An Expeditious Synthesis of β-Indolylketones Catalyzed by p-Toluenesulfonic Acid (PTSA) Using Ultrasonic Irradiation

The investigation of the chemistry of indoles has been, and continues to be, one of the most active areas of heterocyclic chemistry.[1] In particular, β-indolylketones have received much attention as important building blocks for the synthesis of many natural products and other biologically active compounds.[2] In continuation of our work in the synthesis of indole derivates,[3] we describe the remarkable catalytic of PTSA as a cheaper catalyst in ultrasound-accelerated Michael reaction of indole with α, β-unsaturated ketones (2), which provide one of the most efficient routes to the synthesis of β-indolyketones. In all cases, the substitution on the indole nucleus occurred exclusively at the 3-position, and N-alkylation products have not been observed. In addition, the structure of 3a was further confirmed by single crystal X-ray crystallography.     

Asymmetric Synthesis of α, α′-Disubstituted α-Amino Acids Based on Natural (1R)-( + )-Camphor

Optically active nonproteinogenic amino acids[ 1] are valuable compounds of high interest not only owing to their remarkable pharmacological and biological activities, but also for their role as an investigative topographic probe for bioactive conformations of peptides and the mechanisms of enzyme reactions.[2]     

A Cell Solid Structure of cis-1,3-Cyclohexanedicarboxylic Acid and Its Complex Crystal with 4,4''''-Dipyridine

Carboxylic acids are important in crystal engineering because they can form strong and directional O-H…O hydrogen bonds as dimmer and catmer.[1] The dicarboxylic acids (not containing other hydrogen bonding groups) generally form the extended line structure interlinked through dimmer,[2] except that oxalic acid forms both the β-oxalic acid linked by dimmer (finite synthon) and the a-oxalic acid by catmer[3] (infinite synthon). A new molecular packing structure of cis-1,3-cyclohexanedicarboxylic acid (CHDA), which is different from line structure,[4] was gotten (P1/2, Figure 1). The novel structure has dimmer and catmer hydrogen bond pairs in the crystal and the hydrogen bond length of O-H…O is 0.268 nm in catmer and 0.264 nm in dimmer. The bond angles of O=C-O vary from 123.1° to 123.8° in catmer and from 123.1° to 122.0° in dimmer comparing with the ones in line structure.     

Novel Base-Promoted Syntheses ofβ-Indolylketones via a Three- Component Condensation under Ultrasound Irradiation

In recent years, a wide variety of organic compounds bearing indole fragment have been attracted much attention due to the fact that many of them are pharmacologically and biologically active compounds.[1] Among them β-indolylketones are one of the most significant intermediates for the preparation of natural products such as hapalindole D 1.[2] In recent years, the utilization of multicomponent condensations (MCCs) to generate novel, drug-like scaffolds are replete in current organic reactions due to the fact that products can be prepared directly in a single step and the diversity can be achieved simply by varying the reaction substrates. In continuation of our work to synthesize new β-indolylketones,[3] herein, we report a novel base-induced syntheses of new β-indolylketones via a three-component condensation. Deoxybenzoin as carbonyl compound is introduced into the reaction (Scheme 1), and all the reactions were operated under ultrasound irradiation since the utilization of which can accelerate the progress of many reactions and shorten the reaction time.     

Stereoselective Synthesis of C-Glycosides by Suzuki Cross-coupling Reaction

Carbohydrates and their conjugates have been recognized to play a wide variety of metabolic roles in numerous biological processes.[1] Various modified sugars and analogues have been recently synthesized for further investigation of glycosidase reactions and for the development of specific glycosidase inhibitors.[2] As one of the most important carbohydrate mimics, C-glycosides have attracted great attention due to their stability to chemical or enzymatic hydrolysis of the glycosidic linkage. A number of methodologies for the preparation of C-glycosides have been extensively investigated.[3] We have recently reported the syntheses of novel C-glycosyl amino acids and amino-C-disaccharides possessing a ketose form via the stereoselective 1,3-dipolar cycloaddition of exo-methylenesugars (1) and nitrones.[4,5] As a continuation of our research on the synthesis of C-glycosides using exo-methylenesugar as the precursor, we wish to describe here a stereoselective synthesis of C-glycosides by Suzuki cross-coupling reaction.     

