Synthesis of Polymer-supported Chiral Lithium Amide Bases and Application in Asymmetric Deprotonation of Prochiral Cyclic Ketones

Polymer-supported chiral amines were effectively prepared from amino acid derivatives and Merrifield resin. Treatment of polymer-supported amines with n-butyllithium gave the corresponding polymer-suppported chiral lithium amide bases, which were tested in the asymmetric deprotonation reactions of prochiral ketones. The trimethylsilyl enol ethers were obtained in up to 82% ee at room temperature. The polymer-supported chiral lithium amides can be readily recycled and reused without any significant loss of reactivity or selectivity.     

Tandem carbocupration/oxygenation of terminal alkynes

[chemical reaction: see text]. A direct and general synthesis of alpha-branched aldehydes and their enol derivatives is described. Carbocupration of terminal alkynes and subsequent oxygenation with lithium tert-butyl peroxide generates a metallo-enolate. Trapping with various electrophiles provides alpha-branched aldehydes or stereo-defined trisubstituted enol esters or silyl ethers. The tandem carbocupration/oxygenation tolerates alkyl and silyl ethers, esters, and tertiary amines. The reaction is effective with organocopper complexes derived from primary, secondary, and tertiary Grignard reagents and from n-butyllithium.     

Intramolecular Diels-Alder reactions of 4-vinylimidazoles

[reaction: see text] The synthesis of a variety of unsaturated ethers, esters, and amides derived from urocanic acid and their Diels-Alder reactions are reported. Propargylic ethers and esters cyclize with reasonable efficiencies, but the related mono- and unactivated olefins did not cyclize. On the other hand, the corresponding amines and amides, along with the doubly activated ester/amide derivatives participate in the cycloaddition reaction.     

Solid-phase synthesis of 1-substituted tetrahydroisoquinoline derivatives employing BOC-protected tetrahydroisoquinoline carboxylic acids

Compounds containing the tetrahydroisoquinoline ring system were prepared using solid-supported ester derivatives on a nucleophile-sensitive resin, starting from the corresponding BOC-protected amino acids. The key heterocyclic intermediates were obtained from the Pictet-Spengler reaction between ethyl glyoxylate or methyl 4-formylbenzoate and dopamine or 3-hydroxyphenethylamine. After the resulting amino esters were converted to the BOC derivatives, the phenolic hydroxyl groups were alkylated with a series of alkyl halides to afford the corresponding ethers. Ester hydrolysis afforded the BOC-protected tetrahydroisoquinoline carboxylic acid scaffolds, which were then attached to (4-hydroxyphenyl)sulfide resin (Marshall linker) as the corresponding ester. The BOC group was removed under acidic conditions, and the resulting support-bound amine hydrochlorides were converted to the corresponding amides using a set of carboxylic acids. The support-bound amides were liberated with amines to produce the desired tetrahydroisoquinoline carboxamides. Optimization of the resin loading conditions is described in addition to the identification of impurities observed during the development of the optimum conditions for solid-phase synthesis.     

槲皮素衍生物的合成及生物活性研究进展

综述了槲皮素衍生物的合成及生物活性研究进展,介绍了国内外槲皮素氨基酸类、糖苷类、酯类、醚类衍生物及金属配合物的合成方法及其生物活性研究现状.指出槲皮素是一种从天然植物中提取的黄酮醇类化合物,具有抗氧化,抗菌,扩张血管,抗肿瘤及抗突变等多种生物学活性.然而,槲皮素具有水溶性差、生物利用度较低等缺点,临床应用受到限制.为此,国内外学者对其结构进行修饰改造,开发出了一系列具有新颖结构的槲皮素先导化合物,可望为新型槲皮素衍生物的设计合成提供参考.     

