) derivatives (7). These, on hydrolysis followed by oxidation with periodic acid, give hexahydro-1-oxo-1H-indene-5-carboxylic acids (41,46). Compounds5were prepared either by Grignard coupling ofo-methoxybenzyl chloride with allyl halides followed by de-O-methylation with sodium thioethoxide or via reduction of dihydrocoumarins(18–20)to 2-chromanols(21–23)with diisobutylaluminum hydride, followed by Wittig reaction of these with ethyl (triphenylphosphoranylidene)acetate.

ISSN:0008-4042    

DOI:10.1139/v88-001

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The radical chain decomposition of cyclopropylmethyl (1-hydroxy-1-methylethyl)-diazeneat 253–341 K in hexafluorobenzene or in dichloromethane solution containing bromotrichloromethane affords cyclopropylmethyl bromide, 4-bromo-1-butene, 1-bromo-5,5,5-trichloro-2-pentene, and 3,5-dibromo-1,1,1-trichloropentane from the cyclopropylmethyl portion of1. Other major products are nitrogen, acetone, and chloroform. The rate constant for formation of cyclopropylmethyl bromide by attack of cyclopropylmethyl free radicals from1at bromine of BrCCl3was calculated from the product composition using the known rate constant for rearrangement of cyclopropylmethyl radicals to 3-buten-1-yl radicals. At 25 °C,and the temperature dependence is given by, where θ = 2.3RT kcal/mol−1. Non-chain decomposition of (CH3)2C(OH)N=N—R (2, R = Bu, and3, R = Ph) in the presence of excess 1,1,3,3-tetramethylisoindolin-2-yloxyl (4) and bromotrichloromethane afforded BuBr and PhBr, respectively, in yields determined by the relative concentrations of4and BrCCl3. Rate constants for coupling (kc) of Bu• and Ph• with4were assumed to be proportional to rate constants for diffusion controlled reactions,kd, which were estimated from measured viscosities. Values ofand, calculated fromkcand product yields for reactions at 80 °C, are 0.26 × 109and 1.55 × 109 M−1s−1, respectively. The relative radical reactivities toward BrCCl3at 80 °C are Ph, 6; cpm, 5; Bu, 1.

ISSN:0008-4042    

DOI:10.1139/v88-002

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

This work demonstrates that organic compounds can be synthesized up to 1240 times faster in sealed Teflon vessels in a microwave oven than by conventional (reflux) techniques. It is shown that all polar molecules absorb microwave energy rapidly and that the rate of energy absorption varies with the dielectric constant. The rates of reaction of polar molecules in nonpolar solvents are not increased appreciably by the microwave method. Also, the homogeneity of the reaction does not affect the rate enhancement. The rate enhancement arises predominantly because the oven superheats the solvent rapidly. Finally, pressure (temperature) measurements have shown that the maximum rate enhancement is achieved when the proper power level and volume of solvent are used. It appears that rate enhancements of approximately 200 are possible for many reactions if the reaction conditions are optimized.

ISSN:0008-4042    

DOI:10.1139/v88-003

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Two syntheses of the bicyclic α-ketols, 8a-hydroxy-4a-methyl-trans- and -cis-octahydronaphthalen-1(2H)-ones (1and2), have been effected. One involves epoxidation of 4a-methyl-1,2,3,4,4a,5,6,7-octahydronaphthalene (4), followed by hydrolysis and oxidation; direct "hydroxy ketonization" of4was found not to be practicable. The second involves treatment of 3,4,5,6,7,8-hexahydronaphthalen-1(2H)-one (14) with lithium dimethylcuprate, trimethylsilylation of the resulting enolate, oxidation of the enol ether, and hydrolysis. Syntheses of the 2α-deutero derivatives of1and2are also described.

ISSN:0008-4042    

DOI:10.1139/v88-004

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The electrochemical oxidation of [amide-Ag-amide]Ag, [amide-Ag-amide]Et4N, and [amide]Et4N salts of imides and formanilides, in acetonitrile containing tetraethylammonium tetrafluoroborate, at platinum and vitreous carbon electrodes, is a one-electron and irreversible (αn < 1) process leading to an amidyl radicals that preferentially abstracts hydrogen from the medium to give the parent amide.N,N-Coupling (formation of hydrazine derivatives) was observed in the oxidation of the amide-Ag-amide anions of formanilide andp-methoxyformanilide. No coupling was observed in the oxidation of the amide-Ag-amide anion ofp-cyanoformanilide and of imides, and in the oxidation of any of the tetraethylammonium salts (amidyl anions) studied. The formanilidyl radical was trapped byN-tert-butyl-α-phenylnitrone. Attempts to trap the succinimidyl radical by addition to olefins were unsuccessful.

ISSN:0008-4042    

DOI:10.1139/v88-005

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Two novel bicyclic diterpenoides, agelasimine-A (9), and agelasimine-B (10), have been isolated from the orange spongeAgelasmauritiana. Also, a new bromine-containing alkaloid, 5-debromomidpacamide (12), along with midpacamide (13) and methylN-methyl-4,5-dibromopyrrole-2-carboxylate (11), has been isolated. The structures were determined by interpretation of their spectral data. Agelasimine-A and -B exhibit a wide range of interesting biological activities such as cytotoxicity, inhibition of adenosine transfer into rabbit erythrocytes, Ca2+-channel antagonistic action, and α1adrenergic blockade.

