18-Hydroxydolabella-3,7-diene synthase – a diterpene synthase from Chitinophaga pinensis

• Jeroen S. Dickschat,
• Jan Rinkel,
• Patrick Rabe,
• Arman Beyraghdar Kashkooli and
• Harro J. Bouwmeester

Beilstein J. Org. Chem. 2017, 13, 1770–1780, doi:10.3762/bjoc.13.171

• based on the identification of this compound and its Cope rearrangement product β-elemene (2) formed by the thermal impact during GC–MS analysis [19] in E. coli headspace extracts under heterologous expression of the terpene synthase gene (Scheme 1). Here we present the diterpene synthase activity of

• -, sesqui- and diterpene activity by incubation with geranyl (GPP), farnesyl (FPP) and geranylgeranyl diphosphate (GGPP) as substrates, which yielded a single product 3 only from GGPP, but no products from FPP and GPP as demonstrated by GC–MS analysis (Figure 1). The mass spectrum of 3 showed a molecular

Use of costic acid, a natural extract from Dittrichia viscosa, for the control of Varroa destructor, a parasite of the European honey bee

• Kalliopi Sofou,
• Demosthenis Isaakidis,
• Apostolos Spyros,
• Anita Büttner,
• Athanassios Giannis and
• Haralambos E. Katerinopoulos

Beilstein J. Org. Chem. 2017, 13, 952–959, doi:10.3762/bjoc.13.96

• -methylaromadendrin and 7-O-methylaromadendrin-3-acetate (Figure 4) by GC–MS analysis. To the best of our knowledge, these structures are reported for the first time as components of D. viscosa. The conditions of the GC–MS experiment were as follows [51]: The essential oil and extracts were analyzed by GC–MS on a

Unpredictable cycloisomerization of 1,11-dien-6-ynes by a common cobalt catalyst

• Abdusalom A. Suleymanov,
• Dmitry V. Vasilyev,
• Valentin V. Novikov,
• Yulia V. Nelyubina and
• Dmitry S. Perekalin

Beilstein J. Org. Chem. 2017, 13, 639–643, doi:10.3762/bjoc.13.62

• protons. On the basis of 1H–1H and 1H–13C correlation NMR spectra as well as GC–MS analysis we had assigned the structures of these products as the cyclopropane derivatives with internal 4 and exocyclic 5 double bonds (Scheme 2). Our spectral data correlate well with that of similar compounds, which were

Direct arylation catalysis with chloro[8-(dimesitylboryl)quinoline-κN]copper(I)

• Sem Raj Tamang and
• James D. Hoefelmeyer

Beilstein J. Org. Chem. 2016, 12, 2757–2762, doi:10.3762/bjoc.12.272

• equivalents KO(t-Bu) (Table 1, entry 1). After 10 hours the yield of biphenyl was 94% according to GC–MS analysis. A control reaction (Table 1, entry 4) of iodobenzene with benzene/DMF (10:1 v/v) using 2 mol % Cu(I)Br and 30 equivalents KO(t-Bu) gave 5% yield of biphenyl after 10 hours. Reactions performed in

• heterocoupling pathway. The coupling of benzene with p-iodoanisole at 2 mol % loading of catalyst 2 was evaluated (Table 1, entry 2). We were pleased to find that the reaction yielded 4-methoxybiphenyl according to GC–MS analysis, and the isolated yield after flash column chromatography was 77%. Encouraged by

Identification, synthesis and mass spectrometry of a macrolide from the African reed frog Hyperolius cinnamomeoventris

• Markus Menke,
• Pardha Saradhi Peram,
• Iris Starnberger,
• Walter Hödl,
• Gregory F.M. Jongsma,
• David C. Blackburn,
• Mark-Oliver Rödel,
• Miguel Vences and
• Stefan Schulz

Beilstein J. Org. Chem. 2016, 12, 2731–2738, doi:10.3762/bjoc.12.269

• EI mass spectra of unsaturated macrolactones, and 3) show how ring-closing metathesis reaction conditions can be selected to obtain either pure compounds or a library of compounds useful for evaluation of their mass spectra. Results and Discussion The GC–MS analysis of a gular gland extract of

