Synthesis of polyfluoroalkylated glycerol and crown ether

Perfluoroalkylated glycerol (5, 9) and crown ethers (22, 23, 24) were synthesized starting from glycerol. 5 was synthesized by allylation of glycerol 1,2-acetonide followed by perflu-oroalkylation initiated with sodium dithionite, reduction of iodide and hydrolysis in good overall yield and was shown to poccess good surface activities. Glycerol bis-ether (9) was synthesized in a similar way. Allyloxymethyl crown ethers (15, 16, 18) were prepared as key intermediates through multi-step reactions, which were then perfluoroalkylated to give the title crown ethers 22, 23 ,24.     

Synthesis of the C29-C37 bicyclic ether core of (+)-sorangicin A

Construction of the unique bicyclic bis-ether core of the macrolide (+)-sorangicin A has been achieved. This fragment was prepared by utilizing a one-pot cascade of three bond forming events. An epoxide opening of the epoxy tosylate 2 led to the formation of the tetrahydropyran and subsequently to a second epoxide. Finally, a second epoxide opening closed the tetrahydrofuran ring. The bicyclic fragment was synthesized in just nine steps from (E)-cinnamaldehyde.     

Synthesis of the C12-C24 fragment of peloruside A by silyl-tethered diastereomer-discriminating RCM

The C12-C24 fragment of peloruside A has been synthesized using, as a key step, a silyl-tethered ring closing metathesis reaction to form the C16-C17 (Z)-alkene. The metathesis reaction discriminates between diastereoisomers of the starting material. A diphenylsilyl bis-ether provides simultaneous protection for the C15 and C24 hydroxyl groups, and is expected to lead to high 1,5-anti selectivity in subsequent aldol reactions of the methyl ketone, allowing for a convergent stereoselective synthesis of peloruside A.     

Stability of boronic esters - Structural effects on the relative rates of transesterification of 2-(phenyl)-1,3,2-dioxaborolane

Relative rates of reaction of the achiral cyclic phenylboronic ester 2-(phenyl)-1,3,2-dioxaborolane with a wide variety of structurally modified diols, have been studied to understand the factors influencing the relative stabilities of boronic esters. It is found that the alkyl substituents on the α-carbons of diols slow down the transesterification, but produce thermodynamically more stable boronic ester. Six-membered boronic esters are thermodynamically more stable than their corresponding five-membered analogs. Amongst cyclic 1,2-diols, cis-1,2-cyclopentanediol displaces ethylene glycol instantaneously whereas trans-1,2-cyclopentanediol is totally unreactive, which suggests that the cis-stereochemistry of the 1,2-diol is a prerequisite for transesterification. Among the 1,5-diols, diethanolamine displaces ethylene glycol quite rapidly forming a more stable bicyclic chelate in which nitrogen is attached to boron by a coordinating bond (as evident by ¹¹B NMR spectroscopy). The oxygen atom of di(ethylene glycol) and the sulfur atom of 2,2′-thiodiethanol do not assist in displacing the ethylene glycol from their boronic esters.     

Differentiation of the isomeric 1,2-cyclopentanediols by ion-molecule reactions in a triple-quadrupole mass spectrometer

Collisionally activated decompositions and ion-molecule reactions in a triple-quadrupole mass spectrometer are used to distinguish between cis- and trans-1,2-cyclopentanediol isomers. For ion kinetic energies varying from 5 eV to 15 eV (laboratory frame of reference), qualitative differences in the daughter ion spectra of [MH]⁺ are seen when N₂ is employed as an inert collision gas. The cis ?1,2-cyclopentanediol isomer favors H₂O elimination to give predominantly [MH- H₂O]⁺. In the trans isomer, where H₂O elimination is less likely to occur, the rearrangement ion [HOCH₂CHOH]⁺ exists in significantly greater abundance. Ion-molecule reactions with NH₃ under single-collision conditions and low ion kinetic energies can provide thermochemical as well as stereochemical information. For trans ?1,2-cyclopentanediol, the formation of [NH₄]⁺ by proton transfer is an exothermic reaction with the maximum product ion intensity at ion kinetic energies approaching 0 eV. The ammonium adduct ion [M + NH₄]⁺ is of greater intensity for the trans isomer. In the proton transfer reaction with the cis isomer, the formation of [NH₄]⁺ is an endothermic process with a definite translational energy onset. From this measured threshold ion kinetic energy, the proton affinity of cis ?1,2-cyclopentanedioi was estimated to be 886 ± 10 kJ mol^?1.     

