Unraveling the role of prenyl side-chain interactions in stabilizing the secondary carbocation in the biosynthesis of variexenol B

• Moe Nakano,
• Rintaro Gemma and
• Hajime Sato

Beilstein J. Org. Chem. 2023, 19, 1503–1510, doi:10.3762/bjoc.19.107

• presence of the cation–π interaction, the cation is delocalized, resulting in a decrease in cationicity at C10 and a corresponding increase in cationicity at C15. Note that the interconversion of TS_2a-3a to TS_2b-3b requires a significant conformational change, such as a 180 degree rotation of the iPr

Organic thermally activated delayed fluorescence material with strained benzoguanidine donor

• Alexander C. Brannan,
• Elvie F. P. Beaumont,
• Nguyen Le Phuoc,
• George F. S. Whitehead,
• Mikko Linnolahti and
• Alexander S. Romanov

Beilstein J. Org. Chem. 2023, 19, 1289–1298, doi:10.3762/bjoc.19.95

• Supporting Information File 1 for NMR). In DMSO-d6 solution, 4BGIPN isomers do not show interconversion even upon warming to 120 °C, resulting in a similar set of signals. Excellent fit between HRMS and elemental analysis further supports the formation of the isomeric mixture of 4BGIPN as evidenced by the

• benzonitrile acceptor core. We found that the material is formed as a mixture of the rotational isomers that do not experience interconversion upon heating the 4BGIPN solution in DMSO to 120 °C. Two rotational isomers were successfully crystallized to show different up and down orientations of the

The effect of dark states on the intersystem crossing and thermally activated delayed fluorescence of naphthalimide-phenothiazine dyads

• Liyuan Cao,
• Xi Liu,
• Xue Zhang,
• Jianzhang Zhao,
• Fabiao Yu and
• Yan Wan

Beilstein J. Org. Chem. 2023, 19, 1028–1046, doi:10.3762/bjoc.19.79

• -separated states 1CS and 3CS of these emitters are believed to undergo nonefficient slow interconversion, thus the poor rISC will not lead to efficient TADF. Later, a three-state model was proposed, i.e., the 1CS, 3CS, and a locally excited (3LE) state should be involved in the TADF process. The rISC is

Germacrene B – a central intermediate in sesquiterpene biosynthesis

• Houchao Xu and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 186–203, doi:10.3762/bjoc.19.18

• the 13C NMR spectrum [26] indicates that the interconversion between these conformers is a fast process at room temperature. This is in contrast to the findings for germacrene A (2) and hedycaryol (3) that show strong line broadening in the NMR spectra and multiple sets of peaks for different

• Sharpless epoxidation of its derivative 15-hydroxygermacrene (17) showed that this material was racemic, indicating a rapid interconversion between the enantiomers of 17. Consequently, also the enantiomers of 1 may undergo a fast interconversion [52]. The 1H and 13C NMR data of 1 have been reported [26

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• allowed the delivery of trans-decalin 85 in a gram-scale quantity. Birch reduction of the electron-rich aromatic ring, followed by propargylic addition and functional group interconversion (FGI) provided dienyne 86. Compound 86, under the previously developed radical reductive cyclization for 1,6-dienyne

Synthesis of bis-spirocyclic derivatives of 3-azabicyclo[3.1.0]hexane via cyclopropene cycloadditions to the stable azomethine ylide derived from Ruhemann's purple

• Alexander S. Filatov,
• Olesya V. Khoroshilova,
• Anna G. Larina,
• Vitali M. Boitsov and
• Alexander V. Stepakov

Beilstein J. Org. Chem. 2022, 18, 769–780, doi:10.3762/bjoc.18.77

• and TS-4'-exo associate with nitrogen invertomers 4'-endo and 4'-exo of cycloadduct 4', respectively. Next, we determined the Gibbs energy of activation for nitrogen inversion in cycloadducts 4 and 4' to figure out if the invertomers undergo rapid interconversion. Having carried out full geometry

