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

• activation with cycles of violet and green light. Due to the very long-lived metastable cis configuration, 4FAB in vivo use could be of great promise for long term biological studies. Further chemical functionalization of this 4FAB probe with a maleimide functionality allowed clean cross-linking with

• ][20] compared to 2, so a simple one-step route can be used to install the maleimides. It is this functionality that allows coupling (often called "tethering", symbolized as "t" for tetherable in Scheme 1) of the probe with mutant proteins. In our case, we developed a three-step route to install the

• ][13], specifically the spectral separation of the n–π* transitions of the trans and cis configurations. Since the maleimide functionality of 1 is quite hydrolytically sensitive at neutral pH, we characterized precursor 2. This photochrome underwent the expected trans–cis isomerization (Figure 2a). The

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• chirally modified electrodes Electrochemical oxidation reactions have long served as substantial synthetic tool because of their ability to increase the functionality of organic molecules via reversing the polarity of electron-rich functional groups and thereby generating highly reactive intermediates

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

• the maleimide group with its rich biological activity to the tetrapyrrole macrocycles with their unique photophysical properties may result in new conjugates with improved chemical, biological and anticancer characteristics [28]. Moreover, maleimide is a stable functionality that rapidly and

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

• of was retrieved from AspGD [45] under the locus tag AO090026000582. AstC homologs were identified in A. nanangensis via the tBLASTn [44] functionality in Geneious 10.2.6 [46]. The genome sequences for drimane sesquiterpenoid producing Aspergilli were obtained from NCBI where available. This included

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• widely used in the literature (see e.g. [30]); also the term Si-xanthone (for derivatives of 12) is established instead of 9-silaanthracen-10(9H)-one). The conditions tolerated also the use of the unprotected acid functionality of the boroxine 23b (23c, 31%, respectively 56% brsm), while application of

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

• the target molecule. First, the phthalimido group was removed using ethylenediamine [26] followed by acetylation with Ac2O in the presence of pyridine [27] to furnish the desired acetamido functionality. Next, the benzylidene group was hydrolyzed using 80% AcOH at 80 ºC [28]. Further, Zemplén de-O

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

• calculated for the unmodified PNA analogue (20). Unfortunately, no difference between isomers was observed. The potential of the functionality of our compounds could be enhanced by both changing the localization and the number of incorporated photoswitches. To try to maintain the cooperative base pairing, we

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

• Anna Kmieciak and
• Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

• ], conjugated additions to enones [7], and allylic alkylations [8][9]. Another direction of research is the use of phosphines in organocatalysis [10][11] and bifunctional catalysis [12]. Several methods were developed to introduce the phosphine functionality to organic molecules. The reaction of organometallics

• and 18 were assigned using 1H,1H-COSY spectra. The configurations at C4 were established by correlations observed in their 1H,1H-NOESY spectra (Figure 1, Supporting Information File 1). Synthesis of γ-hydroxyphosphines The key step in the synthesis to introduce a phosphine functionality is the thermal

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids

• Gerardo M. Ojeda,
• Prabhat Ranjan,
• Pavel Fedoseev,
• Lisandra Amable,
• Upendra K. Sharma,
• Daniel G. Rivera and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237

• in the Ugi-azide-4CR, see Scheme 1), with tetrazole/isoquinoline hybrids bearing a benzyl (4p), a p-methoxyphenyl (4q) or a tert-butyl (4r) group, respectively, being obtained in good yields. However, the presence of an ester functionality at the tetrazole ring (R1 = CH2CO2Me) led to a significant

Sugar-derived oxazolone pseudotetrapeptide as γ-turn inducer and anion-selective transporter

• Sachin S. Burade,
• Sushil V. Pawar,
• Tanmoy Saha,
• Navanath Kumbhar,
• Amol S. Kotmale,
• Manzoor Ahmad,
• Pinaki Talukdar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2019, 15, 2419–2427, doi:10.3762/bjoc.15.234

• converted to C-3-tetrasubstituted furanoid sugar azido ester 3 as per our reported protocol [12]. Hydrolysis of the ester functionality in 3 with LiOH at room temperature afforded azido acid 4a in 92% yield, while hydrogenation of 3 using 10% Pd/C in MeOH at room temperature for 3 h afforded the amino ester

