The EIMS fragmentation mechanisms of the sesquiterpenes corvol ethers A and B, epi-cubebol and isodauc-8-en-11-ol

• Patrick Rabe and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 1380–1394, doi:10.3762/bjoc.12.132

• EIMS fragmentation mechanisms of the two sesquiterpene ethers corvol ethers A and B, and the sesquiterpene alcohols epi-cubebol and isodauc-8-en-11-ol. Keywords: bacteria; isotopic labelling; mass spectrometry; reaction mechanisms; terpenes; Introduction Gas chromatography coupled to electron impact

• difficult. The profound knowledge about EIMS fragmentation reactions can be used to identify certain structural motifs, e.g., the mass spectra of acyclic carbonyl compounds are often dominated by fragment ions formed via McLafferty rearrangement [4], while cyclohexene derivatives often show major fragment

• , Ryhage and Stenhagen presented detailed studies on the EI mass spectra of deuterated and methyl-branched fatty acid methyl esters that revealed their fragmentation mechanisms [7][8]. Based on this work, we have recently identified various volatile fatty acid methyl esters (FAMEs) in headspace extracts of

Cyclisation mechanisms in the biosynthesis of ribosomally synthesised and post-translationally modified peptides

• Andrew W. Truman

Beilstein J. Org. Chem. 2016, 12, 1250–1268, doi:10.3762/bjoc.12.120

• -trivial due to the variety of unusual post-translational modifications that could take place. This means that product masses and fragmentation patterns are very difficult to predict, especially when peptides are cyclised [161]. Despite these issues, significant progress has been made to develop methods to

Strecker degradation of amino acids promoted by a camphor-derived sulfonamide

• M. Fernanda N. N. Carvalho,
• M. João Ferreira,
• Ana S. O. Knittel,
• Maria da Conceição Oliveira,
• João Costa Pessoa,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2016, 12, 732–744, doi:10.3762/bjoc.12.73

• major fragmentation pathway is due to the loss of 64 Da (SO2) leading to an ion at an even value (m/z 374). The sequential loss of sulfur dioxide plus ammonia gives a fragment ion with m/z 357, indicating an even number of nitrogen atoms. Further loss of a camphor moiety (C10H15NSO2) displays an ion at

• m/z 227 supporting a species having an even number of nitrogen atoms (see Supporting Information File 1, Figure S7 showing a scheme with the fragmentation mechanism of 2). The formulation of 2 was corroborated by accurate mass measurements using QqTOF-MS which led to the following results (M

• . Supporting Information Supporting Information File 81: Experimental spectra for compound 2: FTIR, NMR (1H, 13C, DEPT, HMBC, HSQC, NOESY), ESIMS and the proposed fragmentation mechanism for 2 and 12. Supporting Information File 82: Calculations of the NMR chemical shifts for the assignment of the configuration

Tandem processes promoted by a hydrogen shift in 6-arylfulvenes bearing acetalic units at ortho position: a combined experimental and computational study

• Mateo Alajarin,
• Marta Marin-Luna,
• Pilar Sanchez-Andrada and
• Angel Vidal

Beilstein J. Org. Chem. 2016, 12, 260–270, doi:10.3762/bjoc.12.28

• several mechanistic paths are conceivable, each one involving additional H shifts and a fragmentation step, the opening of the dioxolane ring by a formal β-elimination reaction. A number of additional mechanistic alternatives arise by considering that the experimentally observed transformations of 3 are

My maize and blue brick road to physical organic chemistry in materials

• Anne J. McNeil

Beilstein J. Org. Chem. 2016, 12, 229–238, doi:10.3762/bjoc.12.24

• out to be a three-year research experience. My initial goal was to identify six isomeric fragmentation products that were first observed by former student Dave Thomas (Figure 1). Once identified, I was tasked with elucidating the mechanism(s) that led to those products. What drew me into the lab was

Thermal and oxidative stability of Atlantic salmon oil (Salmo salar L.) and complexation with β-cyclodextrin

• Daniel I. Hădărugă,
• Mustafa Ünlüsayin,
• Alexandra T. Gruia,
• Cristina Birău (Mitroi),
• Gerlinde Rusu and
• Nicoleta G. Hădărugă

