摘要:

Treatment of 3-[2-(4,4-dimethyl-4,5-dihydrooxazolin-2-yl)]-4-phenyl-1,4-dihydropyridine (13) with NaH–DMSO, and then reaction with 1,1-bis(2-methylphenyl)-4-bromobutane (12c) afforded 1-[4,4-bis(2-methylphenyl)butyl]-3-[2-(4,4-dimethyl-4,5-dihydrooxazolin-2-yl)]-4-phenyl-1,4-dihydropyridine (14). Reaction of methyl nicotinate with 2.1 equivalents12cor 1,1-bis(2-methylphenyl)-4-bromo-1-butene (11b) afforded 4,4-bis(2-methylphenyl)butyl 1-[4,4-bis(2-methylphenyl)butyl]pyridinium-3-carboxylate bromide (17) or 4,4-bis(2-methylphenyl)-3-butenyl 1-[4,4-bis(2-methylphenyl)-3-butenyl]pyridinium-3-carboxylate bromide (18), respectively. The nonregioselective reaction of the pyridinium salts(17/18)with PhMgCl in THF at −23 °C using a catalytic amount of CuI afforded a mixture of isomeric 4-phenyl-1,4-dihydropyridyl(21or22)and 6-phenyl-1,6-dihydropyridyl (27or28) products in a ratio of approximately 1:1. All attempts to hydrolyze the 4,4-bis(2-methylphenyl)butyl or 3-butenyl ester moiety of21/22or27/28to a carboxyl group resulted in decomposition products. In contrast, the corresponding 3-(2-cyanoethyl) esters (23,24,29,30) were readily converted to the corresponding carboxyl analogs (25,26,31, 32)via a β-elimination reaction of acrylonitrile using the non-nucleophilic base DBU. The 4-phenyl-1,4-dihydropyridyl (14,25,26) and 6-phenyl-1,6-dihydropyridyl(27/28or31/32)compounds inhibited the in vitro uptake of [3H]GABA into striatal prisms in the 21–44% range at a 10−4 M test compound concentration, relative to the reference drug nipecotic acid (87% inhibition). Structure–activity correlations showed the dihydropyridyl C-3 substituent was a determinant of [3H]GABA uptake where the potency order was CO2H > 2-(4,4-dimethyl-4,5-dihydrooxazolin-2-yl) > CO2(CH2)3CH-(o-tolyl)2and CO2(CH2)2CH=C-(o-tolyl)2. Compounds possessing C-3 and (or) N-1 CO2(CH2)3CH-(o-tolyl)2substituents were generally more potent than analogs having CO2(CH2)2CH=C-(o-tolyl)2substituents. In general, 1,6-dihydropyridyl compounds were more potent than the corresponding 1,4-dihydropyridyl isomers.Keywords: 1,4- and 1,6-dihydropyridines, GABA-uptake inhibitors.

ISSN:0008-4042    

DOI:10.1139/v97-071

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Reaction of the bridged [14]annulenequinone,trans-10b,10c-dimethyl-10b,10c-dihydropyrene-2,7-quinone (12), with malononitrile in the presence of pyridine and TiCl4gave 68% of the deep-purple extended TCNQ derivative, α,α,α′,α′-tetracyano-trans-10b, 10c-dimethyl-10b, 10c-dihydropyrene-2,7-quinodimethide (13). In solution, quinodimethide13appears to form a complex with diethylamine, but is too weak an electron acceptor to form complexes with tetrathiafulvalene, TTF, and related donors. The reduction potential of13was substantially lower than that found for TCNQ itself, and in properties13behaves more like a benzannelated TCNQ derivative, e.g., α,α,α′,α′-tetracyanopentacene-7,14-quinodimethide (11), than a pyrene derivative, e.g., α,α,α′,α′-tetracyanopyrene-2,7-quinodimethide (6). This is in agreement with molecular orbital calculations, which indicate that the LUMOs of13and11are approximately 0.6 eV higher in energy than those for6and TCNQ.Keywords: TCNQ — extended, TCNQ-pyrene derivative, reduction potential, annulene-quinodimethide, electron acceptor — weak.

