Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• by a distortion of polynucleotide helicity upon addition of Phen-Py-1, or this change was a result of uniform orientation of the dye with respect to DNA chiral axis. Binding of Phen-Py-1 to enzyme dipeptidyl peptidase III in an aqueous medium Binding of Phen-Py-1 to dipeptidyl peptidase (DPPIII

• spectra could be caused both by a decrease in DNA helicity or by the uniform orientation of the dye concerning the chiral axis. Dye Phen-Py-1 bound to dipeptidyl peptidase (DPPIII) enzyme mutant E451A with high affinity and showed an interesting spectroscopic response: the excimer emission was totally

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

• ], tert-butyl/α,α-gem-dimethyl [29], or fluorinated groups [30] will preferentially form cis-amides (Figure 1A). Peptoid helicity modulation has also been investigated through specific placement of chiral and achiral monomers [31][32]. Comparatively fewer N-functional monomers capable of promoting trans

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• rotaxanes, the helicity is predetermined by the planar chirality (based on the underlying macrocycle–macrocycle interactions), so that only two diastereoisomers remain for a given BINOL configuration (e.g., (R)-(Rp) and (R)-(Sp) in case of (R)-BINOL). In contrast to the axial chirality of the BINOL unit

• unit on the helicity of the polyacetylene was investigated by CD spectroscopy. Here, no chiral induction was observed for the ammonium species 32, while the N-acylated polymers 33 showed clear Cotton effects in the absorption range of the polymer main chain (490 nm), demonstrating an effective

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

• –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

• ], disulfide- [13], thioether- [14][15][16][17][18][19][20], triazole- [21][22], oxime- [23] and hydrazone formation [24] as well as multicomponent reactions such as the Ugi- or Petasis reaction [25][26][27][28][29][30][31][32]. The content of helicity can moreover be changed by the introduction of a photo

• the group of Verdine and evaluation of optimised staple positions at amino acids 471 (i) and 475 (i + 4) resulted in enhanced helicity and binding affinity to β-catenin, e.g., for peptide StAx-3 [77]. Following the StAx-3 peptide, we designed peptides including bromotryptophan in i-position and an

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

• data given in Table 6, it can be seen that the interplanar angle between the terminal rings A and F of the pyridine-fused [6]helicene 10c is the largest in the series (average value is 62°). The same value for [6]helicene 12 is equal to 56.7° [42]. The helicity of pyrazine-fused [6]helicene 10b and

• -phenanthro[3,4-c]carbazole). The interplanar angle between the two terminal benzene rings of the latter is equal to 56.7°, whereas the same value for the pyridine-fused analog is 62°. The pyrazine-fused [6]helicene demonstrates intermediate helicity (52.8°). In the case of the quinoxaline-fused analog the

Hierarchically assembled helicates as reaction platform – from stoichiometric Diels–Alder reactions to enamine catalysis

• David Van Craen,
• Jenny Begall,
• Johannes Großkurth,
• Leonard Himmel,
• Oliver Linnenberg,
• Elisabeth Isaak and
• Markus Albrecht

Beilstein J. Org. Chem. 2020, 16, 2338–2345, doi:10.3762/bjoc.16.195

• auxiliary, Lewis acid or catalyst. In the previously reported system two different induction pathways were conceivable: (1) A chiral ligand is located close to the diene and controls the stereochemistry of the cycloaddition. (2) The chiral ligand controls the helicity of the helicate (ΔΔ or ΛΛ) and the

• helix induces the stereoselectivity of the Diels–Alder reaction. To find out which of the induction pathways takes over the control of the Diels–Alder reaction in the periphery of the helicates, a specific helicity was induced at an achiral diene bearing helicate. It has been described before that an

• addition of chiral ammonium salts leads to the preference of a specific twist at the helicate [32]. As inductor, (R)-1-phenylethylammonium chloride was added to the racemic hexadiene-substituted helicate [Li3(1)6Ti2]−. The chiral salt influences the helicity of the monomeric complexes and which dimerize to

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• endocyclic CH2 moiety yielded a pair of very broad peaks at ca. 4.8–3.4 ppm. This splitting, which was also observed for cNDA2O, is consistent with slow inversion of helicity occurring at the ethylene bridge. In the 1H NMR spectrum of cNMI2H, the linker CH2 moiety and the 2,6-diisopropylphenyl (dipp) CH unit

