Basic Amino Group Research Articles

Design of a New Chiral Deep Eutectic Solvent Based on 3-Amino-1,2-propanediol and Its Application in Organolithium Chemistry

A chiral glycerol derivative, namely 3-amino-1,2-propanediol, was employed for as the hydrogen bond donor (HBD) in the design of a new deep eutectic solvent (DES) with choline chloride acting as the hydrogen bond acceptor (HBA). The novel mixture was characterized and unambiguously classified as a DES. Furthermore, its synthetic usefulness was demonstrated in the room-temperature n-butyllithium-addition under air to carbonyl compounds and benzyl chloride. In some cases, pure products (100% conversion) were obtained by a simple extractive work-up in up to 72% isolated yield, thus suggesting the potential practical usefulness of this procedure as a green alternative to the classical Schenk procedure in volatile organic solvents for the synthesis of tertiary alcohols. The chirality of the HBD, bearing an interesting basic primary amino group, is an intriguing feature currently under investigation for further exploitation.

Introduction of the Functional Amino Group at the meso Position of Cy3 and Cy5 Dyes: Synthesis, Stability, Spectra and Photolysis of 4‐Amino‐1‐diazo‐2‐butanone Derivatives**

AbstractSearching for photoconvertible or photoactivatable dyes, we considered trimethine (Cy3) and pentamethine (Cy5) fluorophores with a 4‐amino‐1‐diazo‐2‐butanone fragment (H2N(CH2)2COCH=N2) attached to the meso (γ) position of the polymethine chain via the amino group. The Cy3 derivative was prepared. All Cy5 derivatives with the basic amino group at this position decomposed with breaking the polymethine chain. However, amino‐squaraine based Cy5 dyes were found to be stable and accessible. Photolysis of Cy3 and squaraine‐based Cy5 dyes with a 4‐amino‐1‐diazo‐2‐butanone fragment was accompanied with Wolff rearrangement and led to pyrrolidones (in methanol and aprotic solvents) formed via intramolecular cyclization of the intermediate ketenes. In aqueous acetonitrile, ketenes reacted with water and gave carboxylic acids. Both products were non‐fluorescent, though the model Cy5 dyes (without the squaraine fragment) with acylated amino and N‐methylamino groups were found to be fluorescent.

Chiral Bifunctional Phosphine Ligand-Enabled Cooperative Cu Catalysis: Formation of Chiral α,β-Butenolides via Highly Enantioselective γ-Protonation.

α,β-Butenolides with ≥96% enantiomeric excess are synthesized from β,γ-butenolides via a novel Cu(I)-ligand cooperative catalysis. The reaction is enabled by a chiral biphenyl-2-ylphosphine ligand featuring a remote tertiary amino group. Density functional theory studies support the cooperation between the metal center and the ligand basic amino group during the initial soft deprotonation and the key asymmetric γ-protonation. Remarkably, other coinage metals, that is, Ag and Au, can readily assume the same role as Cu in this asymmetric isomerization chemistry.

Synthesis and Antibacterial Activity of Propylamycin Derivatives Functionalized at the 5''- and Other Positions with a View to Overcoming Resistance Due to Aminoglycoside Modifying Enzymes.

Propylamycin (4'-deoxy-4'-propylparomomycin) is a next generation aminoglycoside antibiotic that displays increased antibacterial potency over the parent, coupled with reduced susceptibility to resistance determinants and reduced ototoxicity in the guinea pig model. Propylamycin nevertheless is inactivated by APH(3')-Ia, a specific aminoglycoside phosphotransferase isozyme that acts on the primary hydroxy group of the ribofuranosyl moiety (at the 5''-position). To overcome this problem, we have prepared and studied the antibacterial and antiribosomal activity of various propylamycin derivatives carrying amino or substituted amino groups at the 5''-position in place of the vulnerable hydroxy group. We find that the introduction of an additional basic amino group at this position, while overcoming the action of the aminoglycoside phosphoryltransferase isozymes acting at the 5''-position as anticipated, results in a significant drop in selectivity for the bacterial over the eukaryotic ribosomes that is predictive of increased ototoxicity. In contrast, 5''-deoxy-5''-formamidopropylamycin retains the excellent across-the-board levels of antibacterial activity of propylamycin itself, while circumventing the action of the offending aminoglycoside phosphotransferase isozymes and affording even greater selectivity for the bacterial over the eukaryotic ribosomes. Other modifications to address the susceptibility of propylamycin to the APH(3')-Ia isozyme including deoxygenation at the 3'-position and incorporation of a 6',5''-bis(hydroxyethylamino) modification offer no particular advantage.