Intermediate Detection by SAESI-MS/MS Unveiling the Catalytic Cycle in Negishi Coupling

Becausecarbon dioxideisabundant,cheap andnontoxic in or-ganic synthesis,much work hasbeen done in organic synthesis with carbon dioxide.[1]Allenes are an important series of com-pounds,and there arelots of reports about synthesis of allenes or using allenes as starting materialsin recent years.[2]In our previ-ous work,we reportedthe synthesis of allenoic acids by using 2-alkynyl bromides with zinc powder under CO2atmosphere.[3]In order to synthesizeallenoic acids,at the beginning of our study,1-phenylhept-2-ynyl methyl carbonate 1aand diethyl zinc were used as the substrates for optimization of the reaction conditions under CO2atmosphere.Neither allenoic acid nor its zincate was obtained as we expected.However,a mixture of ethylation prod-uct 2aandβ-H elimination product 3awas formed instead as judged by NMR.β-H elimination is an intrinsic challenge in or-ganometallic reactions involving alkyl species.     

A Novel Synthesis of β-Hydroxy-α-amino Acids

β-hydroxy-α-amino acids constitute an important class of compounds as naturally occurring amino acids and as components of many complex natural products possessing a wide range of biological activities. [1] As a consequence of the essential role played by these amino acids in the biological systems and their utility as synthetic building blocks, a number of useful strategies have been devised for their preparation. [2]     

Cuprous Iodide Catalyzed Synthesis of Diaryl Selenide and Telluride from Organoboronic Acids with Diphenyl Diselenide and Ditelluride

Organoselenium and tellurium compounds have received much attention not only as synthetic reagents or intermediates in organic synthesis but also as promising donor molecules for conductive materials.[1] A number of synthetic methods have been reported to prepare organoselenium and tellurium derivatives. A convenient and general method to introduce a selenium or tellurium moiety into organic molecules is the reaction of a metal selenolate or tellurolate with appropriate electrophiles such as organic halides, acyl chlorides, epoxides, and α, β-enones.[2] However, it is difficult to synthesize the unsymmetrical diarylselenides and tellurides through the reaction of selenide anion with organic halides because of the less reactivity of aryl halides. To accomplish this purpose, the reaction (iodobenzene with phenylselenol)was generally carried out in the presence of catalysts, ligands and strong bases. But, the reaction needs longer time to accomplish and form the products in moderate yields.     

Synthesis of Novel C2-Symmetrical Bidentate Phosphoramidite Ligands for Rh-catalyzed Asymmetric Hydrogenation of β-（Acylamino）acrylates

Enantiomerically pure β-amino acids and their derivatives are especially attractive due to their vital importance for biochemical and medicinal applications1. One of the most convenient paths to β-amino acids involves the asymmetric hydrogenation of the…     

Synthesis of β–Amino Acid Derivatives

In recent years, β-amino acids and their derivatives have attracted considerable attention due to their occurrence in biologically active natural products, such as dolastatins, cyclohexylnorstatine and Taxol. β–Amino acids also find application in the synthesis of β–lactams, piperidines, indolizidines. Moreover, the peptides consisting of β–amino acids, the so-called β–peptides, have been extensively studied recently. Consequently, considerable efforts have been directed to the synthe…     

Spontaneous Polymerization of An Amino Acid Based Amphiphile at Air/water Interface Investigated by ESI-MS and Transmission IR Spectrometry

Self-assemblies of amphiphilic molecules are proposed to play a ubiquitous role at the early stages of evolution in the formation of primitive biopolymers. [1] As regard to the significance of N-phosphoryl amino acids as a model for the co-evolution of protein and nucleic acids at the prebiotic stage, [2] amphiphilic N-phosphoryl amino acids with two hydrophobic tails were synthesized. [3]     