• spectrum is additionally complicated by the partially restricted rotation of the N,N-dimethylamide substituents in the NDA units. In conjunction with the helicity of the ring system, this restriction leads to effective diastereomerism. The three-dimensional structures of all boomerangs were modeled using

Pigmentosins from Gibellula sp. as antibiofilm agents and a new glycosylated asperfuran from Cordyceps javanica

• Soleiman E. Helaly,
• Wilawan Kuephadungphan,
• Patima Phainuphong,
• Mahmoud A. A. Ibrahim,
• Kanoksri Tasanathai,
• Suchada Mongkolsamrit,
• Janet Jennifer Luangsa-ard,
• Souwalak Phongpaichit,
• Vatcharin Rukachaisirikul and
• Marc Stadler

Beilstein J. Org. Chem. 2019, 15, 2968–2981, doi:10.3762/bjoc.15.293

• effects: a first negative at 274 nm (Δε −196) and a positive second one at 252 nm (Δε +203), indicating the helicity of the 6-6′ axis as aR, according to the exciton chirality method [13]. Furthermore, the TDDFT-ECD calculations were performed on three isomers, namely (3R,3′R,6R)-1, (3S,3′S,6S)-1, and (3S

• effect at 271 nm (Δε −155) and a positive second one at 254 nm (Δε +139) indicated the helicity of the 6-6′ axis to be aR. This was also confirmed by comparison of the experimental with TDDFT-calculated ECD spectra of (3′R,3S,6R,12R)-2 and (3′S,3R,6S,12S)-2 (Figure 2). The calculated ECD data for (3′R,3S

α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• compounds transparent in the UV–vis region. In solution, chirality of diols is transfered to the newly in situ-formed complexes. The signs of Cotton effects (CEs) observed in their spectra undergo the helicity rule linking the positive/negative sign of CE at about 300–400 nm with positive/negative sign of O

Chiral bisoxazoline ligands designed to stabilize bimetallic complexes

• Deepankar Das,
• Rudrajit Mal,
• Nisha Mittal,
• Zhengbo Zhu,
• Thomas J. Emge and
• Daniel Seidel

Beilstein J. Org. Chem. 2018, 14, 2002–2011, doi:10.3762/bjoc.14.175

• backbone of complex 16·Ni2(OAc)2 shows a helical arrangement. This helicity is facilitated by the innate stereogenic centers of the oxazoline moieties which is further extended by the flexibility afforded by the amide connections. Naphthyridine ligand 22-H2 was designed as an analogue of ligand 16-H2 that

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

• the molecule (Figure 2). This also underlines how the chirality of the CTV unit propagates along the linkers to induce the propeller shape of the three aromatic rings in the south part of the hemicryptophane. This remote control of the helicity of the southern part by that of the northern CTV unit

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

• Xiang Li,
• Pinhong Chen and
• Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

• engages in double hydrogen bonding to form an 11-membered ring, resulting in the chiral helicity. The helical chirality induced in iodine(III) derivatives of 23 bearing the bislactamide motif was described for 27 with an efficient differentiation of the enantiotopic faces of the styrene substrate. This

Defining the hydrophobic interactions that drive competence stimulating peptide (CSP)-ComD binding in Streptococcus pneumoniae

• Bimal Koirala,
• Robert A. Hillman,
• Erin K. Tiwold,
• Michael A. Bertucci and
• Yftah Tal-Gan

Beilstein J. Org. Chem. 2018, 14, 1769–1777, doi:10.3762/bjoc.14.151

• side-chain residues compared to truncated side-chains or those that introduce electrostatic effects. Finally, our results further correlated helicity with bioactivity. Combined, the results of this study can be used to design novel CSP-based QS modulators with improved pharmacological properties that

• maintain helicity (see Structural Analysis below) and effectively interact with the binding pocket. Thus, pending no unexpected enhancement from isosteric substitutions (e.g., pyridylalanine, cyclohexylalanine, etc.), they are likely not ideal positions for further optimization. With regards to the ComD2

• similar trends (Table S2, Supporting Information File 1). Importantly, the two analogs that exhibited the lowest percent helicity, CSP1-F8FG and CSP1-F11FG, were the least active analogs against the ComD1 receptor (Table 1), supporting the hypothesis that an α-helix is required for effective ComD1 binding

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

• membranes increased significantly when treated with lead peptides compared to controls. Biophysical features such as helicity, hydrophobicity, and net positive charge were identified to play an important role in the anticancer activity of the peptides. Indeed, abrupt changes in peptide hydrophobicity and

Polarization spectroscopy methods in the determination of interactions of small molecules with nucleic acids – tutorial

