Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• treated with triflic anhydride to afford the corresponding triflate 55. Microwave-assisted reduction of compound 55 with pyridinium chloride afforded the α-chloropyridine derivative 56, which was further catalytically dehalogenated with palladium on carbon and formic acid to generate the pyridine scaffold

• 57. Coupling of 57 with Ph2PCl·BH3 resulted in the boron-protected ligand 58, which was deprotected with Et3N. Alternatively, 1,1’-bis(diphenylphosphino)ferrocene (dppf) with palladium(II) acetate was used to catalyze the reduction of 55 generating the pyridine scaffold 57. Subsequent lithiation and

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• appropriate oxime supporting scaffold for experimenting with our novel carbamate esters, because this ring exhibited a better profile compared to the other pyridine analogues [9][11]. In order to provide a structure–activity relationship study, a series of O-carbamoyl conjugates consisted of benzyl as well as

Synthesis and circularly polarized luminescence properties of BINOL-derived bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys)

• Ryo Takishima,
• Yuji Nishii,
• Tomoaki Hinoue,
• Yoshitane Imai and
• Masahiro Miura

Beilstein J. Org. Chem. 2020, 16, 325–336, doi:10.3762/bjoc.16.32

• dehydrogenative coupling adopting oxygen atom as the linker [12][13][14][15][16][17]. In particular, bisbenzofuro[2,3-b:3′,2′-e]pyridines (BBZFPys) were found to exhibit intense photoluminescence with relatively high quantum efficiency (Φflu up to 0.70), indicating that the BBFZPy scaffold may serve as a key

Copper-catalyzed enantioselective conjugate addition of organometallic reagents to challenging Michael acceptors

• Delphine Pichon,
• Jennifer Morvan,
• Christophe Crévisy and
• Marc Mauduit

Beilstein J. Org. Chem. 2020, 16, 212–232, doi:10.3762/bjoc.16.24

• process allowing the selective introduction of a second methyl stereogenic center was then explored to develop a straightforward access to 1,3-deoxypropionate units, a scaffold ubiquitous in numerous natural products (Scheme 17) [40]. Starting from enantioenriched β-methylated aldehyde 37, the

Combination of multicomponent KA² and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones

• Riccardo Innocenti,
• Elena Lenci,
• Gloria Menchi and
• Andrea Trabocchi

Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23

• structure in three single steps (Scheme 1b). This unprecedent molecular scaffold represents a valuable template for medicinal chemistry purpose, as the pyrrolocyclopentenone core is contained in a variety of bioactive molecules [49][50], and can serve as an advanced intermediate for the synthesis of

• respect to 3 and 24, respectively). This feature is promising in view of expanding the array of molecular scaffolds of this nature for drug discovery purpose, as a higher scaffold complexity is generally associated with a more successful outcome in drug discovery and development [69][70][71]. On the other

The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds

• Itamar L. Gonçalves,
• Rafaela R. da Rosa,
• Vera L. Eifler-Lima and
• Aloir A. Merlo

Beilstein J. Org. Chem. 2020, 16, 175–184, doi:10.3762/bjoc.16.20

• components, which may be substituted symmetrically or unsymmetrically [1]. Applications of this scaffold include complexing agents in anion sensors [2] organocatalysts [3], intermediates in heterocycle synthesis [1] and development of compounds with pharmacological effects [4]. Considering the importance of

Potent hemithioindigo-based antimitotics photocontrol the microtubule cytoskeleton in cellulo

• Alexander Sailer,
• Franziska Ermer,
• Yvonne Kraus,
• Rebekkah Bingham,
• Ferdinand H. Lutter,
• Julia Ahlfeld and
• Oliver Thorn-Seshold

Beilstein J. Org. Chem. 2020, 16, 125–134, doi:10.3762/bjoc.16.14

• molecular photoswitch that has only recently been applied as a photoswitchable pharmacophore for control over bioactivity in cellulo. Uniquely, in contrast to other photoswitches that have been applied to biology, the pseudosymmetric hemithioindigo scaffold has allowed the creation of both dark-active and

• hemithioindigo-based indanone-like tubulin inhibitors (HITubs) and optimised their cellular potency as antimitotic photopharmaceuticals. These HITubs feature reliable and robust visible-light photoswitching and high fatigue resistance. The use of the hemithioindigo scaffold also permitted us to employ a para

• cytoskeleton research. Additionally, as the hemithioindigo scaffold allows photoswitchable bioactivity for substituent patterns inaccessible to the majority of current photopharmaceuticals, wider adoption of the hemithioindigo scaffold may significantly expand the scope of cellular and in vivo targets