• isomerized mixtures constitute a library of closely related macrolides differing slightly in position of double bonds and ring size. With the diagnostic mass spectrometric ions discussed above, each compound can be assigned a structure after GC–MS analysis. These mass spectra together with the gas

A detailed view on 1,8-cineol biosynthesis by Streptomyces clavuligerus

• Jan Rinkel,
• Patrick Rabe,
• Laura zur Horst and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 2317–2324, doi:10.3762/bjoc.12.225

• NMR: (2H6)benzene δ = 128.06) [40]. GC–MS analysis An Agilent 7890B gas chromatograph equipped with a HP5-MS silica column (30 m, 0.25 mm inner diameter, 0.50 μm film) connected to an Agilent 5977A inert mass selective detector was used to acquire GC–MS data. Instrumental settings were: (1) inlet

Regiocontroled Pd-catalysed C5-arylation of 3-substituted thiophene derivatives using a bromo-substituent as blocking group

• Mariem Brahim,
• Hamed Ben Ammar,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2016, 12, 2197–2203, doi:10.3762/bjoc.12.210

• expected coupling products 2–4 were obtained in moderate yields. On the other hand, with 4-bromoanisole as an electron-rich aryl bromide, the desired C5-arylated 2-bromothiophene could not be detected by GC–MS analysis of the crude mixture, and a large amount of unreacted 4-bromoanisole was recovered

Practical synthetic strategies towards lipophilic 6-iodotetrahydroquinolines and -dihydroquinolines

• David R. Chisholm,
• Garr-Layy Zhou,
• Ehmke Pohl,
• Roy Valentine and
• Andrew Whiting

Beilstein J. Org. Chem. 2016, 12, 1851–1862, doi:10.3762/bjoc.12.174

• %) according to GC–MS analysis, and the iodinated product 2 was difficult to isolate by chromatography. In light of these results, bromination was conducted with the aim of synthesising the corresponding aryl iodide 2 by halogen exchange (Scheme 3). After careful optimisation of the reaction conditions, the

Mechanistic investigations on six bacterial terpene cyclases

• Patrick Rabe,
• Thomas Schmitz and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 1839–1850, doi:10.3762/bjoc.12.173

• , Figure 1) by GC–MS analysis (Figure S1, Supporting Information File 1) [32], while the enzyme incubations with geranyl diphosphate (GPP) and geranylgeranyl diphosphate (GGPP) gave no products. Although 1 was isolated from vetiver oil (Vetiveria zizanioides, Gramineae) nearly five decades ago [38], the

Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(−)-myrtenol nitrate

• Sean P. Bew,
• Glyn D. Hiatt-Gipson,
• Graham P. Mills and
• Claire E. Reeves

Beilstein J. Org. Chem. 2016, 12, 1081–1095, doi:10.3762/bjoc.12.103

• compared to the starting materials as well as GC–MS analysis (negative ion mode) corroborated the O-nitrate ester groups were present. Although the use of silver nitrate had been validated in our ‘test’ reaction, the use of isoprene as a starting material was clearly not as convenient as first envisaged

A convenient route to symmetrically and unsymmetrically substituted 3,5-diaryl-2,4,6-trimethylpyridines via Suzuki–Miyaura cross-coupling reaction

• Dariusz Błachut,
• Joanna Szawkało and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2016, 12, 835–845, doi:10.3762/bjoc.12.82

• halogenated pyridines and pyrimidines. During our search for new "route markers" of amphetamine analogues synthesized by the Leuckart method, we focused our attention on two groups of heterocycles, that were preliminary identified by GC–MS analysis as 3,4,5-triaryl-2,6-dimethylpyridines P5 [32][33] and 3,5

• with increased reaction time to complete the diarylation. The attachment of small substituents at ortho positions in arylboronic acids did not retard the reaction (products 5, 8, 10, 18, 22, 24, 25, 29). However, the GC–MS analysis revealed an increased formation of the corresponding biaryls, monoaryl

• less than 5%) due to practical problems associated with chromatographic purification. Their structures were therefore proposed on the basis of GC–MS analysis. Since a stepwise transformation of 1 according to route 2 led to a similar inseparable mixture of symmetrical and unsymmetrical diarylpyridines

