Synthesis of new asparagine-based glycopeptides for future scanning tunneling microscopy investigations

• Laura Sršan and
• Thomas Ziegler

Beilstein J. Org. Chem. 2020, 16, 888–894, doi:10.3762/bjoc.16.80

• pathogenesis [1][2][3][4]. Glycosylation is also considered to be one of the most important post-translational modification (PTM) since more than half of all human proteins are glycopeptides or glycoproteins [5]. Therefore, understanding how glycopeptides interact on an intra- and intermolecular level is

A method to determine the correct photocatalyst concentration for photooxidation reactions conducted in continuous flow reactors

• Clemens R. Horn and
• Sylvain Gremetz

Beilstein J. Org. Chem. 2020, 16, 871–879, doi:10.3762/bjoc.16.78

• ) less gas volume [40]. Furthermore, the gas-to-liquid ratio change with the modification of the alpha-terpinene concentration impacts the flow pattern (droplet/bubble size), which could, in turn, have an impact on the conversion [41]. But the main limitation was the light itself, as can be seen in

Copper catalysis with redox-active ligands

• Agnideep Das,
• Yufeng Ren,
• Cheriehan Hessin and
• Marine Desage-El Murr

Beilstein J. Org. Chem. 2020, 16, 858–870, doi:10.3762/bjoc.16.77

• could be circumvented through ligand modification. Phenol oxidation is ubiquitous in biological systems as demonstrated by the involvement of the copper enzymes tyrosinases (type III) in the melanogenesis process. The regioselectivity and reactivity of the oxidation of phenols are strongly dependent on

Efficient synthesis of piperazinyl amides of 18β-glycyrrhetinic acid

• Dong Cai,
• ZhiHua Zhang,
• Yufan Meng,
• KaiLi Zhu,
• LiYi Chen,
• ChangXiang Yu,
• ChangWei Yu,
• ZiYi Fu,
• DianShen Yang and
• YiXia Gong

Beilstein J. Org. Chem. 2020, 16, 798–808, doi:10.3762/bjoc.16.73

• modifications at the C3-OH group of 18β-glycyrrhetinic acid are identified to be relatively common and effective. The modification of the C3-OH group, altering the molecular polarity of 18β-glycyrrhetinic acid, may be an advantage in achieving better cytotoxicity or antiproliferative activity [8][9][10]. For

• -type pentacyclic triterpenoids, and the synthetic methods studied here can also apply to the modification of structurally similar other triterpenoic acids, but further experimental verification is needed. Results and Discussion The synthetic route to 18β-glycyrrhetinic acid piperazinyl amide 4 was

Microwave-assisted efficient and facile synthesis of tetramic acid derivatives via a one-pot post-Ugi cascade reaction

• Yong Li,
• Zheng Huang,
• Jia Xu,
• Yong Ding,
• Dian-Yong Tang,
• Jie Lei,
• Hong-yu Li,
• Zhong-Zhu Chen and
• Zhi-Gang Xu

Beilstein J. Org. Chem. 2020, 16, 663–669, doi:10.3762/bjoc.16.63

• medicinal chemistry. Multicomponent reactions (MCRs) [22][23][24] are emerging tools for assembling complex molecules in a rapid and efficient manner. The four-component Ugi reaction followed by a suitable post modification of [25][26] has become a popular research field for diversity-oriented synthesis [27

Design and synthesis of diazine-based panobinostat analogues for HDAC8 inhibition

• Sivaraman Balasubramaniam,
• Sajith Vijayan,
• Liam V. Goldman,
• Xavier A. May,
• Kyra Dodson,
• Sweta Adhikari,
• Fatima Rivas,
• Davita L. Watkins and
• Shana V. Stoddard

Beilstein J. Org. Chem. 2020, 16, 628–637, doi:10.3762/bjoc.16.59

• hydroxamic moieties [13][14][15], the non-availability of the central core modification stimulated our interest toward altering the central core to evaluate efficacy. We found particular interest in the replacement of the phenyl ring with diazine cores (pyridazines, pyrimidines and pyrazines) as their

Direct borylation of terrylene and quaterrylene

• Haruka Kano,
• Keiji Uehara,
• Kyohei Matsuo,
• Hironobu Hayashi,
• Hiroko Yamada and
• Naoki Aratani

