β-Lactam Ring Opening in the Reformatsky Reaction of (3R,4R)-4-Acetoxy-3-((1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl)azetidin-2-one with Ethyl 4-Bromo-3-oxopentanoate

Russian Journal of Organic Chemistry - The Reformatsky reaction of (3R,4R)-4-acetoxy-3-((1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl)­azetidin-2-one with ethyl 4-bromo-3-oxopentanoate gave...     

Synthesis of pure methyl [(2S,3R,αR)-1-(3-bromo-4-methoxyphenyl)-3-(α-acetoxy)ethyl-4-oxoazetidin-2-carboxylate] and its enantiomer

Synthesis of key intermediates leading to 2-iso-oxacephems was carried out starting from l- and d-threonine. As predicted in our previous paper (Tetrahedron Lett. 1995, 36, 8303–8306) all diastereomers of 2-iso-oxacephems can be prepared from the appropriate enantiomers of the amino acid threonine. The absolute configuration of the 2,3- and α-carbon atoms in the β-lactam structure was determined by X-ray crystallographic studies.     

Synthesis,characterization and epoxidation of hexakis-4-(2-(4-((β-methallyl)oxy)phenyl)propan-2-yl)phenoxycyclotriphosphazene

4-(2-(4-((β-Methallyl)oxy)phenyl)propan-2-yl)phenol was prepared via the reaction of methallyl chloride with bisphenol A and used for the synthesis of hexakis-4-(2-(4-((β-methallyl)oxy)phenyl)propan-2-yl)phenoxycyclotriphosphazene. It was revealed that the latter undergoes the Claisen rearrangement and can be also epoxidized by 3-chloroperbenzoic acid. The obtained epoxide was cured by a treatment with isophorone diamine. The decomposition and glass transition temperatures of cured resin were also estimated (275 and 130?°C, respectively) by DSC and TGA methods.     

Synthesis of 2[(1R,2R)-2-(2,4-Difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-triazol-yl)propyl]-4-[4-tetrafluoropropoxy)phenyl]-3-(2H,4H)-1,2,4-triazol-3-thione—A Novel and Potent Azole Antifungal Agent

A simple approach involving refluxing appropriately disubstituted thiosemicarbazide 8 in presence of formic acid for the synthesis of 1, a potent azole antifungal agent, has been described.     

Synthesis of Quinolone Analogues: 7-[(2S,4R)-2-Aminomethyl-4- hydroxypyrrolidin-1-yl] Quinolones

Quinolone antibacterial agents have emerged as one of the dominant classes chemotherapeutic drugs for the treatment of various bacterial infections1. We have focused our attention on the modification of the C-7 basic group of the quinolone which has been most varied. In 1987, Uno et al.2 reported that 3-hydroxypyrrolidine quinolones showed more active antibacterial activities than Norfloxacin in vivo. In 1998, Fujita et al.3 reported that 2-aminomethylpyrrolidine quinolones have the same …     

Synthesis of 1-[6-Fluoro-(2S)-3H,4H-dihydro-2H-2-chromenyl]-(1R)-1,2- ethanediol and 1-[6-Fluoro-(2R)-3H,4H-dihydro-2H-2-chromenyl]- (1R)-1,2-ethanediol

Benzopyran compounds possess diverse pharmacological properties such as β-blockade, anticonvulsant and antimicrobial.[1,2] Our interest has been focused on the synthesis of 1-[6-Fluoro-2S]-3H,4H-dihydro-2H-2-chromenyl]-(1R)-1,2-ethanediol (6) and 1-[6-fluoro-(2R)-3H,4H-dihydro-2H-2-chromenyl]-(1R)-1,2-ethanediol (7) which are particularly convenient precursor to (S,R,R,R)-NE (8). 8 containing four asymmetrical carbon atoms was reported to be the most active isomer.[3] Chandrasekhar[4] has reported on the synthesis of 8. The key step to synthesize this compound is to obtain the chiral chromanone 6 and 7. 6 was accomplished in 8 steps by the Clasien rearrangement and a one-pot Sharpless asymmetric epoxidation, but the compound 7 was accomplished in 10 steps. Johannes[5] used Zr-catalytic kinetic resolution of allylic ethers and Mo-catalyzed chromene formation to synthesize 8 in 14 steps. However both of the methods request many synthetic steps and expensive reagents.     