ISSN:0008-4042    

DOI:10.1139/v97-072

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The hydrolysis of a pyridine solution of lithium tetrakis(N-dihydropyridyl)aluminate (LDPA), which was prepared at 0 °C, yields a mixture of 1,4-, 1,2-, and 2,5-dihydropyridines (DHPs) in a ratio of 26:37:38. The subsequent reversible base-catalyzed condensation of a 1:1 mixture of 1,2- and 2,5-DHPs carried out in the presence of oxygen affords an 89% yield of (±)-anatabine. When the reaction mixture is allowed to stand in the presence of oxygen, anabasine is slowly formed from anatabine by the reaction of the residual DHPs. Anatabine can also be converted into (±)-anabasine by catalytic hydrogenation.Keywords: lithium aluminum hydride, pyridine, anatabine, anabasine.

ISSN:0008-4042    

DOI:10.1139/v97-073

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

A ring expansion approach to α-cuparenone was accomplished in 5 or 6 steps. The key intermediate is 3-methyl-3-(4-methylphenyl)cyclobutanone, which was derived from a [2 + 2]cycloaddition of dichloroketene on a styrene derivative, followed by dechlorination.Keywords: symmetry, α-cuparenone, ring expansion, sesquiterpene.

ISSN:0008-4042    

DOI:10.1139/v97-074

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

New bisindolylbenzenoids designated petromurins A (1), B (2), C (3), and D (4) were isolated from the ascostromata ofPetromycesmuricatus. These structures were determined by chemical and spectroscopic methods.Keywords:Petromycesmuricatus; bisindolylbenzenoids; petromurin A, B, C, and D; ascostromata;Aspergillusmuricatus.

ISSN:0008-4042    

DOI:10.1139/v97-075

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

TheC3symmetric oxazolinyl ligand1has been synthesized. Compound1catalyzed the addition of diethylzinc to aromatic aldehydes to give secondary alcohols with high enantiomeric excesses (up to 90%).Keywords: diethylzinc, enantioselective synthesis,C3symmetric ligands, enantioselective addition reactions, oxazolinyl ligands.

ISSN:0008-4042    

DOI:10.1139/v97-076

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

(−)-Chenopodanol (2) has been isolated from the liverwortMarchantiachenopodaand its structure determined by spectroscopic techniques as well as by total synthesis. Chenopodene (1) has also been synthesized in an optically active form, resulting in revision of the originally assigned absolute configuration.Keywords: chenopodanol, chenopodene, liverwort,Marchantiachenopoda, sesquiterpene.

ISSN:0008-4042    

DOI:10.1139/v97-077

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

A total synthesis of mycophenolic acid is reported. Diels–Alder reaction of [5-methoxy-3-(1-methoxypropenyl)-4,5-dihydrofuran-2-yloxy]-trimethylsilane with 3-benzenesulfinyl-5H-furan-2-one afforded the hexasubstituted nucleus. The side chain was constructed from the unveiled aldehyde.Keywords: mycophenolic acid, Diels–Alder reaction, pentasubstituted diene.

ISSN:0008-4042    

DOI:10.1139/v97-078

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

A general synthetic approach to diterpenoids of thecis-clerodane family has been developed, leading to the first total synthesis, in racemic form, of 2-oxo-5α,8α-13,14,15,16-tetranorclerod-3-en-12-oic acid (2). The key operation involved is the face-selective Diels–Alder reaction of dienone ester10withtrans-piperylene, giving rise to adduct11containing the decalin nucleus and correct stereogenic centers common to manycis-clerodane diterpenoids.Keywords:cis-clerodanes, general synthetic approach, total synthesis, face-selective Diels–Alder reaction.

ISSN:0008-4042    

DOI:10.1139/v97-079

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Spiroannulation of ketals derived from unsaturated cyclohexenone derivatives by the Lewis acid-catalyzed reaction of 1,2-bis((trimethylsilyl)oxy)cyclobutene5led to spiro[4.5]decene-diones9and30. These were transformed into spiro[4.4]nonene derivatives25and35/36via similar sequences involving ozonolysis and aldol ring reclosure. Reduction of an annular double bond allowed facile closure of a third ring, also by an aldol reaction. This work led to a single oxygenated angular triquinane28from9, and to the tricyclo[6.2.1.01,5]undecane derivative41from30. An oxatricyclo[5.3.1.01,5]undecane derivative19was also obtained from9.Keywords: spiroannulation, geminal acylation, sesquiterpene synthesis.

ISSN:0008-4042    

DOI:10.1139/v97-080

出版商:NRC Research Press    

年代:1997

数据来源: NRC