Cyclic Products Research Articles

Organic Biosignature Degradation in Hydrothermal and Serpentinizing Environments: Implications for Life Detection on Icy Moons and Mars.

Evidence of liquid water is a primary indicator of habitability on the icy moons in our outer solar system as well as on terrestrial planets such as Mars. If liquid water-containing environments host life, some of its organic remains can be fossilized and preserved as organic biosignatures. However, inorganic materials may also be present and water-assisted organic-inorganic reactions can transform the organic architecture of biological remains. Our understanding of the fate of these organic remains can be assisted by experimental simulations that monitor the chemical changes that occur in microbial organic matter due to the presence of water and minerals. We performed hydrothermal experiments at temperatures between 100°C and 300°C involving lipid-rich microbes and natural serpentinite mineral mixtures generated by the subaqueous hydrothermal alteration of ultramafic rock. The products reveal what the signals of life may look like when subjected to water-organic-inorganic reactions. Straight- and branched-chain lipids in unaltered samples are joined by cyclization and aromatization products in hydrothermally altered samples. Hydrothermal reactions produce distinct products that are not present in the starting materials, including small, single-ring, heteroatomic, and aromatic compounds such as indoles and phenols. Hydrothermal reactions in the presence of serpentinite minerals lead to significant reduction of these organic structures and their replacement by diketopiperazines (DKPs) and dihydropyrazines (DHPs), which may be compounds that are distinct to organic-inorganic reactions. Given that the precursors of DKPs and DHPs are normally lost during early diagenesis, the presence of these compounds can be an indicator of coexisting recent life and hydrothermal processing in the presence of minerals. However, laboratory experiments reveal that the formation and preservation of these compounds can only occur within a distinct temperature window. Our findings are relevant to life detection missions that aim to access hydrothermal and serpentinizing environments in the subsurfaces of icy moons and Mars.

Oxalic acid enhanced ferrous/persulfate process for the degradation of triclosan in soil: Efficiency, mechanism and a column study

Triclosan (TCS) is a compound in pharmaceutical and personal care products (PPCPs) that preferentially accumulates in soil and may threaten human health. Iron-based persulfate activation processes (Fe-PAPs) are a promising technique in soil remediation but are limited by their narrow pH application range and resultant iron precipitation. In this study, oxalic acid (OA) was specifically introduced to improve the efficiency of Fe2+-activated persulfate (PS) processes for TCS degradation in soil. The complexation of OA and Fe2+ improved the total iron concentration in the Fe2+/OA/PS system and prevented iron precipitation. Fe-minerals in soil were also dissolved by OA, which participated in PS activation. The most appropriate proportion of Fe2+/OA/PS is 1:1:1, and approximately 85% of the TCS was degraded within 240 min compared with 45% in the Fe2+/PS system. SO4•- and 1O2 played important roles on TCS oxidation, while O2•- and CO2•- mainly participated in the iron cycle. The weak stretch of Fe-O in OA containing treatments in ATR-FTIR measurements provided evidence that OA dissolved the Fe-minerals. The introduction of OA in the Fe2+/PS system in four different soils reduced the negative effect of soil organic matter on TCS degradation. Three types of intermediates including hydroxylation, cleavage of ether bonds and cyclization products, were identified by LC-Q-TOF-MS. Column experiments were used to study the feasibility of in situ chemical oxidation (ISCO) remediation of TCS in the Fe2+/OA/PS system. Our findings indicated the ability of OA to be used as a cheating agent in Fe-PAPs for TCS soil remediation.

A Dual-Purpose Ce(III)-Organic Framework with Amine Groups and Open Metal Sites: Third-Order Nonlinear Optical Activity and Catalytic CO2 Fixation.

