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

• oxidatively decarboxylated cysteine residue onto a Dha residue derived from serine (Figure 5A). Extensive in vitro experiments indicate that decarboxylation of cysteine precedes 1,4-addition and is catalysed by a flavoprotein (EpiD) in epidermin biosynthesis [66][67], which uses flavin mononucleotide (FMN) to

• oxidise the cysteine. A mechanistic proposal based on structural data involves the oxidation of the thiol to a thioaldehyde, which then functions as an electron sink to facilitate decarboxylation to generate the double bond between Cα and Cβ [66] (Figure 5A). The functional characterisation of EpiD led to

• the identification of homologous bacterial flavoproteins (Dfp) that catalyse the decarboxylation of 4’-phospho-N-pantothenoylcysteine to 4’-phosphopantetheine, which is essential for coenzyme A biosynthesis [68] (Figure 5B). This demonstrates how the mechanistic analysis of secondary metabolism can

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• enantioselectivities (up to 99% ee, Scheme 10) [26]. The reaction involved a decarboxylation and an Yb(OTf)3/PyBox (L6)-catalyzed aldol addition. 4 Å Molecular sieves were found to be able to enhance the stereoselectivity. Steric hindrance between substituents and the metal/ligand complex slightly decreased the ee

Enantioselective carbenoid insertion into C(sp³)–H bonds

• J. V. Santiago and
• A. H. L. Machado

Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87

• carboxylate complexes in their homochiral form (Table 1) [39]. Modest enantiomeric excesses were provided by the three tested catalysts. The reactions carried out with complex 17a and 17b show very similar stereoselectivity, forming the R-enantiomer of compound 16 as the main product after decarboxylation

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

• Supporting Information File 3. From these calculations we can draw the following conclusions: i) imines formed by reaction of amino acids with carbonyl compounds have the tendency to lose CO2 upon deprotonation of the carboxyl group. Without a negative charge at the carboxyl group, decarboxylation is

• difficult; ii) whether the deprotonation is followed by a decarboxylation or not, depends on the ability of the remaining molecule to accommodate the negative charge; iii) the best way to achieve this accommodation is by “delocalization” over one or more double bonds. Because of this, imines of 1,2

• -dicarbonyl compounds (like glyoxal and ninhydrin) are particularly well-suited for decarboxylation. When such an imine can establish a zwitterionic structure with a deprotonated carboxyl and a protonated carbonyl oxygen or imine nitrogen, decarboxylation is fast and efficient. When trying to optimize the

Antibiotics from predatory bacteria

• Juliane Korp,
• María S. Vela Gurovic and
• Markus Nett

Beilstein J. Org. Chem. 2016, 12, 594–607, doi:10.3762/bjoc.12.58

• , which is responsible for the production of auriculamide. According to the current biosynthetic model, the scaffold of auriculamide is assembled on an NRPS/PKS enzyme complex. A decarboxylation reaction was proposed to shorten the off-loaded carboxylic acid and to give rise to the unusual end group of

Synthesis and reactivity of aliphatic sulfur pentafluorides from substituted (pentafluorosulfanyl)benzenes

• Norbert Vida,
• Jiří Václavík and
• Petr Beier

Beilstein J. Org. Chem. 2016, 12, 110–116, doi:10.3762/bjoc.12.12

• -benzoquinone with cyclopentadiene afforded the Diels–Alder adducts. Decomposition of 3-(pentafluorosulfanyl)muconolactone in acidic, neutral and basic aqueous media was investigated and the decarboxylation of 2-(pentafluorosulfanyl)maleic acid provided 3-(pentafluorosulfanyl)acrylic acid. Keywords

• : dearomatization; decarboxylation; Diels–Alder reaction; oxidation; pentafluorosulfanyl group; Introduction Fluorinated organic compounds have been one of the foci of chemical industry for the last several decades. The unique properties of fluorine atoms and fluorinated groups have been exploited in various

