Activity assays of NnlA homologs suggest the natural product N-nitroglycine is degraded by diverse bacteria

• Kara A. Strickland,
• Brenda Martinez Rodriguez,
• Ashley A. Holland,
• Shelby Wagner,
• Michelle Luna-Alva,
• David E. Graham and
• Jonathan D. Caranto

Beilstein J. Org. Chem. 2024, 20, 830–840, doi:10.3762/bjoc.20.75

• voltage of 4,500 V and a fragmentation voltage of 175 V. To monitor NNG, 2-NAE, and glyoxylate, extracted ion chromatograms were obtained at m/z 119.0, 105.0, and 73.0, respectively. Ammonium concentrations were determined using a glutamate dehydrogenase assay (Sigma-Aldrich) kit using the manufacturer’s

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• more efficient reactions with alkene 88 (Table 6). In 2022, Oestreich reported the in situ formation of HCl by Lewis acid-induced Grob fragmentation of acid chloride 92 (Scheme 15B) [68]. The inconvenience of this method is that 92 has to be prepared in two steps, including a Birch reduction (Scheme

• ) could be prevented when switching to BCl3 (10 mol %). Interestingly, toluene (94), which is generated as a byproduct of the Grob fragmentation, must react more sluggishly with the generated cationic intermediates compared to chloride, as no alkylations of toluene were reported. In 2017, the Snyder group

• hydride shifts. Regioisomeric mixtures of products as a result of methyl shifts. Applications of the Kropp procedure on a preparative scale. Curious example of polar anti-Markovnikov hydrochlorination. Unexpected and expected hydrochlorinations with AlCl3. HCl generated by Grob fragmentation of 92

New variochelins from soil-isolated Variovorax sp. H002

• Jabal Rahmat Haedar,
• Aya Yoshimura and
• Toshiyuki Wakimoto

Beilstein J. Org. Chem. 2024, 20, 692–700, doi:10.3762/bjoc.20.63

• the planar structure of 1 is consistent with the known siderophore variochelin A, originally reported from V. boronicumulans BAM-48 by Nett et al. [5]. The NMR spectra of 2 are superimposable on those of 1. However, the MS/MS of 2 differs in the fragmentation ion corresponding to a 4-acylamino-7

• C45H79O17N11, as suggested by the HRESIMS data (m/z 1044.5603 for the [M − H]− ion), indicating the loss of two methylene groups (C2H4) from 1. In addition, the MS/MS fragmentation profile of 3 was consistent with those of 1 and 2, except for the loss of 28 mass units in the N-terminal Nγ-acyl-γ-amino acid

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• many applications as radical precursors. Mechanistically, NHPI esters undergo a reductive decarboxylative fragmentation to provide a substrate radical capable of engaging in diverse transformations. Their reduction via single-electron transfer (SET) can occur under thermal, photochemical, or

• fragmentation of 8 affords a radical species 9 in a constructive step towards initiating the radical reaction, a principal competing step is back-electron transfer (BET) to return the closed shell starting materials (Scheme 2B). A recent study showed comparable rates for fragmentation (8 ± 5 × 105 s−1) and BET

• (3.15 to 2.06 × 105 s−1) [34] when employing catalytic IrIII excited state reductants with moderate reducing potentials (E1/2red[IrIV/*IrIII] ≈ −1.13 V vs Fc0/Fc+ in MeCN) [35]. This suggests that in the absence of a sufficiently strong driving force, BET and fragmentation compete to influence the

Substituent-controlled construction of A₄B₂-hexaphyrins and A₃B-porphyrins: a mechanistic evaluation

• Seda Cinar,
• Dilek Isik Tasgin and
• Canan Unaleroglu

Beilstein J. Org. Chem. 2023, 19, 1832–1840, doi:10.3762/bjoc.19.135

• intermediates gives azafulvene-ended secondary intermediates III, V, and VI. The observed intermediates I–VI having sulfonamide or azafulvene ends are in accordance with our previous findings [26][35][36]. In addition, the observation of azafulvene I could be attributed to the fragmentation of tripyrrane 1

GlAIcomics: a deep neural network classifier for spectroscopy-augmented mass spectrometric glycans data

