Halogenation Regulates Supramolecular Chirality at Hierarchical Levels of Self-Assembled N-Terminal Aromatic Amino Acids

Halogenation brings about dramatic variations to the performance of self-assembled organic species, such as luminescence and crystallinity, but it has seldom been utilized for chirality control. Here we show the halogenation effect of self-assembling organic building units on supramolecular chirality and chiroptical responses. N-terminal aromatic amino acids with different substituted halogen atoms at p-phenylalanine residues self-assembled into one-dimensional fibrous structures. Halogenation induced the emergence of macroscopic chirality regardless of halogen properties like electronegativity, generating exclusive homochiral helical structures. Solid-state X-ray structures and time-dependent density functional theory were utilized for calculated electronic circular dichroism spectra, which evidenced the diverse driving forces to enable chiral molecular arrangements, including H-bonds and halogen bonds. Red-shifted luminescence was observed in brominated building units, giving rise to active circularly polarized luminescence. This work elucidates the multiple roles of halogen in chiral self-assembly systems, which provides insight into the rational control over supramolecular chirality and their chiroptical applications.

The Impact of Halogenated Phenylalanine Derivatives on NFGAIL Amyloid Formation

The hexapeptide hIAPP22-27 (NFGAIL) is known as a crucial amyloid core sequence of the human islet amyloid polypeptide (hIAPP) whose aggregates can be used to better understand the wild-type hIAPP's toxicity to β-cell death. In amyloid research, the role of hydrophobic and aromatic-aromatic interactions as potential driving forces during the aggregation process is controversially discussed not only in case of NFGAIL, but also for amyloidogenic peptides in general. We have used halogenation of the aromatic residue as a strategy to modulate hydrophobic and aromatic-aromatic interactions and prepared a library of NFGAIL variants containing fluorinated and iodinated phenylalanine analogues. We used thioflavin T staining, transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) to study the impact of side-chain halogenation on NFGAIL amyloid formation kinetics. Our data revealed a synergy between aggregation behavior and hydrophobicity of the phenylalanine residue. This study introduces systematic fluorination as a toolbox to further investigate the nature of the amyloid self-assembly process.

Selective Arylation of 2-Bromo-4-chlorophenyl-2-bromobutanoate via a Pd-Catalyzed Suzuki Cross-Coupling Reaction and Its Electronic and Non-Linear Optical (NLO) Properties via DFT Studies

In the present study, 2-bromo-4-chlorophenyl-2-bromobutanoate (3) was synthesized via the reaction of 2-bromo-4-chlorophenol with 2-bromobutanoyl bromide in the presence of pyridine. A variety of 2-bromo-4-chlorophenyl-2-bromobutanoate derivatives (5a–f) were synthesized with moderate to good yields via a Pd-catalyzed Suzuki cross-coupling reaction. To find out the reactivity and electronic properties of the compounds, Frontier molecular orbital analysis, non-linear optical properties, and molecular electrostatic potential studies were performed.

Efficient Biocatalytic Synthesis of Dihalogenated Purine Nucleoside Analogues Applying Thermodynamic Calculations

The enzymatic synthesis of nucleoside analogues has been shown to be a sustainable and efficient alternative to chemical synthesis routes. In this study, dihalogenated nucleoside analogues were produced by thermostable nucleoside phosphorylases in transglycosylation reactions using uridine or thymidine as sugar donors. Prior to the enzymatic process, ideal maximum product yields were calculated after the determination of equilibrium constants through monitoring the equilibrium conversion in analytical-scale reactions. Equilibrium constants for dihalogenated nucleosides were comparable to known purine nucleosides, ranging between 0.071 and 0.081. To achieve 90% product yield in the enzymatic process, an approximately five-fold excess of sugar donor was needed. Nucleoside analogues were purified by semi-preparative HPLC, and yields of purified product were approximately 50% for all target compounds. To evaluate the impact of halogen atoms in positions 2 and 6 on the antiproliferative activity in leukemic cell lines, the cytotoxic potential of dihalogenated nucleoside analogues was studied in the leukemic cell line HL-60. Interestingly, the inhibition of HL-60 cells with dihalogenated nucleoside analogues was substantially lower than with monohalogenated cladribine, which is known to show high antiproliferative activity. Taken together, we demonstrate that thermodynamic calculations and small-scale experiments can be used to produce nucleoside analogues with high yields and purity on larger scales. The procedure can be used for the generation of new libraries of nucleoside analogues for screening experiments or to replace the chemical synthesis routes of marketed nucleoside drugs by enzymatic processes.