• aqueous sodium carbonate. However, it underwent decarboxylation in DMSO-d6. Monitoring by NMR showed decarboxylation even at room temperature. After 90 h at ambient temperature the starting compound 4 disappeared and 3-(pentafluorosulfanyl)prop-2-enoic acid (23) was formed. At 65 °C the starting material

A convergent, umpoled synthesis of 2-(1-amidoalkyl)pyridines

• Tarn C. Johnson and
• Stephen P. Marsden

Beilstein J. Org. Chem. 2016, 12, 1–4, doi:10.3762/bjoc.12.1

• the reaction of alanine-derived azlactone 6 with 4-methylpyridine N-oxide (7) we found that when water (in the form of 1 M HCl) was employed as a nucleophile, the product isolated was in fact the 2-(1-benzamidoethyl)-4-methylpyridine (8a), formed by facile decarboxylation of the intermediate

Carbon–carbon bond cleavage for Cu-mediated aromatic trifluoromethylations and pentafluoroethylations

• Tsuyuka Sugiishi,
• Hideki Amii,
• Kohsuke Aikawa and
• Koichi Mikami

Beilstein J. Org. Chem. 2015, 11, 2661–2670, doi:10.3762/bjoc.11.286

• reactions at high temperature (150–200 °C) or under basic conditions to generate fluoroalkyl anion sources for the formation of fluoroalkylcopper species. The fluoroalkylation reactions, which proceed through decarboxylation or tetrahedral intermediates, are useful protocols for the synthesis of

• fluoroalkylated aromatics. Keywords: β-carbon elimination; carbon–carbon bond cleavage; decarboxylation; tetrahedral intermediate; trifluoroacetate; fluoral; trifluoromethylation; Introduction Organofluorine compounds attract attention because of their applicability in various fields, such as medicine

• hemiaminals derived from fluoral (CF3C(OSiMe3)NR2), can generate CnF2n+1Cu via carbon–carbon bond cleavage. Herein we focus on Cu-mediated perfluoroalkylation reactions through which carbon dioxide, the esters, or the N-formylamines are eliminated from the perfluoroalkyl reagents. Review Decarboxylation of

Bifunctional phase-transfer catalysis in the asymmetric synthesis of biologically active isoindolinones

• Antonia Di Mola,
• Maximilian Tiffner,
• Francesco Scorzelli,
• Laura Palombi,
• Rosanna Filosa,
• Paolo De Caprariis,
• Mario Waser and
• Antonio Massa

Beilstein J. Org. Chem. 2015, 11, 2591–2599, doi:10.3762/bjoc.11.279

• to obtain both the enantiomers of chiral bioactive compounds. In this case, we focused on (R,R)-8a, which afforded the required (S)-7 (the absolute configuration has been previously determined by vibrational circular dichroism) [31]. Asymmetric synthesis of 9 by decarboxylation of (S)-7 Although

• poor enantioselectivity (ee <10%) [9], while racemic analogues of 9 were resolved in the past in very low yields [4]. This disappointing picture prompted us to find a viable access route to enantioenriched 9. We thus investigated the decarboxylation of the chiral dimethyl 2-(S)-(1-oxoisoindolin-3-yl

• )malonate ((S)-7), according to Scheme 2. We firstly focused on two well-known mild procedures in order to avoid the classical harsh acidic conditions. Disappointingly, modifications of the Krapcho decarboxylation performed with a LiCl/H2O/DMF mixture under reflux [36][37] led to partial racemization of the

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

• of ethyl (phenylsulfonyl)acetate, a methylsulfonyl anion equivalent, to cyclobutene ester 49 followed by a sequence consisting of saponification, regioselective decarboxylation and reesterification to afford methyl ester 50. The ester group was reduced with lithium aluminum hydride and the resulting

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

• incorporation pattern in the tricyclic aromatic moiety suggests a normal PKS assembly line. Moreover, a decarboxylation step is indicated by incorporation of the acetate methyl carbon atom into C-18. In contrast, the origins of C-13 to C-17 remained unclear because of low incorporation of acetate into this part