Light-controllable dithienylethene-modified cyclic peptides: photoswitching the in vivo toxicity in zebrafish embryos

• Sergii Afonin,
• Oleg Babii,
• Aline Reuter,
• Volker Middel,
• Masanari Takamiya,
• Uwe Strähle,
• Igor V. Komarov and
• Anne S. Ulrich

Beilstein J. Org. Chem. 2020, 16, 39–49, doi:10.3762/bjoc.16.6

• embryotoxicity of dithienylethene-modified peptides upon photoswitching, using 19 analogues based on the β-hairpin scaffold of the natural membranolytic peptide gramicidin S. We established an in vivo assay in two variations (with ex vivo and in situ photoisomerization), using larvae of the model organism Danio

Functionalization of the imidazo[1,2-a]pyridine ring in α-phosphonoacrylates and α-phosphonopropionates via microwave-assisted Mizoroki–Heck reaction

• Damian Kusy,
• Agata Wojciechowska,
• Joanna Małolepsza and
• Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 15–21, doi:10.3762/bjoc.16.3

• of compounds from a common precursor and enables efficient generation of new chemical entities. Imidazo[1,2-a]pyridine constitutes an appealing scaffold in medicinal chemistry. It is present in a number of compounds, which exhibit many interesting biological properties. Its privileged character is

A green, economical synthesis of β-ketonitriles and trifunctionalized building blocks from esters and lactones

• Daniel P. Pienaar,
• Kamogelo R. Butsi,
• Amanda L. Rousseau and
• Dean Brady

Beilstein J. Org. Chem. 2019, 15, 2930–2935, doi:10.3762/bjoc.15.287

• NMR spectroscopy. The mechanism by which IPA facilitates the reaction towards the formation of the cyclic hemiketal and indeed, the desired β-ketonitrile scaffold, has not been conclusively determined in this work. It is well known that strong-base deprotonation of acetonitrile leads to the formation

Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

• Eric J. N. Helfrich,
• Geng-Min Lin,
• Christopher A. Voigt and
• Jon Clardy

Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

• synthases, TCs), respectively, to generate terpene scaffolds and 2) the decoration phase, during which the terpene scaffold can get heavily modified by tailoring enzymes [45][46][47]. Phase 1) terpene scaffold generation Unlike core biosynthetic enzymes or domains of other natural product classes (PKSs and

•  6b) [80]. Despite efforts to characterize individual terpene cyclases and their modes of cyclization, no biosynthetic rules have so far been deduced that can be applied to a broad range of unrelated terpene cyclases. Phase 2) terpene scaffold functionalization Tailoring enzymes are important elements

• is divided into two phases, 1) terpene scaffold generation and 2) terpene scaffold functionalization. Representative examples are shown with the modifications installed in the tailoring step highlighted in red. MEP: 2-C-methyl-ᴅ-erythritol 4-phosphate pathway, MVA: mevalonic acid pathway, IPP

One-pot synthesis of substituted pyrrolo[3,4-b]pyridine-4,5-diones based on the reaction of N-(1-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-2-oxo-2-arylethyl)acetamide with amines

• Valeriya G. Melekhina,
• Andrey N. Komogortsev,
• Boris V. Lichitsky,
• Vitaly S. Mityanov,
• Artem N. Fakhrutdinov,
• Arkady A. Dudinov,
• Vasily A. Migulin,
• Yulia V. Nelyubina,
• Elizaveta K. Melnikova and
• Michail M. Krayushkin

Beilstein J. Org. Chem. 2019, 15, 2840–2846, doi:10.3762/bjoc.15.277

• efficiency and simplicity, granting a convenient access to the pyrrolo[3,4-b]pyridin-5-one scaffold. In addition, single crystal X-ray crystallographic analysis unequivocally confirmed the structure assigned to the obtained products. View of the structure of 1e in the crystal (CCDC: 1921613). Thermal

Design, synthesis and investigation of water-soluble hemi-indigo photoswitches for bioapplications

• Daria V. Berdnikova

Beilstein J. Org. Chem. 2019, 15, 2822–2829, doi:10.3762/bjoc.15.275

• for more than 100 years [18], their photochemical properties are still underexplored and no targeted studies on their photoswitching in aqueous media were performed. The hemi-indigo scaffold exists in two forms that can be photoswitched reveresibly. In most cases, the Z-isomer of hemi-indigo is

