A Synthetic Lectinfor Glucuronate

De novo formation of the aromatic ring is an attractive strategy for atroposelective synthesis, but its application to planar-chiral macrocycles remains challenging. Herein, we report a rhodium-catalyzed enantioselective synthesis of planar-chiral macrocycles via de novo isoquinoline construction. This method is characterized by high levels of enantioselectivity (up to 96% ee), regioselectivity (up to >20:1 rr), and functional group tolerance, providing a series of isoquinoline-based macrocyclic atropisomers. Furthermore, the synthetic utility of this protocol is validated via a mmol-scale reaction and post-modification process of the product. Mechanistic studies, including deuterium labeling, kinetic isotope effect, and DFT calculations, support C─H bond cleavage as the rate-determining step and elucidate the origin of the stereoselectivity.

New heteroleptic zinc dimeric complexes bearing an aminophenolate ligand of a single-site initiator framework were synthesized and characterized by spectroscopic methods, X-ray analysis, and DFT calculations. The theoretical study, verified by the experimental data, explains the catalytic behaviour in the ROP of lactide in the examined zinc complexes. The presented simple DFT protocol constitutes a valuable method for the qualification of the ancillary ligand to rationally design new complexes to improve their catalytic activity.

The successful controlled homopolymerization of acrylonitrile (AN) by cobalt-mediated radical polymerization (CMRP) is reported for the first time. As a rule, initiation of the polymerization was carried out starting from a conventional azo-initiator (V-70) in the presence of bis(acetylacetonato)cobalt(II) ([Co(acac)(2)]) but also by using organocobalt(III) adducts. Molar concentration ratios of the reactants, the temperature, and the solvent were tuned, and the effect of these parameters on the course of the polymerization is discussed in detail. The best level of control was observed when the AN polymerization was initiated by an organocobalt(III) adduct at 0 degrees C in dimethyl sulfoxide. Under these conditions, poly(acrylonitrile) with a predictable molar mass and molar mass distribution as low as 1.1 was prepared. A combination of kinetic data, X-ray analyses, and DFT calculations were used to rationalize the results and to draw conclusions on the key role played by the solvent molecules in the process. These important mechanistic insights also permit an explanation of the unexpected "solvent effect" that allows the preparation of well-defined poly(vinyl acetate)-b-poly(acrylonitrile) by CMRP.

X-ray crystallography and DFT calculations were used to characterize the molecular nature and excited state properties of isomeric photostable azo dyes for textile fibers undergoing extensive sunlight exposure. Structural data in CIF files arising from X-ray analysis are reported and the complete files are deposited with the Cambridge Crystallographic Data Centre as CCDC 1548989 (https://www.ccdc.cam.ac.uk/structures/Search?Ccdcid=1548989) and CCDC 1548990 (https://www.ccdc.cam.ac.uk/structures/Search?Ccdcid=1548990). Data from calculating the vertical electronic excitation of 20 excited states for each dye and from calculating excited state oxidation potential (ESOP) and Frontier HOMO/LUMO isosurfaces are also presented. This data is related to the article “Molecular and excited state properties of isomeric scarlet disperse dyes” (Lim et al., 2018) [1].

An efficient approach for asymmetric synthesis of planar-chiral macrocycles (paracyclophanes) has been disclosed through enantioselective electrophilic aromatic aminations with azodicarboxylates enabled by chiral phosphoric acid catalysis. A wide range of chiral macrocycles bearing varied ring sizes (16 to 23-membered) and functional group-containing ansa chains were readily afforded using this method, with excellent yields and high enantioselectivities (23 examples, up to 99.5 : 0.5 er). Experimental studies and DFT calculations were performed to elucidate the mechanism and origin of stereoselectivities of these reactions. Preliminary utilization of the planar-chiral macrocycle as chiral organocatalyst showcased the potential applications of these novel chiral skeletons.

Efficient alkylation of cyclic silyl enol ethers by diarylmethylium salts

The title compounds were synthesized starting from homophthalic anhydride and a ketimine. The structure of 1'-methyl-1-oxo-2-(pyridine-3-yl-methyl)-2,4-dihydro-1H-spiro[isoquinoline-3,4'piperidine]-4-carboxylic acid was studied by X-ray analysis, ab initio and DFT calculations and the similarity between the conformation in crystalline hydrate state and in water solution was inferred. Derivatives of the parent compound were synthesized and studied by means of theoretical calculations.

Treatment of donor-substituted acetylenes (X−C≡C−X, with X = R−Se, R−Te) with sodium trichloroacetate, followed by hydrolysis, yielded the corresponding cyclopropenones. Their structures could be elucidated by X-ray analysis, and indicated significant overlap between the p-type lone pairs on the chalcogen atoms and the cyclopropenone unit. DFT calculations were carried out on various conformers in order to clarify their relative energy profiles. Methanolysis of these ring systems at room temperature quantitatively afforded α,β-unsaturated esters. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The title cyclic compounds, synthesized by cross-coupling reactions, have nonplanar frameworks, as revealed by X-ray analysis and DFT calculations. The barrier to exchange between the nonplanar structures of the mesityl derivative was determined to be 34 kJ mol−1 by a dynamic NMR method.