Study of the Synthesis of Dextran Derivatives

Abstract

The synthesis of biologically active high-molecular compounds offers an interesting subject for study in polymer chemistry. Dextran, one of the best blood plasma expanders, is a good product for use in synthesizing biologically active water-soluble polymers. This paper discusses the synthesis of water-soluble derivatives of dextran which can be used as drug carriers or as independent physiologically active compounds. The synthesis of these derivatives involved oxidation of dextran, O-alkylation of dextran, subsequent transformation of ethers of dextran containing reactive functional groups, and graft polymerization. Periodate oxidation of dextran resulted in the production of a derivative of dextran containing aldehyde groups: dialdehydedextran. Subsequent oxidation of dialdehyde-dextran with sodium chlorite permitted the introduction of carboxyl groups into the macromolecule of dextran. In order to introduce sulfonic acid, phosphonic, mercapto, chlorhydrinic, cyano, and aromatic amino groups into the macromolecule of dextran, dextran was alkylated with various alkylating reagents. The synthesized products were sulfopropyl, phosphonomethyl, mercaptoethyl, 3-chloro-2-hydroxypropyl, cyanoethyl, and 2-(3′-amino-4′-methoxyphenyl)-sulfonylethyl ethers of dextran. Treatment of the 3-chloro-2-hydroxypropyl ether of dextran with ammonia, amines, and aliphatic and aromatic amino acids produced ethers of dextran containing primary, secondary, and tertiary amino groups and quaternary ammonium groups, as well as residual aliphatic and aromatic amino acids.

Cyanethyl ether of dextran was used to synthesize derivatives of dextran containing thioamide and hydrazidine groups.

Graft copolymers of dextran and polyacrylic acid and of dextran and poly-2-methyl-5-vinylpyridine were synthesized. Redox systems were utilized to initiate graft copolymerizatLon with tetravalent cerium compounds used as oxidants and pentavalent vanadium with dextran or 2-(3′-amino-4′-methoxyphenyl)-sulfonylethyl ether of dextran used as reductant. This method produced graft copolymers with short graft chains.

The availability of the above derivatives of dextran has permitted the linking of drugs to dextran by different types of chemical bonds.     

Nickel‐Catalyzed Amination of Silyloxyarenes through C–O Bond Activation

Silyloxyarenes were utilized as electrophilic coupling partners with amines in the synthesis of aniline derivatives. A diverse range of amine substrates were used, including cyclic or acyclic secondary amines, secondary anilines, and sterically hindered primary anilines. Additionally, a range of sterically hindered and unhindered primary aliphatic amines were employed, which have previously been challenging with other classes of aryl ether electrophiles. Orthogonal couplings of silyloxyarenes with aryl methyl ethers are illustrated, where selectivity between the two C?O electrophiles is determined by ligand control, thereby allowing complementary and selective late‐stage diversification of either electrophile. Finally, a sequential coupling displays the utility of this amination method along with the reversal in intrinsic reactivity between aryl methyl ethers and silyloxyarenes.     

The solid-phase Zincke reaction: preparation of omega-hydroxy pyridinium salts in the search for CFTR activation

A study of structural modifications of MPB-07 was undertaken as part of a synthetic program aimed at discovering small molecules with CFTR activation potential. Solid-phase synthesis techniques were used to prepare derivatives of MPB-07 employing the Zincke reaction for the construction of aromatic, quaternary ammonium salts such as those found in 2 or 3. In this transformation, primary amines react with highly electrophilic N-2,4-dinitrophenylpyridinium (DNP) salt 4 to afford pyridinium salt 8 with release of 2,4-dinitroaniline 6. Thus, the reaction of 1-(2,4-dinitrophenyl)pyridinium salts with various polymer-bound amino ethers, followed by cleavage from the resin, delivers the desired salts in good yield and high purity.     

Access to α‐Amino Acid Esters through Palladium‐Catalyzed Oxidative Amination of Vinyl Ethers with Hydrogen Peroxide as the Oxidant and Oxygen Source

A novel and convenient palladium catalytic system for the synthesis of α‐amino acid esters from simple starting materials is reported. Hydrogen peroxide not only acts as the green oxidant, but also as the oxygen source. This strategy for the conversion of amines and vinyl ethers into highly functionalized and structurally diverse α‐amino acid esters is characterized by the simplicity of the experimental procedure, mild reaction conditions, high atom economy, scalability, and practicability.     