Biocatalysis for the application of CO₂ as a chemical feedstock

• Apostolos Alissandratos and
• Christopher J. Easton

Beilstein J. Org. Chem. 2015, 11, 2370–2387, doi:10.3762/bjoc.11.259

• decarboxylation. In some autotrophs this pathway is known to operate in the reverse (reductive) direction resulting in CO2 fixation through carboxylation [52]. Autotrophic fixation through the reductive TCA cycle was first described by Arnon and Buchanan [53], and hence is also referred to as the Arnon–Buchanan

Convenient preparation of high molecular weight poly(dimethylsiloxane) using thermally latent NHC-catalysis: a structure-activity correlation

• Stefan Naumann,
• Johannes Klein,
• Dongren Wang and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2015, 11, 2261–2266, doi:10.3762/bjoc.11.246

• 5Me-Me-CO2. Note that the fivefold monomer excess was used in case of BnOH being present. Thermal activation of a 5Me-Me-CO2/BnOH/D4 (1:5:500) composition after a latency period of 72 h. NHC-carboxylates part of this study (top) and polymerization scheme with initial thermal decarboxylation and final

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

• Yury A. Sayapin,
• Inna O. Tupaeva,
• Alexandra A. Kolodina,
• Eugeny A. Gusakov,
• Vitaly N. Komissarov,
• Igor V. Dorogan,
• Nadezhda I. Makarova,
• Anatoly V. Metelitsa,
• Valery V. Tkachev,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

• compounds. At the same time, the related molecular system of 1,3-tropolone has been insufficiently investigated. Therefore, the development of methods for the synthesis of 1,3-tropolones and the study of their properties is of considerable interest. The parent compound was first obtained via decarboxylation

C–H bond halogenation catalyzed or mediated by copper: an overview

• Wenyan Hao and
• Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

• -component annulation intermediate 60 which led to the formation of indolizine 61 via oxidative decarboxylation. And the bromination of 61 took place in situ to give products 59 via an unprecedented dehydrogenative bromination (Scheme 19). By making use of the copper-mediated arene C–H bond halogenation

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

• both solution [38][54][55], and solid state studies [62]. This decarboxylation is favorable for precursors that generate stabilized RXCH2• radicals, thus explaining the superior yields and conversions recorded. Radical stabilization from the simple aliphatic acids of Scheme 5 (top) is minimal; so back

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• , 1,3-cyclododecadiene (337) was reacted with maleic anhydride to give the DA product 338 (21%). Later, the DA adduct 338 was heated under reflux in 10% aq tetrahydrofuran to afford the diacid, which on decarboxylation in the presence of lead tetraacetate in a toluene/pyridine mixture delivered compound

Radical-mediated dehydrative preparation of cyclic imides using (NH₄)₂S₂O₈–DMSO: application to the synthesis of vernakalant

• Dnyaneshwar N. Garad,
• Subhash D. Tanpure and
• Santosh B. Mhaske

Beilstein J. Org. Chem. 2015, 11, 1008–1016, doi:10.3762/bjoc.11.113

• synthesis of imides from the combination of aliphatic amines and unsaturated anhydrides. Plausibly, the intermediate amic acid in these cases may be prone to decarboxylation [57] and radical polymerization similar to the acrylamide polymerization using APS as a radical initiator [55]. Encouraged by this

DBU-promoted carboxylative cyclization of o-hydroxy- and o-acetamidoacetophenone

• Wen-Zhen Zhang,
• Si Liu and
• Xiao-Bing Lu

Beilstein J. Org. Chem. 2015, 11, 906–912, doi:10.3762/bjoc.11.102

• thermodynamically stable coumarins. Importantly, the use of an intramolecular in situ trap avoids the problem of decarboxylation during workup. In case of o-acetamidoacetophenones, an acyl migration from nitrogen to carbon was observed. The cross experiment showed that the N to C acyl shift occurred