• Thomas Barillot,
• Baptiste Schindler,
• Baptiste Moge,
• Elisa Fadda,
• Franck Lépine and
• Isabelle Compagnon

Beilstein J. Org. Chem. 2023, 19, 1825–1831, doi:10.3762/bjoc.19.134

• wavelength-dependent laser-induced fragmentation yield. When the frequency of the laser is resonant with a vibrational mode of the molecule, the molecule absorbs the radiation and accumulates internal energy until fragmentation [13]. In previous works we have demonstrated that the monosaccharides or

• oligosaccharides resulting from the fragmentation of a larger precursor possess a very specific IR fingerprint in the 2–4 microns spectral range, that is highly valuable to resolve all types of isomers [4]. Typical experimental IR fingerprint data are shown in Figure 1: they feature the intensities of the

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• [59][60]. 1.3.3 Deactivation by degenerative transfer: Reversible addition-fragmentation chain transfer (RAFT) polymerization is one of the most well-established RDRP technique. It was first proposed in 1998 by Commonwealth Scientific and Industrial Research Organization (CSIRO) researchers Chiefari

α-(Aminomethyl)acrylates as acceptors in radical–polar crossover 1,4-additions of dialkylzincs: insights into enolate formation and trapping

• Angel Palillero-Cisneros,
• Paola G. Gordillo-Guerra,
• Fernando García-Alvarez,
• Olivier Jackowski,
• Franck Ferreira,
• Fabrice Chemla,
• Joel L. Terán and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2023, 19, 1443–1451, doi:10.3762/bjoc.19.103

• atom to zinc enables this SH2 process which represents a rare example of alkylzinc-group transfer to a tertiary α-carbonyl radical. The zinc enolate thus formed readily undergoes β-fragmentation unless it is trapped by electrophiles in situ. Enolates of substrates having free N–H bonds undergo

• without subsequent fragmentation was observed starting from α-(aminomethyl)acrylates having free N–H bonds (Table 2). The reaction of Et2Zn with acrylates 5–7 afforded the desired 1,4-addition products 11–13 in 42–55% yield. Better results were obtained starting from 8a, which delivered adduct 14a in 79

• neither in the β-fragmentation (Scheme 4) nor in the addition across the carbonyl bonds. Overall, the mechanistic investigations support the scenario depicted in Scheme 9. Oxygen (in air) triggers a free-radical chain reaction between α-(aminomethyl)acrylates and dialkylzinc reagents that entails 1,4

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• electrogeneration favor a preassembly with Ar−X that i) upon photoexcitation accesses excited states higher than the first (D1) to bolster reactivity and/or ii) following PET assists in the Ar−X•− fragmentation step. The scope was expanded using triethylphosphite (P(OEt)3), dimethyl disulfide (MeSSMe) and bis

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• radical addition–fragmentation on the latter and most likely to shift the regioselectivity towards 6-exo-trig by a favorable interplay of polar effects [99] failed and furnished only the 1,3-diene 10. Unfortunately, when substrate 10 was subjected to the reaction conditions shown above, only tarry

Eschenmoser coupling reactions starting from primary thioamides. When do they work and when not?

• Lukáš Marek,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2023, 19, 808–819, doi:10.3762/bjoc.19.61

• detected by ESI–MS analysis of the reaction mixture as it has a different fragmentation pattern (easily loses water – see Supporting Information File 1, Figure S1) than the starting isobaric salt 6a (loses benzonitrile and thiobenzamide). However, all attempts to isolate intermediate 7a have always failed

Direct C2–H alkylation of indoles driven by the photochemical activity of halogen-bonded complexes

• Martina Mamone,
• Giuseppe Gentile,
• Jacopo Dosso,
• Maurizio Prato and
• Giacomo Filippini

Beilstein J. Org. Chem. 2023, 19, 575–581, doi:10.3762/bjoc.19.42

• -electron-transfer (BET), a suitable leaving group (LG) needs to be included in one of the precursors. In this manner, reactive intermediates (e.g., radical species) may be generated in solution through the irreversible fragmentation of the substrates [15][21][22]. These intermediates eventually react to

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• Criegee- or a Grob-type fragmentation to generate cyclooctadione 163. Pleuromutilin (1) was then accessed in 4 additional steps (Scheme 32). 4.5 Reductive radical cascade cyclization: toward total synthesis of (−)-6-epi-ophiobolin N (168) and (+)-6-epi-ophiobolin A (173) Despite indisputable success of