Synthesis of Alkyl Halides from Aldehydes via Deformylative Halogenation

An unprecedented deformylative halogenation of aldehydes to alkyl halides is presented. Under oxidative conditions, 1,4-dihydropyridine (DHP), derived from an aldehyde, generated a C(sp3)- radical that coupled with a halogen radical that was generated from inexpensive and atom-economical halogen sources (NaBr, NaI, or HCl), to yield an alkyl halide. Because of the mild conditions, a wide range of functional groups were tolerated, and excellent site selectivity was achieved.

A Convergent Synthesis of Functionalized Alkenyl Halides through Cobalt(III)-Catalyzed Three-Component C-H Bond Addition

A CoIII -catalyzed three-component coupling of C(sp2 )-H bonds, alkynes, and halogenating agents to give alkenyl halides is reported. This transformation proceeds with high regio- and diastereoselectivity, and is effective for a broad range of aryl and alkyl terminal alkynes. Diverse C-H bond partners also exhibit good reactivity for a range of heteroaryl and aryl systems as well as synthetically useful secondary and tertiary amide, urea, and pyrazole directing groups. This multicomponent transformation is also compatible with allenes in place of alkynes to furnish tetrasubstituted alkenyl halides, showcasing the first halo-arylation of allenes.

Highly Regio- and Enantioselective Vicinal Dihalogenation of Allyl Amides

We report a highly regio-, diastereo- and enantioselective vicinal dihalogenation of allyl amides. E- and Z-alkenes with both aryl and alkyl substituents were compatible with this chemistry. This is the result of exquisite catalyst controlled regioselectivity enabling use of electronically unbiased substrates. The reaction employs commercially available catalysts and halenium sources along with cheap inorganic halide salts to affect this transformation. A preliminary effort to extend this chemistry to heterodihalogenation is also presented.

Novel Halogenated Pyrazine-Based Chalcones as Potential Antimicrobial Drugs

Chalcones, i.e., compounds with the chemical pattern of 1,3-diphenylprop-2-en-1-ones, exert a wide range of bio-activities, e.g., antioxidant, anti-inflammatory, anticancer, anti-infective etc. Our research group has been focused on pyrazine analogues of chalcones; several series have been synthesized and tested in vitro on antifungal and antimycobacterial activity. The highest potency was exhibited by derivatives with electron withdrawing groups (EWG) in positions 2 and 4 of the ring B. As halogens also have electron withdrawing properties, novel halogenated derivatives were prepared by Claisen-Schmidt condensation. All compounds were submitted for evaluation of their antifungal and antibacterial activity, including their antimycobacterial effect. In the antifungal assay against eight strains of selected fungi, growth inhibition of Candida glabrata and Trichophyton interdigitale (formerly T. mentagrophytes) was shown by non-alkylated derivatives with 2-bromo or 2-chloro substitution. In the panel of selected bacteria, 2-chloro derivatives showed the highest inhibitory effect on Staphylococcus sp. In addition, all products were also screened for their antimycobacterial activity against Mycobacterium tuberculosis H37RV My 331/88, M. kansasii My 235/80, M. avium 152/80 and M. smegmatis CCM 4622. Some of the examined compounds, inhibited growth of M. kansasii and M. smegmatis with minimum inhibitory concentrations (MICs) comparable with those of isoniazid.

Halogenated benzoate derivatives of altholactone with improved anti-fungal activity

Altholactone exhibited the anti-fungal activity with a high MIC value of 128 μg ml(-1) against Cryptococcus neoformans and Saccharomyces cerevisiae. Fifteen ester derivatives of altholactone 1-15 were modified by esterification and their structures were confirmed by spectroscopic methods. Most of the ester derivatives exhibited stronger anti-fungal activities than that of the precursor altholactone. 3-Bromo- and 2,4-dichlorobenzoates (7 and 15) exhibited the lowest minimal inhibitory concentration (MIC) values against C. neoformans at 16 μg ml(-1), while the 4-bromo-, 4-iodo-, and 1-bromo-3-chlorobenzoates (11-13) displayed potent activity against S. cerevisiae with MIC values of 1 μg ml(-1). In conclusion, this analysis indicates that the anti-fungal activity of altholactone is enhanced by addition of halogenated benzoyl group to the 3-OH group.