合成(3R,4R)-3-[(1'R)-叔丁基二甲基硅氧乙基]-4-乙酰氧基-2-氮杂环丁酮的新方法

(3R,4R)-3-[(1'R)-叔丁基二甲基硅氧乙基]-4'-乙酰氧基-1-对甲氧基苯基-2-氮杂环丁酮依次经铋酸钠/浓硫酸体系氧化和亚硫酸氢钠还原,合成了培南类药物的重要中间体——(3R,4R)-3-[(1'R)-叔丁基二甲基硅氧乙基]-4-乙酰氧基-2-氮杂环丁酮(1),收率62%,纯度98%,其结构经1H NMR,IR和EI-MS表征。     

Diels–Alder reactions of enantiopure [(1S)-isoborneol-10-sulfinyl]- and [(1S-exo)-2-bornylsulfinyl]vinylcyclohexenes with maleimides

Uncatalyzed cycloadditions of enantiopure [(1S)-isoborneol-10-sulfinyl]- and [(1S-exo)-2-bornylsulfinyl]vinylcyclohexenes with N-phenylmaleimide occur with good facial diastereoselectivity, controlled by the sulfur configuration, even if the extent of this stereoselection appears influenced by the structural features of the terpene residue directly linked to the sulfoxide moiety. Complete endo diastereoselectivity is observed in LiClO₄ catalyzed cycloadditions of (R_S)-1-{1-[(1S)-isoborneol-10-sulfinyl]- and (S_S)-1-{1-[(1S-exo)-2-bornylsulfinyl]vinyl}cyclohexenes 4 and 5, respectively. The Diels–Alder reactivity of 5 and (S_S,E)-1-{2-[(1S-exo)-2-bornylsulfinyl]vinyl}cyclohexene 7, with the chiral auxiliary being in a different position with respect to the diene moiety, is also compared, and the results obtained comfirm that 1-sulfinyldienes are less reactive than 2-sulfinyldienes. SnCl₄ catalyzed cycloaddition of 7 with N-methylmaleimide is also performed.     

Structural characterization,thermal investigation,and liquid crystalline behavior of 4-[(4-chlorobenzyl)oxy]-3,4′-dichloroazobenzene

Using the Williamson method, a new dye 4-[(4-chlorobenzyl)oxy]-3,4′-dichloroazobenzene (CODA) with liquid crystalline properties was synthesized. The structure and the thermal behavior of CODA were investigated by means of nuclear magnetic resonance, X-ray diffraction, differential scanning calorimetry, and light polarized optical microscopy techniques. The thermophysical processes were monitored by heating–cooling cycles, but the formation of liquid crystal phases were exhibited only for small values of the cooling rates. For the first heating–cooling cycle, the melting and the solidification processes, thus the characteristic temperatures, are shifted to higher values when compared to the following cycles.     

Voltammetric reduction of 2-(4′-N,N-dimethylaminostyryl)-1-ethyl pyridinium iodide inDMF

The voltammetric reduction mechanism of 2-(4-dimethylaminostyryl)-1-ethyl pyridinium iodide at the hanging dropping mercury electrode has been studied in N,N-dimethylformamide solution containing 0.1 mol dm^–3 tetraethylammonium perchlorate. The depolarizer is reduced via a single diffusion-controlled irreversible two-electron cyclic voltammetric wave. The wave is attributed to the reduction of the azomethine bond of the pyridinium nucleus. Cyclic voltammetric studies indicate that the cv wave follows an ECE mechanism. The chemical reaction is proposed to be a protonation.

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Voltammetrische Reduktion von 2-(4-N,N-Dimethylaminostyryl)-1-ethyl-pyridiniumjodid inDMF

Zusammenfassung Es wurde der voltammetrische Reduktionsmechanismus von 2-(4-N,N-Dimethylaminostyryl)-1-ethyl-pyridiniumjodid in Dimethylformamid-Lösung mit einem Tetraethylammoniumperchlorat-Gehalt von 0.1 mol dm^–3 an der tropfenden Quecksilberelektrode untersucht. Der Depolarisator wird über eine einzige diffusionskontrollierte irreversible Zweielektronenwelle reduziert. Diese Welle wird der Reduktion der Azomethinbindung des Pyridinium-Kerns zugeordnet. Cyclische voltammetrische Untersuchungen zeigen, daß die CV-Welle einem ECE-Mechanismus folgt. Als chemische Reaktion tritt Protonierung ein.

     

Synthesis and Crystal Structure of (2S,2'S,4'R)-2-(1-Hydroxy-1-ethylpropyl)-1-[(1'-p-tosyl-4'-hydroxypyrrolidin-2'-yl)methyl]pyrrolidine

1 INTRODUCTION In recent years, chiral β-amino alcohols have attracted much attention due to their special bio- logical functions and catalytic activities. Chiral β- amino alcohol moieties are usually found not only in natural products (e.g., cinchona alkaloids, ephe- drine, toxal, etc.) with special biological activities[1, 2], but also critical structural segments of some syn- thesized biologically active compounds, such as adrenergic agonists or antagolist[3, 4] and inhibitors for HI…     

Thionyl Chloride–Mediated Synthesis of tert-Butyl ((S)-1-((R)-Oxiran-2-yl)-2-phenylethyl)carbamate with Boc-Involved Neighboring Group Participation

A convenient, high-yielding preparation of tert-butyl ((S)-1-((R)-oxiran-2-yl)-2-phenylethyl)carbamate is described. An efficient chiral inversion as the key step is furnished via Boc-involved neighboring group participation mediated by thionyl chloride. This preparation has significant advantages over the previously reported methods with respect to simplicity, cost efficiency, yield, and purification procedure as well as industry reliability.     

