Inline purification in continuous flow synthesis – opportunities and challenges

• Jorge García-Lacuna and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182

• used to trap carboxylic acids, from which the product can be released with diluted solutions of formic acid [95]. Another strategy that is applicable in the context of biocatalysis involves Ni–NTA resins used for protein purification which are commonly packed in cartridges to enable automated peptide

• dipeptide with the aim to overcome issues found in batch in relation to product stability and scale-up concerns. The peptide coupling reaction was performed continuously aided by a MSMPR crystallizer system. This system ultimately shortened the holding time for the quenched solution, leading to a robust

Navigating and expanding the roadmap of natural product genome mining tools

• Friederike Biermann,
• Sebastian L. Wenski and
• Eric J. N. Helfrich

Beilstein J. Org. Chem. 2022, 18, 1656–1671, doi:10.3762/bjoc.18.178

• -like pathways are canonical type I cis-acyltransferase polyketide synthases (PKSs) and type A non-ribosomal peptide synthetases (NRPSs) (Figure 2A) [25][26]. The substrate specificity of the specificity conferring domains in each module can be predicted from the sequences of adenylation (A) (for NRPS

• ])) [28]. In contrast, discrete multi-enzymatic assemblies utilize distinct, monofunctional enzymes. Examples are terpene (e.g., cyclooctatin (8) [29]), ribosomally synthesized and post-translationally modified peptide (RiPP), or NRPS-independent alkaloid pathways. In the case of terpene biosynthesis

• identification of RiPP BGCs (Figure 3C (e.g., tryptorubin (9) [33])) [21]. In addition, multiple RiPP tailoring enzymes harbor a precursor peptide-binding domain, the so-called RiPP recognition element (RRE) (Figure 3D (e.g., pyrroloquinoline quinone (PQQ, 10) [34])). RRE-derived signature motifs (i.e., short

Simple synthesis of multi-halogenated alkenes from 2-bromo-2-chloro-1,1,1-trifluoroethane (halothane)

• Yukiko Karuo,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1567–1574, doi:10.3762/bjoc.18.167

• an aryl or alkynyl unit [16][17][18][19][20][21][22]. In a biological context, the fluoroalkenyl motif could be incorporated into peptides with the expectation that the fluoroalkenyl unit could serve as a peptide isostere and prevent unexpected hydrolysis of these compounds. Recent studies have shown

Solid-phase total synthesis and structural confirmation of antimicrobial longicatenamide A

• Takumi Matsumoto,
• Takefumi Kuranaga,
• Yuto Taniguchi,
• Weicheng Wang and
• Hideaki Kakeya

Beilstein J. Org. Chem. 2022, 18, 1560–1566, doi:10.3762/bjoc.18.166

• communication in the microbial world. Herein, we report the solid-phase total synthesis and structural confirmation of longicatenamide A. First, commercially unavailable building blocks were chemically synthesized with stereocontrol. Second, the peptide chain was elongated via Fmoc-based solid-phase peptide

• synthesis. Third, the peptide chain was cyclized in the solution phase, followed by simultaneous cleavage of all protecting groups to afford longicatenamide A. Chromatographic analysis corroborated the chemical structure of longicatenamide A. Furthermore, the antimicrobial activity of synthesized

• microbial world. To elucidate the role of compounds 1–4 in the microbial world, developing a strategy to synthesize compounds 1–4, including future derivatization to produce probe molecules, is required. Herein, we report the total synthesis of peptide 1 by Fmoc-based solid-phase peptide synthesis [9] and

Microelectrode arrays, electrosynthesis, and the optimization of signaling on an inert, stable surface

• Kendra Drayton-White,
• Siyue Liu,
• Yu-Chia Chang,
• Sakashi Uppal and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2022, 18, 1488–1498, doi:10.3762/bjoc.18.156

• interactions [5][6][7]. For example, a binding curve generated for the interaction between an RGD-peptide (C-PEG6-GGRGDGP) and its integrin (α5,β1) target is shown in Figure 4 below. A PEG-linker was added to the RGD-peptide so that the peptide would not be buried in the polymer coating the surface of the