Highly Selective Synthesis of Halomon, Plocamenone, and Isoplocamenone

Over 160 chiral vicinal bromochlorinated natural products have been identified; however, a lack of synthetic methods for the selective incorporation of halogens into organic molecules has hindered their synthesis. Here we disclose the first total synthesis and structural confirmation of isoplocamenone and plocamenone, as well as the first selective and scalable synthesis of the preclinical anticancer natural product halomon. The synthesis of these inter-halogenated compounds has been enabled by our recently developed chemo-, regio-, and enantioselective dihalogenation reaction.

Evolution of a unified, stereodivergent approach to the synthesis of communesin F and perophoramidine

Expedient synthetic approaches to the highly functionalized polycyclic alkaloids communesin F and perophoramidine are described using a unified approach featuring a key decarboxylative allylic alkylation to access a crucial and highly congested 3,3-disubstituted oxindole. Described are two distinct, stereoselective alkylations that produce structures in divergent diastereomeric series possessing the critical vicinal all-carbon quaternary centers needed for each synthesis. Synthetic studies toward these challenging core structures have revealed a number of unanticipated modes of reactivity inherent to these complex alkaloid scaffolds. Additionally, several novel and interesting intermediates en route to the target natural products, such as an intriguing propellane hexacyclic oxindole encountered in the communesin F sequence, are disclosed. Indeed, such unanticipated structures may prove to be convenient strategic intermediates in future syntheses.

Synthesis, spectroscopic characterization and theoretical calculations of ClF2CC(O)NPCl3 ([chloro(difluor)acetyl]phosphorimidic trichloride)

The synthesis of [chloro(difluor)acetyl]phosphorimidic trichloride (ClF2CC(O)NPCl3), together with a tentative assignment of the vibrational, NMR and mass spectra, are reported. Quantum chemical calculations (MP2 and B3LYP methods with 6-311+G(d) and 6-311+G(2df,p) basis sets) predict three stable conformers in the gas phase (syn, gauche and anti, defined according to the rotation around both the ClCCN and the CCNP dihedral angles). However, only a single C1 symmetry conformer is observed in the liquid phase, possessing the CO double bond in synperiplanar orientation with respect to the PN double bond, and the ClC bond distorted from the plane defined by the CC(O)NP entity. A Natural Bond Orbital (NBO) analysis was carried out for the title compound and related molecules in order to provide an explanation about the electronic properties.

β-Siloxy-α-haloketones through highly diastereoselective single and double mukaiyama aldol reactions

Double-action haloketones: A super silyl group enabled the first highly diastereoselective Mukaiyama aldol reactions of α-chloro- and α-fluoroketones with a wide range of aldehydes, providing anti-β-siloxy-α-haloketones. This process is compatible with one-pot double-aldol methodology and allows for rapid access to new halogen-modified polyketide fragments bearing up to four contiguous stereocenters.

Catalytic, asymmetric halofunctionalization of alkenes--a critical perspective

Despite the fact that halogenation of alkenes has been known for centuries, enantioselective variants of this reaction have only recently been developed. In the past three years, catalytic enantioselective versions of halofunctionalizations with the four common halogens have appeared and although important breakthroughs, they represent just the very beginnings of a nascent field. This Minireview provides a critical analysis of the challenges that accompany the development of general and highly enantioselective halofunctionalization reactions. Moreover, the focus herein, diverges from previous reviews of the field by identifying the various modes of catalysis and the different strategies implemented for asymmetric induction.

Interrupted Fischer indolization approach toward the communesin alkaloids and perophoramidine

A concise approach toward the total synthesis of the communesin alkaloids and perophoramidine is reported. The strategy relies on the use of the interrupted Fischer indolization to build the tetracyclic indoline core of the natural products. Studies to probe the scope and limitations of this plan are presented. Although the methodology does not tolerate a C8-allyl substituent en route to the challenging vicinal quaternary stereocenters, variation at C7 and on the C ring is permitted.

Quantum-chemical, spectroscopic and X-ray diffraction studies of (E)-2-[(2-Bromophenyl)iminomethyl]-4-trifluoromethoxyphenol

The Schiff base compound (E)-2-[(2-Bromophenyl)iminomethyl]-4-trifluoromethoxyphenol has been synthesised and characterised by IR, UV-vis, and X-ray single-crystal determination. The molecular geometry from X-ray determination of the title compound in the ground state has been compared using the Hartree-Fock (HF) and density functional theory (DFT) with the 6-311++G(d,p) basis set. The calculated results show that the DFT and HF can well reproduce the structure of the title compound. Using the TD-DFT and TD-HF methods, electronic absorption spectra of the title compound have been predicted and good agreement with the TD-DFT method and the experimental determination was found. The predicted nonlinear optical properties of the title compound are much greater than those of urea. In addition, DFT calculations of the title compound, molecular electrostatic potential (MEP), natural bond orbital (NBO), and thermodynamic properties were performed at B3LYP/6-311++G(d,p) level of theory.

