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

• thiotemplated assembly lines, such as type I polyketide synthases (PKS) and nonribosomal peptide synthetases (NRPS), are modular, with each module contributing a distinct fragment to the final product’s core structure – a short-chain carboxylic acid (PKS) or an amino acid (NRPS). The modularly defined template

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

• retention time on UPLC (Figure 3). LC–MS analysis revealed a molecular ion confirming the addition product 12. Under the conditions we used for this chemical reaction it was complete within a few minutes. It has been reported that maleimide–peptide conjugates undergo hydrolysis of the succinimide to give a

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

• have been synthesized via solid-phase peptide synthesis and SN2’ reaction on a Morita–Baylis–Hillman (MBH) residue introduced at the N-terminal of a tetrapeptide. This last step takes advantage of the electrophilic feature of the MBH residue and represents a new cyclization strategy occurring. The

• File 1). Three main absorption bands could be readily observed around 3280, 1650 and 1520 cm−1. The first one was assigned to the stretch for N–H bonds of the peptide linkage. The stretch for the lactam and lactone C=O bonds gives rise to the broad absorption close to 1650 cm−1. The lowering on the

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

• , artificial probes activated by visible-light irradiation are highly desired in biological applications. Here, we report two novel types of visible-light photoswitchable peptide nucleic acids (PNAs) based on the molecular transducers: hemithioindigo and tetra-ortho-fluoroazobenzene. Our study reveals that the

• first compounds here reported, may find applications in different fields such as chemical biology, nanotechnology and materials science. Keywords: azobenzene; hemithioindigo; peptide nucleic acid (PNA); photoswitch; visible-light irradiation; Introduction Light-driven control of oligonucleotide

• -penetrating wavelengths. Peptide nucleic acids (PNAs) [31] are synthetic nucleic acid analogues, in which nucleobases are linked to a repeating N-(2-aminoethyl)glycine polyamide backbone. The lack of phosphate groups provides them with both higher binding affinities to complementary DNA or RNA sequences and

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

• and Research, Pune, Pune 411008, India 10.3762/bjoc.15.234 Abstract The intramolecular cyclization of a C-3-tetrasubstituted furanoid sugar amino acid-derived linear tetrapeptide afforded an oxazolone pseudo-peptide with the formation of an oxazole ring at the C-terminus. A conformational study of

• the oxazolone pseudo-peptide showed intramolecular C=O···HN(II) hydrogen bonding in a seven-membered ring leading to a γ-turn conformation. This fact was supported by a solution-state NMR and molecular modeling studies. The oxazolone pseudotetrapeptide was found to be a better Cl−-selective

• dipeptide 6a in 82% yield, while hydrolysis of 5 using LiOH gave azido acid dipeptide 6b in 88% yield. Coupling of 6a and 6b using CMPI in the presence of Et3N in dichloromethane afforded azido ester tetra-peptide 7 in 73% yield. [20]. The linear azido ester dipeptide 5 and tetrapeptide 7 were individually

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

• irreversible precipitation of a product, and an inevitable shift in dynamic equilibrium. Several types of reversible reactions have been successfully employed in the formation of DCL, including transesterification, peptide bond exchange, disulphide exchange, olefin metathesis and boronic ester formation [189

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

• Rosana Ribić,
• Ranko Stojković,
• Lidija Milković,
• Mariastefania Antica,
• Marko Cigler and
• Srđanka Tomić

Beilstein J. Org. Chem. 2019, 15, 1805–1814, doi:10.3762/bjoc.15.174

• present the design, synthesis and biological evaluation of novel mannosylated desmuramyl peptide derivatives. Mannose was coupled to dipeptides containing a lipophilic adamantane on N- or C-terminus through a glycolyl or hydroxyisobutyryl linker. Adjuvant activities of synthesized compounds were

• investigated in the mouse model using ovalbumin as an antigen. Their activities were compared to the previously described mannosylated adamantane-containing desmuramyl peptide and peptidoglycan monomer. Tested compounds exhibited adjuvant activity and the strongest enhancement of IgG production was stimulated

• by compound 21 (Man-OCH2-ᴅ-(1-Ad)Gly-ʟ-Ala-ᴅ-isoGln). Keywords: adamantane; adjuvant activity; desmuramyl peptide; mannose; Introduction Dendritic cells capture and internalize invading pathogens. Pathogen-associated molecular patterns have been known for a long time to affect the immune system of

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• )-135 instead of the allyl residue opened the way to synthesis of ʟ-(+)-furanomycin and its 5'-epimer. MeBmt (2S,3R,4R,6E)-139 is a nonproteinogenic amino acid found as a constituent of the naturally occurring cyclic peptide cyclosporine currently in medical use as immunosuppressant [89]. Syntheses of