• Tamara Šmidlehner,
• Ivo Piantanida and
• Gennaro Pescitelli

Beilstein J. Org. Chem. 2018, 14, 84–105, doi:10.3762/bjoc.14.5

• the polynucleotide. In special cases of poorly organized ss-polynucleotides, the intensity of the polynucleotide ECD bands may significantly increase while preserving the ECD band fingerprint. If so, one can presume a strong increase of polynucleotide helicity [27]. 3.3.2. Wavelength range > 300 nm

Remarkable functions of sn-3 hydroxy and phosphocholine groups in 1,2-diacyl-sn-glycerolipids to induce clockwise (+)-helicity around the 1,2-diacyl moiety: Evidence from conformation analysis by ¹H NMR spectroscopy

• Yoshihiro Nishida,
• Mengfei Yuan,
• Kazuo Fukuda,
• Kaito Fujisawa,
• Hirofumi Dohi and
• Hirotaka Uzawa

Beilstein J. Org. Chem. 2017, 13, 1999–2009, doi:10.3762/bjoc.13.196

• , namely gt(+), gg(−) and tg, were randomized, while in more polar solvents, the gt(+) conformer with (+)-helicity was amplified at the expense of gg(−) and tg conformers. The sn-3 phosphocholine in phosphatidylcholine exhibited a greater effect on the gt(+) conformer, which was independent of the solvents

• ; deuterium labeling; sn-glycerol; glycerolipids; glycerophospholipids; helicity; Karplus equation; proton NMR spectroscopy; staggered conformers; Introduction Glycerophospholipids, constituting the basic elements of cytoplasm bilayer membranes, are responsible for several cell functions [1][2][3]. These

• conformational properties of a series of 1,2-dibenzoyl-sn-glycerols bearing different sn-3 substituting groups were examined. As shown in Figure 1, gt(+) is one of the gauche conformers with a right-handed (+)-helicity around 1,2-diol, while gg(−) is another gauche conformer with an antipodal left-handed

Aggregation behaviour of a single-chain, phenylene-modified bolalipid and its miscibility with classical phospholipids

• Simon Drescher,
• Vasil M. Garamus,
• Christopher J. Garvey,
• Annette Meister and
• Alfred Blume

Beilstein J. Org. Chem. 2017, 13, 995–1007, doi:10.3762/bjoc.13.99

• side by side within the fibrous aggregate but slightly twisted relative to each other leading to a helical super structure of the fibres. This helicity was previously confirmed by cryo-transmission electron microscopy (cryo-TEM), high resolution atomic force microscopy (AFM) [26], and Monte Carlo

Biomimetic synthesis and HPLC–ECD analysis of the isomers of dracocephins A and B

• Viktor Ilkei,
• András Spaits,
• Anita Prechl,
• Áron Szigetvári,
• Zoltán Béni,
• Miklós Dékány,
• Csaba Szántay Jr,
• Judit Müller,
• Árpád Könczöl,
• Ádám Szappanos,
• Attila Mándi,
• Sándor Antus,
• Ana Martins,
• Attila Hunyadi,
• György Tibor Balogh,
• György Kalaus (†),
• Hedvig Bölcskei,
• László Hazai and
• Tibor Kurtán

Beilstein J. Org. Chem. 2016, 12, 2523–2534, doi:10.3762/bjoc.12.247

• , whose negative 327 nm n–π* Cotton effect (CE) and the positive 289 nm π–π* CE were correlated with M helicity of the fused hetero ring and (2R) absolute configuration [8][9]. The mirror image HPLC–ECD spectra of (R)- and (S)-naringenin were recorded after separating the enantiomers on a Chiralpack IA

• - and 4’-OH protons and the condensed hetero ring had M helicity with envelope conformation and C-2 pointing out of the plane (ωC-8a,O-1,C-2,C-3 = −51.6°, ωC-8a,C-4a,C-4,C-3 = 0.4° for the lowest-energy conformer). The C-2 aryl group was nearly coplanar with the C-2–H-2 bond and the ωH-2,C-2,C-1’,C-2

• groups anchored the orientation of the pyrrolidinone moiety. The two conformers differed in the orientation of the two 4’-OH and the C-2 aryl moiety adopted equatorial orientation with M helicity and envelope conformation of the condensed heteroring. The calculated Boltzmann-averaged ECD spectra of (2R,5