• peptide so that the thiol group in the sidechain could be used to place the molecule the array with the use of an electrochemically initiated Cu(I)-catalyzed cross-coupling reaction (Scheme 1) [9]. To this end, the Cu(I) catalyst needed for the reaction was generated at the electrodes by the reduction of

• Figure 4 representing the average current measured at three such blocks with the error bars indicating the range in the data. The use of the method to probe interactions between a v107-peptide and its targeted VEGF receptors proved equally effective [7]. The binding curve shown in Figure 4 did indicate a

Derivatives of benzo-1,4-thiazine-3-carboxylic acid and the corresponding amino acid conjugates

• Péter Kisszékelyi,
• Tibor Peňaška,
• Klára Stankovianska,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 1195–1202, doi:10.3762/bjoc.18.124

• isolated. Moreover, the coupling of benzothiazines with amino acids was realized. In doing so, an enantioselective synthesis of the nonproteinogenic amino acid 2-amino-3-propylhexanoic acid was accomplished. Keywords: amino acid; benzothiazine; oxidative dimerization; peptide coupling; stereoselective

Synthesis of tryptophan-dehydrobutyrine diketopiperazine and biological activity of hangtaimycin and its co-metabolites

• Houchao Xu,
• Anne Wochele,
• Minghe Luo,
• Gregor Schnakenburg,
• Yuhui Sun,
• Heike Brötz-Oesterhelt and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 1159–1165, doi:10.3762/bjoc.18.120

• , People's Republic of China Institute of Inorganic Chemistry, University of Bonn, Gerhard-Domagk-Straße 1, 53121 Bonn, Germany 10.3762/bjoc.18.120 Abstract An improved synthesis for tryptophan-dehydrobutyrine diketopiperazine (TDD), a co-metabolite of the hybrid polyketide/non-ribosomal peptide

• -AT, [3][4]) polyketide synthase (PKS) and non-ribosomal peptide synthase (NRPS) [2] with a dehydrating bimodule [5][6] involved in the installation of the remaining Z-configured double bond within the polyketide backbone [7]. Furthermore, a cytochrome P450 monooxygenase was recently shown to be

• responsible for the oxidation of deoxyhangtaimycin (3), a compound with antiviral activity, to 1 [8]. The thereby installed hemiaminal function is also the breaking point for 1 into a larger lactone-polyene peptide fragment and a smaller fragment HTM222 (2, named after its molecular mass of 222 Da) [2

Enzymes in biosynthesis

• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 1131–1132, doi:10.3762/bjoc.18.116

• proceed through multistep cationic cascade reactions and usually produce a polycyclic terpene hydrocarbon or alcohol with multiple stereogenic centers. While these transformations require only a single enzyme, polyketide and nonribosomal peptide biosyntheses are catalyzed by megasynthases that follow an

• assembly line logic, with individual domains for each single step [2]. Furthermore, the domains are organized into modules, each of which is responsible for the incorporation of one extender unit into the growing polyketide or peptide chain. With our knowledge today, the function of these large enzyme

A versatile way for the synthesis of monomethylamines by reduction of N-substituted carbonylimidazoles with the NaBH₄/I₂ system

• Lin Chen,
• Xuan Zhou,
• Zhiyong Chen,
• Changxu Wang,
• Shunjie Wang and
• Hanbing Teng

Beilstein J. Org. Chem. 2022, 18, 1032–1039, doi:10.3762/bjoc.18.104

• particularly suitable for peptide chemistry since protecting groups are often required in peptide synthesis [52][53]. These multistep reaction methods are conducive to avoid overmethylation products. Although procedures for the synthesis of monomethylamines have been developed over the past years, the starting

Isolation and biosynthesis of daturamycins from Streptomyces sp. KIB-H1544

• Yin Chen,
• Jinqiu Ren,
• Ruimin Yang,
• Jie Li,
• Sheng-Xiong Huang and
• Yijun Yan

Beilstein J. Org. Chem. 2022, 18, 1009–1016, doi:10.3762/bjoc.18.101

• other compounds. To explore the biosynthesis of daturamycins in S. sp. KIB-H1544, especially the formation mechanism of the tricyclic 6/5/6 scaffold, the biosynthetic gene cluster of daturamycins was found and confirmed by gene knockout experiments. We also characterized the deduced peptide synthetase