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

• FAs (and the corresponding glycerides) are easily degraded by oxidation, especially at higher temperatures. An appropriate method for evaluating the overall FA profile is the gas chromatography–mass spectrometry (GC–MS) analysis of the FAs, derivatized to the corresponding methyl esters. The relative

• triglycerides from ASO of 899.5 g/mol (according to GC–MS analysis) and 1310 g/mol for β-CD hydrate (according to KFT analysis of water content of commercial β-CD). First, 1 mmol (or 3 mmol) of β-CD hydrate (1.313 ± 0.0007 g or 3.939 ± 0.0004 g) was suspended in 12 mL of distilled water and heated to 50 °C in

• mixture was thoroughly milled for 15 min. Afterwards the mixture was cooled to room temperature, washed with ethanol (1 mL) to remove surface oil, and dried to constant mass in a desiccator over MS 4Å. The kneaded complexes were prepared in duplicates. GC–MS analysis of the raw and degraded ASO The FA

Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

• Hynek Balcar,
• Naděžda Žilková,
• Martin Kubů,
• Michal Mazur,
• Zdeněk Bastl and
• Jiří Čejka

Beilstein J. Org. Chem. 2015, 11, 2087–2096, doi:10.3762/bjoc.11.225

• Synthesis, Wroclaw, Poland) for the samples of Ru catalysts and M. Horáček (J. Heyrovský Institute, Prague) for GC–MS analysis. Financial support from Grant Agency of the Czech Republic (P106/12/0189) is gratefully acknowledged.

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• substrate 16 was subjected to RCM in high temperature conditions, a complex mixture of products was obtained (Figure 5). Upon GC and GC–MS analysis, structures of compounds 17–19 were determined (cf. Supporting Information File 1). The substituted complexes were inert in ambient conditions similarly to the

Electrochemical selenium- and iodonium-initiated cyclisation of hydroxy-functionalised 1,4-dienes

• Philipp Röse,
• Steffen Emge,
• Jun-ichi Yoshida and
• Gerhard Hilt

Beilstein J. Org. Chem. 2015, 11, 174–183, doi:10.3762/bjoc.11.18

• conversion was detected by TLC and GC–MS analysis. n-Pentane was added, the mixture was filtered through a short pad of silica and concentrated under reduced pressure. The crude material was dissolved in 5 mL tetrahydrofuran, TBAF (1 M in THF, 1.1 equiv) was added and the mixture was stirred at 0 °C for 3 h

• (1.2–1.5 equiv) were added and stirred at room temperature until complete conversion was detected by TLC and GC–MS analysis. Pentane was added and the mixture was filtered through a short pad of silica. The solvent was evaporated and the crude product was purified by column chromatography to give the

• acetonitrile. Then, the cell was equipped with a platinum plate anode and cathode and electrolysed under a constant current (10 mA, 6.67 mA/cm2) at 20 °C until completion was detected by TLC and GC–MS analysis. Then, 15 mL water were added, the mixture was extracted with diethyl ether (three times 15 mL

Palladium-catalyzed 2,5-diheteroarylation of 2,5-dibromothiophene derivatives

• Fatma Belkessam,
• Aidene Mohand,
• Jean-François Soulé,
• Abdelhamid Elias and
• Henri Doucet

Beilstein J. Org. Chem. 2014, 10, 2912–2919, doi:10.3762/bjoc.10.309

• -methylfuran-3-carboxylate afforded 9 and 10 in 60% and 63% yield, respectively. The reaction of 1 equiv of 2,5-dibromothiophene with 5 equiv of 1-methylpyrrole gave 11 in 78% yield. No significant formation of other polyheterocycles was observed by GC–MS analysis of the crude mixture. Arylation at C4 of 3,5

• 2-bromothiophene (Scheme 6). The reaction of 1 equiv thiophene with 2 equiv of 2-bromothiophene resulted in a poor yield for 7 due to the formation of a mixture of bithiophene 32, terthiophene 7 and also a quaterthiophene (as was observed by GC–MS analysis of the crude mixture). On the other hand