An intramolecular C–N cross-coupling of β-enaminones: a simple and efficient way to precursors of some alkaloids of Galipea officinalis

• Hana Doušová,
• Radim Horák,
• Zdeňka Růžičková and
• Petr Šimůnek

Beilstein J. Org. Chem. 2015, 11, 884–892, doi:10.3762/bjoc.11.99

• Knoevenagel/reduction/hydrolysis/decarboxylation pathway (steps a–d in Scheme 4) to carboxylic acid 10 suffered from low yields of the last two steps (total yield 33%). The attempt to obtain 5a directly from 9 by means of Krapcho decarboxylation [33] failed, as the product was contaminated with inseparable

Trifluoromethyl-substituted tetrathiafulvalenes

• Olivier Jeannin,
• Frédéric Barrière and
• Marc Fourmigué

Beilstein J. Org. Chem. 2015, 11, 647–658, doi:10.3762/bjoc.11.73

• and Discussion Syntheses The reported preparation of 2bc is based on the coupling reaction of the trithiocarbonate 5 with the dithiocarbonate 6bc, affording also the symmetrical coupling product 4bc (Scheme 3) [31]. Further decarboxylation of 2bc with LiBr/DMF afforded 1c while reaction with NH3 in

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

Sequential decarboxylative azide–alkyne cycloaddition and dehydrogenative coupling reactions: one-pot synthesis of polycyclic fused triazoles

• Kuppusamy Bharathimohan,
• Thanasekaran Ponpandian,
• A. Jafar Ahamed and
• Nattamai Bhuvanesh

Beilstein J. Org. Chem. 2014, 10, 3031–3037, doi:10.3762/bjoc.10.321

• formation of 4 is described in Scheme 5. Initially alkynoic acid 2 undergoes decarboxylation to form the copper acetylide (A) in the presence of the Cu+ catalyst which is generated by the reduction of Cu2+ with sodium ascorbate. The obtained copper acetylide undergoes regioselective [3 + 2] cycloaddition

Aspergiloid I, an unprecedented spirolactone norditerpenoid from the plant-derived endophytic fungus Aspergillus sp. YXf3

• Zhi Kai Guo,
• Rong Wang,
• Wei Huang,
• Xiao Nian Li,
• Rong Jiang,
• Ren Xiang Tan and
• Hui Ming Ge

Beilstein J. Org. Chem. 2014, 10, 2677–2682, doi:10.3762/bjoc.10.282

• intermediate 2 undergoes decarboxylation to form 3 through Baeyer–Villiger oxidation to form the 7-membered lactone 4, then hydrolyzation, decarboxylation and lactonization to finally give aspergiloid I (1). Aspergiloid I (1) was evaluated for its cytotoxicity against eleven human cancer cell lines, K562

Gold(I)-catalysed synthesis of a furan analogue of thiamine pyrophosphate

• Amjid Iqbal,
• El-Habib Sahraoui and
• Finian J. Leeper

Beilstein J. Org. Chem. 2014, 10, 2580–2585, doi:10.3762/bjoc.10.270

• ; pyruvate decarboxylase; thiamine diphosphate; Introduction The biologically active form of vitamin B1 is thiamine diphosphate (ThDP, 1, Figure 1), which is an essential cofactor and involved in a number of metabolic pathways, including oxidative and non-oxidative decarboxylation of α-keto acids (e.g

• Breslow [3][4], is given in Scheme 1. After formation of the ThDP ylid, the keto group of the substrate is attacked by the thiazolium C-2 carbanion to form the tetrahedral pre-decarboxylation intermediate 2-(2-lactyl)-ThDP, LThDP. It has been proposed that the covalent attachment of pyruvate to form LThDP

• introduces significant strain, the release of which is a driving force for the decarboxylation [5]. The effects of this type of strain on bond angles and lengths have recently been observed in a high resolution crystal structure of another ThDP-dependent enzyme, transketolase [6]. Another important factor of