Radical Arylation of Phenols,Phenyl Ethers,and Furans

Radical arylations of para‐substituted phenols and phenyl ethers proceeded with good regioselectivity at the ortho position with respect to the hydroxy or alkoxy group. The reactions were conducted with arenediazonium salts as the aryl radical source, titanium(III) chloride as the reductant, and diluted hydrochloric acid as the solvent. Substituted biaryls were obtained from hydroxy‐ and alkoxy‐substituted benzylamines, phenethylamines, and aromatic amino acids. The methodology described offers a fast, efficient, and cost‐effective new access to diversely functionalized biphenyl alcohols and ethers. Free phenolic hydroxy groups, aromatic and aliphatic amines, as well as amino acid substructures, are well tolerated. Two examples for the applicability of the methodology are the partial synthesis of a β‐secretase inhibitor and the synthesis of a calcium‐channel modulator.     

Regio- and stereoselective transfer of p-toluenesulfonamido group from sulfur to carbon: preparation of aminoalcohol derivatives from allylalcohols

A novel methodology for the regio- and stereoselective synthesis of amino alcohol derivatives from allylalcohols/ethers via intramolecular nucleophilic participation by the sulfilimine moiety is disclosed. The sulfilimine moiety is stereospecifically transformed to a sulfinyl moiety with an inverted configuration. The reaction is general and affords highly functionalised products.     

Four-Component Ugi Reaction for Optical Chirality Sensing and Surface Nanoengineering of Chiral Self-Assemblies

Using green chemistry to control chirality at hierarchical levels as well as chiroptical activities endows with new opportunities to the development of multiple functions. Here, the four-component Ugi reaction is introduced for the general and precise optical chirality sensing of amines as well as the surface nanoengineering of chiral soft self-assemblies. To overcome the relatively weak Cotton effects, direct synthesis of a folded peptide structure on a rotatable ferrocene core with axial chirality was accomplished from chiral amine, 1,1’-ferrocenyl dicarboxylic acid, formaldehyde and isocyanide. Enhanced Cotton effects benefiting from the folded structure allow for the precise and quantitative sensing of natural and synthetic chiral amines covering alkyl, aromatic amines and amino acid derivatives. In addition, aqueous reaction enables the modification of amine-bearing dye to microfibers self-assembled from π-conjugated amino acids. Surface dye-modification via Ugi reaction barely changes the pristine morphology, showing non-invasive properties in contrast to dye staining, which is applicable in soft nano/microarchitectures from self-assembly. This work which combines the four-component Ugi reaction to enable precise ee% detection and surface nanoengineering of soft chiral assemblies sheds light on the advanced application of green chemistry to chirality science.     

Room temperature, metal-free synthesis of diaryl ethers with use of diaryliodonium salts

A fast, high-yielding synthesis of diaryl ethers with use of mild and metal-free conditions has been developed. The scope includes bulky ortho-substituted diaryl ethers, which are difficult to obtain by metal-catalyzed protocols. Halo-substituents, racemization-prone amino acid derivatives, and heteroaromatics are also tolerated. The methodology is expected to be of high utility in the synthesis of complex molecules and in the pharmaceutical industry.     

Living cationic polymerization of vinyl monomers: Mechanism and synthesis of new polymers

This paper reviews the recent progress in our research on the living cationic polymerization of vinyl compounds by the hydrogen iodide/iodine (HI/I₂) initiating system, with emphasis on its scope, mechanism, and applications to new polymer synthesis. The scope of the living cationic polymerization has been expanded to include vinyl ethers, propenyl ethers, unsaturated cyclic ethers, and styrene derivatives as monomers. The initiation/propagation mechanism was discussed on the basis of recent direct analysis on the living system by NMR and UV/visible spectroscopy. The proposed mechanism involves a quantitative formation of Hl-vinyl ether adduct [CH₃-CH(OR)-I; l] that is by itself incapable of initiating polymerization. In the presence of iodine, however, the CH-I bond of l is electrophilically activated by iodine and living propagation occurs via the insertion of vinyl ether to the activated CH-I bond. Such living polymerizations were found to proceed in not only nonpolar but polar solvents (CH₂Cl₂) as well. Quenching the living end with amines gave polymers capped with an amino group that in turn enabled us to determine the living end concentration. Applications of the HI/I₂-initiated living process to the synthesis of new bifunctional and block polymers were also described.     