Beilstein J. Org. Chem. 2016, 12, 179–191, doi:10.3762/bjoc.12.20

• intermediates resulting from the oxidation of FAs are monohydroperoxides, hydroperoxy-epidioxides, as well as peroxy-, alkoxy-, and alkyl radicals [16]. Further thermal degradation or fragmentation of these intermediates leads to odor-active carbonyl compounds such as aldehydes, ketones, alcohols and esters

New metathesis catalyst bearing chromanyl moieties at the N-heterocyclic carbene ligand

• Agnieszka Hryniewicka,
• Szymon Suchodolski,
• Agnieszka Wojtkielewicz,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 2795–2804, doi:10.3762/bjoc.11.300

• reactive in CM [35]. In the case of metathetic fragmentation of β-carotene, the use of 9 instead of 1 or 2 improved the regioselectivity. The product of the central C15–C15’ double bond scission was formed preferably. The activity of 9 was comparable to that of 1, albeit lower than 2 (Scheme 4). Regio- and

Recent advances in metathesis-derived polymers containing transition metals in the side chain

• Ileana Dragutan,
• Valerian Dragutan,
• Bogdan C. Simionescu,
• Albert Demonceau and
• Helmut Fischer

Beilstein J. Org. Chem. 2015, 11, 2747–2762, doi:10.3762/bjoc.11.296

• synthesis of these targets presently accessible through controlled and living polymerization techniques including controlled radical polymerizations (CRP) such as atom transfer radical polymerization (ATRP), nitroxide-mediated polymerization (NMP) and reversible addition–fragmentation chain transfer (RAFT

Genicunolide A, B and C: three new triterpenoids from Euphorbia geniculata

• Alia Farozi,
• Javid A. Banday and
• Shakeel A. Shah

Beilstein J. Org. Chem. 2015, 11, 2707–2712, doi:10.3762/bjoc.11.291

• hydroxy group [δC 71.8] in 3. The mass spectrum of compound 3 revealed that the double bond triggered the typical RDA fragmentation of ring B [39] to give densely populated ion peaks at m/z 166 (ring A) and 292 (rings C/D/E) placing the double bond at C-5 [δC 122.0 (C-6), 139.9 (C-5)] [38] and two hydroxy

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• -selectivity of the olefin depends on the ring-size and the choice of catalyst. As a consequence of avoiding ring strain, small- and medium-sized rings are generally obtained with Z-configuration of the alkene. The Grob fragmentation reaction of fused 6,5-bicycles B is usually a concerted process that affords

• cyclononenes in a stereospecific manner [27]. The relative configuration of the leaving group (LG = OTs, OMs, Hal, NR3+) and the adjacent substituent determine the E/Z-geometry of the olefin. A cis-geometry leads to the formation of the E-configured double bond. In general, the Grob fragmentation is the most

• ] of 43 afforded a 4,6,5-tricycle which was converted to the fragmentation precursor 45 in four further steps. A base-mediated Wharton-type Grob fragmentation [33] then served as the key step to construct the cyclononene motif of bicycle 47. Prolonged exposure of the resulting cis-fused 4,9-bicycle 47

Recent highlights in biosynthesis research using stable isotopes

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2015, 11, 2493–2508, doi:10.3762/bjoc.11.271

• EIMS-fragmentation reactions of 34 by comparison of the 13C-including fragments. Singly labeled FPP isotopomers also proved valuable to investigate reprotonation steps in sesquiterpene cyclization mechanisms by incubation in deuterium oxide. The biosynthesis of the recently discovered corvol ethers A

Bromotyrosine-derived alkaloids from the Caribbean sponge Aplysina lacunosa

• Qun Göthel,
• Thanchanok Sirirak and
• Matthias Köck

Beilstein J. Org. Chem. 2015, 11, 2334–2342, doi:10.3762/bjoc.11.254

• proposed to be the same as of 19, chemical fragmentation of 5 releasing from the sponge Aplysina spp. after induction by tissue damage (Figure 4). However, the conversion from 5 to 19 has not been confirmed. A single data set in the 13C NMR spectrum supported the presence of one diastereomer of 1. Compound