Thermal and oxidative stability of the Ocimum basilicum L. essential oil/β-cyclodextrin supramolecular system

• Daniel I. Hădărugă,
• Nicoleta G. Hădărugă,
• Corina I. Costescu,
• Ioan David and
• Alexandra T. Gruia

Beilstein J. Org. Chem. 2014, 10, 2809–2820, doi:10.3762/bjoc.10.298

• . essential oil in comparison with the corresponding β-CD complex. For the first time, the protective capability of natural β-CD for labile basil essential oil compounds has been demonstrated. Keywords: basil; β-cyclodextrin; GC–MS analysis; nanoencapsulation; Ocimum basilicum L. essential oil; thermal and

• concentrations of the complexed essential oil components as well as the degraded compounds were determined by GC–MS analysis (see Supporting Information File 1 for further information). No important variations in the relative concentrations of β-CD nanoencapsulated components or their degradation compounds were

• minutes for every step in a thermostated extractor equipped with a condenser and a magnetic stirring system. The cooled hexane extracts were dried over anhydrous calcium chloride and analyzed using GC–MS. GC–MS analysis of the raw and degraded O. basilicum L. essential oil (non-encapsulated and

Pd/C-catalyzed aerobic oxidative esterification of alcohols and aldehydes: a highly efficient microwave-assisted green protocol

• Marina Caporaso,
• Giancarlo Cravotto,
• Spyros Georgakopoulos,
• George Heropoulos,
• Katia Martina and
• Silvia Tagliapietra

Beilstein J. Org. Chem. 2014, 10, 1454–1461, doi:10.3762/bjoc.10.149

• selectivity were achieved in most cases, apart from 3,5-dimethoxybenzaldehyde and 4-chlorobenzaldehyde. Pd-catalyzed dehalogenation reaction of 4-chlorobenzaldehyde (120 °C for 1.5 h) gave methyl benzoate as main product besides traces of the desired product (detected by GC–MS analysis). Aiming to reduce this

Streptopyridines, volatile pyridine alkaloids produced by Streptomyces sp. FORM5

• Ulrike Groenhagen,
• Michael Maczka,
• Jeroen S. Dickschat and
• Stefan Schulz

Beilstein J. Org. Chem. 2014, 10, 1421–1432, doi:10.3762/bjoc.10.146

• aqueous phase. In our study the volatile bouquet of the actinomycete Streptomyces sp. FORM5 was investigated and several new 2-alkylated pyridines were identified using the closed-loop stripping analysis (CLSA) [7] headspace technique followed by GC–MS analysis and synthesis of the target compounds for

• referenced against TMS (δ = 0.00 ppm) for 1H NMR and CHCl3 (δ = 77.16 ppm) for 13C NMR. GC–MS analysis were performed on an Agilent 7890A gas chromatograph connected to an Agilent 6975 C inert mass detector fitted with a BPX-5 fused silica capillary column (25 m, 0.25 mm i.d., 0.25 μm film). Conditions were

• , concentrated under reduced pressure, and finally subjected to GC–MS analysis. For feeding experiments on the biosynthesis of compound 7 the SM-media was enriched with sodium 13C2-acetate (ISOTEC) in 1 mM (1.7 mg, 0.02 mmol, in 20 mL medium) and 2 mM (3.4 mg, 0.04 mmol, in 20 mL medium) followed by collection

Hindered aryl bromides for regioselective palladium-catalysed direct arylation at less favourable C5-carbon of 3-substituted thiophenes

• Rongwei Jin,
• Charles Beromeo Bheeter and
• Henri Doucet

Beilstein J. Org. Chem. 2014, 10, 1239–1245, doi:10.3762/bjoc.10.123

• GC–MS analysis of the crude mixture. Moreover a high conversion of 86% of this aryl bromide was observed using only 0.5 mol % Pd(OAc)2 as the catalyst. Then, we studied the scope of the coupling of 2-bromo-1,3-dichlorobenzene, using other 3-substituted thiophene derivatives (Scheme 3, Table 1). Both