The present work focuses on the synthesis and properties of a novel multifunctional cerium(III) MOF, [Ce2(data)3(DMF)4]·DMF (data2-: 2,5-diaminoterephthalate), abbreviated as NH2-Ce-MUM-2. Its crystal structure reveals an intricate 3D 4,5-connected framework with a xah topology. This MOF features unique properties, such as open metal sites, presence of free amino groups, and high stability. Two main applications of NH2-Ce-MUM-2 were investigated: (i) as a heterogeneous catalyst in the CO2 fixation into cyclic carbonates and (ii) as a material with third-order nonlinear optical activity. As a model reaction, the cycloaddition of CO2 to propylene oxide to give the corresponding cyclic carbonate was explored under mild conditions, at the atmospheric pressure of carbon dioxide and in the absence of cocatalyst and added solvent. Various reaction parameters were investigated toward optimization and exploration of substrate scope, revealing up to 99% product yields of cyclic carbonate products. Besides, the structure of NH2-Ce-MUM-2 is highly stable, permitting its recyclability and reusability in further catalytic experiments. The significant contributions of free amino groups and open metal sites within this catalyst were particularly considered when proposing a potential mechanism for the reaction. Z-Scan measurements were used to evaluate the nonlinear optical (NLO) properties of NH2-Ce-MUM-2 at various laser intensities. A high two-photon absorption (TPA) under greater incident intensities shows that NH2-Ce-MUM-2 might be applicable in optical switching devices. Besides, the self-focusing effects of NH2-Ce-MUM-2 under various incident intensities were highlighted by the nonlinear index of refraction (n2). By reporting the synthesis and characterization of a novel MOF, along with its highly promising catalytic and NLO behavior, the current study introduces an additional example of multifunctional material into a growing family of metal-organic frameworks.

Reprogramming the Cyclization Cascade of epi-Isozizaene Synthase to Generate Alternative Terpene Products.

The class I sesquiterpene cyclase epi-isozizaene synthase from Streptomyces coelicolor (EIZS) catalyzes the transformation of linear farnesyl diphosphate (FPP) into the tricyclic hydrocarbon epi-isozizaene in the biosynthesis of albaflavenone antibiotics. The active site cavity of EIZS is largely framed by four aromatic residues - F95, F96, F198, and W203 - that form a product-shaped contour, serving as a template to chaperone conformations of the flexible substrate and multiple carbocation intermediates leading to epi-isozizaene. Remolding the active site contour by mutagenesis can redirect the cyclization cascade away from epi-isozizaene biosynthesis to generate alternative sesquiterpene products. Here, we present the biochemical and structural characterization of four EIZS mutants in which aromatic residues have been substituted with polar residues (F95S, F96H, F198S, and F198T) to generate alternative cyclization products. Most notably, F95S EIZS generates a mixture of monocyclic sesquiterpene precursors of bisabolane, a D2 diesel fuel substitute. X-ray crystal structures of the characterized mutants reveal subtle changes in the active site contour showing how each aromatic residue influences the chemistry of a different carbocation intermediate in the cyclization cascade. We advance that EIZS may serve as a robust platform for the development of designer cyclases for the generation of high-value sesquiterpene products ranging from pharmaceuticals to biofuels in synthetic biology approaches.

Synthesis of Bridged N,O‐Heterocyclic 1,6‐Epoxybenzo[c]azocines via Migration‐Annulation Cascade Reaction of α‐Imino Rhodium Carbenes

AbstractA rhodium‐catalyzed cascade migration‐annulation reaction of 1‐sulfonyl‐1,2,3‐triazole has been developed. As the key step, the 1,3‐sulfinate migration of α‐imino rhodium carbene yielded an extended zwitterion, which was intramolecularly trapped by aldehyde group furnishing bridged N,O‐heterocyclic 1,6‐epoxybenzo[c]azocine as the [5+2] cyclization product. This migration‐annulation strategy provides more flexibility for heterocycle synthesis and medium‐sized ring construction, especially for the construction of polycycles with complex skeletons.

Synthesis and Characterization of a Luminescent Cyclic Poly(ethylene oxide)-Polypyridyl Ruthenium Complex.