Molybdenum-catalyzed asymmetric allylic alkylation of 3-alkyloxindoles: reaction development and applications

We report a full account of our work towards the development of Mo-catalyzed asymmetric allylic alkylation reactions with 3-alkyloxindoles as nucleophiles. The reaction is complementary to the Pd-catalyzed reaction with regard to the scope of oxindole nucleophiles. A number of 3-alkyloxindoles were alkylated successfully under mild conditions to give products with excellent yields and good-to-excellent enantioselectivities. Applications of this method to the preparation of indoline alkaloids such as (-)-physostigmine, ent-(-)-debromoflustramine B, and the indolinoquinoline rings of communesin B are reported.

Formation and fate of chlorination by-products in reverse osmosis desalination systems

Chlorination by-products may be formed during pretreatment or posttreatment disinfection in reverse osmosis (RO) desalination systems, potentially posing health, aesthetic and ecological risks. To assess the formation and fate of by-products under different conditions likely to be encountered in desalination systems, trihalomethanes, dihaloacetonitriles, haloacetic acids, and bromophenols were analyzed in water samples from a pilot-scale seawater desalination plant with a chlorine pretreatment system and in benchscale experiments designed to simulate other feed water conditions. In the pilot plant, RO rejection performance as low as 55% was observed for neutral, low-molecular-weight by-products such as chloroform or bromochloroacetonitrile. Benchscale chlorination experiments, conducted on seawater from various locations indicated significant temporal and spatial variability for all by-products, which could not be explained by measured concentrations of organic carbon or bulk parameters such as SUVA(254). When desalinated water was blended with freshwater, elevated concentrations of bromide in the blended water resulted in dihaloacetonitrile concentrations that were higher than those expected from dilution. In most situations, the concentration of chlorination by-products formed from continuous chlorination of seawater or blending of desalinated water and freshwater will not compromise water quality or pose significant risks to aquatic ecosystems.

Allylic and allenic halide synthesis via NbCl(5)- and NbBr(5)-mediated alkoxide rearrangements

Addition of NbCl(5) or NbBr(5) to a series of magnesium, lithium, or potassium allylic or propargylic alkoxides directly provides allylic or allenic halides. Halogenation formally occurs through a metalla-halo-[3,3] rearrangement, although concerted, ionic, and direct displacement mechanisms appear to operate competitively. Transposition of the olefin is equally effective for allylic alkoxides prepared by nucleophilic addition, deprotonation, or reduction. Experimentally, the niobium pentahalide halogenations are rapid, afford essentially pure (E)-allylic or -allenic halides after extraction, and are applicable to a range of aliphatic and aromatic alcohols, aldehydes, and ketones.

Discovery of [(3-bromo-7-cyano-2-naphthyl)(difluoro)methyl]phosphonic acid, a potent and orally active small molecule PTP1B inhibitor

A series of quinoline/naphthalene-difluoromethylphosphonates were prepared and were found to be potent PTP1B inhibitors. Most of these compounds bearing polar functionalities or large lipophilic residues did not show appreciable oral bioavailability in rodents while small and less polar analogs displayed moderate to good oral bioavailability. The title compound was found to have the best overall potency and pharmacokinetic profile and was found to be efficacious in animal models of diabetes and cancer.

2-(2-Chloro-6-fluorophenyl)acetamides as potent thrombin inhibitors

2-(2-Chloro-6-fluorophenyl)acetamides having 2,2-difluoro-2-aryl/heteroaryl-ethylamine P3 and oxyguanidine P1 substituents are potent thrombin inhibitors (K(i)=0.9-33.9 nM). 2-(5-Chloro-pyridin-2-yl)-2,2-difluoroethylamine was the best P3 substituent, yielding the most potent inhibitor (K(i)=0.7 nM). Replacing the P3 heteroaryl group with a phenyl ring or replacing the difluoro substitution with dimethyl or cyclopropyl groups in the linker reduced the affinity for thrombin significantly. The aminopyridine P1s also provided an increase in potency.