• -exo = 2.1 kcal/mol, ΔG‡4'-exo->4'-endo = 0.2 kcal/mol, and ΔG‡4'-endo->4'-exo = 3.8 kcal/mol). Since rapid interconversion takes place, it does not matter via which transition state (ΤS-4-endo or ΤS-4-exo) cycloadduct 4 is formed. The same pattern is consistent with cycloadduct 4'. It should be

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• identified in two consecutive catalytic cycles. As a result, an astounding switchable catalytic system could be based on information processing (Figure 22). The following example of switchable catalysis involves the interconversion of the closed dimeric parallelogram [Cu2(104)2]2+ and the bishomoleptic

• 115 reclaims the proton back (Figure 25, top). As a result, State-II may be afforded under dissipative conditions. A surprising facet of this State-I/State-II interconversion (Figure 24) [112] was the finding that the protonated DABCO (60-H+) was a rather efficient base catalyst for a Knoevenagel

• -I/State-II interconversion in the presence of 116 and 117 was triggered by addition of the fuel acid. The traces in Figure 26 show the amount of Knoevenagel addition product 118 within two subsequent pulses of the fuel. In summary, the examples listed in this subchapter shed some light on the

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• ][38]. In the presence of oxygen, the reduced species is oxidized back to the quinone, thus completing the cycle. In case of naphthoquinones such as menadione, the quinone–semiquinone or quinone–hydroquinone interconversion generates reactive oxygen species (ROS), such as superoxide anion (O2

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• the art and science of selective molecular engineering [1]. To date, organic synthesis has largely been governed by the interconversion of pre-existing functional groups through the use of more traditional transition-metal-catalyzed cross-coupling reactions [2][3][4][5]. Although these reactions have

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

• diastereomers, i.e. cis/trans isomers or conformers with a high interconversion barrier. For complestatin-based macrocyclic peptides, the existence of biaryl atropisomers caused by the indole of tryptophan has been reported [82]. Recently, the occurrence of isomers was also observed in our group for SMC

• 1:44 at 300 K, with an interconversion barrier of 18.7 kcal mol−1 [83]. The experimental P5.1/P5.2 ratio is nearly 1:3, suggesting an energy difference of only 0.9 kcal mol−1 in favour of P5.2. Strain in the macrocycle might be responsible for such slight decrease in the relative energy between the

• hopeless to expect catching energy differences as small as that between P5.1/P5.2 by molecular modelling. Instead, we discuss qualitatively the conformational properties of the macrocycle in the two diastereomers of P5 to determine if conformers may exist with high interconversion barriers, and suggest an

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

• at C-2 but advantageous for the crystallization process. A number of bases was also evaluated by this research group: pyridine gave only a small amount of interconversion, whereas TEA caused rapid interconversion. Furthermore, it was discovered that instant interconversion and crystallization of 56a

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• interconversion of natural products prekinamycin (76) and isoprekinamycin (77) and chemical models of their proposed α-ketol intermediates. a) The natural products are believed to interconvert biologically by a reversible sequence of hydration–rearrangement–dehydration. b) α-Ketol rearrangement of 80, an analogue

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

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

• diverse diseases, such as inflammation, tumor, silicosis, and various lysosomal storage diseases [61][62][63]. Therefore, closely monitoring/visualizing of the lysosomes acidic environment is required to study lysosome-related diseases. Spiropyran (SP) undergoes pH-induced interconversion among protonated

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• (SelfSORT-II). Such type of transmetalation in metal–NHC complexes with a retention of the individual homomeric supramolecular assemblies has not been reported in literature. Recently, a quantitative and reversible structural interconversion of supramolecular structures was achieved by the inclusion and

• transformation of one nanodevice into another [57], for instance, in the reversible interconversion of nanosliders within six and seven-component networks. Upon the addition of three equiv of zinc(II) ions to three equiv of the nanoswitch [Cu(25)]+ (Figure 11b), the equivalent amount of copper(I) was released

• requires a design with a cyclic interconversion of the involved supramolecular architectures. In this respect, the quantitative and reversible cyclic transformation of three metallosupramolecular architectures (Figure 17), i.e., square [Cu4(62)4]4+, triangle [Cu3(62)2(63)]3+, and rectangle [Cu4(62)2(63)2]4