A bifunctional ligand enables efficient gold-catalyzed hydroarylation of terminal unactivated propargylic alcohols with heteroareneboronic acids

Abstract Terminal allylic alcohols are important motifs in natural products, and also key intermediates/precursors in numerous novel reaction transformations. In this study, enabled by a bifunctional ligand featuring a basic amino group, a gold-catalyzed hydroarylation of terminal unactivated propargylic alcohols with heteroareneboronic acids has been first established, and efficiently affords various terminal aryl-substituted allylic alcohols with moderate to high yields under mild conditions.

BODIPYs bearing a dimethylaminopropoxy substituent for imaging and photodynamic inactivation of bacteria

A new BODIPY (BDP 1) bearing a dimethylaminopropoxy group attached to a phenylene unit was synthesized. This compound was brominated to obtain the halogenated analog BDP 2, which was designed to enhance the photodynamic effect of BODIPY to kill bacteria without an intrinsic cationic charge. The basic amino group located at the end of the propoxy bridge can acquire a positive charge by protonation in an aqueous medium, increasing the binding to bacterial cells. Interaction and photokilling activity mediated by these compounds was evaluated in Staphylococcus aureus and Escherichia coli. BDP 1 and BDP 2 were rapidly bound to bacterial cells, showing bioimages with green emission. Complete elimination of S. aureus was detected when cells were incubated with 1 μM BDP 2 and irradiated for 5 min. Comparable photoinactivation was obtained with E. coli, after an irradiation of 30 min. Furthermore, BDP 2 was effective to kill bacteria at very low concentration (0.5 μM). Thus, BDP 1 showed mainly interesting properties as a fluorophore, whereas BDP 2 was highly effective photosensitizer as a broad-spectrum antibacterial agent.

Tetrahydroimidazo[1,2‐a]pyrazine Derivatives: Synthesis and Evaluation as Gαq‐Protein Ligands

The 5,6,7,8‐tetrahydroimidazo[1,2‐a]pyrazine derivative BIM‐46174 and its dimeric form BIM‐46187 (1) are heterocyclized dipeptides that belong to the very few cell‐permeable compounds known to preferentially silence Gαq proteins. To explore the chemical space of Gαq inhibitors of the BIM chemotype, a combinatorial approach was conducted towards a library of BIM molecules. This library was evaluated in a second messenger‐based fluorescence assay to analyze the activity of Gαq proteins through the determination of intracellular myo‐inositol 1‐phosphate. Structure–activity relationships were deduced and structural requirements for biological activity obtained, which were (i) a redox reactive thiol/disulfane substructure, (ii) an N‐terminal basic amino group, (iii) a cyclohexylalanine moiety, and (iv) a bicyclic skeleton. Active compounds exhibited cellular toxicity, which was investigated in detail for the prototypical inhibitor 1. This compound affects the structural cytoskeletal dynamics in a Gαq/11‐independent manner.

Effect of π-conjugation on solid-state fluorescence in highly planar dyes bearing an intramolecular H-bond

Efficient solid emitters with planar architectures are desirable for some practical applications. However, molecules with coplanar structures and conformational rigidity generally exhibit small Stokes shifts, thus resulting in self-absorption. Multi-aromatic hydrocarbons are one typical example that easily undergoes aggregation-caused quenching (ACQ) due to intermolecular π-π interactions. Herein, a highly planar seven-ringed dye containing benzothiazole- and triphenyl-fused moieties (HTpT) without any bulky or propeller-shaped substituent at its periphery was facilely synthesized from a Cu+-catalyzed Scholl reaction. By extending the phenyl in excited-state intramolecular proton transfer (ESIPT)-active dye (HBT) to naphthyl (HNT) and to triphenyl (HTpT), HNT shows hypsochromic emission and small Stokes shift (20 nm) in comparison with parent HBT, and suffers from ACQ. Contrarily, HTpT exhibits bright red solid-state fluorescence (λem: 600 nm, Φf: 22.7%) with a 200 nm Stokes shift. Steady-state fluorescence spectra, theoretical calculations, and X-ray diffraction analysis are performed to elucidate these different photo-physical properties. In addition, unlike most lysosomal targeting probes containing proton-binding amino or morpholine moieties, which can cause an “alkalinizing effect” that interferes with the activity of normal cells, HTpT without a basic amino group can specifically light up cellular lysosomes.

Acid-Base Interaction Enhancing Oxygen Tolerance in Electrocatalytic Carbon Dioxide Reduction.