• to the amide NH(I) and NH(II), respectively. The signal at δ 1.80 ppm, integrating for two protons, was assigned to the presence of an NH2 functionality. In the 13C NMR spectrum, the appearance of signals at δ 170.8, 170.6 and 166.7 ppm were assigned to the lactone/amide carbonyl functionalities. The

• signal at δ 163.0 ppm was assigned to the -C=N functionality. The 1H,15N-HSQC and 1H,15N-HMBC spectra showed a signal at δ 246.0 ppm that was assigned to the imine (C=N-) nitrogen. The signal at δ 26.2 ppm was assigned to the amine (NH2) nitrogen. The signals at δ 112.8 and δ 114.1 ppm were due to the

Targeted photoswitchable imaging of intracellular glutathione by a photochromic glycosheet sensor

• Xianzhi Chai,
• Hai-Hao Han,
• Yi Zang,
• Jia Li,
• Xiao-Peng He,
• Junji Zhang and
• He Tian

Beilstein J. Org. Chem. 2019, 15, 2380–2389, doi:10.3762/bjoc.15.230

• the photochromic fluorescence reporter into GSH-responsive MnO2 nanosheets, a highly efficient photoswitchable hybrid biosensor is successfully presented with the demanded functionality for precise cell imaging. Results and Discussion Synthesis of dithienylethene fluorescence reporter (Glyco-DTE) The

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

Harnessing enzyme plasticity for the synthesis of oxygenated sesquiterpenoids

• Melodi Demiray,
• David J. Miller and
• Rudolf K. Allemann

Beilstein J. Org. Chem. 2019, 15, 2184–2190, doi:10.3762/bjoc.15.215

• , the presence of an ethereal oxygen atom containing π-acid functionality alongside its inductive withdrawal effect has a profound effect on the carbocationic reactivity of the intermediates. Of course a fully comprehensive interpretation of these results, regarding potentially interesting aspects such

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

• function as 2π, 4π, 6π or 10π components (Table 2). This functionality is dependent both on the other reactant partner, and the electronic effects of the fulvene substituents [96][97][98][99][153][156]. As an example, in [4 + 2] cycloadditions, fulvenes will participate as 4π components (diene), provided

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

• conformational structures to complex anions in the gas phase and in the solid state owing to the anion–π noncovalent interactions between anions and the tetrazine rings. The easy accessibility, cylindroid cavity and diverse functionality would engender phthalimide-containing functionalized O6-corona[3]arene[3

The cyclopropylcarbinyl route to γ-silyl carbocations

• Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

• borohydride reduction of the ester functionality of 63 gave a separable mixture of alcohols 64 and 65. The stereochemistry of the product 65 was established using nOe studies. Cyano to carbomethoxy conversion in 65 to give alcohol 66 was straightforward. Triflate derivatives 67 and 68 were prepared since

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• performed a Cu(OAc)2-Et3N-mediated coupling reaction of α-azido ketones 115 with pyridinium ylides 114 using oxygen as a green oxidant (Scheme 40). The oxo-functionality present in α-azido ketones increased its acidity thus making it a good organic synthon. Optimization of the reaction conditions revealed

Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments

• Guojuan Li,
• Chunying Fan,
• Guo Cheng,
• Wanhua Wu and
• Cheng Yang

Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164

• versatile functionality [9] in recent years. Pillar[5]arenes [10], are cyclic pentamers composed of 1,4-dialkoxybenzene units connected through methylene bridges at the para-position and have a unique symmetrical architecture with an overall cylindrical or pillar-like shape. By virtue of their rigid and

• symmetrical structures, as well as highly tunable functionality, the studies on pillar[5]arenes have been developed rapidly in various areas, such as artificial transmembrane channels [11][12], molecular complexation [13][14] and nonporous adaptive crystals [15][16][17]. One of the features of pillar[5]arenes

Transient and intermediate carbocations in ruthenium tetroxide oxidation of saturated rings

• Manuel Pedrón,
• Laura Legnani,
• Maria-Assunta Chiacchio,
• Pierluigi Caramella,
• Tomás Tejero and
• Pedro Merino

Beilstein J. Org. Chem. 2019, 15, 1552–1562, doi:10.3762/bjoc.15.158

• with ruthenium tetroxide allows to introduce an oxygenated functionality (alcohol or carbonyl) into a saturated carbon skeleton [7]. Moreover, if oxygen or nitrogen atoms are present, the reaction leads to the formation of esters [8][9] or amides [10][11], respectively (Scheme 1). The reaction is