We report the synthesis of a macrocyclic poly(ethylene oxide) (PEO) connected by one [Ru(bpy)3]2+ unit (where bpy = 2,2'-bipyridine), a photoactive metal complex that provides photosensitivity and potential biomedical applications to this polymer structure. The PEO chain provides biocompatibility, water solubility, and topological play. The macrocycles were successfully synthesized by copper-free click cycloaddition between a bifunctional dibenzocyclooctyne (DBCO)-PEO precursor and 4,4'-diazido-2,2'-bipyridine, followed by complexation with [Ru(bpy)2Cl2]. The cyclic product accumulated efficiently in MCF7 cancer cells and exhibited a longer fluorescence lifetime than its linear analogue, likely due to differences in the accessibility of the ligand-centered/intraligand states of Ru polypyridyls in both topologies.

Acenaphto[1,2-k]fluoranthene: Role of the Carbon Framework Transformation for Tuning Electronic Properties

Acenaphtho[1,2-k]fluoranthene (1) is synthesized via tandem cyclization during the dehydrofluorination of 1,4-di(1-naphthyl)-2,5-difluorobenzene (2) on activated γ-Al2O3. Presence of residual hydroxyl groups in alumina reduce the yield of target product 1 because of the side hydrolysis of fluoroarenes with the formation a product of partial cyclization, 9-(1-naphthyl)fluoranthen-8-ol (1b). The formation of negative ions (NI) of compounds 1 and 2 in the gas phase is studied by means of dissociative electron attachment (DEA) spectroscopy. Long-lived molecular NIs 1 and 2 are registered at the thermal energies of electrons, and patterns of their fragmentation are established. The adiabatic electron affinities of compounds 1 and 2 are estimated in the Arrhenius approximation and equal 1.17 ± 0.12 and 0.71 ± 0.07 eV, respectively, which agree with data from quantum chemical modeling at the level of the density functional theory (DFT). Electronic transitions for compounds 1 and 2 are studied via optical absorption and fluorescence spectroscopy. Fluorescence quantum yields are measured, and the resulting data are interpreted according to the time dependent DFT. The electrochemical properties of compounds 1, 1b, and 2 are studied via cyclic voltamperometry, and the levels of boundary molecular orbitals are estimated on the basis of their formal potentials of reduction and oxidation.

Acenaphto[1,2-k]fluoranthene: Role of the Carbon Framework Transformation for Tuning Electronic Properties

Acenaphtho[1,2-k]fluoranthene (1) is synthesized via tandem cyclization during the dehydrofluorination of 1,4-di(1-naphthyl)-2,5-difluorobenzene (2) on activated γ-Al2O3. Presence of residual hydroxyl groups in alumina reduce the yield of target product 1 because of the side hydrolysis of fluoroarenes with the formation a product of partial cyclization, 9-(1-naphthyl)fluoranthen-8-ol (1b). The formation of negative ions (NI) of compounds 1 and 2 in the gas phase is studied by means of dissociative electron attachment (DEA) spectroscopy. Long-lived molecular NIs 1 and 2 are registered at the thermal energies of electrons, and patterns of their fragmentation are established. The adiabatic electron affinities of compounds 1 and 2 are estimated in the Arrhenius approximation and equal 1.17 ± 0.12 and 0.71 ± 0.07 eV, respectively, which agree with data from quantum chemical modeling at the level of the density functional theory (DFT). Electronic transitions for compounds 1 and 2 are studied via optical absorption and fluorescence spectroscopy. Fluorescence quantum yields are measured, and the resulting data are interpreted according to the time dependent DFT. The electrochemical properties of compounds 1, 1b, and 2 are studied via cyclic voltamperometry, and the levels of boundary molecular orbitals are estimated on the basis of their formal potentials of reduction and oxidation.

