Stereospecific Michael addition of dithioester enethiolates with acyclic enones

Cis lithium enethiolates, generated from substituted dithioesters, undergo 1,4-addition uith vapious β-monosubstituted α-unsaturated ketones. With acyclic enones one of the tw resulting diastereomeric 5-oxodithioesters is predominantly formed (ratio up to 95 : 5). Its anti configuration was proven by chemical correlation in one case. Evidence for fhe stereospecificity of this Michael, addition is given.     

First catalytic enantioselective synthesis of the cocaine abuse therapeutic agent (S)-(+)-1-(4-{2-[bis(4-fluorophenyl)methoxy]ethyl}piperazin-1-yl)-2-phenyl-2-propanol

(S)-(+)-1-(4-{2-[Bis(4-fluorophenyl)methoxy]ethyl}piperazin-1-yl)-2-phenyl-2-propanol, which is a promising candidate as a cocaine abuse therapeutic agent, is prepared in several steps. The key asymmetric step is the catalytic enantioselective addition of dimethylzinc to either 2-chloro or 2-bromoacetophenone catalyzed by the use of different chiral isoborneolsulfonamide ligands in the presence of titanium tetraisopropoxide. The synthesis of a new isoborneolsulfonamide ligand bearing a trifluromethyl substituent and its use in this addition is also presented.     

无外加催化剂条件下邻取代芳香醛与5,5-二甲基-1,3-环己二酮的反应研究

在DMF溶剂中,不外加催化剂使邻取代芳香醛(1)与5,5-二甲基-1,3-环己三酮(2)发生缩合和加成反应生成3,3,6,6-四甲基-4a-羟基-9-芳基-1,8二氧化-2,3,4,4a,5,6,7,8,9a-十氢化-1H氧杂蒽(3a～3d)。在同样条件下,邻羟基芳香醛与5,5-二甲基-1,3-环己三酮则发生缩合,加成和脱水反应生成3,3-二甲基-9-(5,5-二甲基-3-羟基-2-环己烯-1-酮-2-基)-1-氧代-2,3,4,9-四氢化-1 氧杂蒽(4a～4b)。用单晶X-射线分析法确定了产物3a和4a的晶体结构。     

Characterization of the activity of L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-be nzopyran-6-yl-hydrogen phosphate] potassium salt in hydroxyl radical elimination

The effect of L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H -1-benzopyran-6-yl-hydrogen phosphate] potassium salt (EPC-K1) on hydroxyl radical (*OH) elimination was studied using electron spin resonance (ESR) and spectrophotometric experiments. The addition of EPC-K, and *OH scavengers eliminated the *OH generated from Cu2+/H2O2, Fe2+/H2O2 and H2O2/UV-irradiation reaction systems. However, in competitive reactions using different concentrations of a spin-trap agent, the addition of the *OH scavenger altered the IC50 values, whereas the addition of EPC-K1 and a metal chelater did not change the value in the Cu2+/H2O2 and Fe2+/H2O2 reaction systems. The addition of EPC-K1 and metal chelater changed the ESR signal for free Cu2+. The spectrophotometric experiments confirmed that the addition of EPC-K1 and metal chelater altered the absorption spectra due to CuCl2 and FeSO4, whereas the *OH scavenger did not alter the spectra. Therefore, it was demonstrated that EPC-K, has the ability both to scavenge *OH directly and to inhibit the generation of *OH by the chelation of Cu2+ and Fe2+.     

Syntheses and properties of 2-[(dimethylamino)methyl]-1-hydroxyferrocene and its derivatives

A 1,2-disubstituted ferrocene derivative, 2-[(dimethylamino)methyl]-1-hydroxyferrocene (I), was prepared from 2-[(dimethylamino)methyl]-1-iodoferrocene via 2-[(dimethylamino)methyl]-1-acetoxyferrocene. On complexation, compound I served as a stable monovalent chelate ligand of a 1,2-disubstituted ferrocene derivative. In addition, a dihydroxy derivative, 2-(hydroxymethyl)-1-hydroxyferrocene, was obtained from hydrolysis of the methiodide formed from I.     

Synthesis and antifungal activities of (2R,3R)-2-aryl-1-azolyl-3-(substituted amino)-2-butanol derivatives as topical antifungal agents.