Pentacoordinate and tetracoordinate carbon and boron compounds (27, 38, 50-52, 56-61) bearing an anthracene skeleton with two oxygen or nitrogen atoms at the 1,8-positions were synthesized by the use of four newly synthesized tridentate ligand precursors. Several carbon and boron compounds were characterized by X-ray crystallographic analysis, showing that compounds 27, 56-59 bearing an oxygen-donating anthracene skeleton had a trigonal bipyramidal (TBP) pentacoordinate structure with relatively long apical distances (ca. 2.38-2.46 A). Despite the relatively long apical distances, DFT calculation of carbon species 27 and boron species 56 and experimental accurate X-ray electron density distribution analysis of 56 supported the existence of the apical hypervalent bond even though the nature of the hypervalent interaction between the central carbon (or boron) and the donating oxygen atom was relatively weak and ionic. On the other hand, X-ray analysis of compounds 50-52 bearing a nitrogen-donating anthracene skeleton showed unsymmetrical tetracoordinate carbon or boron atom with coordination by only one of the two nitrogen-donating groups. It is interesting to note that, with an oxygen-donating skeleton, the compound 61 having two chlorine atoms on the central boron atom showed a tetracoordinate structure, although the corresponding compound 60 with two fluorine atoms showed a pentacoordinate structure. The B-O distances (av 2.29 A) in 60 were relatively short in comparison with those (av 2.44 A) in 59 having two methoxy groups on the central boron atom, indicating that the B-O interaction became stronger due to the electron-withdrawing nature of the fluorine atoms.

The first dialkyl-substituted silicon-chalcogen doubly bonded compounds [R2Si=X; R2=1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl, X = S (4), Se (5), and Te (6)]were synthesized by the reactions of an isolable dialkylsilylene R2Si: (3) with phosphine sulfide, elemental selenium, and elemental tellurium, respectively. Systematic changes of characteristics of silicon-chalcogen double bonds are elucidated by X-ray analysis, UV-vis spectroscopy, and DFT calculations. In the solid state, the unsaturated silicon atom in 4-6 adopts planar geometry and the extent of the shortening of Si=X double bonds from the corresponding Si-X single bonds decreases in the order 4 > 5 > 6. In the absorption spectra of 4-6, pi -->pi* transition bands are observed distinctly in addition to n -->pi* transition bands. Both the n -->pi* and pi -->pi* transitions are red-shifted in the order 4 < 5 < 6, and the difference between the energies of the two transitions is kept almost constant among 4-6. The tendency is explained using the qualitative perturbation theory and is reproduced by the DFT calculations for model silanechalcogenones. Addition reactions of water, methanol, and isoprene to 4-6 are reported.

The first stereocontrolled Cu-catalyzed sequential 1,6/1,4-asymmetric conjugate addition (ACA) of C-metalated hard nucleophiles to cyclic dienones is reported. The use of DiPPAM (diphenylphosphinoazomethinylate) followed by a phosphoramidite as the stereoinducing ligands facilitated both high ee values for the 1,6-ACA and high de values for the 1,4-ACA reaction components, which thus gave enantioenriched 1,3-dialkylated moieties. The absolute configurations were determined by using vibrational circular dichroism (VCD) and optical rotatory dispersion (ORD) spectroscopy, in combination with DFT calculations and X-ray analysis. Interestingly, DFT calculations for the mechanism of enantioselective 1,6-addition by using an unprecedented Cu-Zn bimetallic catalytic system confirmed this attribution. Lastly, exploring intramolecular cyclization avenues for enantioenriched 1,3-dialkylated products provided access to the challenging drimane skeleton.

Anthracene–diacetylene cyclic dimers having two alkoxy groups (OMe, OEt, or OPr groups) at the intraannular positions were synthesized by dimerization of 1,8-diethynylanthracene precursors. For the OEt and OPr compounds, anti- and syn-stereoisomers that differed in the direction of the alkyl groups were separated by chromatography. Kinetic measurements showed that the barriers to isomerization from syn-isomer to anti-isomer were 124 and &amp;gt;146 kJ mol−1 for the OEt and OPr compounds, respectively. The molecular structures of these compounds were examined by X-ray analysis and DFT calculations. The preference for anti-isomers is attributable to the intramolecular C–H···O hydrogen bonds. The effects of substituents on the molecular structures and the barriers to isomerization are discussed.

Two 1,8-anthrylene cyclic trimers with acetylene or diacetylene linkers were synthesized by macrocyclization with the Eglinton coupling. These compounds have nonplanar and strained cyclic structures with significant bending deformations of acetylene carbons as revealed by X-ray analysis and DFT calculation. The effects of the molecular structures on the 13C NMR chemical shifts and the electronic spectra are discussed.

A new series of 1,2,4-triazine unsymmetrical disulfanes were prepared and evaluated as anticancer activity compounds against MCF-7 human breast cancer cells with some of them acting as low micromolar inhibitors. Evaluation of the cytotoxicity using an MTT assay, the inhibition of [3H]-thymidine incorporation into DNA demonstrated that these products exhibit cytotoxic effects on breast cancer cells in vitro. The most effective compounds with 59 and 60 µM compared to chlorambucil with 47 µM were disulfanes bearing methyl and methoxy substituent in an aromatic ring. Furthermore, all new 14 compounds were obtained with 22–74% yield via mild and efficient synthesis of the sulfur–sulfur bond formation from thiols and symmetrical disulfanes using 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ). The molecular structure of the newly obtained compounds was confirmed by X-ray analysis. The conformational preferences of disulfide system were characterized using theoretical calculations at DFT level and statistical distributions of C–S–S–C torsion angle values based on the Cambridge Structural Database (CSD). The DFT calculations and CSD searching show two preferential conformations for C–S–S–C torsion angle close to ± 90° and relatively large freedom of rotation on S–S bond in physiological conditions. The molecular docking studies were performed using the human estrogen receptor alpha (ERα) as molecular target to find possible binding orientation and intermolecular interactions of investigated disulfanes within the active site of ERα. The S…H–S and S…H–C hydrogen bonds between sulfur atoms of bisulfide bridge and S–H and C–H groups of Cys530 and Ala350 as protein residues play crucial role in interaction with estrogen receptor for the most anticancer active disulfane.Graphical abstract