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

• peptides, proteins and nucleic acids and to evade undesired immune responses, monodisperse PEGs are required or highly desired [12][13]. To meet the needs of monodisperse PEGs, significant efforts have been made to develop stepwise methods for their synthesis [14][15][16][17][18][19][20][21][22][23][24][25

• 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

• Haopei Wang Zachary T. Ball Department of Chemistry, Rice University, Houston TX, USA 10.3762/bjoc.17.202 Abstract Photo-responsive modifications and photo-uncaging concepts are useful for spatiotemporal control of peptides structure and function. While side chain photo-responsive modifications

• ” amide products can and does occur under physiological conditions, the rates of this hydrolysis are slow for the simple models in this study. Within more complex peptides or proteins, selectivity in photocleavage pathways may differ significantly, depending on local chemical environment. It is also worth

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

• cytotoxicity compared to hoshinoamide B. Herein, we report the initial progress on the total synthesis of hoshinomaide A. The key challenges for the total synthesis of hoshinoamide A are the coupling of highly methylated amino acids and the purification of hydrophobic peptides. Results and Discussion As shown

Total synthesis of the O-antigen repeating unit of Providencia stuartii O49 serotype through linear and one-pot assemblies

• Tanmoy Halder and
• Somnath Yadav

Beilstein J. Org. Chem. 2021, 17, 2915–2921, doi:10.3762/bjoc.17.199

• development [1][2][3][4][5][6][7][8]. This objective has been proposed to be achieved by the synthesis of chemically homogeneous glycoconjugates bearing the O-antigen oligosaccharide conjugated to peptides for eliciting the desired immune response through vaccines [9][10][11][12][13][14][15][16][17][18][19

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

• posttranslational modifications of peptides in proteomics can be adapted to specifically identify glycopeptides. What is also obvious for glycobioinformatics is that it needs an own language that is understood by both computers and researchers to facilitate the exchange of glyco-specific information as well as the

• 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

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

• cryogels include fertilizers for agrochemical applications [103], peptides [104], proteins [37], and growth factors [81][105][106]. For example, Lee et al. reported the use of a double cryogel structure for the delivery of growth factor for enhanced bone regeneration [105]. 5.4. Cryogels in wound healing

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

• peptides and proteins have been linked to nanotechnology. DQA and TPP are both cationic and lipophilic molecules and therefore able to easily pass the mitochondrial membrane [15][16][17][18][19]. TPP is the most-studied mitochondrial targeting agent and has shown to accumulate 1000 times more in the

• non-specific protein absorption. Su et al. [40] investigated the effects of a protein corona on active and passive targeting using 20 different types of PEGylated gold nanoparticles, which were decorated with cyclic RGD (arginylglycylaspartic acid) peptides. As a result, the active targeting

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

• Zsanett Benke,
• Attila M. Remete and
• Loránd Kiss

Beilstein J. Org. Chem. 2021, 17, 2051–2066, doi:10.3762/bjoc.17.132

• of natural products (especially macrocycles) [12], alkaloids [13], amino acids and functionalized biomolecules such as peptides [14][15][16][17][18][19][20] or various drugs [21]. Due to the ring strain, bicyclic systems and derivatives, such as norbornadiene derivatives can easily be converted

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• called “heparin crisis” in 2008 [4]. In addition, the heterogeneity of naturally sourced samples poses a severe bottleneck to the molecular characterization of polysaccharides that dwarfs in comparison to other biomolecules like peptides and nucleic acids. Establishing structure–property correlations is

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• the late-stage modification of amino acids and peptides in 2016 (Scheme 27A and B) [159]. The methodology facilitated the targeted C–H oxidative modifications in amino acids and peptides concomitant with the preservation of the α-center chirality in good yields and broad scope regarding the number of

• , several products were submitted to a subsequent metathesis mediated by Grubbs-II catalyst and a further palladium-catalyzed C=C reduction and DG-removal process, from which the desired macrocyclic peptides were obtained in good to excellent yields (Scheme 35C). Recently, again Ackermann and co-workers

Natural products in the predatory defence of the filamentous fungal pathogen Aspergillus fumigatus

• Jana M. Boysen,
• Nauman Saeed and
• Falk Hillmann

Beilstein J. Org. Chem. 2021, 17, 1814–1827, doi:10.3762/bjoc.17.124

• ; non-ribosomal peptides; polyketides; secondary metabolism; virulence; Introduction To thrive in their natural habitats all organisms from bacteria and fungi to plants and animals need access to sufficient nutritional sources and have to defend themselves against both, competitors and predators