Synthesis and conformational preferences of short analogues of antifreeze glycopeptides (AFGP)

• Małgorzata Urbańczyk,
• Michał Jewgiński,
• Joanna Krzciuk-Gula,
• Jerzy Góra,
• Rafał Latajka and
• Norbert Sewald

Beilstein J. Org. Chem. 2019, 15, 1581–1591, doi:10.3762/bjoc.15.162

• have shown a strong influence of the stereochemistry of amino acid residues on the peptide chain stability, which could be connected to the antifreeze activity of these compounds. A better understanding of the mechanism of action of antifreeze glycopeptides would allow applying these materials, e.g

• binds onto the ice surface via hydrophobic groups and “walks” on the flat ice surface, which is a completely new hypothesis [16]. The antifreeze activity of these biopolymers is highly related to the stereochemical features of the peptide backbone and the glycosyl moiety. Previously it was assumed that

• the saccharide moiety is conformationally well-defined by the peptide backbone and the whole structure adopts a polyproline II (PP II) helix [17]. Antifreeze activity strongly relies on the stereochemistry of the amino acid residues. Earlier studies have shown that AFGP analogues containing either an

Efficiency Eff_syn of complex syntheses as multicomponent reactions, its algorithm and calculations based on concrete criteria

• Heiner Eckert

Beilstein J. Org. Chem. 2019, 15, 1425–1433, doi:10.3762/bjoc.15.142

• demonstrate the enormous influence of branching on the overall yield yoa and synthesis efficiency Effsyn. Fragment strategy: fragment linking in peptides synthesis In synthetic peptide chemistry, amino acids are sequentially built up to form long oligo/polypeptides. For reasons of transparency, we have

Genomics-inspired discovery of massiliachelin, an agrochelin epimer from Massilia sp. NR 4-1

• Jan Diettrich,
• Hirokazu Kage and
• Markus Nett

Beilstein J. Org. Chem. 2019, 15, 1298–1303, doi:10.3762/bjoc.15.128

• homologs in the mic cluster from R. solanacearum GMI1000 [13]. A closer inspection of the loci shows a strong conservation of two core biosynthesis genes, namely micC and micG. On the other hand, the nonribosomal peptide synthetase (NRPS) gene micH is missing in the Massilia locus. As evidenced by

Doebner-type pyrazolopyridine carboxylic acids in an Ugi four-component reaction

• Maryna V. Murlykina,
• Oleksandr V. Kolomiets,
• Maryna M. Kornet,
• Yana I. Sakhno,
• Sergey M. Desenko,
• Victoriya V. Dyakonenko,
• Svetlana V. Shishkina,
• Oleksandr A. Brazhko,
• Vladimir I. Musatov,
• Alexander V. Tsygankov,
• Erik V. Van der Eycken and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2019, 15, 1281–1288, doi:10.3762/bjoc.15.126

• discovery. The target products containing a heterocyclic core bound to a peptide-like chain also showed a broad spectrum of biological activity: β-secretase (BACE1) inhibitory activity [15]; inducing apoptosis in colorectal cancer cells [16]; antimalarial activity against a chloroquine (CQ) non-resistant

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

• and complexity-generating processes [2][3] have proven success in peptide ligation [4] and macrocyclization [5][6], protein glycoconjugation [7], lipidation of peptides [8] and glycosides [9], and carbohydrate modification [10]. A special class of lipidic biomolecules are the steroids, which can be

• the installation of peptidomimetic chains at different positions of the steroidal skeleton, which enabled rigidifying the pendant peptide chains [29]. Scheme 7 depicts two selected examples of this work, showing the possibility of incorporating isocyanide groups at furostanic and cholanic steroids and

• to possess physicochemical and biological features different from those of the two separate molecular entities [57][58]. Despite nature does not provide examples of steroid–peptide conjugates, chemists have produced such conjugates to be employed as protease-like artificial enzymes [59] as mimics of

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

• Abstract The multicomponent synthesis of prolyl pseudo-peptide catalysts using the Ugi reaction with furfurylamines or isocyanides is described. The incorporation of such a polymerizable furan handle enabled the subsequent polymerization of the peptide catalyst with furfuryl alcohol, thus rendering

• employ a three-component, diastereoselective variant of the Ugi reaction for the synthesis of a prolyl pseudo-peptide catalyst, which proved effective in an organocatalytic conjugate addition reaction [6]. Later, our groups developed an Ugi reaction-based multicomponent approach enabling the structure

• diversification of prolyl pseudo-peptide catalysts [7], which also proved great efficacy in organocatalytic asymmetric Michael reactions. As extension of this concept to the field of immobilized organocatalysts, we reported the use of the multicomponent approach for the synthesis of silica-grafted peptide