Copper-catalyzed aerobic radical C–C bond cleavage of N–H ketimines

• Ya Lin Tnay,
• Gim Yean Ang and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2015, 11, 1933–1943, doi:10.3762/bjoc.11.209

• cleavage of N–H ketimines. Treatment of N–H ketimines having an α-sp3 hybridized carbon under Cu-catalyzed aerobic reaction conditions resulted in a radical fragmentation with C–C bond cleavage to give the corresponding carbonitrile and carbon radical intermediate. This radical process has been applied for

• 1aa most likely via the corresponding iminyl radical, that undergoes radical fragmentation to afford the corresponding C-radical and carbonitrile 5a [55]. Thus, it is deduced that oxaspirocyclohexadienone 3a was formed through oxygenation of the putative C-radical. Moreover, in this transformation

• , that undergoes β-carbon fragmentation to give p-tolunitrile (5a) and biaryl-2-isopropyl radical B (Scheme 5a). The aerobic oxygenation of C-radical B affords peroxy radical C, that is presumably reduced by Cu(I) species through the Fenton-type mechanism [57] to give alkoxy radical D [58]. Subsequent

Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

• Louis P. Sandjo,
• Victor Kuete and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183

• composition leading to the deduction of the structure. Mass fragmentation The mass spectrometry spectrum of pyridoacridines contains very little information due to the lack of fragments. Independent of the ionization source used to determine the elemental composition (ESI, DIC, APCI, FAB, or EI), molecules

• with compact, and fused rings do not undergo fragmentation and only their corresponding ion peak is observed [47]. However, those containing a side chain show a few ion peaks corresponding to the sequential fragmentation of the latter. This observation is supported by the mass spectrometry data of

• styelsamine B (6) and sagitol (26), whose fragments could be used to determine the pyridoacridine skeleton (Figures 1–4) [42][45][55]. The electron-impact mass spectrometry of subarine (37) showed good fragmentation because of the partial flexibility of the structure (Figure 5) [40]. Recent synthesis of

Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides

• Hanmo Zhang,
• E. Ben Hay,
• Stephen J. Geib and
• Dennis P. Curran

Beilstein J. Org. Chem. 2015, 11, 1649–1655, doi:10.3762/bjoc.11.181

• /fragmentation. Tin hydride-mediated cyclizations of 2-halo-N-(3-methyl-N-sulfonylindole)anilines provide spiro[indoline-3,3'-indolones] or spiro-3,3'-biindolines (derived from imine reduction), depending on the indole C2 substituent. Cyclizations of 2-haloanilide derivatives of 3-carboxy-N-sulfonyl-2,3

• ; radical cyclization; radical fragmentation; spiro-indoles; Introduction Radical additions and cyclizations of ene-sulfonamides are useful reactions in a number of settings. The primary products of these reactions, α-sulfonamidoyl radicals, are often thought to undergo elimination reactions of sulfonyl

• undergoes rapid hydration to hemiaminal 29 followed by fragmentation and enol/lactam tautomerization to give formamide 25. We show here direct fragmentation of 29, in what is essentially the lactam/formamide version of a retro-Claisen (or retro-Dieckmann reaction). However, it is also possible that

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• semiconductor and releasing neutral radicals. Albini and coworkers reported on the use of benzyltrimethylsilanes 43 [66]. Hole oxidation with photoexcited dispersions of TiO2 gave rise to radical cations that underwent fragmentation with release of benzyl type radicals. The latter reductively benzylated

Structure and conformational analysis of spiroketals from 6-O-methyl-9(E)-hydroxyiminoerythronolide A

• Ana Čikoš,
• Irena Ćaleta,
• Dinko Žiher,
• Mark B. Vine,
• Ivaylo J. Elenkov,
• Marko Dukši,
• Dubravka Gembarovski,
• Marina Ilijaš,
• Snježana Dragojević,
• Ivica Malnar and
• Sulejman Alihodžić

