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A general, scalable two-step regio- and diastereoselective method has been described for the synthesis of versatile alkaloid-type azetidines from simple building blocks with excellent overall yields. In the kinetically controlled reaction, only the formation of the strained four-membered ring can be achieved instead of the thermodynamically favorable five-membered rings under appropriate conditions. Remarkable functional group tolerance has also been demonstrated. In this paper, we give a new scope of Baldwin's rules by density functional theory (DFT) calculations with an explicit solvent model, confirming the proposed reaction mechanisms and the role of kinetic controls in the stereochemical outcome of the reported transition-metal-free carbon-carbon bond formation reactions.

A variety of quaternary aryl amino acid derivatives can be synthesised using tandem SN2 / Smiles rearrangement chemistry involving aryl sulfonamides and alpha-chloro carbonyl compounds. The reaction harnesses a sulfur dioxide extrusion pathway to construct a C-N and C-Caryl bond under simple conditions with no requirement for organometallics or transition metal catalysts. The reaction is also successful for alkenyl sulfonamides, producing sterically congested quaternary alkene amino acid derivatives

Vinyl alcohol (VA) copolymers having fine tunable polarities are emerging materials in drug delivery applications. VA copolymers rendering well-defined molecular architecture (C/OH ratio = 2, 4, 5 and 8) were used as carriers for model drug compound, fluorescein, which exhibited significantly different release characteristics depending on the polarity of the polymers. Based on the preliminary drug release tests the well-defined VA copolymer having C/OH = 5 ratio, poly(vinyl alcohol alt-propenylene) copolymer (PVA-5) was selected for nanocomposite synthesis. Sorafenib anticancer drug was embedded into PVA-5 (C/OH = 5 ratio) nanoparticles by nanoprecipitation resulting in nanoparticles exhibiting unusual cubic shape . The sorafenib-loaded nanocomposites showed continuous release during a day and concentration-dependant cytotoxicity on HT-29 cancer cells. This might be interpreted by the sustained release of the drug.

Copolymers containing hydroxyl (i.e. vinyl alcohol, VA) or fluorine functionalities are synthetic macromolecules having prominent biomedical applications. The concentration of hydroxyl groups along the polymer chain controls the polymer polarity. Moreover, the introduction of perfluorinated organic moieties via the OH functionalities may lead to macromolecules having potential magnetic resonance imaging (MRI) active properties. The ring-opening metathesis polymerization (ROMP) reaction using well-defined ruthenium-catalyzed systems is one of the most promising synthetic tools to fabricate such polymers. Co-polymerization of norbornene grafted pyridino-18-crown-6 ether (7) with fluorine-functionalized norbornenes (10 and 11) results in polymers bearing host molecular moieties. It has been demonstrated that the complexation of these host copolymers with biogenic amines including dopamine hydrochloride (12) and L-alanyl-L-lysine dipeptide hydrochloride (13) is straightforward. Based on the 1H NMR investigation of the 7 and 12 complexation, an equilibrium constant of log K = 4.3 ± 0.6 could be calculated. The in situ1H NMR investigations have revealed that the complex formation of 13 with monomer 7 and perfluorinated copolymer cp-7-10 takes place via both the lysine –NH3+ and the alanine –NH3+ moieties. However, in the case of homopolymer poly-7, the lysine–NH3+ group coordination was observed exclusively. According to theoretical calculations, molecular switching of the crown ether structure of both the 7 monomer and its cp-7-10 copolymer were observed from 90 degrees bent to planar structure upon –NH3+ ion coordination.

In this paper, we present an additional, new cage-GABA compound, called 4-amino-1-(4′-dimethylaminoisopropoxy-5′,7′-dinitro-2′,3′-dihydro-indol-1-yl)-1-oxobutane-γ-aminobutyric acid (iDMPO-DNI-GABA), and currently, this compound is the only photoreagent, which can be applied for GABA uncaging without experimental compromises. By a systematic theoretical design and successful synthesis of several compounds, the best reagent exhibits a high two-photon efficiency within the 700–760 nm range with excellent pharmacological behavior, which proved to be suitable for a complex epileptic study. Quantum chemical design showed that the optimal length of the cationic side chain enhances the two-photon absorption by 1 order of magnitude due to the cooperating internal hydrogen bonding to the extra nitro group on the core. This feature increased solubility while suppressing membrane permeability. The efficiency was demonstrated in a systematic, wide range of in vitro single-cell neurophysiological experiments by electrophysiological as well as calcium imaging techniques. Scalable inhibitory ion currents were elicited by iDMPO-DNI-GABA with appropriate spatial–temporal precision, blocking both spontaneous and evoked cell activity with excellent efficiency. Additionally, to demonstrate its applicability in a real neurobiological study, we could smoothly and selectively modulate neuronal activities during artificial epileptic rhythms first time in a neural network of GCaMP6f transgenic mouse brain slices.