2-Aryl-1-azolyl-3-(substituted amino)-2-butanol derivatives I were prepared by ring-opening reaction of epoxides II with excess amine, and their antifungal activities were evaluated as topical agents. Azolyl-cyclic amine derivatives with a methylene group showed extremely strong activity with a broad spectrum in vitro. In general, anti-Trichophyton mentagrophytes activities of most of the topical antifungal agents are substantially reduced by addition of keratin (a major constituent of the keratinized tissue). However, the triazole derivative (2R,3R)-2-(2,4-difluorophenyl)-3-(4-methylenepiperidino)-1-(1H-1,2 ,4- triazol-1-yl)-2-butanol ((-)-40, KP-103) showed very little deactivation by addition of keratin. This biological characteristic of triazole derivative (-)-40 resulted in excellent therapeutic efficacy on dermatophytosis superior to that of the corresponding imidazole derivative ((-)-41).     

Synthesis of 1-halophenyl 4-(2-imidazolyl)-1-butanones and 5-(2-imidazolyl)-1-pentanones and their ketalization with glycerol

An alternate synthesis of 1-(2,4-dichlorophenyl)-4-(2-imidazolyl)-1-butanones 5d is presented after 1-[(dimethylamino)methyl- and 1-methyl]-2-lithioimidazole failed to be substituted satisfactorily by 2-(2,4-dichlorophenyl)-2-(3-iodopropyl)-1,3-dioxolane ( 3b ). The Pinner addition of ethanol to 2-(2,4-dichlorophenyl)-2-(3-cyanopropyl)-1,3-dioxolane yielded the corresponding imidate which was reacted with 1-amino-2,2-dimethoxyethane to form an amidine. Hot dilute hydrochloric acid converted this ami-dine to the 2-imidazolyl ketone 5b . Syntheses of homologous 1-(4-chloro- and 2,4-dichlorophenyl)-4-(2-imidazolyl)-1-pentanones 20 are described. Ketalizations of 5 and 20 with glycerol formed imidazolyl 1,3-dioxolanyl alcohols. Selective N- and O-alkylations of some of these imidazolyl alcohols are described.     

Concise total synthesis of (-)-8-epigrosheimin

A highly efficient route was developed to synthesize (-)-8-epigrosheimin in four steps from aldehyde 2 based on a substrate-controlled method. The key steps of the synthesis included (1) a stereo- and regioselective allylation addition, (2) an intramolecular translactonization, and (3) an aldehyde-ene cyclization.     

Synthesis of 1-alkyl-2,3-dihydro-2-(4-pyridinyl)-1H-isoindoles as potential selective serotonin reuptake inhibitors

Two 2,3-dihydro-2-(4-pyridinyl)-1H-isoindoles 2a,b have been synthesized by the reaction of isoindoline with 4-chloropyridines. In addition, a number of 1-alkyl-2,3-dihydro-2-(4-pyridinyl)-1H-isoindoles 2c-h were obtained from 2-(4-pyridinyl)phthalimide (5). The addition of alkyl Grignard reagents to 5 gave 1-alkylhydroxyisoindolones 6a-f which, in two cases 6a,b , were dehydrated and subjected to three separate reductions to give targets 2c,d . In three cases, the intermediate hydroxyisoindolones 6c-e were reduced in one step to the target compounds 2c-g with lithium aluminum hydride-aluminum chloride. When 6f , the product of the addition of phenyl Grignard to 5 , was subjected to these conditions, a hydroxyisoindoline 7 was obtained which was further reduced to 2h with triethylsilane-trifluoroacetic acid. The lithium aluminum hydride-aluminum chloride conditions were successfully applied to the synthesis of a 1-benzyl-4-piperidine derivative 21.     

Asymmetric synthesis of (1R,2S,3R)-3-methylcispentacin and (1S,2S,3R)-3-methyltranspentacin by kinetic resolution of tert-butyl (+/-)-3-methylcyclopentene-1-carboxylate