Cyclic Products and Optimal Traps in Cyclic Birth and Death Chains

A birth-death chain is a discrete-time Markov chain on the integers whose transition probabilities $p_{i,j}$ are non-zero if and only if $|i-j|=1$. We consider birth-death chains whose birth probabilities $p_{i,i+1}$ form a periodic sequence, so that $p_{i,i+1}=p_{i \mod m}$ for some $m$ and $p_0,\ldots,p_{m-1}$. The trajectory $(X_n)_{n=0,1,\ldots}$ of such a chain satisfies a strong law of large numbers and a central limit theorem. We study the effect of reordering the probabilities $p_0,\ldots,p_{m-1}$ on the velocity $v=\lim_{n\to\infty} X_n/n$. The sign of $v$ is not affected by reordering, but its magnitude in general is. We show that for Lebesgue almost every choice of $(p_0,\ldots,p_{m-1})$, exactly $(m-1)!/2$ distinct speeds can be obtained by reordering. We make an explicit conjecture of the ordering that minimises the speed, and prove it for all $m\leq 7$. This conjecture is implied by a purely combinatorial conjecture that we think is of independent interest.

Review of mineral resource management in a circular economy infrastructure

Purpose is to substantiate foundations of sustainable management of mineral resources while implementing a circular economy model. Methods. The study has applied following research approaches: synthetic method (unification of the singled out aspects); induction method (analysis of a circular economy features); life cycle assessment (evaluation of the product influence on the environment from the viewpoint of each stage of its life cycle); circular economy toolkit (determination and evaluation of the periodicity of circular economy products and indicators); and circular economy indicator prototype (evaluation of the cyclic product efficiency). Findings. Circular economy is one of the key directions of a sustainable development policy as for conservation and protection of mineral resources; it is aimed at more efficient use and improvement of raw material extraction from industrial waste. Formation of a market infrastructure of the circular economy has been proposed based upon mining sector waste use to process it and reduce as well as to repurpose wasteless production and secondary processing of raw materials. The need has been substantiated to contribute to conservation of mineral resources for their sustainable use on the basis of the development of market infrastructure of a stable economy and mining sector waste use to process it and reduce as well as to repurpose wasteless production and secondary processing of raw materials. Originality. A concept for further development of the circular economy market infrastructure has been specified as a platform of production waste supply/demand to optimize the use and conservation of mineral resources on the principles of sustainable growth. It has been proposed to analyze assessment of business development along the lines of a circular economy while calculating parameters when manufacturing is applying primary mineral resources and industrial waste as a raw material for its further processing. Practical implications. The proposed approach of interaction between economic entities on the basis of a circular economy will provide rational use of mineral resources and contribute to the development of a sector of industrial waste processing. The abovementioned will help terminate decrease in the availability of mineral resources and form new milestones of social development on the principles of environmental friendliness and rationalism in the process of interaction with nature.

Filamentous Fungi-Derived Orsellinic Acid-Sesquiterpene Meroterpenoids: Fungal Sources, Chemical Structures, Bioactivities, and Biosynthesis.

Fungi-derived polyketide-terpenoid hybrids are important meroterpenoid natural products that possess diverse structure scaffolds with a broad spectrum of bioactivities. Herein, we focus on an ever-increasing group of meroterpenoids, orsellinic acid-sesquiterpene hybrids comprised of biosynthetic start unit orsellinic acid coupling to a farnesyl group or/and its modified cyclic products. The review entails the search of China National Knowledge Infrastructure (CNKI), Web of Science, Science Direct, Google Scholar, and PubMed databases up to June 2022. The key terms include "orsellinic acid", "sesquiterpene", "ascochlorin", "ascofuranone", and "Ascochyta viciae", which are combined with the structures of "ascochlorin" and "ascofuranone" drawn by the Reaxys and Scifinder databases. In our search, these orsellinic acid-sesquiterpene hybrids are mainly produced by filamentous fungi. Ascochlorin was the first compound reported in 1968 and isolated from filamentous fungus Ascochyta viciae (synonym: Acremonium egyptiacum; Acremonium sclerotigenum); to date, 71 molecules are discovered from various filamentous fungi inhabiting in a variety of ecological niches. As typical representatives of the hybrid molecules, the biosynthetic pathway of ascofuranone and ascochlorin are discussed. The group of meroterpenoid hybrids exhibits a broad arrange of bioactivities, as highlighted by targeting hDHODH (human dihydroorotate dehydrogenase) inhibition, antitrypanosomal, and antimicrobial activities. This review summarizes the findings related to the structures, fungal sources, bioactivities, and their biosynthesis from 1968 to June 2022.