Synthesis and biological evaluation of truncated derivatives of abyssomicin C as antibacterial agents

• Leticia Monjas,
• Peter Fodran,
• Johanna Kollback,
• Carlo Cassani,
• Thomas Olsson,
• Maja Genheden,
• D. G. Joakim Larsson and
• Carl-Johan Wallentin

Beilstein J. Org. Chem. 2019, 15, 1468–1474, doi:10.3762/bjoc.15.147

• methicillin- and vancomycin-resistant Staphylococcus aureus (MRSA and VRSA) with minimum inhibitory concentration (MIC) values of 4 and 13 µg/mL, respectively [4]. AbC belongs to a small family of NPs and two congeners of this family lacking the enone functionality, abyssomicins B and D, were discovered at

• simplified structure that still includes all structural features that have been previously found to be essential for activity. This truncated derivative still has the tetronate functionality and the enone-equipped 11-membered ring system but lacks the oxabicyclo[2.2.2]octane unit. In addition to a simplified

• truncated derivatives of AbC to harbor activity against Gram-positive bacteria are that the 11-membered ring is intact and that this macrocycle is equipped with an enone functionality [4][5]. In accordance with these previous findings, compounds 4 and 5 were found not to inhibit the growth of any of the

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

• -related counterpart: C6C···C5C = 3.50 Å (Figure 4b). The C4 methoxy and the heterocyclic diazo functionality of 8 are linked through an interesting arrangement along the b axis that can be described either as a OCH2–H···π (N=N) or as a bifurcated N···H(CH2O)···N interaction. This motif is close to

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

• functionality. This can be explained by the higher reactivity of the aldehyde functionalities upon imine formation with both aliphatic and aromatic amines. However, steroidal ketones can also participate in Ugi reactions if no additional, more reactive carbonyl components are present. As shown in Scheme 6, this

• aldehyde and an enol functionality, which was subsequently reacted with isocyanide 31 – derived from cholesterol – and 3,5-dimethoxyaniline leading to the steroid–tetrahydropyridine hybrid 32 in good yield and excellent diastereoselectivity. As previously proven by the authors in their synthetic program on

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

• incorporate proline [15] and the furan functionality into pseudo-peptide catalysts. As shown in Scheme 2, Boc-L-proline and acetone were employed as acid and oxo components, respectively, in combination either with furfurylamine and cyclohexyl isocyanide or with (S)-α-methylbenzylamine and furfuryl isocyanide

Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids

• Herman O. Sintim,
• Hamad H. Al Mamari,
• Hasanain A. A. Almohseni,
• Younes Fegheh-Hassanpour and
• David M. Hodgson

Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116

• glyoxylate (3 → 4 → 5) [14][15], followed by an acid-catalysed rearrangement to generate the desired dideoxysqualestatin core 6 with the requisite tricarboxylate functionality installed. While we had earlier established the viability of this approach in a racemic model study (X = H) [14], extension to an

• % yield [21], gave α-diazo ester 13 in 76% yield following reaction with NaOMe. Furthermore, our earlier racemic model study had established that deprotection and oxidation of a secondary silyl ether in the presence of α-diazo ester functionality was feasible, which constitutes precedent for the

• generation of the ketone functionality in 3 [14]. These observations led us to examine the possibility of substrate assembly through Seebach’s tartrate alkylation methodology. In 1981, Seebach and Naef communicated that (R,R)-tartrate acetonide 7 could be deprotonated and undergo stereoselective alkylation

Electrophilic oligodeoxynucleotide synthesis using dM-Dmoc for amino protection

• Shahien Shahsavari,
• Dhananjani N. A. M. Eriyagama,
• Bhaskar Halami,
• Vagarshak Begoyan,
• Marina Tanasova,
• Jinsen Chen and
• Shiyue Fang

Beilstein J. Org. Chem. 2019, 15, 1116–1128, doi:10.3762/bjoc.15.108

• thioester. Using the technology, the sensitive groups can be installed at any location within the ODN sequences without using any sequence- or functionality-specific conditions and procedures. Keywords: Dmoc; electrophilic; oligonucleotides; protecting group; solid-phase synthesis; Introduction After over