• provided. Additionally, synthetic peculiarities of the introduction of an RNA-affine alkylamino substituent to the hemi-indigo scaffold are discussed. Results and Discussion Synthesis of hemi-indigo derivatives Z-1a–c The synthesis of hemi-indigo derivatives Z-1a–c with different substitution patterns of

• File 1). Introduction of an alkylamino substituent to the hemi-indigo scaffold Based on the data on photoswitching in water (vide supra), the dimethoxy-substituted hemi-indigo Z-1c was selected as a core structure for the design of RNA binders with photoswitchable properties [12]. To increase the

Chemical tuning of photoswitchable azobenzenes: a photopharmacological case study using nicotinic transmission

• Lorenzo Sansalone,
• Jun Zhao,
• Matthew T. Richers and
• Graham C. R. Ellis-Davies

Beilstein J. Org. Chem. 2019, 15, 2812–2821, doi:10.3762/bjoc.15.274

• properties of the tetrafluoroazobenzene (4FAB) scaffold. Ultraviolet light switching and rapid thermal relaxation of the metastable cis configuration are the main drawbacks associated with standard AB-based switches. We designed our photoprobes to take advantage of the excellent thermodynamic stability of

• -step synthetic approach allowed the installation of a trimethylammonium (TA) head onto the 4FAB scaffold, by means of an alkyl spacer, to afford a free diffusible 4FABTA probe. TAs are known to agonize nicotinic receptors, so 4FABTA was tested on mouse brain slices and enabled reversible receptor

• preserving all the favorable photophysical properties of the parent 4FAB scaffold, however, the tetrafluoro motif can significantly perturb pharmacophore–protein interactions. In contrast, we found that the freely diffusible 4FABTA probe could be pre-set with green light into an OFF state that was

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• molecules, since the 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) scaffold was first described by Tsien, it has been widely used in biological systems and has given rise to a wealth of derivatives [1]. Key to the wide interest in this cation binder are its high specificity for Ca2+ ions

A combinatorial approach to improving the performance of azoarene photoswitches

• Joaquin Calbo,
• Aditya R. Thawani,
• Rosina S. L. Gibson,
• Andrew J. P. White and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

• scaffold, the theoretical calculations at the PBE0-D3/6-31G** level indicate that an insertion of electron-poor fluorine atoms in the ortho-position of the aryl ring (4pzH-F1 and 4pzH-F2) leads to an increase in the half-life from ca. 1000 days in 4pzH to 2000 days in 4pzH-F1 and to 4000 days in 4pzH-F2

• 4pzH, with t1/2 = 2000 and 15000 days for 4pzH-OMe1 and 4pzH-OMe2, respectively, and 34000 days for 4pzH-Pyr1 (Table 1). Unexpectedly, the inclusion of two bulky pyrrolidine groups in ortho (4pzH-Pyr2) leads to a decrease in t1/2 (76 days). For the arylazopyrazole scaffold 4pzMe, in line with the trend

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

• Zachary Lee,
• Brandon R. Jones,
• Nyochembeng Nkengbeza,
• Michael Phillips,
• Kayla Valentine,
• Alexis Stewart,
• Brandon Sellers,
• Nicholas Shuber and
• Karelle S. Aiken

Beilstein J. Org. Chem. 2019, 15, 2747–2752, doi:10.3762/bjoc.15.265

• , sulfone, and methyl/ethyl ester substrates at room temperature under the mild reaction conditions employed. Conclusion The studies described herein confirm the existence of an α-iodo intermediate in the iodine-mediated hydration of alkynes on a keto scaffold and also demonstrate that the reaction is

• , as well as phosphonate and sulfone analogues of the keto scaffold. Notably, the existence of the iodo intermediate points at the potential to synthesize α-substituted targets upon further development of the method. 1H NMR investigations on the iodine-mediated hydration of 8 (the range of 1.75–5.25

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

• . Maleimides are considered as a biologically important scaffold that possess almost all types of biological activities including antibacterial and antifungal activity [24], anticancer activity [25], cox-2 inhibitor and anti-inflammatory, antidiabetic activity [26] and photodynamic activity [27]. Attaching of

Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

• Natascha Breuer,
• Irina Gruber,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262

• of the 1H-pyridines 5f and 5g with an electron-withdrawing and an electron-donating substituent is located on the 1H-pyridine core, the ester and cyano substituents and also on the electron-rich aryl substituent. For the LUMO, the coefficient density is spread over the whole scaffold (Figure 16

• the core and the phenyl substituent in 6-position. Donor substituents in 4-position and acceptor substituents in 6-position cause a coefficient density shift towards the 4-substituent. The coefficient density in the LUMO in all compounds is spread over the whole scaffold. Conclusion The