Stereochemical differentiation of cyclic glycols by ion-molecule reactions in a quadrupole mass spectrometer using dimethyl ether acetonitrile and 2-S-pyrrolidinemethanol

In this study, ion-molecule reactions using chemical ionization in the positive ion mode using dimethyl ether, acetonitrile and 2-S-pyrrolidinemethanol as reagent gases have been used to distinguish between cis- and trans-1,2-cyclopentanediol and cis- and trans-1,2-cyclohexanediol. In the gas phase, the stereospecific ion-molecule reaction gives characteristic ions and substantial differences are observed in their relative abundances from which the diastereoisomers of those cyclic glycols can be clearly differentiated. Copyright 2000 John Wiley & Sons, Ltd.     

Reactions of the trimethylsilyl ion with 1,2-cyclopentanediol isomers in the collision region of a triple quadrupole instrument

Ion-molecule reactions with the trimethylsilyl ion were used to distinguish between cis- and trans-1,2-cyclopentanediol isomers. The ion kinetic energy of [Si(CH₃)₃]⁺ was varied from 0 eV to 15 eV (center of mass frame of reference). At low ion kinetic energies (<4 eV), there are significant differences in the relative stabilities and decomposition behavior of the adduct ions [M + Si(CH₃)₃]⁺. The cis-1,2-cyclopentanediol isomer favors decomposition of [M + Si(CH₃)₃]⁺ to yield the hydrated trimethylsilyl ion [Si(CH₃)₃OH₂]⁺ at m/z 91. For the trans isomer, the formation of the hydrated trimethylsilyl ion is an endothermic process with a definite threshold ion kinetic energy.     

Cyclocarbopalladation: 5-exo-dig cyclization versus direct Stille cross-coupling reaction. The influence of the alpha,beta-propargylic substitution

Several bicyclic compounds bearing a 1,2-cyclopentanediol have been prepared from various anti- or syn-gamma-bromopropargylic diols and cis-dioxolanes under palladium(0) catalysis. The reaction proceeds through a 5-exo-dig cyclocarbopalladation. When the corresponding trans-dioxolanes are used, the only products isolated are obtained from a direct Stille cross-coupling reaction. [reaction: see text]     

Polycyclic N-hetero compounds. XXVII. Synthesis and investigation of the antidepressive activity of a B-Homo-11,13,15-triazasteroid and its related compoundsd

A synthesis of 1,2,5,6-tetrahydro-4H-benzo[3,4]cyclohepta[1,2-e]imidazo[1,2-c]pyrimidine (XII) having a novel ring system is described. Antidepressive activity of XII and its precursors VII-X was screened by inhibitory action of reserpine-induced hypothermia.     

One step synthesis of pyrido[1,2-a]benzimidazole derivatives of aryloxypyrazole and their antimicrobial evaluation

A new series of pyrido[1,2-α]benzimidazole derivatives bearing the aryloxypyrazole nucleus have been synthesized by base-catalyzed cyclocondensation reaction through multi-component reaction（MCR） approach.All the synthesized compounds were investigated against a representative panel of pathogenic strains using broth microdilution minimum inhibitory concentration（MIC） method for their in vitro antimicrobial activity.Reviewing the data,majority of the compounds were found to be active against employed pathogens.SAR study explores that antimicrobial activity is strongly depends on the nature of the substituents at the ether linked aryl ring attached to the pyrazole unit,together with the substituent present on the C₅ of the benzimidazole unit.     