Stereoselective synthesis and absolute configuration of (1′R,3R,4R)-4-acetoxy-3-(2′,2′,2′-trifluoro-1′-hydroxyethyl)azetidin-2-one

The title compound 3, an intermediate in the synthesis of fluorocarbapenems, is obtained with high stereocontrol by the condensation of (R)-(+)-ethyl 4,4,4-trifluoro-3-hydroxybutanoate with N-trimethylsilyl cinnamylidenimine. X-Ray diffraction analysis of the condensation product and chemical correlations allowed the unambiguous determination of the absolute configuration.     

Synthesis of 5-Substituted-3-[(2’R,4’R)-4’-Hydroxy-2’-hydroxymethyltetrahydrofuran-4’-yl]-1,2,4-oxadiazoles and Their Epimers

The syntheses of 5-substituted-3-[( 2' R, 4' R)-4 ' -hydroxy-2 ' -hydroxymethyltetra-hydrofuran-4' -yl]D-1 ,2, 4-oxadiazoles and their epimers were accomplished with the aid of th construction of 1,2, 4-oxadiazoles by condensation of O-acylated cyanohydrins with hydroxylamine via intramolecular transacylation and subsequent cyclization.     

NMR study on (1α, 2β, 4β, 5α, 7β)-7-[(hydroxydi-2-thienylacetyl) oxy]-9,9-dimethyl-3-oxa-9-azoniatricyclo [3.3.1.02,4] nonane bromide monohydrate

The structure of (1α, 2β, 4β, 5α, 7β)-7-[(hydroxydi-2-thienylacetyl) oxy]-9,9-dimethyl-3-oxa-9-azoniatricyclo [3.3.1.0^2,4] nonane bromide monohydrate was studied using 1D and 2D NMR techniques. Complete NMR assignments of the compound were obtained using DEPT, H–H COSY, as well as HMQC and HMBC heteronuclear correlation techniques.     

Stereoselective Synthesis and Characterization of (Z)-(−)-4-(1′-Alkoxyl-1′-alkyloxycarbonyl-methylidene)-5(R)-[(1R)-menthyloxy]-γ-butyrolactones

Abstract

A series of enantiomerically pure (Z)-(?)-4-(1′-alkyloxy-1′-alkyloxycarbonyl-methylidene)-5(R)-[(1R)-menthyloxy]-γ-butyrolactones were synthesized and characterized in good to excellent yields via O-alkylation of (4R,5R)-(?)-4-ethoxyoxalyl-5-[(1R)-menthyloxy]-γ-butyrolactone with alkyl halides in the presence of K₂CO₃ in acetone at room temperature.     

Synthesis,characterization, spectroscopy,X-ray structure and gaussian hybrid computational investigation of (−)-(S)-1-[2-(benzenesulfonamido)-3-phenylpropanoyl]-4-[(4-methyl)phenyl]thiosemicarbazide

Abstract

The molecule (?)-(S)-1-[2-(benzenesulfonamido)-3-phenylpropanoyl]-4-[(4-methyl)phenyl] thiosemicarbazide was synthesized and its structure analyzed by X-ray diffraction to understand its geometry, and inter/intra-molecular interactions. Theoretical calculations were carried out using DFT and TD-DFT methods with B3LYP/6-31G(d, p) and B3LYP/6-31G?+?(d, p) basis sets. Theoretical bond parameters, harmonic vibration frequencies, and chemical shifts are in good agreement with the experimental results. Electronic properties of the molecule derived from frontier orbitals, molecular electrostatic potential, and theoretical UV-Visible spectrum are validated experimentally.     

Crystal Structure of 3- (4-Methoxyphenyl )- 1-methylpyrrolo [2, 1-b] benzothiazole

lINTR0DUCTI0NSincebiologicalandpharmacol0gicalactivitieshavebeenwellknownfornumer-ousheterocyc1icar0matictricyc1es""',muchattenti0nhasbeenpaidtothesynthesisoftheheterocycliccompoundswithnovelringsystem(').Inrecentyears,ourwork-inggr0uphassynthesizedaseries0f1,5-benzothiazepineandl,5-benz0diazepinetri-cyclicderivativesandstudiedtheirstructurest4~10i.l,3-Disubstituded-pyrr0l0F2,1-bjbenz0thiazo1eshavebeenobtainedasmainbyproductsinthecycloadditionreactionofl,5-benzothiazepineswithdichl0rocarbe…