Polyisobutylene is a unique, fully saturated polymer with a variety of useful properties ranging from outstanding biocompatibility and barrier behavior to high thermal, oxidative, and chemical stability. This chapter provides a brief overview on endfunctional polyisobutylenes (PIBs) prepared by quasiliving carbocationic polymerization (QLCCP) of isobutylene and on the applications of the resulting terminally functionalized PIBs by us as macroinitiators and macromonomers to create novel macromolecular architectures not existed earlier. These include novel ABA triblock and ABCBA pentablock copolymers and polymer conetworks, such as amphiphilic and cyanoacrylate-telechelic PIB-based conetworks with various high added value application possibilities, such as ion conducting membranes, robust pH-reponsive hydrogels, nanohybrids as highly efficient nanocatalysts, elastic wound closure films, etc.

Cross metatheses of tung oil, a nonedible vegetable oil and α-eleostearic acid ((9Z,11E,13E)-octadeca-9,11,13-trienoic acid, ESA) methyl ester (1), obtained from tung oil containing the same highly unsaturated, conjugated double bonds, have been carried out with cis-1,4-diacetoxy-2-butene (2) using Hoveyda-Grubbs (3-HG2) or Grubbs second or third generation catalysts (3-G2 or 3-G3). The reactions followed by Pd/C-catalyzed hydrogenation give methyl 11-acetoxyundecanoate (4) as a polyester raw material, 1,6-diacetoxy-hexane (5) as a precursor of 1,6-hexanediol (6) polyurethane monomer, and heptyl acetate as a fragrance (7) in 53–99% yields after Pd/C-catalyzed hydrogenation. The one-pot isomerization metathesis of α-linolenic acid ((9Z,12Z,15Z)-9,12,15-octadecatrienoic acid, ALA) methyl ester (7) using 2 as cross coupling agent, RuHCl(CO)(PPh3)3 (9) as isomerization, and 3-G2 as a metathesis catalyst followed by Pd/C catalyzed hydrogenation leads also to the formation of 5 and the homologues of 4 and 7 in ...

Cross-metathesis (CM) of conjugated polyenes, such as 1,6-diphenyl-1,3,5-hexatriene ( 1 ) and α-eleostearic acid methyl ester ( 2 ) with several olefins, including 1-hexene, dimethyl maleate and cis -stilbene as model compounds has been carried out using (1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene)-dichloro( o -isopropoxyphenylmethylene)ruthenium (Hoveyda-Grubbs 2nd generation, HG2 ) catalyst. The feasibility of these reactions is demonstrated by the observed high conversions and reasonable yields. Thus, regardless of the relatively low electron density, =CH–CH= conjugated units of molecules, including compound 2 as a sustainable, non-foodstuff source, can be utilized as building blocks for the synthesis of various value-added chemicals via olefin metathesis. DFT-studies and the product spectrum of the self-metathesis of 1,6-diphenyl-1,3,5-hexatriene suggest that a Ru η 1 -allylidene complex is the active species in the reaction.

The present study reports regio- and highly diastereoselective preparative methods for the synthesis of versatile alkaloid-type compounds from oxiranylmethyl tetrahydroisoquinolines. 2,5-Methanobenzo[ c]azepines or azetidine-fused heterocycles were synthesized in tandem reactions depending on the absence or presence of a BF3 co-reagent. A high functional group tolerance has also been demonstrated. DFT calculations with an explicit solvent model confirmed the proposed reaction mechanisms and the role of kinetic controls on the stereochemical outcome of the reported new methods.

In order to improve the fluorescence properties of the green fluorescent protein chromophore, p‑HOBDI ((5‑(4‑hydroxybenzylidene)‑2,3‑dimethyl‑3,5‑dihydro‑4H‑imidazol‑4‑one), sixteen dihydroimidazolone derivates were synthesized from thiohydantoin and arylaldehydes. The synthesis developed is an efficient, novel, one-pot procedure. The study provides a detailed description of the spectroscopic characteristics of the newly synthesized compounds, using p‑HOBDI as a reference. The new compounds all exhibited significantly stronger fluorescence than p‑HOBDI, up to 28 times higher quantum yields. An experimental and theoretical investigation of the relationship of the fluorescence properties with the molecular structure was also carried out. A good correlation was found between the emission wavenumber and the Hammett constant of the functional group, which suggests the intermolecular charge transfer (ICT) mechanism between the aromatic groups.