Synthesis of aryl-substituted thieno[3,2-b]thiophene derivatives and their use for N,S-heterotetracene construction

• Nadezhda S. Demina,
• Nikita A. Kazin,
• Nikolay A. Rasputin,
• Roman A. Irgashev and
• Gennady L. Rusinov

Beilstein J. Org. Chem. 2019, 15, 2678–2683, doi:10.3762/bjoc.15.261

• -heteroacenes, including ones with TT-scaffold (Figure 1), which have promising electronic features, have been developed and are further investigated [12][13][14]. At present, the challenge is to develop effective ways of constructing the TT-based compounds, such as S- and N,S-heteroacenes, in order to

• synthesis [16], viz., the interaction of ethyl thioglycolate with ethyl 3-chlorobenzo[b]thiophene-2-carboxylates, to form a benzo[b]thieno[2,3-d]thiophene scaffold [17][18], we have decided to apply a similar approach to the synthesis of aryl-substituted TT derivatives. Thus, 3-chloro- or 3-bromothiophene-2

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

• the BTD-4APTEG molecule, which is the net result of its electron density withdrawal character. The HOMO orbital distributes over the BTD basic scaffold and the vicinal ring but does not involve participation of the side chain of the chromophore. The electron density difference between the ground S0

Nanangenines: drimane sesquiterpenoids as the dominant metabolite cohort of a novel Australian fungus, Aspergillus nanangensis

• Heather J. Lacey,
• Cameron L. M. Gilchrist,
• Andrew Crombie,
• John A. Kalaitzis,
• Daniel Vuong,
• Peter J. Rutledge,
• Peter Turner,
• John I. Pitt,
• Ernest Lacey,
• Yit-Heng Chooi and
• Andrew M. Piggott

Beilstein J. Org. Chem. 2019, 15, 2631–2643, doi:10.3762/bjoc.15.256

• ), three methyl groups (C-13, C-14, C-15) and three hydroxy groups (1-OH, 6-OH, 9-OH). Detailed analysis of the 2D NMR data for 1 (Table S3 in Supporting Information File 1) confirmed the presence of a drimane sesquiterpenoid lactone scaffold. A search of the literature revealed 1 to be almost identical to

• is synthesised by a PKS [32]. The A. nanangensis genome was sequenced and a draft assembly of the genome was generated. A local BLASTp search of the A. nanangensis genome using the drimane synthase AstC as query returned a hit on scaffold 3, FE257_006542, which was immediately flanked by a highly

• . insuetus CBS 107.25 (Figure 2). A homologous cluster was also found in A. pseudodeflectus CBS 756.74, though it is located on a truncated assembly scaffold. In total, six genes are conserved across these species: the HR-PKS (FE257_006541), HAD-like terpene synthase (FE257_006542) and FAD-binding

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

• was based on the conservation of the 16-membered macrocyclic scaffold and the apolar tripeptidyl moiety found in the solonamides. Both features are important to guarantee the interference with S. aureus QS [12][13][14][15]. The ester linkage of the lactone core was substituted by the sulfide group

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

• Universiteit Amsterdam, 1081 HZ, Amsterdam, The Netherlands present address: Institute of Functional Genomics, Université de Montpellier, Unité 5302 CNRS and Unité U1191, INSERM, 34090 Montpellier, France 10.3762/bjoc.15.244 Abstract We report a detailed structure–activity relationship for the scaffold of

• CXCR3 agonists are scarce and are mostly limited to peptidomimetics [25], which makes our published biaryl series a notable exception [24]. The general scaffold of these biaryl ligands consists of a polycycloaliphatic anchor and a biaryl moiety both linked to an ammonium ion. Depending on the

• that, using 360 nm light, a PPS of high percentage of cis-isomer (PPS360) can be reached. Literature evidence [7][29][30] suggests that this scaffold would have sufficiently long half-lives of the PSS state, i.e., the cis-isomer only slowly reverts to trans in the dark, which was confirmed by early

In search of visible-light photoresponsive peptide nucleic acids (PNAs) for reversible control of DNA hybridization

• Lei Zhang,
• Greta Linden and
• Olalla Vázquez

Beilstein J. Org. Chem. 2019, 15, 2500–2508, doi:10.3762/bjoc.15.243

• cis-form did not show any decomposition under these conditions (Figure S27C, Supporting Information File 1), unlike when the oF4Azo was grafted onto a pyrrole scaffold [48]. Next, we explored if the inclusion of oF4Azo as monomer surrogate within the PNA sequence could affect its hybridization to a