• molecules like non-ribosomal peptides (NRP), polyketides (PK), terpenes or indole alkaloids [10][11]. The vast majority of fungal BGCs is found in the genomes of members of the Basidiomycota and Ascomycota including the genus Penicillium in which the first BGC was identified in 1990 [12][13][14

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• biologically active small molecules and complex peptides. Keywords: bioactive molecules; 3d transition metals; late-stage functionalization; manganese catalyst; sustainable catalysis; Introduction Manganese, a 3d transition metal, allows for a potentially ideal sustainable catalytic system because of the

• active molecules and complex peptides, which are of great importance to medicinal chemists and are categorized according to the transformations involved. Review Manganese-catalyzed late-stage C–H fluorination The fluorination of organic molecules [13][14][15][16], a highly valuable synthetic

• -economical approach to several tryptophan-containing peptides with significant potential for drug discovery and medicinal chemistry. Positional selectivity was observed at the C2 position due to the presence of the pyrimidine directing group. Interestingly, alkynylative conjugation of tryptophan to a steroid

A systems-based framework to computationally describe putative transcription factors and signaling pathways regulating glycan biosynthesis

• Theodore Groth,
• Rudiyanto Gunawan and
• Sriram Neelamegham

Beilstein J. Org. Chem. 2021, 17, 1712–1724, doi:10.3762/bjoc.17.119

• the addition of GlcNAc to processed N-linked glycan structures. These include all the MGAT enzymes. 7) GalNAc-type O-glycans: O-linked glycans are attached to serine (Ser) or threonine (Thr) on peptides, where GalNAc is the root carbohydrate. This is mediated by a family of about 20 Golgi-resident

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

• , many research groups have worked on chemical modifications to the backbone and nucleobases of PNA, as well as conjugating PNA to other biomolecules (e.g., cell-penetrating peptides) [4]. The present review summarizes the most significant efforts and achievements in optimizing various aspects of PNA

• ][159][160]. Looking forward, conjugation of PNA with various delivery enhancing compounds, most notably cell-penetrating peptides (CPP) that deliver the conjugates mainly through endocytosis (Figure 11) has become one of the most promising approaches to improving cellular uptake of PNA [161][162

• covalent conjugation of PNA to delivery enhancing compounds. Cell-penetrating peptides derived from natural proteins: The initial success of PNA delivery involved PNA conjugates taken up by receptor-mediated endocytosis. Pardridge and co-workers successfully demonstrated in vivo delivery and blood-brain

Enhanced target cell specificity and uptake of lipid nanoparticles using RNA aptamers and peptides

• Roslyn M. Ray,
• Anders Højgaard Hansen,
• Maria Taskova,
• Bernhard Jandl,
• Jonas Hansen,
• Citra Soemardy,
• Kevin V. Morris and
• Kira Astakhova

Beilstein J. Org. Chem. 2021, 17, 891–907, doi:10.3762/bjoc.17.75

• peptides, Tat and T7, did not increase BBB penetration above the aptamer-loaded LNPs alone. Moreover, we found that these targeted LNPs exhibit low immunogenic and low toxic profiles and that targeted LNPs can traverse the BBB to potentially deliver drugs into the target tissue. This approach highlights

• ) represent an effective platform for delivering small molecules, RNA, or DNA into target cells [1]. LNPs have been successfully deployed via different administration routes in vivo to distribute cargo into target tissues [2][3][4][5][6][7][8]. By changing lipid composition [6] and/or including short peptides

• of LNPs through the notoriously protective BBB is to use short positively charged peptides or receptor-specific ligands, both of which have shown to be effective at increasing transport of LNPs, nucleotides, and small molecules through the BBB [9][15][16][17]. For example, the short positively

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• absorption of EDA complex in the visible-light region. In 2020, Xu and colleagues [39] proposed a visible-light-promoted alkylation reaction using Katritzky salts such as 128 and glycine derivative 127 (or glycine segments in peptides) initiated by an EDA complex. This successfully realized the simple

• synthesis of unnatural α-amino acids 129 and precise alkylation modification of peptides in the later stage (Scheme 45). Even in the presence of other amino acid residues, this protocol has excellent regio- and chemoselectivity, providing a sequence of novel corresponding dipeptides with good yield. The