Hybrid electrodes with improved O2 tolerance and capability of CO2 conversion into liquid products in the presence of O2 are presented. Aniline molecules are introduced into the pore structure of a polymer of intrinsic microporosity to expand its gas separation functionality beyond pure physical sieving. The chemical interaction between the acidic CO2 molecule and the basic amino group of aniline renders enhanced CO2 separation from O2 . Loaded with a cobalt phthalocyanine-based cathode catalyst, the hybrid electrode achieves a CO Faradaic efficiency of 71 % with 10 % O2 in the CO2 feed gas. The electrode can still produce CO at an O2 /CO2 ratio as high as 9:1. Switching to a Sn-based catalyst, for the first time O2 -tolerant CO2 electroreduction to liquid products is realized, generating formate with nearly 100 % selectivity and a current density of 56.7 mA cm-2 in the presence of 5 % O2 .

Acid–Base Interaction Enhancing Oxygen Tolerance in Electrocatalytic Carbon Dioxide Reduction

AbstractHybrid electrodes with improved O2 tolerance and capability of CO2 conversion into liquid products in the presence of O2 are presented. Aniline molecules are introduced into the pore structure of a polymer of intrinsic microporosity to expand its gas separation functionality beyond pure physical sieving. The chemical interaction between the acidic CO2 molecule and the basic amino group of aniline renders enhanced CO2 separation from O2. Loaded with a cobalt phthalocyanine‐based cathode catalyst, the hybrid electrode achieves a CO Faradaic efficiency of 71 % with 10 % O2 in the CO2 feed gas. The electrode can still produce CO at an O2/CO2 ratio as high as 9:1. Switching to a Sn‐based catalyst, for the first time O2‐tolerant CO2 electroreduction to liquid products is realized, generating formate with nearly 100 % selectivity and a current density of 56.7 mA cm−2 in the presence of 5 % O2.

Structure Modeling of the Norepinephrine Transporter.

The norepinephrine transporter (NET) is one of the monoamine transporters. Its X-ray crystal structure has not been obtained yet. Inhibitors of human NET (hNET) play a major role in the treatment of many central and peripheral nervous system diseases. In this study, we focused on the spatial structure of a NET constructed by homology modeling on Drosophila melanogaster dopamine transporter templates. We further examined molecular construction of primary binding pocket (S1) together with secondary binding site (S2) and extracellular loop 4 (EL4). The next stage involved docking of transporter inhibitors: Reboxetine, duloxetine, desipramine, and other commonly used drugs. The procedure revealed the molecular orientation of residues and disclosed ones that are the most important for ligand binding: Phenylalanine F72, aspartic acid D75, tyrosine Y152, and phenylalanine F317. Aspartic acid D75 plays a key role in recognition of the basic amino group present in monoamine transporter inhibitors and substrates. The study also presents a comparison of hNET models with other related proteins, which could provide new insights into their interaction with therapeutics and aid future development of novel bioactive compounds.

Steroid Alkaloids from Holarrhena africana with Strong Activity against Trypanosoma brucei rhodesiense.

In our continued search for natural compounds with activity against Trypanosoma brucei, causative agent of human African trypanosomiasis (HAT, “sleeping sickness”), we have investigated extracts from the leaves and bark of the West African Holarrhena africana (syn. Holarrhena floribunda; Apocynaceae). The extracts and their alkaloid-enriched fractions displayed promising in vitro activity against bloodstream forms of T. brucei rhodesiense (Tbr; East African HAT). Bioactivity-guided chromatographic fractionation of the alkaloid-rich fractions resulted in the isolation of 17 steroid alkaloids, one nitrogen-free steroid and one alkaloid-like non-steroid. Impressive activities (IC50 in µM) against Tbr were recorded for 3β-holaphyllamine (0.40 ± 0.28), 3α-holaphyllamine (0.37 ± 0.16), 3β-dihydroholaphyllamine (0.67 ± 0.03), N-methylholaphyllamine (0.08 ± 0.01), conessimine (0.17 ± 0.08), conessine (0.42 ± 0.09), isoconessimine (0.17 ± 0.11) and holarrhesine (0.12 ± 0.08) with selectivity indices ranging from 13 to 302. Based on comparison of the structures of this congeneric series of steroid alkaloids and their activities, structure-activity relationships (SARs) could be established. It was found that a basic amino group at position C-3 of the pregnane or pregn-5-ene steroid nucleus is required for a significant anti-trypanosomal activity. The mono-methylated amino group at C-3 represents an optimum for activity. ∆5,6 unsaturation slightly increased the activity while hydrolysis of C-12β ester derivatives led to a loss of activity. An additional amino group at C-20 engaged in a pyrrolidine ring closed towards C-18 significantly increased the selectivity index of the compounds. Our findings provide useful empirical data for further development of steroid alkaloids as a novel class of anti-trypanosomal compounds which represent a promising starting point towards new drugs to combat human African trypanosomiasis.