A stereoselective intramolecular halo-etherification of chiral enamides in the synthesis of halogenated cyclic ethers

A stereoselective halo-etherification of chiral enamides is described here. This work provides an approach to halogen containing cyclic ethers and reveals further mechanistic insights to the chemistry of chiral enamides.

Synthetic studies on perophoramidine and the communesins: construction of the vicinal quaternary stereocenters

An efficient synthetic strategy for installation of the two vicinal quaternary carbon centers of the communesins is reported. Key steps include the O-allylation/Claisen rearrangement of spirolactone systems, which are formed by tandem intramolecular Heck cyclization/carbonylation. Substituent and solvent effects on the stereochemical outcome of the Claisen rearrangements have been examined. The stereochemical assignment of the allyl spirolactone previously reported as 17 has now been revised to 31, which has the communesin relative configuration at the quaternary carbons. Key C-allyl spirolactone 59 bearing functional handles required for the communesin core has been constructed with a 9.8:1 diastereomer ratio.

Facile synthesis of fluoroalkenes by palladium-catalyzed reductive defluorination of allylic gem-difluorides

Chemo- and stereoselective synthesis of fluoroalkenes was achieved in excellent yields via Pd-catalyzed C-F bond activation. In this transformation, Et3N plays a crucial role to produce reactive hydride species such as Ph(EtO)SiH2 and Ph(EtO)2SiH by promoting dehydrogenative coupling. The reaction proceeds efficiently at 50 degrees C with a variety of substrates and is also useful for the synthesis of fluoroalkene peptidomimetics.

Cu-Catalyzed Tandem C−N Bond Formation for the Synthesis of Pyrroles and Heteroarylpyrroles

A highly efficient Cu-catalyzed tandem C-N bond-forming reaction of 1,4-dihalo-1,3-dienes has been developed. The transformation allows the synthesis of pyrroles and heteroarylpyrroles with a wide variety of functional groups and substitution patterns from readily available precursors.

N-(4-(4-(2-Halogenophenyl)piperazin-1-yl)butyl) substituted cinnamoyl amide derivatives as dopamine D2 and D3 receptor ligands

A series of eight substituted N-(4-(4-(2-halogenophenyl)piperazin-1-yl)butyl)-3-phenylacryl amide derivatives have been synthesized and screened for binding affinities at dopamine hD(2) and hD(3) receptors. All compounds have shown high to remarkable receptor affinities and some have led to distinct selectivity for D(3) receptors. Highest D(3)-receptor affinity has been observed for 3-(4-aminophenyl)-N-(4-(4-(2-fluorophenyl)piperazin-1-yl)butyl)acryl amide (hD(3) K(i) 0.9 nM; hD(2) K(i) 17.4 nM). Selectivity ratio has been best for 3-(4-chlorophenyl)-N-(4-(4-(2-fluorophenyl)piperazin-1-yl)butyl)acryl amide with a 56-fold preference for hD(3) versus hD(2). A functional activity test has been performed by a mitogenesis test for N-(4-(4-(2-fluorophenyl)piperazin-1-yl)butyl)-3,3-diphenylacryl amide, which, surprisingly, has shown full agonist properties.

Influence of chloride concentration on the formation of AOX in UV oxidative system

In this study, the effects of chloride ion concentration and pH on UV oxidation treatment were examined. Acetone and sodium dodecyl sulfate (ABS) were used as organic substances. The treatment efficiencies of these chemicals by UV/H(2)O(2) oxidation using a laboratory scale UV-free surface reactor (UV-FSR) with or without Cl(-) addition at different pH values was compared. Results of this study indicated that Cl(-) concentration and the chemical structure of the substances are more decisive than pH in the oxidation process. There was no AOX at the start of the experiments but as a result of oxidation a de novo synthesis of AOX was observed, and these AOX(de novo) compounds were destroyed during the treatment. Treatment was followed by TOC and AOX measurements. Approximately 98% and 95% TOC removal efficiencies were obtained for the treatment of acetone and ABS containing wastewaters, respectively.

Mild TiIII- and Mn/ZrIV-catalytic reductive coupling of allylic halides: efficient synthesis of symmetric terpenes

Two new efficient methods for the regioselective homocoupling of allylic halides using either catalytic TiIII or the combination Mn/ZrIV catalyst have been developed. The regio- and stereoselectivity of the process proved to increase significantly when the Mn/ZrIV catalyst is used as the coupling reagent and when cyclic substituted allylic halides are used as substrates. The use of Lewis acids such as collidine hydrochloride allowed the quantity of catalyst to be lowered up to 0.05 equiv. We have proved the utility of these protocols with the synthesis of different terpenoids such as (+)-beta-onoceradiene (1), (+)-beta-onocerine (2), squalene (5), and advanced key-intermediates in the syntheses of (+)-cymbodiacetal (3) and dimeric ent-kauranoids as xindongnin M (4a).

