Thiophene/selenophene-based S-shaped double helicenes: regioselective synthesis and structures

• Mengjie Wang,
• Lanping Dang,
• Wan Xu,
• Zhiying Ma,
• Liuliu Shao,
• Guangxia Wang,
• Chunli Li and
• Hua Wang

Beilstein J. Org. Chem. 2022, 18, 809–817, doi:10.3762/bjoc.18.81

• ; selenophene; thiophene; Introduction Given their esthetically pleasing helical structures, inherent helical chirality, and extended π-conjugation, helicenes have attracted extensive research attention. Helicenes are generally divided into carbohelicenes and heterohelicenes. The rapid development of

• single-crystal analysis (Figure 3). Both DH-1 and DH-2 belong to the triclinic space group P-1. After double oxidative photocyclizations of 5a and 5b, DH-1 and DH-2 are compressed into S-shaped double helical structures (Figure 3A and B), which consist of one [5]helicene and one [6]helicene. The two

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

• P5 successfully quenches such biologically unfavourable conformation and significantly increases the probability of forming helical structures that closely resemble the active conformation of axin’s binding domain. Both, cis and trans isomers form α-helices with a high probability, yet the trans

• , analysis of the structural diversity of the two isomers of P5 indicates that P5 cis (P5.1) is more disordered (see Supporting Information File 1, Table S3), which also correlates with a blue-shifted absorption minimum compared to P5 trans (P5.2). In the partially helical structures of aAxWt (i.e., second

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

• studies revealed that long β(1–3)-glucan structures adopt a parallel, triple helical structures [146]. A glycosynthase derived from Bacillus licheniformis could polymerize glycosyl fluoride donors to prepare artificial mixed linkage β-glucans with an average molecular mass of 10–15 kDa [147]. The better

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

• backbone to attach additional nucleobases, which enable these “double face” PNAs to form higher order double and triple helical structures [87][88]. Ly and co-workers followed up on the promising conformational properties of γ-hydroxymethyl PNA by extending the side chain into a miniPEG modification

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• structural distortions caused by A/B junctions within the helical structures [207]. 2',4'-diF-modified siRNA sequences were capable of triggering RNAi with high efficiency, and the incorporation of multiple residues in the guide (antisense) strand yielded more potent siRNAs than those containing LNA or FANA

• -methyl (Figure 9I) nucleosides leads to a slight destabilization of helical structures due to the adoption of a C2'-endo (south) conformation [212][213]. When fluorine is incorporated at C2' instead of 2'-OMe (Figure 9J), these 4'-C-aminoalkyl nucleosides are found to stabilize both dsRNA and siRNA to a

Helicene synthesis by Brønsted acid-catalyzed cycloaromatization in HFIP [(CF₃)₂CHOH]

• Takeshi Fujita,
• Noriaki Shoji,
• Nao Yoshikawa and
• Junji Ichikawa

Beilstein J. Org. Chem. 2021, 17, 396–403, doi:10.3762/bjoc.17.35

• sequence. Synthesis of (a) [5]helicene and (b) [6]helicene. Synthesis of helicenes with double helical structures. Synthesis of hetero[4]-, [5]-, and [6]helicenes. Supporting Information Supporting Information File 56: Detailed experimental procedures and spectral data. Acknowledgements We acknowledge

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• ). Keywords: azine-fused helicenes; carbazole-based [6]helicenes; helical structures; Introduction [n]Helicenes are polycyclic aromatic molecules with nonplanar screw-shaped helical skeletons formed by n-ortho-fused benzene or other aromatic rings. Their helical structure is a consequence of the steric

Naphthalene diimide bis-guanidinio-carbonyl-pyrrole as a pH-switchable threading DNA intercalator

