Fluorinated maleimide-substituted porphyrins and chlorins: synthesis and characterization

• Valentina A. Ol’shevskaya,
• Elena G. Kononova and
• Andrei V. Zaitsev

Beilstein J. Org. Chem. 2019, 15, 2704–2709, doi:10.3762/bjoc.15.263

• covalently conjugates thiol groups of cysteine residues in proteins or peptides by the thio-Michael addition to the double bond of the maleimide to form a corresponding succinimidyl thioether. Conjugation of the cysteine sulfhydryl group with maleimide moieties allows us to prepare the bioconjugates

Plasma membrane imaging with a fluorescent benzothiadiazole derivative

• Pedro H. P. R. Carvalho,
• Jose R. Correa,
• Karen L. R. Paiva,
• Daniel F. S. Machado,
• Jackson D. Scholten and
• Brenno A. D. Neto

Beilstein J. Org. Chem. 2019, 15, 2644–2654, doi:10.3762/bjoc.15.257

• better conjugation with the 4AP substituent at the C4 carbon of the BTD heterocyclic core. The ionic nature of the structure in combination with a hydrophilic anion (MeSO3−, methanesulfonate) and the presence of the hydrophilic domain (triethylene glycol monomethyl ether) make the dye a water-soluble BTD

• the BTD-4APTEG is twisted by nearly 30° with respect to the NH fragment (see Figure S5 in Supporting Information File 1). Although this torsion diminishes the strength of the H-bond and conjugation, the effect is not strong enough to affect the emissive properties of the designed structure, as noted

Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence

• Vânia F. Pais,
• Tristan Neumann,
• Ignacio Vayá,
• M. Consuelo Jiménez,
• Abel Ros and
• Uwe Pischel

Beilstein J. Org. Chem. 2019, 15, 2612–2622, doi:10.3762/bjoc.15.254

• the verification of the effect of aromatic conjugation (naphthyl, anthryl, pyrenyl) and electron-donor strength (naphthyl versus 4-methoxynaphthyl) on the photophysical properties. Beside the observation of interesting dual emission properties for these dyes, some showed a pronounced ratiometric

Chemical synthesis of the pentasaccharide repeating unit of the O-specific polysaccharide from Escherichia coli O132 in the form of its 2-aminoethyl glycoside

• Debasish Pal and
• Balaram Mukhopadhyay

Beilstein J. Org. Chem. 2019, 15, 2563–2568, doi:10.3762/bjoc.15.249

• reducing end of the target pentasaccharide that will allow further conjugation using the terminal amine without affecting the glycosidic stereochemistry. Further retrosynthetic analysis of the target pentasaccharide 1 revealed that a [3 + 2] strategy will be the most suitable one for the total synthesis of

• pentasaccharide repeating unit of the O-specific polysaccharide of Escherichia coli O132 was accomplished through a convergent [3 + 2] strategy. The target pentasaccharide was obtained as its 2-aminoethyl glycoside that offers further possibilities for conjugation with suitable aglycons without hampering the

Synthesis of novel sulfide-based cyclic peptidomimetic analogues to solonamides

• José Brango-Vanegas,
• Luan A. Martinho,
• Lucinda J. Bessa,
• Andreanne G. Vasconcelos,
• Alexandra Plácido,
• Alex L. Pereira,
• José R. S. A. Leite and
• Angelo H. L. Machado

Beilstein J. Org. Chem. 2019, 15, 2544–2551, doi:10.3762/bjoc.15.247

• wavenumber values for the lactone C=O stretch was also observed for bands assigned to the C=C bonds as consequence of their conjugation. Evaluation of the growth inhibition and hemolytic activity of S. aureus for the solonamide analogues Initially, the antibacterial activity of all analogues 9 was tested by

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• -isomers are generally assumed to have an intrinsically higher electron density due to the disruption of the conjugation between the two rings of the azobenzene through the N=N bond. Moreover, the electronic properties of the inner substituent Y have been proven to be of strategic use in increasing the

Experimental and computational electrochemistry of quinazolinespirohexadienone molecular switches – differential electrochromic vs photochromic behavior

• Eric W. Webb,
• Jonathan P. Moerdyk,
• Kyndra B. Sluiter,
• Benjamin J. Pollock,
• Amy L. Speelman,
• Eugene J. Lynch,
• William F. Polik and
• Jason G. Gillmore

Beilstein J. Org. Chem. 2019, 15, 2473–2485, doi:10.3762/bjoc.15.240

• photochromism results from a spirocyclic ring-opening or other isomerization which results in increased conjugation. Electrochromism is also of increasing materials relevance, e.g., for self-dimming automotive mirror and aircraft window darkening applications [6][7][8]. In electrochromic applications, the color