Theoretical study on the isomerization of propargyl derivative to conjugated diene under Au(I)-catalyzed reaction: A DFT study

Pure and hybrid quantum mechanical calculations were performed to study the pathway of the isomerization of propargyl derivative to conjugated diene under the catalysis of Au(I) complex derived from the biphenyl-2-ylphosphine with a basic amino group on the pendant phenyl ring. It was previously proposed that a push–pull driving force operates orthogonally during the progress of the reaction. Our study reveals that this push–pull force is syn-periplanar rather than orthogonal. Steric pressure by the phosphine ligand, together with the push–pull interaction favors the transformation of η2 to η1 mode of Au complex. These effects are responsible for the increasing acidity of the transferring proton. The bent structure of the product suffers from the reduced steric pressure, thus favors the formation of the conjugated diene.

Synthesis, spectroscopic properties and photodynamic activity of a fulleropyrrolidine bearing a basic amino group and its dicationic analog against Staphylococcus aureus

Abstract N-Methyl-2-[4-(3-N,N-dimethylaminopropoxy)phenyl]fulleropyrrolidine (MPC60) was synthesized by 1,3-dipolar cycloaddition reaction of 4-(3-N,N-dimethylaminopropoxy)benzaldehyde, N-methylglycine and fullerene C60 in 43% yield. The amine groups of MPC60 were methylated with dimethyl sulfate to obtain a dicationic fullerene DPC602+ in 96 % yield. Absorption spectra of these fullerenes in N,N-dimethylformamide (DMF) and toluene/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/water reverse micelles showed strong absorptions in the UV region, with a peak at 430 nm and broader range of absorption up to 710 nm. Fluorescence quantum yields of about 10−4 were calculated for these compounds in DMF. A higher singlet molecular oxygen, O2(1Δg), generation was found for MPC60 than DPC602+ in DMF. The photodynamic activity of these photosensitizers remained high in a simple biomimetic AOT system. Also, the formation of superoxide anion radical induced by MPC60 and DPC602+ was detected in presence of NADH. Decomposition of l -tryptophan in DMF mediated by both fullerenes indicated a possible contribution of type I photoprocess. Photosensitized inactivation of Staphylococcus aureus was investigated using different conditions. Cell suspensions of 108 cells/mL incubated with 0.5 μM fullerene and irradiated for 30 min exhibited a 4.4 and 5.0 log decrease of cell survival by MPC60 and DPC602+, respectively. Therefore, these fullerene derivatives can be used as effective photosensitizers for the photodynamic inactivation of S. aureus cells.

IR spectrum of the protonated neurotransmitter 2-phenylethylamine: dispersion and anharmonicity of the NH3(+)-π interaction.

The structure and dynamics of the highly flexible side chain of (protonated) phenylethylamino neurotransmitters are essential for their function. The geometric, vibrational, and energetic properties of the protonated neutrotransmitter 2-phenylethylamine (H(+)PEA) are characterized in the N-H stretch range by infrared photodissociation (IRPD) spectroscopy of cold ions using rare gas tagging (Rg = Ne and Ar) and anharmonic calculations at the B3LYP-D3/(aug-)cc-pVTZ level including dispersion corrections. A single folded gauche conformer (G) protonated at the basic amino group and stabilized by an intramolecular NH(+)-π interaction is observed. The dispersion-corrected density functional theory calculations reveal the important effects of dispersion on the cation-π interaction and the large vibrational anharmonicity of the NH3(+) group involved in the NH(+)-π hydrogen bond. They allow for assigning overtone and combination bands and explain anomalous intensities observed in previous IR multiple-photon dissociation spectra. Comparison with neutral PEA reveals the large effects of protonation on the geometric and electronic structure.

Anticancer activity and DNA binding property of the dimers of triphenylethylene–coumarin hybrid with two amino side chains