Highly Efficient Monophosphine-Based Catalyst for the Palladium-Catalyzed Suzuki−Miyaura Reaction of Heteroaryl Halides and Heteroaryl Boronic Acids and Esters

A highly active and efficient catalyst system derived from a palladium precatalyst and monophosphine ligands 1 or 2 for the Suzuki-Miyaura cross-coupling reaction of heteroaryl boronic acids and esters has been developed. This method allows for the preparation of a wide variety of heterobiaryls in good to excellent yields and displays a high level of activity for the coupling of heteroaryl chlorides as well as hindered aryl and heteroaryl halides. Specific factors that govern the efficacy of the transformation for certain heterocyclic motifs were also investigated.

Chemical transformation of prostaglandin-A2: a novel series of C-10 halogenated, C-12 hydroxylated prostaglandin-A2 analogues

[reaction: see text] Synthesis of a novel class of C-10 halogenated and C-12 oxygenated prostaglandin-A(2) derivatives (6a-6c) has been accomplished. (15S)-Prostaglandin-A(2) (1), from the gorgonian Plexaura homomalla, served as the starting material for the synthesis. The absolute configuration was determined using NMR.

In Vitro and In Vivo Metabolism of a Gamma-Secretase Inhibitor BMS-299897 and Generation of Active Metabolites in Milligram Quantities with a Microbial Bioreactor

BMS-299897 is a gamma-secretase inhibitor that has the potential for treatment of Alzheimer's disease. The metabolism of [(14)C]BMS-299897 was investigated in human liver microsomes, in rat, dog, monkey and human hepatocytes and in bile duct cannulated rats. Seven metabolites (M1-M7) were identified from in vitro and in vivo studies. LC-MS/MS analysis showed that M1 and M2 were regioisomeric acylglucuronide conjugates of BMS-299897. Metabolites M3, M4 and M6 were identified as monohydroxylated metabolites of BMS-299897 and M5 was identified as the dehydrogenated product of monooxygenated BMS-299897. In vivo, 52% of the radioactive dose was excreted in bile within 0-6 h from bile duct cannulated rats following a single oral dose of 15 mg/kg of [(14)C]BMS-299897. Glucuronide conjugates, M1 and M2 accounted for 80% of the total radioactivity in rat bile. In addition to M1 and M2, M7 was observed in rat bile which was identified as a glucuronide conjugate of an oxidative metabolite M5. For structure elucidation and pharmacological activity testing of the metabolites, ten microbial cultures were screened for their ability to metabolize BMS-299897 to form these metabolites. Among them, the fungus Cunninghamella elegans produced two major oxidative metabolites M3 and M4 that had the same HPLC retention time and mass spectral properties as those found in in vitro incubations. NMR analysis indicated that M3 and M4 were stereoisomers, with the hydroxyl group on the benzylic position. However, M3 and M4 were unstable and converted to their corresponding lactones readily. Based on x-ray analysis of the synthetically prepared lactone of M3, the stereochemistry of benzylic hydroxyl group was assigned as the R configuration. Both the hydroxy metabolites (M3 and M4) and the lactone of M3 showed gamma-secretase inhibition with IC(50) values similar to that of the parent compound. This study demonstrates the usefulness of microbial systems as bioreactors to generate metabolites of BMS-299897 in large quantities for structure elucidation and activity testing. This study also demonstrates the biotransformation profile of BMS-299897 is qualitatively similar across the species including rat, dog, monkey and human which provides a basis to support rat, dog and monkey as preclinical models for toxicological testing.