Stereoselective Synthesis of α-Aminonitril on Glucose Templates

Both proteinogenic and non proteinogenic α-amino acids are of particular interest as constituents of peptide factors, peptidomimetics and antibiotics for the construction of modern selective drugs. [1] Furthemore, α-amino acid derivatives are interesting building units for chiral-pool syntheses of enantiomerically pure natural products. [2] Numerous efforts in modern organic synthesis are centered on the synthesis of enantiomerically pure α-amino acids. [3] During the past three decades efficient methods of asymmetric synthesis of α-amino acids have been developed; most of them are based on electrophilic transformations of organometallic intermediates. [4] Using the concept that the chirality of the carbohydrates can be exploited for diastereoselective reactions, Kunz and his cooperator had developed a Strecker synthesis with glycosyl amines as chiral auxiliaries. [5]     

THE MOLECULAR MECHANISM OF PHOTOPORPHYRIN (YHPD)''''S PHOTOSENSITIZATION——LASER RAMAN SPECTROSCOPIC STUDY OF MICROCOSMIC AND PHOTOSENSITIVE DAMAGE OF YHPD TO PROTEIN

Laser Raman spectroscopy was used to investigate the microcosmic and photosensitive damage of YHPD to lysozyme, of which the three-dimensional structure has been elucidated. The experimental results shown by various damages of the main-chain and side-chain of lysozyme are as follows: (ⅰ) Phe and Cys are also damaged by photosensitization of YHPD, except for Trp, Tyr, Met, 1/2Cys and His; (ⅱ) the order of the photosensitized sensitivity of various groups of these amino acids have been described; (ⅲ) Trp and Tyr buried in the three-dimensional structure of the protein are damaged very greatly, and (ⅳ) the main-chain conformation of the protein has changed considerably, such as a decrease in orderly structure (α-helix, β-sheet and β-turn) and a simultaneous increase in random coil.     

Design and Synthesis of p/m-[p-（un）Substituted Phenylsulfonamido]phenyl β-Diketo Acids and Quinoxalone Derivatives

Diketo acid derivatives are potent and selective HIV-1 integrase inhibitors. To investigate the detailed synthesis of those derivatives, a series of p/m-[p-（un）substituted phenylsulfonamido]phenyl β-diketo acid derivatives have been designed and synthesized. The quinoxalone derivatives as the potential bioisosteres of the biologically labile β-diketoacid pharmacophores have also been synthesized from reactions of the corresponding diketo acids with o-phenylenediamine. The structures of all diketo acid （ester） and quinoxalone derivatives were confirmed by 1^H NMR, 13^C NMR, IR, HRMS and/or MS （ESI）. X-ray crystallographic analysis of 11b demonstrates a similar arrangement of the side chain of quinoxalone derivatives with the parent diketoacids due to the intramolecular hydrogen bond （O…H-N） and the sp^2 hybridization configuration of the two nitrogen atoms of the quinoxalone ring.     

Synthesis of 2-[2H]-2-(1-methylalkyl)succinic acids

We describe a specific procedure for the synthesis of deuterium-labelled 2-(1-methylalkyl)succinate established via alkylation of diethyl malonate,Krapcho decarboxylation reaction with D_2O and hydrolysis reaction.Two novel compounds,2-[~2H]-2-ethylsuccinic acid and 2-[~2H]-2-(1-methylheptyl)succinic acid were prepared via this synthetic route and characterized by mass spectrometry and 'H NMR.The results showed that the 2-(1-methylalkyl)succinic acids were deuterated at the β-position,which is considered as an important reaction centre in the anaerobic degradation of n-alkanes.     