Stereo- and regioselective hydroboration of 1-exo-methylene pyranoses: discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

• Alexander Dahlqvist,
• Axel Furevi,
• Niklas Warlin,
• Hakon Leffler and
• Ulf J. Nilsson

Beilstein J. Org. Chem. 2019, 15, 1046–1060, doi:10.3762/bjoc.15.102

• sequence of larger glycans [1][2][3]. Some galectins contain one CRD and occur as monomers or dimers, including galectins -1, -2, -7, -10 and -13 in humans. Others contain 2 different CRDs within the same peptide sequence and include galectins -4, -8, -9 and -12. Galectin-3 contains one CRD and a long N

Heck- and Suzuki-coupling approaches to novel hydroquinone inhibitors of calcium ATPase

• Robert J. Kempton,
• Taylor A. Kidd-Kautz,
• Soizic Laurenceau and
• Stefan Paula

Beilstein J. Org. Chem. 2019, 15, 971–975, doi:10.3762/bjoc.15.94

• tether to BHQ that terminated in a leucine moiety to obtain target 14. Similar to related compounds based on the structure of the natural product thapsigargin, 14 displayed inhibitory potency against SERCA activity. This makes 14 a suitable candidate for the future attachment of a deactivating peptide to

• cytotoxic agent. The problem of concomitant toxicity to healthy cells has been circumvented by attaching a short peptide (His-Ser-Ser-Lys-Leu-Gln-Leu) to a tether at TG’s C-8 position (1b). This modification renders the inhibitor inactive [3]. Prostate cancer cells produce on their surface the serine

• protease PSA (prostate-specific antigen) that is capable of cleaving the peptide bond between Gln and Leu, thereby producing an active TG analogue that can enter the cancer cell and kill it by triggering apoptosis. Apoptosis occurs as the result of elevated cytosolic calcium levels, which are caused by

Synthesis of (macro)heterocycles by consecutive/repetitive isocyanide-based multicomponent reactions

• Angélica de Fátima S. Barreto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2019, 15, 906–930, doi:10.3762/bjoc.15.88

• formaldehyde allowed the rapid production of eight functionalized macrocycles (Scheme 30). Another method using repetitive Ugi reactions has been described for the macrocyclization of peptides [48]. The approach was based on double Ugi-4CR involving a peptide diacid, a diisocyanide, methylamine and

• paraformaldehyde (Scheme 31a). Subsequently, it was observed that varying the amine component (C-protected amino acids) allowed the obtention of exocyclic elements of diversity as observed in macrocycles 162a and b (Scheme 31b). The process allows the increase of the peptide sequence as well as the inclusion of

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• shaking and stirring [89]. Peptide-chain containing distal thiol groups underwent an aerial oxidation process to give different disulfide-containing macromolecules. They observed that under mechanical shaking conditions preferentially the cyclic hexamer 33 is formed, whereas stirring resulted in formation

• interactions of alternating hydrophilic and hydrophobic units in the peptide chains played the vital role in the system. Friščić and Aav with co-workers reported the first solvent-free mechanochemical synthesis of hemicucurbiturils [90] through the anion template effect of dynamic covalent chemistry [47][91

• thermodynamic control. Preferential formation of hexamer 33 under mechanochemical shaking via non-covalent interactions of peptide chains. Anion templated mechanochemical synthesis of macrocycles cycHC[n] by validating the concept of dynamic covalent chemistry. Hydrogen-bond-assisted [2 + 2]-cycloaddition

Efficient synthesis of pyrazolopyridines containing a chromane backbone through domino reaction

• Razieh Navari,
• Saeed Balalaie,
• Saber Mehrparvar,
• Fatemeh Darvish,
• Frank Rominger,
• Fatima Hamdan and
• Sattar Mirzaie

Beilstein J. Org. Chem. 2019, 15, 874–880, doi:10.3762/bjoc.15.85

• Razieh Navari Saeed Balalaie Saber Mehrparvar Fatemeh Darvish Frank Rominger Fatima Hamdan Sattar Mirzaie Peptide Chemistry Research Center, K. N. Toosi University of Technology, P. O. Box 15875-4416, Tehran, Iran, Tel: +98-21-23064226, Fax: +98-21-22889403 Medical Biology Research Center

Synthesis of a novel category of pseudo-peptides using an Ugi three-component reaction of levulinic acid as bifunctional substrate, amines, and amino acid-based isocyanides

• Maryam Khalesi,
• Azim Ziyaei Halimehjani and
• Jürgen Martens

Beilstein J. Org. Chem. 2019, 15, 852–857, doi:10.3762/bjoc.15.82

• for the Ugi reaction. This article provides a facile and convenient one-pot procedure for the synthesis of peptide-like heterocyclic molecules containing 2-pyrrolidone (γ-lactam), amide and ester functional groups with good to excellent yields. Keywords: amino acid-based isocyanides; levulinic acid