Synthesis of a Cyclooctapeptide, Cyclopurpuracin, and Evaluation of Its Antimicrobial Activity.

Cyclopurpuracin is a cyclooctapeptide isolated from the methanol extract of Annona purpurea seeds with a sequence of cyclo-Gly-Phe-Ile-Gly-Ser-Pro-Val-Pro. In our previous study, the cyclisation of linear cyclopurpuracin was problematic; however, the reversed version was successfully cyclised even though the NMR spectra revealed the presence of a mixture of conformers. Herein, we report the successful synthesis of cyclopurpuracin using a combination of solid- and solution-phase synthetic methods. Initially, two precursors of cyclopurpuracin were prepared, precursor linear A (NH2-Gly-Phe-Ile-Gly-Ser(t-Bu)-Pro-Val-Pro-OH) and precursor linear B (NH-Pro-Gly-Phe-Ile-Gly-Ser(t-Bu)-Pro-Val-OH, and various coupling reagents and solvents were trialled to achieve successful synthesis. The final product was obtained when precursors A and B were cyclised using the PyBOP/NaCl method, resulting in a cyclic product with overall yields of 3.2% and 3.6%, respectively. The synthetic products were characterised by HR-ToF-MS, 1H-NMR, and 13C-NMR, showing similar NMR profiles to the isolated product from nature and no conformer mixture. The antimicrobial activity of cyclopurpuracin was also evaluated for the first time against S. aureus, E. coli, and C. albicans, showing weak activity with MIC values of 1000 µg/mL for both synthetic products, whereas the reversed cyclopurpuracin was more effective with an MIC of 500 µg/mL.

Cyclic Tetrapeptide Natural Product Asperterrestide A: Total Synthesis and Structural Revision

We have studied for the total synthesis of asperterrestide A, which is a cyclic tetrapeptide natural product reported to be composed of D-alanine, anthranilic acid, (2R,3S)-3-hydroxy-N-methylphenylalanine, and D-isoleucine or D-allo-isoleucine. We initially performed the total synthesis of the reported structure of asperterrestide A via solid-phase peptide synthesis and macrocyclization in solution. However, the spectral data of the synthetic (9R,25R)-derivative did not match those of the natural product. Then, we considered the true structure should be the (9S,25S)-stereoisomer because all NOE correlations predicted from its three-dimensional structures obtained by theoretical calculations were consistent with those observed in the natural product. Thus, the (9S,25S)-stereoisomer was synthesized through solution-phase synthesis because N-acylation of a polymer-supported (2S,3S)-3-hydroxy-N-methylphenylalanine derivative resulted in low yield. The (9S,25S)-stereoisomer was successfully synthesized and was found to be identical to the natural product. Therefore, the stereochemical configuration of asperterrestide A was corrected from (9R,25R) to (9S,25S). We also tested whether the DFT calculation of carbon chemical shifts can discriminate stereoisomers of cyclic tetrapeptides. After conformational analysis of four possible stereoisomers of asperterrestide A, Boltzmann-weighted carbon chemical shifts based on DFT calculations using Spartan’20 revealed a DP4 accuracy of 96%, which is sufficient to determine the stereochemical configuration among the stereoisomers. In addition, three 9-deoxy derivatives were synthesized and the cell growth inhibitory activity of the five synthetic compounds against human cancer cells (U937, MOLT-4, and A549) was evaluated. The results showed that the (9S,25S)-stereoisomer is as potent as asperterrestide A, whereas the (9R,25R)-derivative is not. The (9S,25S)-3-deoxy analogs were found to be equipotent to the natural product although the activity of the (9S,25R)-deoxy analog was lost.