Beilstein J. Org. Chem. 2020, 16, 621–627, doi:10.3762/bjoc.16.58

• tetra-borylated quaterrylene despite a low yield. The post modification of rylenes enables us to prepare their borylated products as versatile units after creating the rylene skeletons. Keywords: borylation; π-conjugation; oligorylene; single crystal X-ray structure; solubility; Introduction Compared

• groups. All the substituents of the terrylenes and quaterrylenes were installed before creating the rylene skeleton and no derivatives have been produced by the post modification probably because their low solubility hampers such strategy. Therefore, the substituents on the rylene skeleton have been

Synthesis of disparlure and monachalure enantiomers from 2,3-butanediacetals

• Adam Drop,
• Hubert Wojtasek and
• Bożena Frąckowiak-Wojtasek

Beilstein J. Org. Chem. 2020, 16, 616–620, doi:10.3762/bjoc.16.57

• chiral centers for the synthesis of both enantiomers of disparlure 1 and 3 and monachalure 2 and 4. Compound 14 also offers the possibility of selective modification of one of the substituents as well as sequential introduction of aliphatic chains. After deprotection of the butanediacetal group, diols 5

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• system. Equations 1–4 summarize these events discussed above whose rate constants quantify the individual processes. They occur from the S1 while no triplet states have been reported yet for the cyanines shown in Table 1. A modification of these patterns with more heavy atoms would definitively drive

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• electron transfer and modification of the oxidation state of the transition metal complexes. Such systems can be combined with different metals, for example, Ni, Co, Cu, Ru, Ir, etc. However, unexpectedly, copper is less toxic and can be utilized to catalyze reactions without the requirement of a ligand

• easily. Recently, aerobic oxidation with visible light and photoredox catalysts has also gained a lot of attention in the modification and generation of new C–H functionalization methodologies [81][82]. The above-mentioned advantages make the photoredox processes a versatile tool in diverse fields, and

Synthesis and herbicidal activities of aryloxyacetic acid derivatives as HPPD inhibitors

• Man-Man Wang,
• Hao Huang,
• Lei Shu,
• Jian-Min Liu,
• Jian-Qiu Zhang,
• Yi-Le Yan and
• Da-Yong Zhang

Beilstein J. Org. Chem. 2020, 16, 233–247, doi:10.3762/bjoc.16.25

• , compound II4 was safe for weed control in maize fields at a rate of 150 g ai/ha, and was identified as the most potent candidate for a novel HPPD inhibitor herbicide. The compounds described herein may provide useful guidance for the design of new HPPD inhibiting herbicides and their modification

• . Keywords: aryloxyacetic acid; herbicidal activity; 4-hydroxyphenylpyruvate dioxygenase; modification; synthesis; Introduction 4-Hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27, HPPD), which belongs to the family of non-heme FeII-containing enzymes, is a vital enzyme for tyrosine catabolism. This enzyme

Synthesis, liquid crystalline behaviour and structure–property relationships of 1,3-bis(5-substituted-1,3,4-oxadiazol-2-yl)benzenes

• Afef Mabrouki,
• Malek Fouzai,
• Armand Soldera,
• Abdelkader Kriaa and
• Ahmed Hedhli

Beilstein J. Org. Chem. 2020, 16, 149–158, doi:10.3762/bjoc.16.17

• the fluorine atom leads to a subtle modification of properties such as melting point, mesophase morphology, transition temperatures, optical anisotropy, dielectric anisotropy, and visco-elasticity [5][6][7][8][9][10]. Therefore, many fluorinated liquid crystals have been prepared, and the fluoro

Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst

• Abhijit Paul,
• Debnath Chatterjee,
• Srirupa Banerjee and
• Somnath Yadav

Beilstein J. Org. Chem. 2020, 16, 140–148, doi:10.3762/bjoc.16.16

• successful with a bromo-substituted substrates 3e and 3f, demonstrating that the methodology was suitable for substrates with the potential for further late-stage modification. Steric effects were also explored with C2-substituted substrate 3i and 3j, and no significant decline in product formation was

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

• ]pyridine ring has been synthesized via the microwave-assisted Mizoroki–Heck reaction. The efficient modification of the imidazo[1,2-a]pyridine ring has been achieved as late-stage functionalization, enabling and accelerating the generation of a library of compounds from a common precursor. Keywords: α