O‐Alkylation of Pyridine Aldo‐ and Ketoximes with Dihalohydrins under Phase‐Transfer Conditions

Phase‐transfer‐catalyzed alkylation of (E)‐pyridine aldo‐ and (E)‐ketoximes with dihalohydrins in the benzene (or DMSO)/10% aq. NaOH system in the presence of tetradecylammonium bromide proceeds regiospecifically to afford the corresponding O‐halohydrins in good yields. In this study, first O‐halohydrin derivatives were converted into glycidyl ether derivatives, and then a new series of amino alcohols were synthesized by the condensation of amines with these glycidyl ethers.     

Efficient and rapid synthesis of N-substituted isoquinolin-1-ones under mild conditions: Facile access to doryanine derivatives

We describe the simple and efficient synthesis of N-substituted isoquinolin-1-one derivatives. Initiating with the coupling of benzoic acids containing vinyl ethers with different amines, followed by rapid intramolecular cyclization under acidic conditions at room temperature, N-substituted isoquinolin-1-ones were furnished in high yields. The utility of this simple and mild cyclization method was demonstrated through the practical synthesis of natural product doryanine and its analogues.     

Pt‐Catalyzed Synthesis of Functionalized Symmetrical and Unsymmetrical Disilazanes

In nearly every total synthesis, silylating agents are employed in synthetic steps to protect sensitive functional groups. A Pt‐catalyzed hydrosilylation of various unsaturated substrates to prepare novel symmetrical and unsymmetrical disilazanes is described. The developed synthetic methodology is widely applicable and tolerates all manner of functional groups (e.g., amines, ethers, esters, halogens, silanes, etc.). To demonstrate the value of the described method, mono‐substituted 1,1,3,3‐tetramethyldisilazanes were further selectively converted to completely new unsymmetrical derivatives.     

Synthesis of bis‐ and tris‐organophosphorus substituted amines and amino acids with PCH2N Fragments

The aminomethylation of the derivatives of trivalent organophosphorus acids, containing PH and POSiMe₃ fragments with various bis‐ and tris(alkoxymethyl)amines and bis(alkoxymethyl)amino acids, is proposed as a convenient method for the synthesis of new bis‐ and trisphosphorylated amines and amino acids as well as their derivatives with four and five coordinated phosphorus. Also the three‐components systems of phosphorous acid, paraformaldehyde, and amines are thoroughly investigated via the treatment of reaction mixtures with bis(trimethylsilyl)amine. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:430–440, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20616     

Advances in the field of the synthesis of amino derivatives of terpenoids

Information on the synthesis of amino derivatives of monoterpenes by the reduction of oximes by the Leuckart reaction, and by the reductive amination of ketones by amines and nitriles is generalized. The stereochemistry of the amines formed as the result of the above-mentioned reactions is discussed.     

Partial reduction of annulated heterocycles as a general route to medium rings containing oxygen and nitrogen

The preparation of annulated furans and pyrroles is described as part of a general strategy for the synthesis of medium ring heterocycles. After Birch reduction, the corresponding dihydro compounds were oxidatively cleaved to produce medium ring ethers and amines in an efficient manner. This methodology was successfully applied to the formation of eight- and nine-membered cyclic ethers and nine-membered cyclic amines. Attaching a chiral auxiliary (bismethoxymethylpyrrolidine) to the furan allowed the formation of nine-membered ethers in 95% ee.