ISSN:0008-4042    

DOI:10.1139/v88-006

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The chemical structure of a novel lactone isolated from the discolored heartwood of living western red cedar (WRC) (ThujaplicataDonn.) trees has been determined as 3,3,4,7,7,8-hexamethyl-2,6-dioxa-1,5-anthracene-dione, and given the trivial name thujin (1). The isolation, purification, and determination of the structure were carried out by a combination of chemical, chromatographic, and spectroscopic methods.

ISSN:0008-4042    

DOI:10.1139/v88-007

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

77Se and1H nuclear magnetic resonance spectra have been measured for selenols (RSeH), diselenides (RSeSeR), and selenenyl sulfides (RSeSR′), including selenenyl sulfides formed by reaction of glutathione and penicillamine with selenocystine and related diselenides. Exchange processes strongly affect the77Se and1H nuclear magnetic resonance spectra of all three classes of compounds. Sharp, exchange-averaged resonances are observed in the1H nuclear magnetic resonance spectra of selenols; however, selenol proton exchange causes the77Se resonances to be extremely broad over the pH range where the selenol group is titrated. Selenol/diselenide exchangealso results in exchange-averaged1H resonances for solutions containing RSeH and RSeSeR; however, the77Se resonances were too broad to detect. Exchange reactions have similar effects on nuclear magnetic resonance spectra of solutions containing selenols and selenenyl sulfides. The results indicate selenol/diselenide exchange is much faster than thiol/disulfide exchange. The77Se chemical shift depends on the chemical state of the selenium, e.g., titration of the selenol group of selenocysteamine causes the77Se resonance to be shielded by 164 ppm, oxidation of the selenol to form the diselenide selenocystamine causes a deshielding of 333 ppm, and oxidation to form the selenenyl sulfideresults in a deshielding of 404 ppm.77Se chemical shifts were found to be in the range −240 to −270 ppm (relative to (CH3)2Se) for selenolates, approximately −80 ppm for selenols, 230–360 ppm for diselenides, and 250–340 ppm for selenenyl sulfides. The77Se chemical shift is also affected by titration of neighboring carboxylic acid and ammonium groups, and their pkAvalues can be calculated from77Se chemical shift data.

ISSN:0008-4042    

DOI:10.1139/v88-008

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Synthesis of new carbocyclic analogs of 1-(2′,3′-dideoxy-glycero-pentofuranosyl)pyrimidine nucleosides having the uracil (34), 2-thiouracil (33), 2-thiothymine (31), cytosine (44), and 5-methylcytosine (43) bases is described. The nucleoside analogs having the uracil, 2-thiouracil, and 2-thiothymine bases were prepared by couplingcis-3-aminocyclopentanemethanol (8) with 3-ethoxypropenoyl isocyanate (26), 3-ethoxypropenoyl isothiocyanate (25), and 3-methoxy-2-methylpropenoyl isothiocyanate (23), respectively, to give the corresponding acyl urea (30) and acyl thioureas (29and27). The acyl urea was cyclized in 2 NH2SO4and the acyl thioureas in 15 Naqueous ammonia to give the corresponding nucleoside analogs. The nucleoside analogs containing the cytosine (44) and 5-methylcytosine (43) bases were prepared from the uracil and thymine nucleoside analogs, respectively, by way of the 4-chloropyrimidinone intermediates (42and41). The synthesis ofcis-3-aminocyclopentanemethanol (8) from norbornene by way ofcis-1,3-cyclopentanedicarboxylic acid anhydride (3) is also described. In addition, the ease of nucleophilic opening of compound3is compared to the opening of camphoric anhydride (9), which contains acis-vicinal substituent at position 2. The relative ease of opening of compound3is discussed with respect to the effect, observed in an earlier study, that acis-vicinal acetoxy group has on the course of the nucleophilic opening of such anhydrides. The1H magnetic resonance spectra at 200 MHz of all of the synthetic intermediates and of the nucleoside analogs have been determined and discussed. The nucleoside analogs were screened for cell-growth inhibition using K-562 cells. Nucleoside analogs having the 2-thiouracil (33), 2-thiothymine (31), cytosine (44), and 5-methylcytosine (43) bases showed some growth inhibition with activity 150 to 300 times lower than that shown by 5-fluorouracil in this test system.

ISSN:0008-4042    

DOI:10.1139/v88-009

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A semiempirical approach for predicting13C nuclear magnetic resonance chemical shifts of acyclic hydrocarbons has been adapted to a microcomputer program. A series of methyl and dimethyl substituted cholesterols has been studied using this program, and the predicted shifts are in agreement with literature reports. Preferred conformations of the steroidal side chains have been also predicted and agree with previous studies. A simple rule for analyzing the trends in the chemical shift of the carbon C-20, which is sensitive to changes in the configuration at C-22, is also given, not only for hydrocarbon side chains but also for hydroxy substituted compounds.

ISSN:0008-4042    

DOI:10.1139/v88-010

出版商:NRC Research Press    

年代:1988

数据来源: NRC