Synthetic Study toward Triterpenes from the Schisandraceae Family of Natural Products.

Triterpenoid natural products from the Schisandraceae family have long presented a significant synthetic challenge. Lancifodilactone I, a member of the family not previously synthesized, was identified as a key natural product target, from which many other members could be synthesized. We envisaged that the core ring system of lancifodilactone I could be accessed by a strategy involving palladium-catalysed cascade cyclisation of a bromoenynamide, via carbopalladation, Suzuki coupling and 8π-electrocyclisation, to synthesize the core 7,8-fused ring system. Exploration of this strategy on model systems resulted in efficient syntheses of 5,6- and 5,8-fused systems in high yields, which represent the first such cyclisation where the ynamide nitrogen atom is 'external' to the forming ring system. The enamide functionality resident in the cascade cyclisation product was found to be less nucleophilic than the accompanying tri-/tetrasubstituted alkene(s), enabling regioselective oxidations. Application of this strategy to 7,6-, and 7,8-fused systems, and ultimately the 'real' substrate, was ultimately thwarted by the difficulty of 7-membered ring closure, leading to side product formation. Nevertheless, a tandem bromoenynamide carbopalladation, Suzuki coupling and 6/8π-electrocyclisation was shown to be a highly efficient tactic for the formation of bicyclic enamides, which may find applications in other synthetic contexts.

Discovery and biosynthesis of tricyclic copper-binding ribosomal peptides containing histidine-to-butyrine crosslinks

Cyclic peptide natural products represent an important class of bioactive compounds and clinical drugs. Enzymatic side-chain macrocyclization of ribosomal peptides is a major strategy developed by nature to generate these chemotypes, as exemplified by the superfamily of ribosomally synthesized and post-translational modified peptides. Despite the diverse types of side-chain crosslinks in this superfamily, the participation of histidine residues is rare. Herein, we report the discovery and biosynthesis of bacteria-derived tricyclic lanthipeptide noursin, which is constrained by a tri amino acid labionin crosslink and an unprecedented histidine-to-butyrine crosslink, named histidinobutyrine. Noursin displays copper-binding ability that requires the histidinobutyrine crosslink and represents the first copper-binding lanthipeptide. A subgroup of lanthipeptide synthetases, named LanKCHbt, were identified to catalyze the formation of both the labionin and the histidinobutyrine crosslinks in precursor peptides and produce noursin-like compounds. The discovery of the histidinobutyrine-containing lanthipeptides expands the scope of post-translational modifications, structural diversity and bioactivity of ribosomally synthesized and post-translational modified peptides.

SYNTHESIS OF TERMINAL 2-ALKENYL(ALKYNYL)THIO-5-CYANO-6-(p-DIMETHYLAMINOPHENYL)PYRIMIDIN-4-ONES

Functionalized pyrimidines possess a wide spectrum of biological activity. In particular, they have antitumor, antiviral, and anticonvulsant activities, exhibit anti-inflammatory and analgesic effects, and they are inhibitors of aldose reductase, SecA ATPase, azide, and plant growth. The search for methods of synthesis of new functionalized and condensed pyrimidine derivatives is an urgent problem.
 Alkenyl-functionalized mono- and polycyclic pyrimidines are promise substrates for studying the regioselectivity of electroph ilic heterocyclization reactions under the influence of halogen-containing electrophilic agents, and halogen- and chalcogen-functionalized cyclization products showed high antibacterial, antifungal, and antimalarial activity. The introduction of new functional groups capable to modification into such alkenylpyrimidines can significantly affect their reactivity and change/enhance the biological activity of the halocyclization products. We proposed the synthesis of 2-alkenyl(alkynyl)thio derivatives of 5-cyano-6-(p-dimethylaminophenyl)-pyrimidin-4-one containing a cyano group labile to functionalization. As a result of alkylation of 2-thioxo-5-cyano-6-(p-dimethylaminophenyl)pyrimidin-4-one with unsaturated alkyl halides in an alkaline medium, the terminal alkenyl (allyl, methallyl) and alkynyl (propargyl) thioethers of cyanopyrimidine were obtained, promising for heterocyclization with halogen-containing electrophilic reagents .
 Keywords: 2-thioxo-5-cyano-pyrimidin-4-one; alkylation; alkenylthiopyrimidinone; alkynylthiopyrimidinone.