• S. sp. KIB-H1544, we conducted the following experiments. Firstly, the genome of S. sp. KIB-H1544 was sequenced, and bioinformatic analysis yields the three-genes cluster (NCBI accession number: ON973849) encoded by datA (peptide synthetase), datB (NAD-dependent dehydratase), and datC (limonene-1,2

First series of N-alkylamino peptoid homooligomers: solution phase synthesis and conformational investigation

• Maxime Pypec,
• Laurent Jouffret,
• Claude Taillefumier and
• Olivier Roy

Beilstein J. Org. Chem. 2022, 18, 845–854, doi:10.3762/bjoc.18.85

• -substituted glycines [1][2]. They retain the same backbone as peptides except that the side chains are located on the nitrogen atoms of the amide bonds and thus represent an important class of peptide biomimetics [3][4][5], generally with improved cell permeability [6] and proteolytic resistance [7][8

Synthesis and late stage modifications of Cyl derivatives

• Phil Servatius and
• Uli Kazmaier

Beilstein J. Org. Chem. 2022, 18, 174–181, doi:10.3762/bjoc.18.19

• Phil Servatius Uli Kazmaier Organic Chemistry, Saarland University, Campus C4.2, 66123 Saarbrücken, Germany 10.3762/bjoc.18.19 Abstract A peptide Claisen rearrangement is used as key step to generate a tetrapeptide with a C-terminal double unsaturated side chain. Activation and cyclization give

• , such as histone deacetylases. Keywords: chelated enolate; Claisen rearrangement; HDAC inhibitor; peptide; late stage modification; Introduction Among natural products, peptidic structures have entered the limelight due to their extraordinary biological activities [1]. Often found as secondary

• metabolites for self-defense in different microorganisms, peptidic natural products are assembled either by ribosomal synthesis or by non-ribosomal peptide synthetases (NRPS) [2]. Macrocyclic peptides are pervasive throughout this class of natural products and often show improved stability against proteolytic

Synthesis and bioactivity of pyrrole-conjugated phosphopeptides

• Qiuxin Zhang,
• Weiyi Tan and
• Bing Xu

Beilstein J. Org. Chem. 2022, 18, 159–166, doi:10.3762/bjoc.18.17

• phosphopeptides exhibit comparable activities with that of 1 against HeLa cells at 200 μM, they, differing from 1, are largely compatible with HeLa cells at 400 μM. Enzymatic dephosphorylation of 2–10, at 400 μM is unable to induce a dramatic morphological transition of the peptide assemblies observed in the case

• merits, such as ease of design and tailoring (based on the known structures from proteins), good biocompatibility and degradability, and low immunogenicity. For example, recent works have demonstrated the potential of peptide assemblies for a wide range of applications, including drug delivery [8][9][10

• ][11], collagen mimic [12], antibacterial [13][14], biomineralization [15][16], mimicry of amyloids [17], cell cultures [18], and tissue engineering [19]. Particularly, the use of enzyme-instructed self-assembly (EISA) [20][21] of peptide assemblies has expanded the applications of peptide assemblies

Ready access to 7,8-dihydroindolo[2,3-d][1]benzazepine-6(5H)-one scaffold and analogues via early-stage Fischer ring-closure reaction

• Irina Kuznetcova,
• Felix Bacher,
• Daniel Vegh,
• Hsiang-Yu Chuang and
• Vladimir B. Arion

Beilstein J. Org. Chem. 2022, 18, 143–151, doi:10.3762/bjoc.18.15

• lithium hydroxide monohydrate [29] to give the desired indole-2-acetic acid (14) in 95% yield. The peptide coupling reaction [30] of indole-2-acetic acid (14) and 2-iodoaniline afforded 15 in 23% yield (Scheme 3). Subsequent protection of both the indole and the amide nitrogen with tert-butyloxycarbonyl

• batch of 1a was reduced. It is likely that 2a can be cyclized by base catalysis, or by using common peptide coupling reagents (e.g., EDCI, HATU) upon saponification of the ester group. However, we opted for a trimethylaluminum-mediated amidation reaction [4][39] to give rise to 8-benzyl-7-hydroindolo

Regioselective synthesis of methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates as new amino acid-like building blocks