• attributing the small spectral changes to the presence of electrolyte in the electrolyzed solutions, to an interaction with air, or to a side reaction in solution. The shorter wavelength for electrogenerated 5a,b may result from slightly less planarity and decreased conjugation versus the photogenerated 4a,b

Excited state dynamics for visible-light sensitization of a photochromic benzil-subsituted phenoxyl-imidazolyl radical complex

• Yoichi Kobayashi,
• Yukie Mamiya,
• Katsuya Mutoh,
• Hikaru Sotome,
• Masafumi Koga,
• Hiroshi Miyasaka and
• Jiro Abe

Beilstein J. Org. Chem. 2019, 15, 2369–2379, doi:10.3762/bjoc.15.229

• of the photochromic reactions to visible light are to extend the π-conjugation and to utilize photosensitizers. Especially, triplet photosensitizers, which form the triplet state of a molecule by the triplet–triplet energy transfer, have been frequently used in photoresists, photodynamic therapy, and

• assigned to the transient absorption of the benzil unit of Benzil-PIC. The absorption is slightly shifted to the red as compared to those of benzil probably due to the extended π-conjugation of the benzil unit connected to the PIC unit. The two peaks continuously shift to the shorter wavelength (503 and

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• . Oligothiophenes are highly fluorescent [6][7], and therefore, we reasoned that their incorporation into DAEs with oxidized 2-alkylbenzo[b]thiophene units might produce fluorescent open forms in addition to the intrinsic fluorescence of the closed forms. In particular, we expected that the prolonged conjugation

• , decoration of the core structures 3 and 6 (Scheme 1) with thiophene rings lowered the switching quantum yields by several orders of magnitude. It became obvious that the rate of cyclization and cycloreversion reactions decreased when the conjugation path became longer (transition from the unsubstituted core

Synthesis of a dihalogenated pyridinyl silicon rhodamine for mitochondrial imaging by a halogen dance rearrangement

• Jessica Matthias,
• Thines Kanagasundaram,
• Klaus Kopka and
• Carsten S. Kramer

Beilstein J. Org. Chem. 2019, 15, 2333–2343, doi:10.3762/bjoc.15.226

• membranes. Recently, a silicon rhodamine for selective mitochondrial staining was developed by conjugation of the SiR core with ten different amines varying in lipophilicity [46]. The authors showed that the optimal range of clogP values for mitochondrial targeting ranges from 5.50 to 6.33. As mentioned

• pyridinyl motif. In fact, only two pyridinyl silicon rhodamines (13 and 14) are known so far, although halogenated pyridines are highly interesting for further functionalization or vector conjugation by nucleophilic aromatic substitution. For the implementation of the dihalogenated pyridine motif into the

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• )•+ radical cations having dithienylethene bridges [21][22]. This was achieved by a regulation of the π-conjugation length through photoinduced formation/dissociation of σ bonds in the bridge, which was accomplished with changeovers from a localized system (class I) to a moderately delocalized one (class II

• means that the π orbital of the central C=O moiety does not contribute to the π-conjugation in the HOMOs. Such HOMO properties would be understood by comparison with a well-known reference bis(NAr3) derivative MeO-TPD, in which the NAr3 units are directly connected through a σ-bond [6]. MeO-TPD shows a

Click chemistry towards thermally reversible photochromic 4,5-bisthiazolyl-1,2,3-triazoles

• Chenxia Zhang,
• Kaori Morinaka,
• Mahmut Kose,
• Takashi Ubukata and
• Yasushi Yokoyama

Beilstein J. Org. Chem. 2019, 15, 2161–2169, doi:10.3762/bjoc.15.213

• large [6]; (3) when the substituent groups on the ring-closing carbon atoms are strongly electron-withdrawing [7]; or (4) when the dialkylamino group on the side chain [8] or a carbon atom of the conjugation system in a strained closed form [9] are protonated. Terarylenes [10][11], one of the closely

• constructing the conjugation system around the central cyclohexadiene moiety (Scheme 5). In Scheme 5a, the single bonds of 3c written in red are shorter than in the other two compounds, implying that they have a stronger double bond character. Similarly, the double bonds of 3c written in green are longer

• that the lone pair on this nitrogen atom participates in the conjugation in the molecular core more strongly than in 1c and 2c. This distinctive character of 3c originates from the electron-withdrawing cyano groups in the molecule. Data on the terminal phenyl rings in Scheme 5 do not give any

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• singlet state oxygen to form similar peroxide, epoxide or epidioxide [16] derivatives, which can be isolated at room temperature (Scheme 4). An interesting physical characteristic of pentafulvene derivatives is their bright colour, which results from their cross conjugation, and varies with substitution