New methods for efficient preparation of optically active compounds developed recently are reported. Combination of selective organometallic, organocatalytic, phase transfer catalytic and catalytic hydrogenation reactions provided numerous new optically active members of the families of atropisomeric 1-phenylpyrrole derivatives, 4-aminobutan-1-ol and 3,4-disubstituted pyrrolidine derivatives and optically active α- and β-aminophosphonic acids. The products can be used as valuable new chiral ligands or organocatalysts and can serve as building blocks of practically important biologically active compounds.

Some N- and O-protected hydroxyazetidine derivatives were hydrogenated to the corresponding amines or aminoalcohols over a Pd/C catalyst, in different solvents (methanol, dichloromethane, tetrahydrofuran), at 30–60 °C and 1–10 bar. These amino compounds, formed during hydrogenolytic ring opening and/or deprotecting reactions, are potential starting materials for preparing optically active, practically important pyrrolidine derivatives.

The first enzyme-catalyzed kinetic resolution of tert-butyl-3-hydroxy-4-phenylpyrrolidine-1-carboxylate is presented. Enzyme, solvent and temperature optimization resulted in a new resolution method with E = 40 enantioselectivity. The acetate derivative of the (+)-(3S,4R) enantiomer formed while the (−)-(3R,4S) isomer remained intact. Very good enantioselectivities (E > 200) were achieved in the enzyme-catalyzed alcoholysis of the racemic acetate in i-propanol and t-butanol where the (+)-(3S,4R) enantiomer was prepared in pure form (ee > 99.7%). Absolute configuration of the (−)-(3R,4S)-enantiomer was determined by single crystal X-ray diffraction method.

A novel, superbase induced diastereoselective transformation of benzylamino groups containing oxiranes has provided a series of trans-1,2,3-trisubstituted azetidines in good yields. The reaction of the corresponding optically active cis-2,3-disubstituted oxirane yielded the azetidine derivative as a single enantiomer. The structures of the new azetidines were confirmed by NMR spectroscopic methods and, in one case, by single crystal diffraction measurements.

An efficient method for the palladium mediated hydrogenation of an optically active, N-protected aminooxetane derivative has been developed. Using appropriate solvents, in a one-step reaction, a chiral 1,4-aminoalcohol derivative [(2S,3R)-4-amino-3-benzoyloxy-2-benzylbutan-1-ol] was formed over a Pd/C catalyst, during hydrogenolytic ring opening and debenzylation reactions.

An efficient method for the palladium mediated hydrogenation of an optically active, O -protected hydroxyoxetane derivative has been developed. Using appropriate solvents, in a one-step reaction, optically active 1,4-diol was formed over a Pd/C catalyst, during hydrogenolytic ring opening and detritylation reactions.

A variety of dihydrofuran (XIV), tetrahydrofuran (IX), dioxole (III), (VII) and pyrrolidine derivatives (XII) is prepared starting from triol (I) or its partially protected analogues.

Novel, superbase promoted stereoselective rearrangement reactions of chiral oxirane derivatives provided chiral oxetane and azetidine derivatives. An optically active 3,4-disubstituted pyrrolidine was synthetised via catalytic hydrogenolysis of an oxetane derivative followed by ring closure of the formed optically active aminoalcohol.

Not all amide bonds are created equally. The purpose of the present paper is the reinterpretation of the amide group by means of two concepts: amidicity and carbonylicity. These concepts are meant to provide a new viewpoint in defining the stability and reactivity of amides. With the help of simple quantum-chemical calculations, practicing chemists can easily predict the outcome of a desired process. The main benefit of the concepts is their simplicity. They provide intuitive, but quasi-thermodynamic data, making them a practical rule of thumb for routine use. In the current paper we demonstrate the performance of our methods to describe the chemical character of an amide bond strength and the way of its activation methods. Examples include transamidation, acyl transfer and amide reductions. Also, the method is highly capable for simple interpretation of mechanisms for biological processes, such as protein splicing and drug mechanisms. Finally, we demonstrate how these methods can provide information about photo-activation of amides, through the examples of two caged neurotransmitter derivatives.