Synthesis of purines and adenines containing the hexafluoroisopropyl group

• Viacheslav Petrov,
• Rebecca J. Dooley,
• Alexander A. Marchione,
• Elizabeth L. Diaz,
• Brittany S. Clem and
• William Marshall

Beilstein J. Org. Chem. 2020, 16, 2739–2748, doi:10.3762/bjoc.16.224

• as a function of the temperature, which enabled an extrapolation of the population differences at an elevated temperature (via the van ‘t Hoff equation). The latter experiments provided information directly on the kinetics of the interconversion between the sites. A series of spectra were then

• acquired at elevated temperature; here, the kinetics of the interconversion between the sites could be derived directly from the linewidth. Figure 3 illustrates the spectra acquired over a range of temperatures using compound 3a as an example. With the rate constants of the interconversion between the

• referenced to internal tetramethylsilane or trichlorofluoromethane. The spectra were acquired at 298 K. Dynamic NMR experiments The dynamics of rotamer interconversion were studied on a Bruker AVIIIHD spectrometer with a 9.4 T magnetic field, equipped with a 10 mm F{H} probe suitable for high- and low

Leveraging glycomics data in glycoprotein 3D structure validation with Privateer

• Haroldas Bagdonas,
• Daniel Ungar and
• Jon Agirre

Beilstein J. Org. Chem. 2020, 16, 2523–2533, doi:10.3762/bjoc.16.204

• intermediate interconversion library. A foundation for such interconversion libraries exists in the form of the carbohydrate validation software Privateer. The program is able to compute individual monosaccharide conformations from a glycoprotein model, check whether the modelled carbohydrates atomistic

NMR Spectroscopy of supramolecular chemistry on protein surfaces

• Peter Bayer,
• Anja Matena and
• Christine Beuck

Beilstein J. Org. Chem. 2020, 16, 2505–2522, doi:10.3762/bjoc.16.203

• a direct measure of the fraction bound and can be used directly to determine the dissociation constant (KD), provided sufficient saturation can be reached [83]. Line broadening occurs due to chemical exchange, that is the interconversion of at least two species in an equilibrium, e.g., the free and

• biomolecules with KDs in the µM range fall, the line shape and signal intensity do not directly correlate with fraction bound. It is possible to extract the kinetic interconversion rates from a full line shape analysis. The KD can then be calculated from the ratio of the on and off rate (KD = koff/kon

Rearrangement of o-(pivaloylaminomethyl)benzaldehydes: an experimental and computational study

• Csilla Hargitai,
• Györgyi Koványi-Lax,
• Tamás Nagy,
• Péter Ábrányi-Balogh,
• András Dancsó,
• Gábor Tóth,
• Judit Halász,
• Angéla Pandur,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2020, 16, 1636–1648, doi:10.3762/bjoc.16.136

• interconversion of these conformers is slow in the NMR time-scale. Although the NMR spectra have been measured in CDCl3, we are convinced that the conformations observed in CDCl3 are in good accordance with the ones computed considering the implicit solvent effect of DCM. Based on the structural similarity, the

One-step route to tricyclic fused 1,2,3,4-tetrahydroisoquinoline systems via the Castagnoli–Cushman protocol

• Aleksandar Pashev,
• Nikola Burdzhiev and
• Elena Stanoeva

Beilstein J. Org. Chem. 2020, 16, 1456–1464, doi:10.3762/bjoc.16.121

• should be noted that due to the planar amide fragment the interconversion of the different conformers could be largely suppressed. The X-ray analysis of the above-mentioned (−)-trans-22 [35] and trans-1-ethylbenzo[a]quinolizin-4-ones [40] showed a distortion of the B and C rings, while the substituent at

Synthesis and anticancer activity of bis(2-arylimidazo[1,2-a]pyridin-3-yl) selenides and diselenides: the copper-catalyzed tandem C–H selenation of 2-arylimidazo[1,2-a]pyridine with selenium