Substituted 3-and 5-formylpyridin-2-ones in the synthesis of 1-aryl-1, 6-naphthyridinone derivatives

New 1-aryl-6-[2-(dimethylamino)vinyl]4-oxo-1,4-dihydropyrimidine-5-carbonitriles and 4-arylamino-2-oxo-1,2-dihydropyridine-3-carbonitriles containing electron-withdrawing substituents in the benzene ring were synthesized from enamino amides and dimethylformamide dialkylacetals. The influence of various dimethylformamide acetals on the yield of 3-(4-chloro-anilino)-2-cyano-5-(dimethylamino)penta-2,4-dienoic acid N-(dimethylamino)methyl-ideneamide was investigated in the reaction of these acetals with 3-(4-chloroanilino)-2-cyanocrotonamide. New 4-arylamino-5-formyl-2-oxo-1,2-dihydropyridine-3-carbonitriles and 4-arylamino-2-oxo-1,2-dihydropyridine-3-carbaldehydes containing electron-withdrawing substituents in the benzene ring were synthesized. The latter compounds were converted into new substituted l,6-naphthyridinones by the action of various CH acids. A new approach to the synthesis of 4-(4-fluoroanilino)-5-formyl-2-oxo-1,2-dihydropyridine-3-carbonitrile using dimethylformamide diisopropylacetal under mild conditions was developed. The comparative reactivity of the formyl group in the reactions of 4-arylamino-5-formyl-2-oxo-1,2-dihydropyridine-3-carbonitriles and in 4-arylamino-2-oxo-1,2-dihydropyridine-3-carb-aldehydes with malononitrile was determined using HPLC.     

Research on heterocyclic compounds. XX. Synthesis of trifluoromethyl derivatives of fused imidazole systems

A series of heterocyclic compounds having an imidazole ring fused with another ring with a bridgehead nitrogen atom and bearing a trifluoromethyl moiety was synthesized by reaction of 3-bromo-1,1,1-trifluoroacetone with various heteroarylamines. In some cases, an intermediate compound obtained together with the required product was isolated and its structure was elucidated: e.g., starting from 2-aminopyridine we have obtained 2-trifluoromethylimidazo[1,2-a]pyridine and 2-hydroxy-2-trifluoromethyl-2,3-dihydro-1H-imidazo [1,2-a]pyridinium bromide. Such results confirmed the mechanism previously proposed for this reaction.     

新型双大环二正丁基锡羧酸酯的合成、晶体结构及生物活性

在乙醇钠催化下, 将3-(1,2亚丙二硫基)亚甲基-2,4-二羰基戊烷与2-羰基苯氧乙酸进行缩合反应, 获得了柔性二元酸配体1[4-(1,2-亚丙二硫基)亚甲基-3,5-二羰基-1,6-庚二烯-1,7-二(2-羰基苯)氧乙酸(LH2)]. 再将配体1与二正丁基氧化锡进行脱水反应, 获得新型二正丁基锡羧酸酯配合物2. 采用元素分析、1H NMR、 IR及晶体结构测定等手段对配体1和配合物2进行了结构表征, 配合物2是以菱形环Sn2O2为中心对称的二聚体结构, 中心菱形环通过氧原子与2个环外锡原子相连. 每个羧基分别与环内锡和环外锡原子配位, 形成2个对称的六元环, 3个环呈梯形排列, 将整个分子分割成2个对称的二十二元大环. 初步研究了其杀菌活性和抗癌活性.     

Polycyclic N-heterocyclic compounds. XLIV. Synthesis of the novel B,D-Dihomo-11,13,15-triazasteroidal skeleton and their effect on reserpine-induced hypothermia and inhibitory activity on platelet aggregation

Synthesis of benzo[3,4]cyclohepta[1,2-e]pyrimido[1,2-c]pyrimidines, corresponding to the B,D-dihomo-11,13,15-triazasteroidal skeleton as a novel ring system is described. Their effects on reserpine-induced hypothermia in mice and inhibitory activity against collagen-induced platelet aggregation were also investigated.     

Synthesis of 1,2-azidoalcohols from epoxides using a task-specific protic ionic liquid: 1-hydrogen-3-methylimidazolium azide

A task-specific ionic liquid as an environmentally eco-friendly green catalyst has been synthesized and used in the ring opening of epoxides under green conditions. In order to use protic ionic liquids (PIL), we decided to synthesize 1,2-azidoalcohols via a ring opening reaction of epoxides with 1-hydrogen-3-methylimidazolium azide ([Hmim]N₃), which actually acts as a solvent, a reagent and an activator of the epoxide ring. The reaction was carried out in short times (50–70 min) at 70 °C to give 1,2-azidoalcohol in 80–94% isolated yields.     