• prominent and studied MCRs is the Ugi reaction. The Ugi four-component condensation reaction (U-4CC) between an aldehyde, an amine, a carboxylic acid and an isocyanide provides a rapid preparation of α-aminoacyl amide or pseudo-peptide derivatives. These biologically active peptide-like molecules can be

Synthesis of acylglycerol derivatives by mechanochemistry

• Karen J. Ardila-Fierro,
• Andrij Pich,
• Marc Spehr,
• José G. Hernández and
• Carsten Bolm

Beilstein J. Org. Chem. 2019, 15, 811–817, doi:10.3762/bjoc.15.78

• biomolecules that constitute the cell do also experience the effects of the mechanical forces. For example, from the moment a nascent peptide begins growing in the ribosome, such peptide experiences mechanical signals that regulate the speed of protein synthesis [2]. Not surprisingly, the natural ability of

• peptides to endure mechanical stress in nature has allured scientists to evaluate the mechanical stability of proteins by using single-molecule nanomechanical techniques (e.g., magnetic and optical tweezers or atomic force microscopy) [3][4]. Additionally, the resilience of the peptide bond to mechanical

Solid-phase synthesis of biaryl bicyclic peptides containing a 3-aryltyrosine or a 4-arylphenylalanine moiety

• Iteng Ng-Choi,
• Àngel Oliveras,
• Lidia Feliu and
• Marta Planas

Beilstein J. Org. Chem. 2019, 15, 761–768, doi:10.3762/bjoc.15.72

• resulting biaryl monocyclic peptidyl resin leading to the formation of the expected biaryl bicyclic peptide. This study provides the first solid-phase synthesis of this type of bicyclic compounds being amenable to prepare a diversity of synthetic or natural biaryl bicyclic peptides. Keywords: borylation

• -terminal groups of the peptide and their putative target. This method has been used for the macrocyclization of peptides through, for example, copper-catalyzed azide–alkyne cycloadditions [14], ring-closing olefin metathesis [13] or the formation of an aryl–aryl bond between the side chain of two aromatic

• , the cyclization of linear peptides through aryl–aryl bond formation confers a relative conformational constraint on the peptide scaffold. Moreover, the resulting biaryl motif is able to participate in π–π interactions with aromatic and hydrophobic residues, and also in π-cation interactions with

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

• Jan Hendrik Lang and
• Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

• assembled by solution-phase synthesis and an open-chain analogue of the natural product was obtained. Keywords: jasplakinolide; marine natural products; Negishi coupling; polyketides; stereoselective synthesis; Introduction Our program on the synthesis of biologically active natural products with peptide

• Suberites japonicus (Thiele) has been synthesized only once, with relay ring-closing metathesis being the key step [9]. Characteristically, seragamides A–E exhibit a L-threonine unit at the C-terminus of the peptide moiety. There is a considerable body of work on the synthesis of the C12 polyketide section

• with literature data we converted 7 to the free carboxylic acid carrying a TBS-protected hydroxy group at C8 by silylation with TBSOTf/2,6-lutidine, followed by saponification with LiOH. To investigate whether polyketide 7 could be coupled in an unprotected form with the peptide fragment of seragamide

Synthesis and SAR of the antistaphylococcal natural product nematophin from Xenorhabdus nematophila

• Frank Wesche,
• Hélène Adihou,
• Thomas A. Wichelhaus and
• Helge B. Bode

Beilstein J. Org. Chem. 2019, 15, 535–541, doi:10.3762/bjoc.15.47

• moiety itself are required for bioactivity [16]. These findings suggest a specific interaction of this electrophilic moiety with a nucleophile. Such an interaction was previously reported for the macrocyclic peptide cyclotheonamide A, isolated from marine sponge Theonella sp. Cyclotheonamide A is

Selectivity in multiple multicomponent reactions: types and synthetic applications

• Ouldouz Ghashghaei,
• Francesca Seghetti and
• Rodolfo Lavilla

Beilstein J. Org. Chem. 2019, 15, 521–534, doi:10.3762/bjoc.15.46

• consecutive reactions lead to adducts displaying a diversity of substituents at several positions, which, in principle, can be located at will, in a controlled manner. For instance, the combination of a Petasis 3CR with an Ugi 4CR led to a peptide structure with six diversity points arising directly from the

• illustrate a repetitive Ugi 4CR-deprotection-Ugi 4CR protocol to obtain peptide nucleic acid (PNA) oligomers (Scheme 13A) [49], peptidic tetrazoles and hydantoinimides (Scheme 13B) [50], respectively. Incidentally, the later processes take place in solid phase, which enhances their synthetic suitability. The