• Mio Matsumura,
• Tsutomu Takahashi,
• Hikari Yamauchi,
• Shunsuke Sakuma,
• Yukako Hayashi,
• Tadashi Hyodo,
• Tohru Obata,
• Kentaro Yamaguchi,
• Yasuyuki Fujiwara and
• Shuji Yasuike

Beilstein J. Org. Chem. 2020, 16, 1075–1083, doi:10.3762/bjoc.16.94

• ). The interconversion of the diselenide 2 and the selenide 3 is also possibility in this reaction, with the expected mechanism shown in Scheme 3. The oxidative addition of the copper catalyst to the diselenide 2 generates the intermediate E, which is then attacked by an imidazopyridine 1 at the 3

Chemical synthesis of tripeptide thioesters for the biotechnological incorporation into the myxobacterial secondary metabolite argyrin via mutasynthesis

• David C. B. Siebert,
• Roman Sommer,
• Domen Pogorevc,
• Michael Hoffmann,
• Silke C. Wenzel,
• Rolf Müller and
• Alexander Titz

Beilstein J. Org. Chem. 2019, 15, 2922–2929, doi:10.3762/bjoc.15.286

• performed following solution phase Boc-protected peptide coupling and functional group interconversion (Scheme 1). The central alanine carrying nonnatural derivatives were sequentially synthesized from C- to N-terminus, using ester protected glycine or sarcosine and coupling to Boc-protected ᴅ- or ʟ-alanine

A chiral self-sorting photoresponsive coordination cage based on overcrowded alkenes

• Constantin Stuckhardt,
• Diederik Roke,
• Wojciech Danowski,
• Edwin Otten,
• Sander J. Wezenberg and
• Ben L. Feringa

Beilstein J. Org. Chem. 2019, 15, 2767–2773, doi:10.3762/bjoc.15.268

• supramolecular coordination complexes consisting of a Pd2L4 stoichiometry. As shown by NMR, CD and X-ray studies, as well as DFT calculations, these complexes form cage-like structures by chiral self-sorting. Photochromic ligands derived from first generation molecular motors enable light-driven interconversion

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• developed an electrochemical approach for a Sharpless asymmetric dihydrohydroxylation of alkenes using an osmium complex [63]. In this protocol, the traditional chemical oxidant was replaced by an anode that regenerates [FeCN)6]3− via an Os(VIII) to Os(VI) interconversion. Similarly, Torri and co-workers

Acid-catalyzed rearrangements in arenes: interconversions in the quaterphenyl series

• Sarah L. Skraba-Joiner,
• Carter J. Holt and
• Richard P. Johnson

Beilstein J. Org. Chem. 2019, 15, 2655–2663, doi:10.3762/bjoc.15.258

• [20][21]. One classic example of arenium ion chemistry is the interconversion of terphenyl isomers 1–3 (Scheme 1). This rearrangement was first reported by Allen and Pingert in 1942 [22] and then independently rediscovered by Olah and Meyer twenty years later [23]. Interconversion of isomers 1–3 is

• facile acid-catalyzed interconversion, as well as the fact that m-terphenyl (2) is favored at equilibrium (observed ratio 1:2:3 is <1:69:31) and used theory to explain this product selectivity [25]. This preference is consistent with formation of the most stable arenium ion intermediate, as shown by DFT

• extended polyphenyls but the factors controlling interconversion of isomers are poorly understood [30][31][32][33]. As one recent example, Jasti and co-workers showed that cycloparaphenylenes undergo rapid acid-catalyzed rearrangement which precludes using Scholl-type chemistry in this series [30]. In the

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

• Andrey G. Lvov,
• Max Mörtel,
• Anton V. Yadykov,
• Frank W. Heinemann,
• Valerii Z. Shirinian and
• Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

• for realization of light-triggered guest uptake/release [52] and light-controlled interconversion between distinct supramolecular assemblies [53]. Ligand 6 featuring two coordination sites in the heteroaryl moiety and bridge provides unique opportunities to construct novel macrocyclic systems. Our