Lithium Carbenoids−Ultra-Reactive Yet Selective Reagents for Methylenation and Halomethylenation of Sulfones1

The first efficient, one-pot method for methylenation of p-toluyl sulfones (i.e., the transformation of p-MePhSO2CHR2 into R2CCH2) is described. Methods for effecting that transformation involving alkylation of sulfones with reagents of the general formula MCH2X, where M = SiMe3, SnR3, and MgCl (the Julia method) have been previously described. However, the silicon reagent is completely unreactive toward many sulfones, the tin reagent typically affords only moderate yields, and the magnesium reagent typically gives incomplete reaction (9-40% starting material). This article reports that excellent yields are obtained by alkylating the sulfone with the more ionic lithium methylene carbenoids (LiCH2X, where X = Cl, Br, and I). For example, treatment of sulfone 1 with 3 equiv of n-BuLi (THF, -100 degrees C) followed by 2 equiv of CH2Br2 affords olefin 2 in 96% yield. Although the carbenoid is generated in the presence of a 1:2 mixture of alpha-lithio-sulfone and n-BuLi, it reacts selectively with the alpha-lithio-sulfone (Krel = 9.6 +/- 0.8 with LiCH2Br). The chlorocarbenoid LiCH2Cl reacts somewhat less selectively (Krel = 3.5). The alkyl-substituted carbenoid n-BuCHBrLi reacts > or = 40 times more slowly than LiCH2Br, suggesting that olefination occurs by the SN2 mechanism rather than by metal-assisted ionization (MAI), the mechanism by which cyclopropyl and vinylidene carbenoids react with nucleophiles. Finally, sulfones can be transformed into vinyl halides by treatment with 3 equiv of n-BuLi (THF, -78 degrees C), followed by >2 equiv of diisopropylamine, followed by 3 equiv of dihalomethane (CH2X2, where X2 = Cl2, BrCl, Br2, or I2). All products are formed in high yield and purity.

Diversity Synthesis Using the Complimentary Reactivity of Rhodium(II)- and Palladium(II)-Catalyzed Reactions

Rhodium(II)-catalyzed reactions of aryldiazoacetates can be conducted in the presence of iodide, triflate, organoboron, and organostannane functionality, resulting in the formation of a variety of cyclopropanes or C-H insertion products with high stereoselectivity. The combination of the rhodium(II)-catalyzed reaction with a subsequent palladium(II)-catalyzed Suzuki coupling offers a novel strategy for diversity synthesis.

A Simple Catalytic Method for the Regioselective Halogenation of Arenes

This paper describes a mild palladium-catalyzed method for the regioselective chlorination, bromination, and iodination of arene C-H bonds using N-halosuccinimides as oxidants. These transformations have been applied to a wide array of substrates and can provide products that are complementary to those obtained via conventional electrophilic aromatic substitution reactions. [reaction: see text]

Synthesis, structural, thermal and optical studies of 1-ethyl-2,6-dimethyl-4-hydroxy pyridinium halides

1-Ethyl-2,6-dimethyl-4-hydroxy pyridinium chloride dihydrate and bromide dihydrate salts have been synthesized and their single crystals were grown by the slow evaporation of aqueous solution at 30 degrees C. The grown crystals were characterized by elemental analysis, FT-NMR and FT-IR techniques to confirm the formation of the expected compound. Optical transmittance window in aqueous solution was found to be 275-1100 nm by UV-vis-NIR technique. Thermogravimetric and differential thermal analyses reveal thermal stability and the presence of two water molecules in the crystal lattices. The crystal structure of chloride salt was also determined by X-ray diffraction method.

Biomimetic Approach to Perophoramidine and Communesin via an Intramolecular Cyclopropanation Reaction

[reaction: see text] Starting from tryptamine 4 and isatin 5, a biomimetic approach to the pentacyclic substructure 1 of perophoramidine and communesin was developed. The key steps were to create a stable three/six bicyclic system 2 on the 2,3-double bond of an indole derivative 3 by an intramolecular cyclopropanation, followed by ring opening of the resulting cyclopropane ring with the in situ generated amine group of an aniline.

Construction of β-Haloenamides via Direct Copper-Promoted Coupling of Lactams with 2-Chloro and 2-Bromo Vinyliodides

[reaction: see text] Cu(I)-catalyzed coupling of lactams with (E)-2-chlorovinyliodides or (E)-2-bromovinyliodides produces the corresponding beta-haloenamides in moderate to excellent yields.

Atom Transfer Cyclization Catalyzed by InCl3 via Halogen Activation

[reaction: see text] Indium trichloride was found to be an efficient catalyst for the cyclization of allylic halides and alkynes with atom transfer in methylene chloride. Mechanistic evidence supports a cationic reaction pathway with Lewis acid activation of the allylic halogen. Concomitant nucleophilic attack by the alkyne and trapping with halide led to atom transfer cyclization products. Depending on alkyne substitution, a bromine atom was transferred from the substrate or a chlorine atom was transferred from the solvent.