Synthesis of Tetrahydrofurans and Pyrrolidines by Copper-Catalyzed Oxy/Aminoarylation of Alkenes.

An efficient copper-catalyzed inter/intramolecular oxy/aminoarylation of γ-hydroxy/aminoalkenes with diaryliodonium triflates is reported. Simple activation of these arylating agents with copper(II) triflate in dichloromethane triggers a smooth activation of the alkene, which is simultaneously trapped by the internal nucleophile, yielding, depending upon its nature, a range of highly substituted tetrahydrofurans and pyrrolidines. The cyclization was moreover found to be stereospecific, with diastereoisomeric alkenes yielding diastereoisomers of the cyclized product, and could be extended to oxyalkynylation.

Synthesis of Drimane-8α,11-diol Using Terpene Cyclase from Bacillus Megaterium

Chemo-enzymatic synthesis of drimane-8α,11-diol from farnesol derivatives using a terpene cyclase from Bacillus megaterium is achieved. Farnesol was not suitable for enzymatic transformation. On the other hand, farnesol derivatives in which the hydroxy group is protected with a conventional protecting group underwent cyclization to give the corresponding drimane-8α,11-diol derivatives. One of the cyclized products was transformed into 1 under mild conditions. Chemo-enzymatic synthesis of drimane derivatives from farnesol derivatives are achieved. Among farnesol derivatves, MOM protected farnesol was found to be superior substrate to other farnesol derivatives. The resulting drimane derivatives are easily converted to the target natural product in one step.

Copper-Mediated C4-Benzylations of 5-Aminopyrazoles with 3-Indoleacetic Acids

Herein, we present a copper-mediated C4-benzylation of 5-aminopyrazoles with 3-indoleacetic acids. Various benzylated 5-aminopyrazoles are prepared in good-to-excellent yields under basic and ligand-free conditions in the presence of copper acetate. Moreover, this benzylation method is applicable to other substrates, including naphthylamine, 2-aminochromen-4-one, and enamines. Some products exhibit antiproliferative activities against cancer cell lines. In addition, the C4-benzylated products are cyclized into 1H-pyrazolo[4',3':6,7]azepino[3,4-b]indoles with aldehydes via one-pot two-step processes; notably, the cyclized products exhibit fluorescence emissions with large Stokes shifts.

Cyclic products of Szegö kernels and spin structure sums. Part I. Hyper-elliptic formulation

The summation over spin structures, which is required to implement the GSO projection in the RNS formulation of superstring theories, often presents a significant impediment to the explicit evaluation of superstring amplitudes. In this paper we discover that, for Riemann surfaces of genus two and even spin structures, a collection of novel identities leads to a dramatic simplification of the spin structure sum. Explicit formulas for an arbitrary number of vertex points are obtained in two steps. First, we show that the spin structure dependence of a cyclic product of Szegö kernels (i.e. Dirac propagators for worldsheet fermions) may be reduced to the spin structure dependence of the four-point function. Of particular importance are certain trilinear relations that we shall define and prove. In a second step, the known expressions for the genus-two even spin structure measure are used to perform the remaining spin structure sums. The dependence of the spin summand on the vertex points is reduced to simple building blocks that can already be identified from the two-point function. The hyper-elliptic formulation of genus-two Riemann surfaces is used to derive these results, and its SL(2, ℂ) covariance is employed to organize the calculations and the structure of the final formulas. The translation of these results into the language of Riemann ϑ-functions, and applications to the evaluation of higher-point string amplitudes, are relegated to subsequent companion papers.