Varioloid A, a new indolyl-6,10b-dihydro-5aH-[1]benzofuro[2,3-b]indole derivative from the marine alga-derived endophytic fungus Paecilomyces variotii EN-291

• Peng Zhang,
• Xiao-Ming Li,
• Xin-Xin Mao,
• Attila Mándi,
• Tibor Kurtán and
• Bin-Gui Wang

Beilstein J. Org. Chem. 2016, 12, 2012–2018, doi:10.3762/bjoc.12.188

• of the C-13 indol and dihydro-5aH-[1]benzofuro [2,3-b]indole moieties. The different biaryl torsional angles produced markedly different computed ECD spectra for the conformers having M and P helicity such as the two lowest-energy computed B3LYP/6-31G(d) conformers (Figure 4). The two high-wavelength

• order to explore the possibility of axial chirality, torsional angle scans were performed on the lowest-energy M (conformer A) and P (conformer B) helicity gas-phase conformers or atropodiastereomers. Rotational energy barriers between the two isomers were estimated to be ca. 35–42 kJ/mol for TS1 (ωC12

• showed that there is no axial chirality in 1, and equilibrating conformers with M and P helicity are present in solution as obtained in the conformational analysis. The Boltzmann-weighted ECD spectra calculated for both the gas-phase and the solvent model conformers of (2R,3R)-1 at B3LYP/TZVP, BH&HLYP

Supramolecular chemistry: from aromatic foldamers to solution-phase supramolecular organic frameworks

• Zhan-Ting Li

Beilstein J. Org. Chem. 2015, 11, 2057–2071, doi:10.3762/bjoc.11.222

• diameter of approximately 0.8 nm. Thus, 21 complexed alkylated saccharide derivatives and a guest with three hydroxyl groups in chloroform. The binding also induced the backbone of 21 to produce helicity bias [38]. The methoxy groups of 22a–c are all located inwards. These oxygen atoms are potential

• and aliphatic ammonium and, at high concentrations in chloroform, a chiral aliphatic ammonium induced 23 to produce helicity bias. One important difference between fluorine and alkoxy groups is that fluorine does not cause a steric effect on aromatic stacking. Zeng and co-workers demonstrated this

Star-shaped tetrathiafulvalene oligomers towards the construction of conducting supramolecular assembly

• Masahiko Iyoda and
• Masashi Hasegawa

Beilstein J. Org. Chem. 2015, 11, 1596–1613, doi:10.3762/bjoc.11.175

• ]. The three TTF units with chiral citronellyl and dihydrocitronellyl chains led to helical one-dimensional stacks in solution to produce fibers that have morphologies depending on the nature of the chiral alkyl group, although an achiral counterpart showed no helicity. C3-symmetric truxene-TTFs 7a–c

Synthesis of a sucrose dimer with enone tether; a study on its functionalization

• Zbigniew Pakulski,
• Norbert Gajda,
• Magdalena Jawiczuk,
• Jadwiga Frelek,
• Piotr Cmoch and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2014, 10, 1246–1254, doi:10.3762/bjoc.10.124

• mixed with a chiral diol ligand forms complexes active in ECD in which a transfer of ligand chirality to the in situ-formed complex occurs in solution. Thus, stereochemistry of vic-diols can be easily assigned based on the helicity rule developed for this class of compounds. This rule correlates the

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

• the K-4’-F3Ile spectrum demonstrates a complete loss of helicity in the corresponding peptide (Figure 2). The drastic decrease in helix propensity upon fluorination has been previously attributed to a possible burial of fluorocarbon side chains in the unfolded state of the model peptide [8]. The

• to a reduced α-helicity in comparison to its unbranched analogue ([ω]Leu= 1.06 [8]). This effect is amplified for K-4’-F3Ile which carries the voluminous CF3 group on its β-carbon atom. The close proximity of this sterically demanding group to the peptide backbone seems to prevent the formation of α

Molecular assembly of amino acid interlinked, topologically symmetric, π-complementary donor–acceptor–donor triads

• M. B. Avinash,
• K. V. Sandeepa and
• T. Govindaraju

Beilstein J. Org. Chem. 2013, 9, 1565–1571, doi:10.3762/bjoc.9.178

• excitonic cotton effects (Figure 3c–f). In DMSO, 2 (Figure 3c) and 3 (Figure 3e) exhibit a weak CD signal above 350 nm suggesting minimal excitonic coupling of NDI chromophores. However, CD studies for 2 (Figure 3d) and 3 (Figure 3f) in NMP show positive excitonic cotton effects indicating P-type helicity