Beilstein J. Org. Chem. 2015, 11, 1447–1457, doi:10.3762/bjoc.11.157

• formation of compounds 2–4. Supporting Information Supporting Information File 236: Observed nOe contacts (Tables SI1–4), proton vicinal coupling constants used for molecular modelling calculations (Table SI5) and accurate mass measurements (Table SI7) for compounds 2–4, as well as HRMS fragmentation for

A new and efficient procedure for the synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones

• Marcelo Isidoro P. Reis,
• Vinícius R. Campos,
• Jackson A. L. C. Resende,
• Fernando C. Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2015, 11, 1235–1240, doi:10.3762/bjoc.11.137

• synthetic and biological applications [40]. These substances are easily prepared from commercially available amines and formaldehyde in toluene in yields ranging from 75–90%. Barluenga and coworkers [41] have previously shown that 1,3,5-triazinanes undergo fragmentation at elevated temperatures to form 3

Reactions of nitroxides 15. Cinnamates bearing a nitroxyl moiety synthesized using a Mizoroki–Heck cross-coupling reaction

• Jerzy Zakrzewski and
• Bogumiła Huras

Beilstein J. Org. Chem. 2015, 11, 1155–1162, doi:10.3762/bjoc.11.130

• /z 124 and 109 (Scheme 2). The peaks at m/z 154, 124 and 109 were thoroughly analyzed for the acrylate 3, as an example. Proposed elemental composition of the fragmentation ions at m/z 154, 124, 109 for the acrylate 3 were confirmed by the measurement of their exact mass: m/z 154 (calculated C9H16NO

Peptide–polymer ligands for a tandem WW-domain, an adaptive multivalent protein–protein interaction: lessons on the thermodynamic fitness of flexible ligands

• Katharina Koschek,
• Vedat Durmaz,
• Oxana Krylova,
• Marek Wieczorek,
• Shilpi Gupta,
• Martin Richter,
• Alexander Bujotzek,
• Christina Fischer,
• Rainer Haag,
• Christian Freund,
• Marcus Weber and
• Jörg Rademann

Beilstein J. Org. Chem. 2015, 11, 837–847, doi:10.3762/bjoc.11.93

• building block N-methacryloyl-β-alaninyl-S-benzyl thioester under reversible addition–fragmentation chain-transfer (RAFT) conditions yielding a thioester-containing copolymer with 13.3 kDa and polydispersity of 1.2, which we denominated as NCL-polymer [10]. NCL-polymer was converted into multivalent

Discrete multiporphyrin pseudorotaxane assemblies from di- and tetravalent porphyrin building blocks

• Mirko Lohse,
• Larissa K. S. von Krbek,
• Sebastian Radunz,
• Suresh Moorthy,
• Christoph A. Schalley and
• Stefan Hecht

Beilstein J. Org. Chem. 2015, 11, 748–762, doi:10.3762/bjoc.11.85

• . The formation of unspecific complexes as well as fragmentation upon ionization have been found to be quite limited so that the picture obtained from the mass spectra can be expected to provide realistic insights into the composition of the complexes present in solution. As all stereoisomers have the

Highly selective generation of vanillin by anodic degradation of lignin: a combined approach of electrochemistry and product isolation by adsorption

• Dominik Schmitt,
• Carolin Regenbrecht,
• Marius Hartmer,
• Florian Stecker and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2015, 11, 473–480, doi:10.3762/bjoc.11.53

• electrolysis time to 5% of the initially applied with planar electrodes. Another important factor for the efficiency of the selective degradation to 1 is the reaction temperature. At elevated temperatures usually decoiling or fragmentation takes place in the lignin particles [35][36]. This is very important to

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• these radicals are often non-selective and are accompanied by the formation of alcohols, carbonyl compounds, and fragmentation products. The examples of the C–O bond formation between two molecules using O-electrophiles are rare; electron-deficient peroxides with a specific structure can act as O

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• photoinitiation in the presence of excess t-BuOK. The photoinduced ET to the amide-anion resulted in its radical anion. After fragmentation of the C–I bond, an intramolecular cyclization occurred, and after acidification of the reaction medium, the oxidized phenanthridine compounds were obtained in very good