Conjugate addition of lithium dibenzylamide to tert-butyl (+/-)-3-methylcyclopentene-1-carboxylate occurs with high levels of stereocontrol, with preferential addition of lithium dibenzylamide to the face of the cyclic alpha,beta-unsaturated acceptor anti- to the 3-methyl substituent. High levels of enantiorecognition are observed between tert-butyl (+/-)-3-methylcyclopentene-1-carboxylate and an excess of lithium (+/-)-N-benzyl-N-alpha-methylbenzylamide (10 eq.) (E > 140) in their mutual kinetic resolution, while the kinetic resolution of tert-butyl (+/-)-3-methylcyclopentene-1-carboxylate with lithium (S)-N-benzyl-N-alpha-methylbenzylamide proceeds to give, at 51% conversion, tert-butyl (1R,2S,3R,alphaS)-3-methyl-2-N-benzyl-N-alpha-methylbenzylaminocyclopentane-1-carboxylate consistent with E > 130, and in 39% yield and 99 +/- 0.5% de after purification. Subsequent deprotection by hydrogenolysis and ester hydrolysis gives (1R,2S,3R)-3-methylcispentacin in > 98% de and 98 +/- 1% ee. Selective epimerisation of tert-butyl (1R,2S,3R,alphaS)-3-methyl-2-N-benzyl-N-alpha-methylbenzylaminocyclopentane-1-carboxylate by treatment with KO'Bu in 'BuOH gives tert-butyl (1S,2S,3R,alphaS)-3-methyl-2-N-benzyl-N-alpha-methylbenzylaminocyclopentane-1-carboxylate in quantitative yield and in > 98% de, with subsequent deprotection by hydrogenolysis and ester hydrolysis giving (1S,2S,3R)-3-methyltranspentacin hydrochloride in > 98% de and 97 +/- 1% ee.     

1-(2'-苯基-1', 2', 3'-三唑-4'-甲酰基)-4-芳基氨基硫脲及其 环化产物的合 成

以2-苯基-1,2,3-三唑-4-甲酰肼为原料合成了几种新的1-(2'-苯基-1',2',3'-三唑-4'-甲酰基)-4-芳基氨基硫脲,在不同条件下环化,制得一系列新的1,3,4-噻二唑、1,3,4-恶二唑和1,2,4-均三唑衍生物。化合物的结构经元素分析、IR、^1HNMR和MS确证,并对其波谱性质进行了讨论。     

1-(Triorganylsilyl)-2-(triethoxysilyl)ethanes

Conclusions The conditions were found for the hydrosilylation of CH₂=CHSi(OC₂H₅)₃ with triorganylsilanes in the presence of H₂PtCl₆ · 6H₂O in isopropanol, which assured a high yield (>90%) of the 1-(triorganylsilyl)-2-(tri-ethoxysilyl)ethanes. These conditions were used to synthesize 27 new 1-(triorganylsilyl)-2-(triethoxysilyl)-ethanes.The addition of (C₂H₅O)₃SiH to (CH₂=CHSi(CH₃)₃ in the presence of the same catalyst gave 1-(trimethyl-silyl)-2-(triethoxysilyl)ethane in 98.6% yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1622–1625, July, 1976.     

Bromination of N-(o-Aminophenyl)-cis-4-cyclohexene-1,2-dicarboximide and cis-2-(2-Benzimidazolyl)-4-cyclohexene-1-carboxylic Acid

Exhaustive oxidative bromination of N-(o-aminophenyl)-cis-4-cyclohexene-1'2-dicarboximide and2-(2-benzimidazolyl)-cis-4-cyclohexene-1-carboxylic acid results in bromine addition at the double bond.Under more severe conditions, the addition of bromine at the double bond is accompanied by bromination ofthe aromatic ring. The latter process does not occur in the exhaustive bromination of cis-2-(2-benzimidazolyl)-4-cyclohexene-1-carboxylic acid.     

Synthesis and pharmacological evaluation of 2-(1-alkylpiperidin-4-yl)-n-[(1r)-1-(4-fluorophenyl)-2-methylpropyl]acetamide Derivatives as Novel Antihypertensive Agents

We synthesized and evaluated the inhibitory activity of a series of 2-(1-alkylpiperidin-4-yl)-N-[(1R)-1-(4-fluorophenyl)-2-methylpropyl]acetamide derivatives against T-type Ca(2+) channels. Structure-activity relationship studies revealed that the position of the amide structure was important for the potent inhibitory activity toward T-type Ca(2+) channels. In addition, the introduction of an appropriate substituent on the pendant benzene ring played a crucial role for the selectivity towards T-type Ca(2+) channels over L-type Ca(2+) channels and the potent bradycardic activity of these derivatives. Oral administration of N-[(1R)-1-(4-fluorophenyl)-2-methylpropyl]-2-(1-{2-[2-(2-methoxyethoxy)phenyl]ethyl}piperidin-4-yl)acetamide (4f), which had superior selectivity for T-type Ca(2+) channels over L-type Ca(2+) channels, lowered blood pressure in spontaneously hypertensive rats without inducing reflex tachycardia, which is often caused by traditional L-type Ca(2+) channel blockers.     