• be generated in situ from methyl(2-methylenecyclopropyl)(phenyl)sulfonium tetrafluoroborate (Scheme 13b). As pentafulvenes are the most commonly studied fulvenes, it follows that there is a great deal of literature surrounding their reactivity in cycloaddition reactions. Due to conjugation, they can

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• averaged distances from 1.363 to 1.367 Å (Table 1). The C1–C2 and C4–C5 distances vary between 1.447 and 1.421 Å, respectively, indicating poor conjugation through these bonds, as a result of a partial loss of the aromaticity of the central benzene ring. This feature is confirmed also by the deviation of

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

• Meng-Di Gu,
• Yao Lu and
• Mei-Xiang Wang

Beilstein J. Org. Chem. 2019, 15, 1976–1983, doi:10.3762/bjoc.15.193

• was evident that six bridging oxygen atoms formed roughly a plane. Interestingly, three tetrazine rings are procumbent on the plane while three phthalimide units were almost perpendicular to the plane. Judging from the bond lengths, all oxygen atoms in the linking positions tended to form conjugation

Norbornadiene-functionalized triazatriangulenium and trioxatriangulenium platforms

• Roland Löw,
• Talina Rusch,
• Tobias Moje,
• Fynn Röhricht,
• Olaf M. Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1815–1821, doi:10.3762/bjoc.15.175

• parameter controlling the cis–trans rate acceleration of azobenzenes and not the length of the spacer [1]. A full conjugation path from the azobenzene on top through the ethynyl spacer and the platform to a bulk gold surface shortens the half-life of the metastable cis-isomer from days to seconds even

• complete conjugation path across the double bond of norbornadiene to the metal. Additionally, it is known that electron-withdrawing groups in 2 or 3 position change the triplet energy hypersurface in such a way that a triplet excited quadricyclane 1b decays into the ground state of the norbornadiene 1a [9

• ], which is a precondition for an efficient QC→NBD isomerization via our postulated non-adiabatic singlet→triplet→singlet mechanism. Results and Discussion If our proposed spin change mechanism, mediated by the conducting electrons in bulk gold were correct, interruption of the conjugation path and

A golden opportunity: benzofuranone modifications of aurones and their influence on optical properties, toxicity, and potential as dyes

• Joza Schmitt and
• Scott T. Handy

Beilstein J. Org. Chem. 2019, 15, 1781–1785, doi:10.3762/bjoc.15.171

• shift of this lambda max by roughly 40 nm to around 338 nm, presumably due to their donating effect and conjugation with the carbonyl oxygen. Halogen substituents at the 6-position generally had little effect, with the exception of the most electron-withdrawing fluorine, which resulted in a slight blue

• expected due to the lack of direct conjugation with the carbonyl as well as the only modest electronic effects of alkyl, chlorine, and bromine. In general, the substituent effects are all fairly modest and result in fairly moderate changes in the extinction coefficient (although hydroxy substitution does

Synthesis, photophysical and electrochemical properties of pyridine, pyrazine and triazine-based (D–π–)₂A fluorescent dyes

• Keiichi Imato,
• Toshiaki Enoki,
• Koji Uenaka and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2019, 15, 1712–1721, doi:10.3762/bjoc.15.167

• electron-donating and electron-accepting abilities of the D and A moieties and the expansion of π conjugation, respectively, can lead to a decrease in the energy gap between the HOMO and LUMO because the highest occupied molecular orbital (HOMO) is localized over the π-conjugated system containing the D

Diazocine-functionalized TATA platforms

• Roland Löw,
• Talina Rusch,
• Fynn Röhricht,
• Olaf Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1485–1490, doi:10.3762/bjoc.15.150

• to the trans-form, which slowly returns back to the stable cis-isomer. To investigate the thermal trans→cis isomerization as a function of the conjugation to the metal surface, we connected the acetylene spacer in meta (weak conjugation) and in para (strong conjugation) position. Both isomers form

• the metal surface [11][18]. With increasing π-conjugation from the azobenzene into the platform, and thus coupling to the gold surface, the activation barrier drops to almost zero (≈8 kJ mol−1) and the frequency factors (log A) become negative [11]. Vanishing barriers and low frequency factors are

• the azo group, providing a full π-conjugation path of the N=N unit through the ethynyl spacer into the platform. Diazocine-TATA 2 is connected in meta-position and thus interrupting conjugation [24][25]. Both diazocine-TATAs are equipped with methoxy groups, which serve as “reporter units” indicating

Introduction of an isoxazoline unit to the β-position of porphyrin via regioselective 1,3-dipolar cycloaddition reaction