Novel dimers of triphenylethylene–coumarin hybrid containing two amino side chains were designed and synthesized by the condensation of three dicarboxylic acids with the amino monomeric hybrids catalyzed by HATU and DIPEA at room temperature. All the dimeric compounds exhibited significant anti-proliferative activity against four cancer cells at IC50 of near 10 μM, and higher than their corresponding monomeric compounds except compound 9b. Among them, compounds 9a (R = NEt2) linked by sebacamide and 8b (R = piperidinyl) linked by adipamide were the best ones, respectively. UV–Vis, fluorescence, and circular dichroism (CD) spectroscopies and thermal denaturation exhibited that the monomeric compounds 6b and the dimers 7b, 8b, and 9b had significant interactions with Ct-DNA by the intercalative mode of binding. The order of their anti-proliferative activities was 8b > 7b> 6b > 9b, in accordance with that of their DNA binding properties. Novel dimers of triphenylethylene–coumarin hybrid containing two amino side chains were designed and synthesized. All the dimeric compounds exhibited significant anti-proliferative activity against cancer cells. Both the length of the linker and the basic amino group had certain effects on their anti-proliferative activity. Anticancer activity and DNA binding property of the dimers of triphenylethylene–coumarin hybrid with two amino side chains

Self-hydrolyzing maleimides improve the stability and pharmacological properties of antibody-drug conjugates.

Many antibody-drug conjugates (ADCs) are unstable in vivo because they are formed from maleimide-containing components conjugated to reactive thiols. These thiosuccinimide linkages undergo two competing reactions in plasma: elimination of the maleimide through a retro-Michael reaction, which results in loss of drug-linker from the ADC, and hydrolysis of the thiosuccinimide ring, which results in a derivative that is resistant to the elimination reaction. In an effort to create linker technologies with improved stability characteristics, we used diaminopropionic acid (DPR) to prepare a drug-linker incorporating a basic amino group adjacent to the maleimide, positioned to provide intramolecular catalysis of thiosuccinimide ring hydrolysis. This basic group induces the thiosuccinimide to undergo rapid hydrolysis at neutral pH and room temperature. Once hydrolyzed, the drug-linker is no longer subject to maleimide elimination reactions, preventing nonspecific deconjugation. In vivo studies demonstrate that the increased stability characteristics can lead to improved ADC antitumor activity and reduced neutropenia.

Soft propargylic deprotonation: designed ligand enables Au-catalyzed isomerization of alkynes to 1,3-dienes.

By functionalizing the privileged biphenyl-2-ylphosphine with a basic amino group at the rarely explored 3′ position, the derived gold(I) complex possesses orthogonally positioned “push” and “pull” forces, which enable for the first time soft propargylic deprotonation and permit the bridging of a difference of >26 pKa units (in DMSO) between a propargylic hydrogen and a protonated tertiary aniline. The application of this design led to efficient isomerization of alkynes into versatile 1,3-dienes with synthetically useful scope under mild reaction conditions.

Synthesis of 2-[{4-(t-amino-1-yl) but-2-yn-1-yl }oxy]-1,3- benzothiazole derivatives as H3-antagonists

Aminoacetylenicoxybenzothiazole derivatives were synthesized from the reaction of 2hydroxybenzothiazole with 3-bromoprop-1-yne to generate 2-(prop-2-ynl-1-yloxy)-1,3-benzothiazole (RM-1). A mixture of 2-(prop-2-yn-1-yloxy)-1,3-benzothiazole, paraformaldehyde, cyclic amine and cuprous chloride catalytic amount, in peroxide-free dioxane through Mannich reaction yielded the desired aminoacetylenicoxybenzothiazoles (RM2-7). The mp, IR, 1H-NMR, C-NMR and elemental analysis were consistent with the assigned structures. The design of these compounds as H3 antagonists was based on the rationalization for the important criteria needed to overlap effectively with H3 receptor to induce antagonistic activity. These criteria are: 1) The basic amino group for ionic binding. 2) The acetylenic group for electrostatic interaction. 3) The 2-butyne provide the appropriate distance between the basic nitrogen and benzthiazole. 4) Oxy ether to provide hydrogen bonding with H3 receptor and 5) benzothiazole group found in H3 antagonists and many other biologically active compounds. The docking results showed that all the designed compounds have a good H3 receptor antagonism especially RM-7 which have -6 (kcal/mol). These results provide a good lead to design more effective H3 antagonists in managing Alzheimer's and other diseases like depression, epilepsy, schizophrenia and many other CNS disorders.

Simplified aminocoumarin analogues as anticancer agents: Amino isosteric replacement in the noviose moiety resulted in substantial enhancement of antiproliferative activity

Abstract Simplified aminocoumarin analogues, either noviosylated or simple basic heterocycle attached 3-amido-coumarin compounds, are known to be promising anticancer agents targeting the C-terminal ATP-binding site of Hsp90. In this study, 3′-amino isosteric replacement in the noviose moiety of two known noviose containing Hsp90 C-terminal inhibitors was synthetically realized for the first time. In vitro evaluation of these compounds suggested that the introduction of a basic amino group into the noviose subunit resulted in significant improvement of their cytotoxicities.