Nitrogen bridgehead compounds VIII . Ring transformations IV . Synthesis and reactions of 2,3-Cycloalkylene-4H-pyrido [1,2-a] pyrimidin-4-ones

By condensing alicyclic β-ketocarboxylates with substituted 2-aminopyridines in polyphosphoric acid or phosphoryl chloride-polyphosphoric acid, numerous 2,3-tri-, tetra-, penta- and hexamethylene-4H-pvrido[1,2-a]pyrimidin-4-ones were synthesized for pharmacological purposes. The stability and several reactions of the title compounds were studied. The 6-substituted-4H-pyrido[1,2-a]pyrimidin-4-ones were transformed into 1,8-naphthyridines in good yields independent of the ring size of ring C . The characteristic differences in the ir and uv spectra of the pyrido-pyrimidines and the corresponding naphthyridines are discussed. Catalytic hydrogenation of the pyrido[1,2-a]pyrimidin-4-ones furnished the corresponding 6,7,8,9-tetrahydropyrido-[1,2-a]pyrimidin-4-one derivatives. It was found that the A and C rings attached to the pyrirnidinone ring in solutions of unsubstituted tetrahydropyrido[1,2-a]pyrimidin-4-ones are flexible, whereas in the 6-methyl derivatives the conformer containing the 6-methyl group in axial position predominates.     

A novel and efficient 4-oxothiazolidine-1,2-dithiole rearrangement induced by Lawesson's reagent

Functionalized 1,2-dithioles have been synthesized by a ring opening-closing process of 5-substituted- and 5-unsubstituted-2-alkylidene-4-oxothiazolidines with Lawesson's reagent. The ¹³C NMR data confirmed the meso-ionic structure of these aromatic-type 1,2-dithioles.     

Chemistry of Dioxacyclanes: XI. Synthesis and Properties of Unsaturated Derivatives of 1,3-Dioxolanes

1'3-Dioxolanes were synthesized by reactions of 3-cyclohexenecarboxaldehyde, 5-norbornene-2-endo-carboxaldehyde with 1,2-ethanedithiol and 3-(2-propenyloxy)- and 3-propoxy-1,2-propanediols, aswell as of propionaldehyde, benzaldehyde, and trichloroacetaldehyde with the latter two thiols. Dichlorocarbene addition, bromination, and epoxidation of the ring C = C were accomplished, and activity of the resulting products as dienophiles in Dield-Alder reactions was assessed.     

N,N'-二(2-羟苄基)取代咪唑烷的合成、表征及抑菌活性

利用生物活性叠加原理,将"邻羟苯基"和"咪唑烷"分子片断有机结合,以水杨醛和乙二胺为起始原料,经缩合、NaBH4还原制得N,N'-二邻羟苄基乙二胺(2),进而与芳醛类化合物缩合关环,合成了8种N,N'-二(2-羟苄基)取代咪唑烷类化合物(3a～3h). 化合物的结构经1H NMR、IR、MS和元素分析等测试技术进行了表征. 结果表明,水杨醛与乙二胺的缩合反应,可专一性地生成对称双缩席夫碱化合物(1);芳醛上的取代基对缩合关环反应有显著影响,邻、对位吸电基可使芳醛的羰基活化,有利于缩合关环反应的进行,邻、对位供电基可使芳醛的羰基钝化,不利于缩合关环反应进行. 抑菌测试结果表明,质量分数为0.1%时,N,N'-二(2-羟苄基)取代咪唑烷化合物对不同菌株的抑菌活性具有明显的特异性,对白色念珠菌、大肠杆菌的抑菌率达100%.     

Mutagenic heterocyclic nitrogen compounds related to protein pyrolysates. 1. Derivatives of dipyrido[1,2-a:3′,2′-d]imidazole

2-Amino-6-methyldipyrido[1,2-a:3′-2′-d]imidazole is one of the mutagenic principles of L-glutamic acid and casein pyrolysates. We prepared several isomeric amines of this compound, as well as their homologues methylated in different positions on the heterocyclic ring, either by nitration of the ring followed by reduction or from appropriate 4-azidodipyrido[1,2-a:3′,2′-d]imidazoles. The latter compounds, the heterocyclic ring itself and various functional derivatives (hydroxylated, carboxylated, hydrazinic) were synthesized from 2-aminoimidazo[1,2-a]pyridines via various reactions which are described herein.