• confirmed by the presence in a number of pharmaceuticals [2][3]. The imidazo[1,2-a]pyridine-ring modification via Pd-catalyzed reactions is broadly reported in the literature [3], however, such functionalizations for more complex molecules are not very common. On the other hand, the Mizoroki–Heck reaction

Synthesis of C-glycosyl phosphonate derivatives of 4-amino-4-deoxy-α-ʟ-arabinose

• Lukáš Kerner and
• Paul Kosma

Beilstein J. Org. Chem. 2020, 16, 9–14, doi:10.3762/bjoc.16.2

• selective ester cleavage at a later stage. The glycal ester derivatives themselves offered additional options for the preparation of transition state analogues but can also be fully deprotected to provide hydrolytically stable substrate derivatives in the correct anomeric configuration. Modification of

Extension of the 5-alkynyluridine side chain via C–C-bond formation in modified organometallic nucleosides using the Nicholas reaction

• Renata Kaczmarek,
• Dariusz Korczyński,
• James R. Green and
• Roman Dembinski

Beilstein J. Org. Chem. 2020, 16, 1–8, doi:10.3762/bjoc.16.1

• common framework for materials with potent biological properties [6][7][8][9][10]. Modification on this site of the nucleobase usually does not interfere with Watson–Crick base pairing. For example, C-5-modified pyrimidines are well tolerated by commercial polymerases [11][12]. Alkynyl modifications not

• only provide a biological impact but also create a synthetic handle for further functionalization/modification. Among others, alkynyl uridines undergo cycloisomerization to potent antiviral agents, furopyrimidines [13], related halofuropyrimidines [14], and can be converted into interstrand dimers [15

Chemical synthesis of tripeptide thioesters for the biotechnological incorporation into the myxobacterial secondary metabolite argyrin via mutasynthesis

• David C. B. Siebert,
• Roman Sommer,
• Domen Pogorevc,
• Michael Hoffmann,
• Silke C. Wenzel,
• Rolf Müller and
• Alexander Titz

Beilstein J. Org. Chem. 2019, 15, 2922–2929, doi:10.3762/bjoc.15.286

• ) by the Kalesse group [15]. In 2011, Wu et al. reduced the length to 14 linear steps for the total synthesis of argyrins A and E [16]. Finally, Chen et al. described a synthesis yielding several derivatives of argyrin A with modification of the 4’-methoxytryptophan residue [17]. Changing the 4

• possibility resides in the dehydroalanine-sarcosine motif and modification seems possible as deduced from the crystal structure [11] of argyrin with elongation factor G1. Despite the successful implementation of total syntheses of argyrin derivatives, a more rapid access towards diversity in the argyrins and

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

• for the number of five-carbon units that form their hydrocarbon skeletons. Our review focuses on sesqui- (C15) and diterpenes (C20) because these subgroups, after undergoing extensive oxidative modification, have molecular characteristics that are most similar to those of known drugs. Emphasis will be

• are shown in Figure 10a) [129]. While only a limited number of bacterial CYPs for terpene modification has been characterized, many of them were reported to exhibit substrate promiscuity (Supporting Information File 1, Table S2). These promiscuous CYPs do not necessarily co-localize with TC-encoding

• examples of terpene modification by bacterial CYPs. a) Hydroxylation [89]. b) Carboxylation, hydroxylation, and ring contraction [41]. c) Ether formation [90]. d) Rearrangement [91]. Off-target effects observed during heterologous expression of terpenoid BGCs. Unexpected oxidation of 34b by an

Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles

• Hoang Huy Do,
• Saif Ullah,
• Alexander Villinger,
• Joanna Lecka,
• Jean Sévigny,
• Peter Ehlers,
• Jamshed Iqbal and
• Peter Langer

Beilstein J. Org. Chem. 2019, 15, 2830–2839, doi:10.3762/bjoc.15.276

• changes of the substitution pattern allow for a modification of the selectivity and activity of these compounds to these enzymes. Docking studies of h-ENPP1 inhibitors Molecular docking of the most potent compounds 5c and 6a (for ENPP1) and for 6e (exhibiting dual inhibition for both isozymes) were