• , 136.6, 136.4, 133.1, 130.8, 129.7, 128.0, 122.1, 15.8; Anal. calcd for C11H8Cl2S (243.15): C, 54.34; H, 3.32; found: C, 54.19; H, 3.17. Traces of 8a and 8c were also detected by GC–MS analysis of the crude mixture. 4-Chloro-2-(2,6-dichlorophenyl)thiophene (9b): From 2-bromo-1,3-dichlorobenzene (0.226 g

• , 124.9, 121.4; Anal. calcd for C10H5Cl3S (263.57): C, 45.57; H, 1.91; found: C, 45.67; H, 1.90. Traces of 9a and 9c were also detected by GC–MS analysis of the crude mixture. Ethyl 5-(2,6-dichlorophenyl)thiophene-3-carboxylate (10b): From 2-bromo-1,3-dichlorobenzene (0.226 g, 1 mmol) and ethyl thiophene

Structure elucidation of female-specific volatiles released by the parasitoid wasp Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)

• Armin Tröger,
• Teris A. van Beek,
• Martinus E. Huigens,
• Isabel M. M. S. Silva,
• Maarten A. Posthumus and
• Wittko Francke

Beilstein J. Org. Chem. 2014, 10, 767–773, doi:10.3762/bjoc.10.72

• stereoisomers of the target diene 14 was obtained via 2,4,6-trimethylnonanal (13) [15]. GC–MS-analysis of this mixture revealed a 3:1 dominance of the E-configurated racemates over the earlier eluting Z-series. The chromatogram showed seven well-separated peaks, indicating that only two isomers co-eluted (see

Asymmetric total synthesis of a putative sex pheromone component from the parasitoid wasp Trichogramma turkestanica

• Danny Geerdink,
• Jeffrey Buter,
• Teris A. van Beek and
• Adriaan J. Minnaard

Beilstein J. Org. Chem. 2014, 10, 761–766, doi:10.3762/bjoc.10.71

• , not even with freshly prepared 14. Moreover, in none of the successive steps the impurity could be separated and therefore also this approach was abandoned. Although NMR and GC–MS analysis of the mixture gave no conclusive evidence for the nature of the impurity, double bond isomers of 15 could

[²H₂₆]-1-epi-Cubenol, a completely deuterated natural product from Streptomyces griseus

• Christian A. Citron and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 2841–2845, doi:10.3762/bjoc.9.319

• ], followed by extraction with dichloromethane and GC–MS analysis of headspace extracts. While 2-MIB (1), caryolan-1-ol (2) and 1-epi-cubenol (3) were all produced during growth on full medium (65.GYM), consistent with previous results using other full media [26], only for 3 similar levels of production were

Halogenated volatiles from the fungus Geniculosporium and the actinomycete Streptomyces chartreusis

• Tao Wang,
• Patrick Rabe,
• Christian A. Citron and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 2767–2777, doi:10.3762/bjoc.9.311

• benzyltrimethylammonium tetrachloroiodate in moderate yield (34%) [22]. All six compounds were subjected to GC–MS analysis using the same type of GC column as for the headspace extract from Geniculosporium (HP5-MS) and their retention indices together with the NMR spectroscopic data are summarised in Table 2. Mass

• CLSA followed by GC–MS analysis of the obtained headspace extracts, led to a surprising result. The extracts contained a trace compound that was readily identified from its mass spectrum and comparison to an authentic standard as methyl 2-iodobenzoate (23, Figure 6A). This compound was observed as the

Activation of cryptic metabolite production through gene disruption: Dimethyl furan-2,4-dicarboxylate produced by Streptomyces sahachiroi

• Dinesh Simkhada,
• Huitu Zhang,
• Shogo Mori,
• Howard Williams and
• Coran M. H. Watanabe

Beilstein J. Org. Chem. 2013, 9, 1768–1773, doi:10.3762/bjoc.9.205

• flow rate of 0.75 mL/min in 254 nm UV. The same program was used for LC–APCI analysis. For GC–MS analysis, the sample was diluted 1:10 in DCM and was performed on an Ultra GC/DSQ (ThermoElectron, Waltham, MA). A Rxi-5ms gas chromatographic column was utilized with dimensions of 60 m length, 0.25 mm i.d