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• diphenyldiazomethanes, available reagents carrying substituents on the phenyl rings. For example, covalent attachment of C60 to peptides is performed through a phenyl spacer, as it was demonstrated in a synthesis of fulleride 27 [89]. The latter compound was designed specifically for suppressing a HIV enzyme. The

• dimethoxymethanofullerene 7. Synthesis of fullerene monoesters and symmetric diesters 8–10 and 11–12, respectively. The synthetic route to the first fullerene–peptide conjugate 16. Synthesis of bioactive fullerene peptides 19 and 20. Synthesis of amino acid–fullerene derivatives 21 and 22. (BtOH is 1H-benzotriazol-1-ol

Synthesis and physicochemical evaluation of fluorinated lipopeptide precursors of ligands for microbubble targeting

• Masayori Hagimori,
• Estefanía E. Mendoza-Ortega and
• Marie Pierre Krafft

Beilstein J. Org. Chem. 2021, 17, 511–518, doi:10.3762/bjoc.17.45

• , which involves the use of targeting ligands, such as monoclonal antibodies, antibody fragments, proteins, peptides, and other small molecules, including vitamins and carbohydrates [7][8]. The targeting ligands are coupled to the surface of the carrier to selectively target tumor cells that overexpress a

• safety [15][16][17]. Various effective receptor-binding peptides have been identified by the phage display technology [18]. The peptides can be readily prepared through solid-phase peptide synthesis (SPPS), a highly reproducible method with minimal side reactions. Many peptide–lipid conjugates

• penetrating properties, such as the transactivator of the transcription (TAT) peptide. Moreover, peptides being smaller than the antibodies generally induce a lower immunogenicity [15][16][17]. Micro- and nanocarriers are often covered by poly(ethylene glycol) (PEG) stealth coatings that significantly enhance

Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• and phosphonate-linked analogues of naturally occurring peptides. They are more stable than phosphonopeptides and have been widely applied as enzyme inhibitors, haptens for the production of antibodies, biological agents, and prodrugs. The synthetic strategies towards phosphonodepsipeptides are

• phosphonodepsipeptides with C-1-hydroxyalkylphosphonic acids. Keywords: alkylation; mimetic; multicomponent condensation; peptide; phosphonopeptide; phosphonodepsipeptide; phosphonylation; Introduction Both, phosphonopeptides and phosphonodepsipeptides are phosphorus analogues of peptides [1][2][3][4][5]. The

• phosphonopeptides are peptides with a phosphonamidate bond instead of an amide bond whereas the phosphonodepsipeptides are peptides with a phosphonate linkage instead of an amide. Phosphonodepsipeptides are structurally close analogues of depsipeptides (Figure 1). In general, phosphonodepsipeptides are more stable

Biochemistry of fluoroprolines: the prospect of making fluorine a bioelement

• Vladimir Kubyshkin,
• Rebecca Davis and
• Nediljko Budisa

Beilstein J. Org. Chem. 2021, 17, 439–460, doi:10.3762/bjoc.17.40

• easily handled both as free amino acids and as residues in peptides and proteins. Nonetheless, when compared to the parent proline structure, fluoroprolines possess a number of altered properties. Some properties of the amino acids in common model compounds are summarized in Table 1 and will be discussed

• compared to proline (Figure 5) [19]. Although, the difference is small, it may have an impact on the overall features of the peptides and proteins that rely on polarity. 2.4 Proline puckering In addition to the general impact of fluorination, there are some properties specifically attributed to the proline

• extended helix that attained its name from the original discovery in polymeric proline. The PII helix occurs in various proteins, and it is particularly common in proline-rich sequence fragments [100]. Studies of oligomeric peptides showed that the replacement of proline with R-Flp exerts a stabilizing

¹⁹F NMR as a tool in chemical biology

• Diana Gimenez,
• Aoife Phelan,
• Cormac D. Murphy and
• Steven L. Cobb

Beilstein J. Org. Chem. 2021, 17, 293–318, doi:10.3762/bjoc.17.28

• increasingly prominent in 19F NMR studies owing to their improved spectral properties. Among the first perfluorinated amino acids to be reported was perfluoro-tert-butylhomoserine (8), which was synthesized by Marsh and co-workers and incorporated into a variety of antimicrobial peptides, including MSI-78, for

• , all peptides where 8 was introduced could be detected even at concentrations as low as 5 μM, demonstrating that pFtBSer is a highly sensitive tool to study binding events by way of 19F NMR chemical shift and nuclear relaxation changes. In addition to homoserine, perfluorinated analogues of both