• Jolita Bruzgulienė,
• Greta Račkauskienė,
• Aurimas Bieliauskas,
• Vaida Milišiūnaitė,
• Miglė Dagilienė,
• Gita Matulevičiūtė,
• Vytas Martynaitis,
• Sonata Krikštolaitytė,
• Frank A. Sløk and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2022, 18, 102–109, doi:10.3762/bjoc.18.11

• peptide-like structure. Heterocyclic amino acids and related compounds have been used to prepare synthetic DNA-encoded compound libraries for the discovery of small molecule protein ligands [23][24][25]. Recently, a highly specific and potent p38α kinase inhibitor containing a 3-amino-1-phenyl-1H-pyrazole

Efficient and regioselective synthesis of dihydroxy-substituted 2-aminocyclooctane-1-carboxylic acid and its bicyclic derivatives

• İlknur Polat,
• Selçuk Eşsiz,
• Uğur Bozkaya and
• Emine Salamci

Beilstein J. Org. Chem. 2022, 18, 77–85, doi:10.3762/bjoc.18.7

• biological activities, especially applications in the field of medicinal chemistry. β-Amino acids (i.e., amino acids containing an extra methylene group in the backbone) occur naturally in peptidic structures [1][2][3][4][5] and have been used in peptide design to obtain mixed peptides that retain their

Peptide stapling by late-stage Suzuki–Miyaura cross-coupling

• Hendrik Gruß,
• Rebecca C. Feiner,
• Ridhiwan Mseya,
• David C. Schröder,
• Michał Jewgiński,
• Kristian M. Müller,
• Rafał Latajka,
• Antoine Marion and
• Norbert Sewald

Beilstein J. Org. Chem. 2022, 18, 1–12, doi:10.3762/bjoc.18.1

• , Universitätsstr. 25, 33615 Bielefeld, Germany Department of Chemistry, Middle East Technical University, 06800, Ankara, Turkey Department of Bioorganic Chemistry, Wrocław University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wrocław, Poland 10.3762/bjoc.18.1 Abstract The development of peptide

• stapling techniques to stabilise α-helical secondary structure motifs of peptides led to the design of modulators of protein–protein interactions, which had been considered undruggable for a long time. We disclose a novel approach towards peptide stapling utilising macrocyclisation by late-stage Suzuki

• –Miyaura cross-coupling of bromotryptophan-containing peptides of the catenin-binding domain of axin. Optimisation of the linker length in order to find a compromise between both sufficient linker rigidity and flexibility resulted in a peptide with an increased α-helicity and enhanced binding affinity to

Stepwise PEG synthesis featuring deprotection and coupling in one pot

• Logan Mikesell,
• Dhananjani N. A. M. Eriyagama,
• Yipeng Yin,
• Bao-Yuan Lu and
• Shiyue Fang

Beilstein J. Org. Chem. 2021, 17, 2976–2982, doi:10.3762/bjoc.17.207

• frequently adopted. For example, in peptide synthesis, peptides with acid-labile side chain protections can be selectively cleaved from the acid-labile 2-chlorotrityl resin with dilute TFA [34]. In RNA synthesis, the acid-sensitive 2'-TOM protecting groups can survive the acidic conditions for removing the 5

A photochemical C=C cleavage process: toward access to backbone N-formyl peptides

• Haopei Wang and
• Zachary T. Ball

Beilstein J. Org. Chem. 2021, 17, 2932–2938, doi:10.3762/bjoc.17.202

• -formyl amide products have unique properties and reactivity, but are difficult or impossible to access by traditional synthetic approaches. Keywords: formyl peptide; nitroaryl compound; nitroso compound; olefin cleavage; photocleavage; Findings The photochemistry of nitroaromatic functional groups has

• , which leads to formyl products from formal oxidative cleavage of a C=C bond. Our interest in vinylogous analogues of 2-nitroaryl photoreactive groups stems from studies into alkenylboronic acid reagents for Chan–Lam-type modification of peptide backbone N–H bonds, directed by a proximal histidine

• ) provide entry into similar photo-uncaging chemistries for amide release. Figure 1C shows an example of this concept applied to a peptide substrate. Reaction of the peptide i with an alkenylboronic acid reagent iv in the presence of a copper(II) salt in water provides access to the backbone N–H