Investigation of cationic ring-opening polymerization of 2-oxazolines in the “green” solvent dihydrolevoglucosenone

• Solomiia Borova and
• Robert Luxenhofer

Beilstein J. Org. Chem. 2023, 19, 217–230, doi:10.3762/bjoc.19.21

• distributions (ε) and (δ) of low intensity can be attributed to a methyl-initiated and proton-initiated PEtOx formed after termination at position C2 with the final fragmentation of the formed ester group during the MALDI-TOF MS assay carrying Na+ and H+ ions, respectively. It is well known that water and

• + (δ) ion doping could also be observed (Figure S10 in Supporting Information File 1). It is important to note that fragmentation during analysis cannot be excluded. The SEC traces of the resulting PEtOx after initiation with BnBr show monomodality and a relatively broad molar mass distribution (Ð

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• reverse (3 + 2) cycloaddition which expels a heteroatomic anion via a β-elimination-type mechanism somewhat similar to a classical Grob-type fragmentation. Similarly, 1,3-dithiolanes undergo fragmentation at relatively low reaction temperatures, limiting their synthetic application to alkylation with

• generality in this aspect. In principle, 1,4-dithianes should offer good options for the development as C2-synthons that are complementary in scope to the more widely used 1,3-dithianes, but the β-fragmentation problem (cf. Scheme 2) hampers their easy derivatization. It should be noted that this elimination

• of this heterocycle is quite challenging due to the ease of the β-fragmentation pathway of lithiated derivatives (Scheme 2). Chlorination or oxygenation of the ring sulfur atom(s) in 1, followed by Pummerer-type rearrangement and elimination, affords a straightforward access to the more useful

Digyalipopeptide A, an antiparasitic cyclic peptide from the Ghanaian Bacillus sp. strain DE2B

• Adwoa P. Nartey,
• Aboagye K. Dofuor,
• Kofi B. A. Owusu,
• Anil S. Camas,
• Hai Deng,
• Marcel Jaspars and
• Kwaku Kyeremeh

Beilstein J. Org. Chem. 2022, 18, 1763–1771, doi:10.3762/bjoc.18.185

• acid and the elaborate system of aliphatic side chains, the sequence tag ions generated by systematic loss of amino acids were each subjected to several facile losses of H2O, –CH3, –C2H2O and CO resulting in the generation of several peaks in the LC–HRESIMSn spectrum. The b and y ion fragmentation

Using UHPLC–MS profiling for the discovery of new sponge-derived metabolites and anthelmintic screening of the NatureBank bromotyrosine library

• Sasha Hayes,
• Aya C. Taki,
• Kah Yean Lum,
• Joseph J. Byrne,
• Merrick G. Ekins,
• Robin B. Gasser and
• Rohan A. Davis

Beilstein J. Org. Chem. 2022, 18, 1544–1552, doi:10.3762/bjoc.18.164

• , fragmentation of the mitochondrial tubular network, chromosome misalignment, and cell cycle arrest in mitosis in LNCaP prostate cancer cells [38]. The bastadin structure class is well-documented within the literature for their cytotoxic activity [37][39][40][41], with both bastadins 4 and 8 exhibiting in vitro

Polymer and small molecule mechanochemistry: closer than ever

• José G. Hernández

Beilstein J. Org. Chem. 2022, 18, 1225–1235, doi:10.3762/bjoc.18.128

• BMPF mechanophore into glassy and rubbery polymeric networks such as poly(butyl methacrylate) and a poly(hexyl methacrylate) [28]. Upon treatment of the polymeric material 2 in a mixer mill (Figure 1b), the BMPF units underwent a mechanical homolytic fragmentation of the O−O peroxide bond, releasing

Identification of the new prenyltransferase Ubi-297 from marine bacteria and elucidation of its substrate specificity

• Jamshid Amiri Moghaddam,
• Huijuan Guo,
• Karsten Willing,
• Thomas Wichard and
• Christine Beemelmanns