• Poulami Jana,
• Filip Šupljika,
• Carsten Schmuck and
• Ivo Piantanida

Beilstein J. Org. Chem. 2020, 16, 2201–2211, doi:10.3762/bjoc.16.185

• chiral properties of the DNA or RNA helical structures [12][13], could also take advantage of induced CD spectrum (ICD) in the visible spectrum range of small achiral dyes, which they show only upon binding to DNA/RNA [14]. Moreover, with recent advances in fluorescence emission-based polarisation

pH- and concentration-dependent supramolecular self-assembly of a naturally occurring octapeptide

• Goutam Ghosh and
• Gustavo Fernández

Beilstein J. Org. Chem. 2020, 16, 2017–2025, doi:10.3762/bjoc.16.168

• structures, which, upon dilution, transformed into helical structures and further to random coils. Such pH-responsiveness and concentration-dependent conformational changes may provide access to new potential peptide candidates for biomedical applications, which are currently underway in our laboratory

A hemicryptophane with a triple-stranded helical structure

• Augustin Long,
• Olivier Perraud,
• Erwann Jeanneau,
• Christophe Aronica,
• Jean-Pierre Dutasta and
• Alexandre Martinez

Beilstein J. Org. Chem. 2018, 14, 1885–1889, doi:10.3762/bjoc.14.162

• observed in solid state. NMR studies suggest that this propeller-like arrangement also occurs in solution. Further investigations are in progress in order to propagate the chirality of the CTV to even more remote opposite sites through the formation of such triple helical structures. 1H NMR spectrum of 1

Natural and redesigned wasp venom peptides with selective antitumoral activity

• Marcelo D. T. Torres,
• Gislaine P. Andrade,
• Roseli H. Sato,
• Cibele N. Pedron,
• Tania M. Manieri,
• Giselle Cerchiaro,
• Anderson O. Ribeiro,
• Cesar de la Fuente-Nunez and
• Vani X. Oliveira Jr.

Beilstein J. Org. Chem. 2018, 14, 1693–1703, doi:10.3762/bjoc.14.144

• ]. These peptides have similar characteristics such as a positive charge, amphipathic structure, defined secondary structures in hydrophobic environments, and rapid anticancer activity [12][19]. Helical structures are the most common structural motifs of ACPs. Their stable amphipathic structures tend to be

Oligonucleotide analogues with cationic backbone linkages

• Melissa Meng and
• Christian Ducho

Beilstein J. Org. Chem. 2018, 14, 1293–1308, doi:10.3762/bjoc.14.111

• retained base-pairing fidelity and improved cellular uptake have been reported for some oligonucleotides with structural similarity to Letsinger's first-generation aminoalkylated phosphoramidates. Bruice's guanidinium- and S-methylthiourea-linked systems have a pronounced tendency to form triple-helical

• structures with native nucleic acids, which makes a direct comparison with the other approaches difficult. Bruice's data suggest retained base-pairing fidelity for fully cationic oligomers, which is in remarkable contrast to our results obtained for NAA-modified oligonucleotides. The latter showed excellent

Opportunities and challenges for the sustainable production of structurally complex diterpenoids in recombinant microbial systems

• Katarina Kemper,
• Max Hirte,
• Markus Reinbold,
• Monika Fuchs and
• Thomas Brück

Beilstein J. Org. Chem. 2017, 13, 845–854, doi:10.3762/bjoc.13.85

• synthases (TPS) are classified into three groups which mainly comprise α-helical structures that are designated as α-, β- and γ-domains [45]. Structural and catalytic diversity, especially of plant terpene synthases, originate in various combinations of these domains [46]. The three groups of terpene

Interactions between cyclodextrins and cellular components: Towards greener medical applications?