First total synthesis of hoshinoamide A

• Haipin Zhou,
• Zihan Rui,
• Yiming Yang,
• Shengtao Xu,
• Yutian Shao and
• Long Liu

Beilstein J. Org. Chem. 2021, 17, 2924–2931, doi:10.3762/bjoc.17.201

• -sensitive Plasmodium falciparum. Herein, we describe the first total synthesis of hoshinoamide A by the combination of liquid-phase and solid-phase peptide synthesis. Liquid-phase synthesis is to improve the coupling yield of ʟ-Val3 and N-Me-ᴅ-Phe2. Connecting other amino acids efficiency and convergence is

• achieved by solid-state synthesis. Our synthetic strategy could synthesize the target peptide in high yield with good purity Keywords: antimalarial; highly methylated polypeptides; hoshinoamides; total synthesis; Introduction Malaria is an insect-borne infectious disease caused by parasites of the genus

• in Scheme 1, we initially tested Fmoc solid-phase peptide synthesis (SPPS) [13] to get 2-chlorotrityl resin-bound Pro1-(N-Me)-Phe2 dipeptide 2 under the conditions of HCTU and DIPEA. Unfortunately, the N-Me coupling proceeded in low yield (<10%). In order to improve the coupling yield of the hindered

GlycoBioinformatics

• Kiyoko F. Aoki-Kinoshita,
• Frédérique Lisacek,
• Niclas Karlsson,
• Daniel Kolarich and
• Nicolle H. Packer

Beilstein J. Org. Chem. 2021, 17, 2726–2728, doi:10.3762/bjoc.17.184

• article by Barnett et al. [2] uses molecular dynamics to show that O-linked glycosylation alters peptide conformation, which influences the binding of the peptides to antibodies, despite the fact that glycans are not directly involved in the binding. Another molecular modeling article by Fogarty et al. [3

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

• ammonolysis in methanol affords compound 1c. The silylation of 1c with TBDPSCl was carried out, and then coupling reaction with tert-Boc-Met-Leu-Phe-OH in the presence of DCC and HOBt provided compound 98. The tert-Boc protecting group was further removed in formic acid, and the resulting nucleoside peptide

Adjusting the length of supramolecular polymer bottlebrushes by top-down approaches

• Tobias Klein,
• Franka V. Gruschwitz,
• Maren T. Kuchenbrod,
• Ivo Nischang,
• Stephanie Hoeppener and
• Johannes C. Brendel

Beilstein J. Org. Chem. 2021, 17, 2621–2628, doi:10.3762/bjoc.17.175

• bonding moieties are either urea-based or peptide-based (i.e., phenylalanine) units, the dodecyl chains act as hydrophobic shields to induce the amphiphilic assembly in water and prevent the surrounding water from interfering with the hydrogen bonds in the interior [29]. Attaching a hydrophilic PEO chain

Cryogels: recent applications in 3D-bioprinting, injectable cryogels, drug delivery, and wound healing

• Luke O. Jones,
• Leah Williams,
• Tasmin Boam,
• Martin Kalmet,
• Chidubem Oguike and
• Fiona L. Hatton

Beilstein J. Org. Chem. 2021, 17, 2553–2569, doi:10.3762/bjoc.17.171

• injecting through a conventional needle [18]. Gelatin was chosen for its inherent peptide sequences that facilitate cell adhesion and enzymatic degradation. Gelatin is also low cost and safe to use in human testing as shown in a work done by Nichol et al. [77]. The bulk mechanical behaviour, structure, and

Post-functionalization of drug-loaded nanoparticles prepared by polymerization-induced self-assembly (PISA) with mitochondria targeting ligands

• Janina-Miriam Noy,
• Fan Chen and
• Martina Stenzel

Beilstein J. Org. Chem. 2021, 17, 2302–2314, doi:10.3762/bjoc.17.148

• ]. PENAO triggers cell apoptosis by targeting the ANT protein, which is located in the mitochondria. More specifically, PENAO binds to the thiols located on the ANT peptide loops Cys57 and Cys257, which results in the formation of stable cyclic dithioarsinite complexes [5]. Arsenic drugs do not only bind