Beilstein J. Org. Chem. 2022, 18, 722–731, doi:10.3762/bjoc.18.72

• farnesylation of 8-HQA; B) calculated MS2 fragmentation pattern of farnesylated 8-HQA; C) extracted ion chromatogram (EIC) for m/z 394.2376 (tR 18.03 min, red arrow) of enriched UbiA-297 protein fractions, cell-membrane fraction containing UbiA-297 (Maribacter sp. MS6), denaturated enriched UbiA-297 (negative

• , and point mutated UbiA-297 (R145A) from Maribacter sp. MS6; E and F) HRMS and MS2 spectrum showing fragmentation of prenylated 8-HQA (m/z 394.2367, tR 18.03 min). Supporting Information Supporting Information File 176: Sequence analysis and copies of MS/MS and NMR spectra. Acknowledgements We would

Amamistatins isolated from Nocardia altamirensis

• Till Steinmetz,
• Wolf Hiller and
• Markus Nett

Beilstein J. Org. Chem. 2022, 18, 360–367, doi:10.3762/bjoc.18.40

• : R1 = H, R2 = H, R3 = H; 4: R1 = H, R2 = OH, R3 = H; 5: R1 = CHO, R2 = OH, R3 = OH. 1H,1H COSY and selected 1H,13C HMBC correlations in compounds 1 and 6. MS–MS fragmentation of amamistatins (1–5). Proposed biosynthesis of amamistatins isolated in this study. 1H and 13C NMR spectroscopic data for

Tenacibactins K–M, cytotoxic siderophores from a coral-associated gliding bacterium of the genus Tenacibaculum

• Yasuhiro Igarashi,
• Yiwei Ge,
• Tao Zhou,
• Amit Raj Sharma,
• Enjuro Harunari,
• Naoya Oku and
• Agus Trianto

Beilstein J. Org. Chem. 2022, 18, 110–119, doi:10.3762/bjoc.18.12

• /succinic acid module (Scheme 1, paths E1 and E2). The third elimination product, C15-ketene (structure in square brackets, Scheme 1) was not observed, but a pentadecenoate anion, appearing at m/z 239, warranted the existence of fragmentation path E3 and also the chain length of the acyl unit. Hydration of

• acquired on a quadrupole time-of-flight mass spectrometer in the negative ion mode. MS/MS fragmentation pathway for compound 1. 1H and 13C NMR data for tenacibactin K (1) in DMSO-d6. 1H and 13C NMR data for tenacibactins L (2) and M (3) in DMSO-d6. Cytotoxicity data of compounds 1–3. Supporting

Adjusting the length of supramolecular polymer bottlebrushes by top-down approaches

• Tobias Klein,
• Franka V. Gruschwitz,
• Maren T. Kuchenbrod,
• Ivo Nischang,
• Stephanie Hoeppener and
• Johannes C. Brendel

Beilstein J. Org. Chem. 2021, 17, 2621–2628, doi:10.3762/bjoc.17.175

• interest. While ultrasonication (US) represents a standard but rather harsh fragmentation technique, we additionally introduced dual asymmetric centrifugation (DAC) as an excellent alternative top-down method for effective, more controlled, and adaptable preparation of polymer nanostructures [24][25][26

• ][27][28]. Both methods are applied for fragmentation of initially µm-long SPBs based on BTU–PEO and BTP–PEO conjugates. The resulting nanofibers were characterized in detail by cryogenic transmission electron microscopy (cryoTEM), as well as by asymmetrical flow field-flow fractionation measurements

• comparably mild treatment already caused a significant fragmentation of the µm-long fibers, resulting in structures of 50–200 nm length according to the cryoTEM images after 10 min of treatment (Figure 2). An average fiber length of 92 ± 51 nm and 74 ± 39 nm for BTU DAC (10 min, 1,000 rpm) and BTP DAC (10

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• substituted hydrazones obviated their generation in situ, and as ethanol was identified as a better solvent in the initial coupling step, no solvent exchange was necessary in the fragmentation step of the hydrazide intermediate. The addition of triethylamine and heating the reaction to 80 °C for 1 hour were

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• carbonyl derivative. Guareschi found that the fragmentation was quantitative when an ethanolic solution of the imide was treated with magnesium hydroxide, poorly soluble but sufficient to ionize the cyanopyridone. It should be pointed out that the identification of gaseous compounds was not at all trivial