• estrogen receptor (ER) co-activator peptides and enabled the sensitive detection of their protein–peptide interaction inhibition by the ER antagonist tamoxifen [20]. Significantly, different secondary structure conformational preferences were also found among the diastereomers of perfluoro-tert

Supramolecular polymerization of sulfated dendritic peptide amphiphiles into multivalent L-selectin binders

• David Straßburger,
• Svenja Herziger,
• Katharina Huth,
• Moritz Urschbach,
• Rainer Haag and
• Pol Besenius

Beilstein J. Org. Chem. 2021, 17, 97–104, doi:10.3762/bjoc.17.10

• rods in the range of several hundred nanometers (Figure 2B,C, and Figure S4 in Supporting Information File 1). These results thus confirm our conclusions from CD spectroscopy and prove an ionic strength-dependent β-sheet ordering in neutral or anionic sulfated dendritic peptides. Under physiological

Semiautomated glycoproteomics data analysis workflow for maximized glycopeptide identification and reliable quantification

• Steffen Lippold,
• Arnoud H. de Ru,
• Jan Nouta,
• Peter A. van Veelen,
• Magnus Palmblad,
• Manfred Wuhrer and
• Noortje de Haan

Beilstein J. Org. Chem. 2020, 16, 3038–3051, doi:10.3762/bjoc.16.253

• File 2) but may occur at the peptide portion as well [24][25][26]. Formylation is likely introduced by the exposure of the tryptic peptides to formic acid during the acid precipitation of sodium deoxycholate in the final step of the sample preparation and during subsequent storage [24]. Within the

• ). The y- and Y-fragment ions of (glyco)peptides with Cys oxidation showed a characteristic neutral loss of 107.0041 Da (C2H5O2NS), as reported for singly oxidized carbamidomethylated Cys through an elimination reaction in the gas phase (Figures S13 and S16–S18, Supporting Information File 2) [27

• ]. Peptides with Cys oxidation had a similar elution behavior as the unoxidized isomeric counterparts (with an additional hexose instead of a fucose unit), leading to a high degree of ambiguous, albeit often illogical compositions (e.g.. for the LSL cluster, Figure S16, Supporting Information File 2 and Table

Secondary metabolites of Bacillus subtilis impact the assembly of soil-derived semisynthetic bacterial communities

• Heiko T. Kiesewalter,
• Carlos N. Lozano-Andrade,
• Mikael L. Strube and
• Ákos T. Kovács

Beilstein J. Org. Chem. 2020, 16, 2983–2998, doi:10.3762/bjoc.16.248

• , Kgs. Lyngby, Denmark 10.3762/bjoc.16.248 Abstract Secondary metabolites provide Bacillus subtilis with increased competitiveness towards other microorganisms. In particular, nonribosomal peptides (NRPs) have an enormous antimicrobial potential by causing cell lysis, perforation of fungal membranes

• to understand their ecological role. Keywords: Bacillus subtilis; bacterial community; chemical ecology; Lysinibacillus fusiformis; nonribosomal peptides; surfactin; Introduction In nature, bacteria live in complex communities where they interact with various other microorganisms. Most microbial

• Bacillus spp. produce various SMs [33][34]. The most prominent and bioactive SMs are nonribosomal peptides (NRPs), of which isoforms belong to the families of surfactins, fengycins, or iturins [35][36] (Figure 1). They are biosynthesised by large enzyme complexes, nonribosomal peptide synthetases (NRPSs

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

Beilstein J. Org. Chem. 2020, 16, 2971–2982, doi:10.3762/bjoc.16.247

• recognition; peptide-based; Introduction Molecular recognition involving amino acids or peptides are important factors in biochemical and medicinal processes [1][2][3]. Amino acids work as biosynthetic building blocks or as signaling molecules. For example, the well-known neurotransmitters glutamate and γ

• a bound glutamate molecule [4]. Peptides often work as signaling molecules or hormones, such as small neuropetide endorphins, produced by the central nervous system to relieve stress or enhance pleasure. They produce signaling cascades in the brain by interacting with opiate receptors. Sometimes

• antibiotic, is used for the treatment of resistant bacterial infections. Its interaction with a small peptidic segment of the bacteria cell wall is a classic example of molecular recognition [6][7]. Peptides are often substrates for protease enzymes [8][9]. Enzymologists have studied the chemical principles