Design and Synthesis of 1-Benzyl-3-(a-hydroxy-(un)substituted benzylidene)pyrrolidine-2,4-diones as Potential Herbicides

The inhibitors of 4-hydroxyphenylpyruvate dioxygenase (HPPD, EC 1.13.11.27) are an new kind of herbicides.[1]Generally, in structure, potent herbicides of this kind must possess: (1) a tricarbonyl methane structure and one of the three carbonyl groups must be a subustituted benzoyl group; (2) the compound must be able to enolise so that the enolate is capable of inhibiting HPPD enzyme by competitive combination with Fe2+, the reaction center of HPPD enzyme.[2]Recently, we noticed that the 3-acyltetramic acids form an expanding group of antibiotics and pigments from micro-organisms,[3] they display a range of biological activities[4] and all of this kind compounds possess all of the characters mentioned above. Tests of their antimicrobial activities indicated that the structure of the acyl substituent at the 3-position was important to many typical antibiotics.[4～6] These characters stimulated us to study this kind of compounds so as to discover new herbicides. In this report, we synthesized a series of compounds 3 and tested their herbicidal activities to investigate their structure-activity relationships.     

One-Pot Synthesis of N-Phosphoryl Amino Acids

Phosphoramidates have been considered as an important class of rationally designed therapeutics especially asoligonucleotide analogs employed as antisene and antigene agents. [1] N-Phosphoryl amino acids are of biological andpharmaceutical interest, [2] and can be used as the building blocks in synthesis of polypeptides. [3]     

Concise synthesis of valuable chiral N-Boc-β-benzyl-β-amino acid via construction of chiral N-Boc-3-benzyl-5-oxoisoxazolidine through cross-metathesis/conjugate addition/oxidation

Valuable chiral N-Boc-β-benzyl-β-amino acid was concisely synthesized via construction of chiral NBoc-3-benzyl-5-oxoisoxazolidine through cross-metathesis/conjugate addition/oxidation.All of the starting materials for the synthesis of chiral N-Boc-β-benzyl-β-amino acid are cheap,and two-step short procedure make it easy for the rapid construction of various chiral β-arylmethyl-β-amino acids and important drugs,such as sitagliptin phosphate.     

Catalytic enantioselective synthesis of β-amino alcohols by nitrene insertion

Chiral β-amino alcohols are important building blocks for the synthesis of drugs, natural products, chiral auxiliaries, chiral ligands and chiral organocatalysts. The catalytic asymmetric β-amination of alcohols offers a direct strategy to access this class of molecules. Herein, we report a general intramolecular C(sp³)–H nitrene insertion method for the synthesis of chiral oxazolidin-2-ones as precursors of chiral β-amino alcohols. Specifically, the ring-closing C(sp³)–H amination of N-benzoyloxycarbamates with 2 mol% of a chiral ruthenium catalyst provides cyclic carbamates in up to 99% yield and with up to 99% ee.The method is applicable to benzylic, allylic, and propargylic C–H bonds and can even be applied to completely non-activated C(sp³)–H bonds, although with somewhat reduced yields and stereoselectivities. The obtained cyclic carbamates can subsequently be hydrolyzed to obtain chiral β-amino alcohols. The method is very practical as the catalyst can be easily synthesized on a gram scale and can be recycled after the reaction for further use. The synthetic value of the new method is demonstrated with the asymmetric synthesis of a chiral oxazolidin-2-one as intermediate for the synthesis of the natural product aurantioclavine and chiral β-amino alcohols that are intermediates for the synthesis of chiral amino acids, indane-derived chiral Box-ligands, and the natural products dihydrohamacanthin A and dragmacidin A.     

An effective synthesis of β-aryl substituted isotetronic acids via Suzuki coupling

Isotetronic acids are of great agricultural and pharmacological relevance and occur in a number of natural products. A convenient synthetic pathway to β-aryl substituted isotetronic acid derivatives was developed via Suzuki cross-coupling of the corresponding β-bromo substituted isotetronic acid derivatives with arylboronic acids under palladium acetate catalysis. Good to excellent yields have been achieved