• Loïc Leclercq

Beilstein J. Org. Chem. 2016, 12, 2644–2662, doi:10.3762/bjoc.12.261

• exert also a stabilizing effect by establishing H-bonds with the outer rim of the CD molecules. Interestingly, the extent of complexation depends significantly on the base composition and the double- or triple-helical structures. In contrast to native CDs, cationic CDs are known to interact strongly

End-group-functionalized poly(N,N-diethylacrylamide) via free-radical chain transfer polymerization: Influence of sulfur oxidation and cyclodextrin on self-organization and cloud points in water

• Sebastian Reinelt,
• Daniel Steinke and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 680–691, doi:10.3762/bjoc.10.61

• defined by J. M. Lehn in the 1970`s as “chemistry of the intermolecular bond” [1][2]. However, its origin goes back to Fisher`s “lock and key” model and also to Watson and Cricks description of the role of H-bonds in DNA double helical structures. Both examples represent the importance of non-covalent

Conformation of dehydropentapeptides containing four achiral amino acid residues – controlling the role of L-valine

• Michał Jewgiński,
• Joanna Krzciuk-Gula,
• Maciej Makowski,
• Rafał Latajka and
• Paweł Kafarski

Beilstein J. Org. Chem. 2014, 10, 660–666, doi:10.3762/bjoc.10.58

• and co-workers described that the insertion of an ester at the chiral residue of the dehydropeptide sequence induces left-handed helical structures. However, in the case of peptide 3, the analysis of the torsion angle values of the main chain clearly indicates that the insertion of one chiral L-Val

Synthesis of enantiomerically pure (2S,3S)-5,5,5-trifluoroisoleucine and (2R,3S)-5,5,5-trifluoro-allo-isoleucine

• Holger Erdbrink,
• Elisabeth K. Nyakatura,
• Susanne Huhmann,
• Ulla I. M. Gerling,
• Dieter Lentz,
• Beate Koksch and
• Constantin Czekelius

Beilstein J. Org. Chem. 2013, 9, 2009–2014, doi:10.3762/bjoc.9.236

• -helical structures, resulting in a helix propensity of zero [13]. Here, we show that if isoleucine’s δ-methyl group is substituted with CF3, the α-helix propensity of this amino acid is partially retained. Conclusion We synthesized two diastereoisomers of 5,5,5-trifluoroisoleucine ((2S,3S)-5-F3Ile and (2R

Partial thioamide scan on the lipopeptaibiotic trichogin GA IV. Effects on folding and bioactivity

• Marta De Zotti,
• Barbara Biondi,
• Cristina Peggion,
• Matteo De Poli,
• Haleh Fathi,
• Simona Oancea,
• Claudio Toniolo and
• Fernando Formaggio

Beilstein J. Org. Chem. 2012, 8, 1161–1171, doi:10.3762/bjoc.8.129

• the 18 lowest energy structures are listed in Table S-I, Supporting Information File 1). Due to heavily overlapped ROE signals, the helical structures originated from the MD calculations appear not to superimpose perfectly in correspondence with the first three residues of the sequence. Even with this

• experimental limit, the residues belonging to the central and C-terminal parts of the sequence showed values of torsion angles corresponding to those characteristic of right-handed helices (Table S-II, Supporting Information File 1). The helical structures are stabilized by intramolecular H-bonds throughout

Intramolecular bridges formed by photoswitchable click amino acids

• Christian Hoppmann,
• Ronald Kühne and
• Michael Beyermann

Beilstein J. Org. Chem. 2012, 8, 884–889, doi:10.3762/bjoc.8.100

• regulated by light, showing different biopotencies dependent on the trans/cis isomeric state of the photocontrollable bridge [6]. In the achievement of an efficient and “clean” thiol–ene click reaction between the vinyl function of PSCaa and the cysteine residue within α-helical structures, the spacing

• the cysteine S atom of the built-in photocontrollable bridge (Figure 1). The range of distances covered by the cis form was found to be between 4 and 11 Å, and between 10 and 14 Å by the trans form. Therefore, in α-helical structures the cis form of PSCaa is expected to be compatible with an i,i+4

• inefficient (Scheme 2). In contrast, in aqueous buffered solution, in which both peptides adopted no preferred conformation, the click products of either peptide 1 (i,i+4) or 2 (i,i+7) were obtained equally. These findings indicate that in α-helical structures, i,i+4 spacing of PSCaa and the cysteine residue