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

• with their poor solubility and reduced photoswitching efficiency in aqueous medium. In many cases, approaches to improve the water solubility by chemical modification of the photochromic scaffolds are not straightforward because the introduction of substituents often interferes with the desired

• -indigo derivative bearing an alkylamino substituent of a shorter length on the indoxyl N atom has been reported so far [20]. Modification of the phenyl ring by method II was successful and allowed to obtain the desired hemi-indigo 2 as a pure Z-isomer with 24% yield (Scheme 2) [12]. Importantly, the

Diversity-oriented synthesis of spirothiazolidinediones and their biological evaluation

• Sambasivarao Kotha,
• Gaddamedi Sreevani,
• Lilya U. Dzhemileva,
• Milyausha M. Yunusbaeva,
• Usein M. Dzhemilev and
• Vladimir A. D’yakonov

Beilstein J. Org. Chem. 2019, 15, 2774–2781, doi:10.3762/bjoc.15.269

• derivatives 15 were isolated in good yields (Scheme 5). Since TZDs are pharmaceutically important targets, we intended to prepare spirocyclic derivatives of thiazolidinedione. In this context, N-carboxy ester and N-propargyl derivatives of thiazolidinedione were prepared, which on further modification, can

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

• cathodes in the presence of chiral inductors, including tertiary amines, optically active proteins, and alkaloids [19][20], in 1975, Miller’s group reported the first example of the modification of electrodes via covalent binding [21]. They chemically modified air-oxidized graphite electrodes via treatment

• corresponding alcohol 2 with 14.7% optical yield [21]. Control experiments confirmed that the modified electrodes served as chiral inductors (Scheme 1). In 1982, Fujihira and Osa reported the modification of Raney nickel powder electrodes with optically active tartaric acid and used these electrodes for the

• be used for the chemical modification of electrodes to achieve asymmetric induction in electrosynthesis [25][26]. They showed that carbon electrodes modified with poly[RuIII(L)2Cl2]+ (generated from the electropolymerization of [RuIII(L)2Cl2]+ complexes 19 on the carbon surface) can effectively

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

• , we verified that this switchable modification delivers a slightly different hybridization behavior in the PNA. Thus, both melting experiments and strand-displacement assays showed that in all the cases the trans-isomer is the one with superior binding affinities. Alternative versions, inspired by our

• used, we gained versatility using the divergent linear approach introduced by Seitz (Scheme 1) [42]. This strategy enabled the straightforward access to functionalized PNA via on-resin coupling of the corresponding photoswitch in good yields. Of note, this post-synthetic modification is compatible with

• in the precedent of azobenzene-PNA [51], the C-terminus modification displayed the highest isomer difference but modest, in our case. Furthermore, always when a clear difference between isomers was detected, the duplexes containing the trans-oF4Azo were more stable than those with the cis-form. In

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

• efficiently. The use of the nonhygroscopic and cheaper sodium acetate decreased the yield (Table 1, entry 5), whereas the absence of the acetate salt additive led to a very low reaction yield (Table 1, entry 6). Neither removal of the oxidant (Table 1, entry 7) nor further modification of the reaction

• in the literature supporting the chelation of metal centers by a tetrazole ring during the C–H activation processes, in which the tetrazole may also act as directing group [55][56][57][58][59][60][61]. The closely related triazole ring has also been used for the C–H modification of amino acids and

Current understanding and biotechnological application of the bacterial diterpene synthase CotB2

• Ronja Driller,
• Daniel Garbe,
• Norbert Mehlmer,
• Monika Fuchs,
• Keren Raz,
• Dan Thomas Major,
• Thomas Brück and
• Bernhard Loll

Beilstein J. Org. Chem. 2019, 15, 2355–2368, doi:10.3762/bjoc.15.228

• available via the CotB2 mutants is the necessity of further decoration with functional groups, like hydroxylations or epoxidations, to induce the desired bioactivity (Scheme 3). Modification descriptions in the next chapters are composed according to the atom numbering in (Scheme 3). Lead structure for the

• ], density functional theory calculations [33] as well as QM/MM simulations [37]. Variants of CotB2 open the route to a novel product portfolio with altered cyclic carbon skeletons, which can be converted into bioactive compounds by chemo-enzymatic methodologies. Modification descriptions are composed