• Xiujun Liu,
• Xiang Ma and
• Yaqing Feng

Beilstein J. Org. Chem. 2019, 15, 1434–1440, doi:10.3762/bjoc.15.143

• Soret band and two weak Q bands. When compared to the spectrum of the precursor 2, a blue shift of ≈10 nm was observed in those of 3a or 3b, which may result from the loss of partial conjugation after the cycloaddition reaction between the nitrile oxides and C=C double bond. However, the substitution at

Formation of an unexpected 3,3-diphenyl-3H-indazole through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate

• Andrew T. King,
• Hugh G. Hiscocks,
• Lidia Matesic,
• Mohan Bhadbhade,
• Roger Bishop and
• Alison T. Ung

Beilstein J. Org. Chem. 2019, 15, 1347–1354, doi:10.3762/bjoc.15.134

• presented in Figure 3. The crystal and refinement data are given in Table 1. The 3H-indazole 8 (–N=N–CRR–) has a break in its conjugation at the sp3 carbon atom when it is compared to the 1H-indazole isomer –NH–N=CH– that is fully conjugated with the benzo group. Therefore, the 3H-indazole isomer is higher

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• as the conjugation of steroids to amino acids, peptides and carbohydrates. We demonstrate that steroids are available with almost all types of MCR reactive functionalities, e.g., carbonyl, carboxylic acid, alkyne, amine, isocyanide, boronic acid, etc., and that steroids are suitable starting

• supramolecular chemistry applications. Keywords: conjugation; heterocycles; macrocycles; multicomponent reactions; steroids; Review 1 Introduction The utilization of multicomponent reactions (MCRs) [1] for the derivatization of biomolecules has continuously grown over the last years. These diversity-oriented

• the steroidal nucleus, the assembly of nitrogen-heterocycles fused to the steroid-ring system, the steroid conjugation and macrocyclization, all relying on MCRs. 2 Modification of the steroidal nucleus and the side chain 2.1 Isocyanide-based MCRs 2.1.1 Steroids as carbonyl component: One of the first

Ugi reaction-derived prolyl peptide catalysts grafted on the renewable polymer polyfurfuryl alcohol for applications in heterogeneous enamine catalysis

• Alexander F. de la Torre,
• Gabriel S. Scatena,
• Oscar Valdés,
• Daniel G. Rivera and
• Márcio W. Paixão

Beilstein J. Org. Chem. 2019, 15, 1210–1216, doi:10.3762/bjoc.15.118

• ) – derived from a renewable resource like sugar cane biomass – for the incorporation of chiral pyrrolidine-based motifs capable to catalyze relevant asymmetric reactions. The incorporation of an organocatalyst into a polymer support requires either conjugation to the polymer or functionalization with a

Self-assembly behaviors of perylene- and naphthalene-crown macrocycle conjugates in aqueous medium

• Xin Shen,
• Bo Li,
• Tiezheng Pan,
• Jianfeng Wu,
• Yangxin Wang,
• Jie Shang,
• Yan Ge,
• Lin Jin and
• Zhenhui Qi

Beilstein J. Org. Chem. 2019, 15, 1203–1209, doi:10.3762/bjoc.15.117

• ]. However, we recently found that benzo-21-crown-7 (B21C7) displays impressive high water solubility in comparison with other macrocyclic hosts [55]. Moreover, the conjugation of B21C7s to the well-known supramolecular BTA core leads to the observation of special topological effects on ion selectivity in

A chemically contiguous hapten approach for a heroin–fentanyl vaccine

• Yoshihiro Natori,
• Candy S. Hwang,
• Lucy Lin,
• Lauren C. Smith,
• Bin Zhou and
• Kim D. Janda

Beilstein J. Org. Chem. 2019, 15, 1020–1031, doi:10.3762/bjoc.15.100

• States has necessitated the development of new strategies to treat addiction. Monoclonal antibodies and antidrug vaccines provide a tool that both aids addiction management and reduces the potential for overdose. Dual drug vaccines formulated by successive conjugation or by mixture have certain drawbacks

• two individual vaccines together (admixture vaccine) [9][10]; or 2) successive conjugation steps of one hapten and then the second to a carrier protein [11][12]. To specifically address the escalating incidence of fentanyl-contamination in heroin, we investigated the efficacy of an admixture of

• carboxylic acids, allowing direct coupling of haptens to the carrier protein. Hapten conjugation reaction with carrier proteins BSA and KLH Test reactions on submilligram scale (0.1 mg hapten:0.1 mg BSA, 1 mg/mL protein) were performed with activated HF-1 and BSA, resulting in a moderate number of haptens