Arylamide dendrimers with flexible linkers via haloacyl halide method

[reaction: see text] Soluble arylamide dendrons with flexible linkers, peripheral ester or carboxyl groups (R), and focal amino or halogen functionalities (F) were synthesized from aryl glycineamide (AG) building blocks. The AG blocks were prepared in high yields from trivial starting materials by Fischer's haloacyl halide method, which also could be extended to the dendrimer synthesis itself. The G2 AG dendrons were coupled to a Pd porphyrin core, demonstrating outstanding encapsulation efficiency in aqueous solutions.

Platinum Oxide Catalyzed Silylation of Aryl Halides with Triethylsilane: An Efficient Synthetic Route to Functionalized Aryltriethylsilanes

The first platinum-catalyzed selective silylation of aryl halides including aryl iodides and bromides having an electron-withdrawing group is described. The reaction takes place rapidly in NMP with triethylsilane as a silicon source and sodium acetate to provide functionalized aryltriethylsilanes in moderate to good yields. Heteroaromatic halides also were found to be readily silylated with triethylsilane. The procedure is chemoselective and tolerates a wide variety of functional groups.

Synthesis of novel phenylacetic acid derivatives with halogenated benzyl subunit and evaluation as aldose reductase inhibitors

In the course of our ongoing studies several substituted benzyloxyphenylacetic acids were prepared. Comparison of their aldose reductase inhibition with the biological activity obtained for recently evaluated benzoic acid analogues revealed the critical role of a methylene spacer between the aromatic core and the acidic function. Starting from the most potent derivative (i.e. 5d, IC50 = 20.9 microM) further structural modifications were performed and their influence on the inhibitory effect was established.

Chlorofluoroiodomethane as a potential candidate for parity violation measurements

CHFClI is among the more favorable molecules for parity violation (PV) measurements in molecules. Despite the fact that calculated PV effects are two orders of magnitude smaller than in some organometallic compounds, CHFClI displays interesting features which could make possible a new experimental PV test on this molecule. Indeed, ultrahigh resolution spectroscopy using an ultrastable CO(2) laser is favored by several intrinsic properties of this molecule. For example, the high vapor pressure of CHFClI allows investigation by supersonic beam spectroscopy. Indeed, the spectroscopic constants have been accurately determined by microwave and millimetre wave spectroscopy. This is important for the subsequent selection of an appropriate absorption band of CHFClI that could be brought to coïncide with the absorption of CO(2). Partially resolved (+)- and (-)-CHFClI enantiomers with respectively 63.3 and 20.5% ee's have been recently prepared and analyzed by molecular recognition using chiral hosts called cryptophanes. Finally, the S-(+)/R-(-) absolute configuration was ascertained by vibrational circular dichroïsm (VCD) in the gas phase.

Regioselective Haloaromatization of 1,2-Bis(ethynyl)benzene via Halogen Acids and PtCl2. Platinum-Catalyzed 6-π Electrocyclization of 1,2-Bis(1‘-haloethenyl)benzene Intermediates

[reaction: see text] Treatment of 1,2-bis(ethynyl)benzene (1) with aqueous HX (X = Br, I) in hot 3-pentanone (100-105 degrees C, 2 h) afforded 1,2-bis(1'-haloethenyl)benzene species 2-Br and 2-I in 98% and 95% yields, respectively. The hydrochlorination of endiyne 1 failed to proceed at elevated temperature but was implemented efficiently by PtCl2 (5 mol %) in hot 3-pentanone (100 degrees C, 2 h) to give 1,2-bis(1'-chloroethenyl)benzene 2-Cl in 80% yield. In the presence of PtCl2 (5 mol %), these halides 2-Cl,2-Br, and 2-I were subsequently converted to 1-halonaphthalenes 3-Cl, 3-Br, and 3-I in the mother solution via sequential 6-pi electrocyclization and dehalogenation reactions. PtCl2 (5 mol %) also effected direct haloaromatization of endiyne 1 with HX (X = Cl, Br, I) and gave 1-halonaphthalenes 3-Cl, 3-Br, and 3-I in 64-71% yields. This investigation reports the scope and the regioselectivity of haloaromatization of various enediynes catalyzed by PtCl2.

New Agents with Antimycobacterial Activity

In this paper, we report that a series of structurally simple a-halogenoacetamides show potent and excellent antimycobacterial activities against drug-sensitive Mycobacterium tuberculosis H(37)Rv and drug-resistant M. avium.