On the easy oxidation of (R)-2-[N-(1-phenylethyl)amino]-1-cyclopentenedithiocarboxylic acid to its disulfide dimer

The physical and spectroscopic data of (R)-2-[N-(1-phenylethyl)amino]-1-cyclopentenedithiocarboxylic acid are reviewed and the synthesis of (R)-di-[2-(N-(1-phenylethyl)amino]-1-cyclopentenedithiocarboxylic acid disulfide is described. The product resulting from the conjugate addition of the dithioacid to 2(5H)-furanone is also characterised.     

Triethylamin-mediated addition of 2-aminoethanethiol hydrochloride to chalcones: Synthesis of 3-(2-aminoethylthio)-1-(aryl)-3-(thiophen-2-yl) propan-1-ones and 5,7-diaryl-2,3,6, 7-tetrahydro-1,4-thiazepines

The triethylamin-mediated addition of 2-aminoethanethiol hydrochloride to chalcone analogs was investigated. This addition, bearing a 2-thienyl group at the 3-position, gave the only addition adduct at room temperature in 3 h, whereas the chalcones bearing the 2-furyl group at the 1-position gave an addition-cyclization product (1, 4-thiazepine) in the same conditions. The effect of the groups to the reaction was investigated by changing the 1- and 3-position groups. The chalcones bearing the 2-thienyl group at the 1-position and the others afforded the mixture of products in different ratio at rt for 0.5–24 h. Moreover, the addition–cyclization products (1,4-thiazepine) were obtained under reflux conditions in 36 h. The structures of the synthesized compounds were elucidated by ¹H NMR, ¹³C NMR, infrared, and elemental analysis.     

Synthesis and Spectrophotometric Studies of 2-(1, 3, 4 -Triazolylazo) -5-Diethylamino Phenol and 2-(5-Carboxy-1, 3, 4-Triazolylazo) -5- Diethylamino Phenol

Inasearchfornewsensitiveandselectiveorganicreagents,athoroughstudyofsomeofthequinolylazo,pyridylazocompoundshasbeenreported'-'.Buttriazolylazocompoundshavenotbeenstudied.Inthispapef,2-(l,3,4-triazolylazo)-5-diethyIaminophenol(TZAPN)and2-(5-carboxy-l,3,4-triazoiylazo)-diethyIaminophenoI(CTZAPN)wereprepared,theconditionsofthisreactionwithcobaltwerestudied.Itwasfoundthatthereagentshadhighsensitivityandselectivityinthedeterminationofmicrogramamountsofcobaltundertheconditionsestablished.Thest…     

Dipotassium Hydrogen Phosphate Powder Catalyzed Stereoselective O-Vinylation of 1-(2-Hydroxy-1-naphthyl)-1-ethanone

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by 1-(2-hydroxy-1-naphtyl)-1-ethanone leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce corresponding stabilized phosphorus ylides. Dipotassium hydrogen phosphate powder was found to catalyze the conversion of stabilized phosphorus ylides to dialkyl (E, Z)-2-(1-acetyl-2-naphthyl)-2-butenedioates under thermal and microwave conditions in a solventless system.     

Synthesis and Spectrophotometric Studies of 2-(2-Imidazolylazo)-5- Dicthylamino Phenol

Inasearchfornewsensitiveandselectiveorganicreagents,athoroughstudyofslomeofthequinolylazo,pridylazocompoundshasbeenreported.'-'Buttriazolylazoandimidazolylazocompoundshavenotbeenstudied.Inanearliespaper,'wehavereportedthesynthesisandspectrophotometricstudiesof2-(l,3,4-triazolylazo)-5-diethy\phenoland2-(5-carboxy-l,3,4-triazolylazo)phenol.Inthispaper,2-(2imidazolylazo)-5-diethylaminophenol(IZAPN)wasprepared,theconditionsofitsreactionwithcobaltwerestudied.Itwasfoundthatthereagenthadhighsensiti…     

C-24 stereochemistry of marine sterols: (22E)-24-(isopropenyl)-22-dehydrocholesterol and 24-isopropenylcholesterol

The C-24 configuration of (22E,24xi)-24-isopropenyl-22-dehydrocholesterol (1), which was recently isolated from the Colombian Caribbean sponge, Topsentia ophiraphidites, was investigated. Synthesis of the stereodefined (24R)- and (24S)-(22E)-24-isopropenyl-22-dehydrocholesterols (1a, 1b) followed by (1)H- and (13)C-NMR data comparison of these sterols established the (24R)-configuration of 1. In addition, (24R)- and (24S)-24-isopropenylcholesterols (2a and 2b) were also synthesized and their NMR data are provided. The C-24 configurations of the samples of 24-isopropenylcholesterol reported previously are discussed.