Reaction of selected carbohydrate aldehydes with benzylmagnesium halides: benzyl versus o-tolyl rearrangement

• Maroš Bella,
• Bohumil Steiner,
• Vratislav Langer and
• Miroslav Koóš

Beilstein J. Org. Chem. 2014, 10, 1942–1950, doi:10.3762/bjoc.10.202

• technique. When reporting assignments of NMR signals, the data for the phenyl moiety are identified by a prime. The EI mass spectra (70 eV) were obtained on a Q-Tof Premier instrument (Waters). Column chromatography was performed as flash chromatography on Silica Gel 60 (E. Merck, 0.063–0.200 mm). The IR

Syntheses of ¹⁵N-labeled pre-queuosine nucleobase derivatives

• Jasmin Levic and
• Ronald Micura

Beilstein J. Org. Chem. 2014, 10, 1914–1918, doi:10.3762/bjoc.10.199

• with hydrazine hydrate. The previously published route [11] recommended N-Boc functionalization of the preQ1 base in the crude reaction mixture to enable flash chromatography on SiO2 followed by cleavage of the auxiliary function, however, although robust in handling, the yields were rather modest. We

Structure/affinity studies in the bicyclo-DNA series: Synthesis and properties of oligonucleotides containing bc^en-T and iso-tricyclo-T nucleosides

• Branislav Dugovic,
• Michael Wagner and
• Christian J. Leumann

Beilstein J. Org. Chem. 2014, 10, 1840–1847, doi:10.3762/bjoc.10.194

• use of compound 6 as nucleobase acceptor improved the yield of nucleosides 7α,β in general and led to an acceptable β:α = 2.5:1 ratio of anomers. Subsequent saponification of 7α,β (unseparable by flash chromatography) proved to be tricky and after testing a series of standard techniques, only

• treatment with Bu4NOH in a mixed organic/aqueous solvent gave nucleosides 8α,β in good yield. It was at this step where the two anomers could be readily separated by flash chromatography. Continuing with 8β the synthesis of 10 was concluded by standard tritylation (→ 9) and phosphitylation. To extend on the

• ,β in a ratio of β:α = 1.2:1. After standard tritylation of 11α,β the anomeric mixture 12α,β became separable by flash chromatography and the corresponding β-nucleoside 12β could be smoothly converted into the phosphoramidite 13 by standard methods. Structural properties of nucleosides To get an

Sacrolide A, a new antimicrobial and cytotoxic oxylipin macrolide from the edible cyanobacterium Aphanothece sacrum

• Naoya Oku,
• Miyako Matsumoto,
• Kohsuke Yonejima,
• Keijiroh Tansei and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2014, 10, 1808–1816, doi:10.3762/bjoc.10.190

• the availability of genetic resources. Experimental General methods Cosmosil 75C18-PREP (Nacalai Tesque Inc., 75 µm) was used for ODS flash chromatography. NMR spectra were obtained by a Bruker AVANCE 500 spectrometer at 500 MHz for 1H. Residual solvent peaks at δH/δC 7.27/77.0 ppm in CDCl3 were used

One-pot stereoselective synthesis of α,β-differentiated diamino esters via the sequence of aminochlorination, aziridination and intermolecular S_N2 reaction

• Yiwen Xiong,
• Ping Qian,
• Chenhui Cao,
• Haibo Mei,
• Jianlin Han,
• Guigen Li and
• Yi Pan

Beilstein J. Org. Chem. 2014, 10, 1802–1807, doi:10.3762/bjoc.10.189

• separated, and the aqueous phase was extracted with ethyl acetate (3 × 10 mL). The combined organic layers were washed with brine, dried over anhydrous sodium sulfate, and concentrated to dryness. Purification by flash chromatography (EtOAc/hexane, from 1:20 to 1:3, v/v) provided final products 5. ORTEP

Convergent synthetic methodology for the construction of self-adjuvanting lipopeptide vaccines using a novel carbohydrate scaffold

• Vincent Fagan,
• Istvan Toth and
• Pavla Simerska

Beilstein J. Org. Chem. 2014, 10, 1741–1748, doi:10.3762/bjoc.10.181

• removed during work-up. The residue was alkylated with sodium hydride and propargyl bromide in dry tetrahydrofuran (THF) to give intermediate 7, which was not isolated. The methoxy ester was hydrolyzed in situ by addition of sodium hydroxide. Acid–base extraction and purification by flash chromatography

• . Treatment of commercially available Fmoc-Lys-OH with lauroyl chloride, in the presence of diisopropylethylamine (DIPEA), gave lipidated Fmoc-lysine (8) in 35% yield after flash chromatography (Scheme 3A). The low yield could be attributed to the formation of a significant amount of a dimeric lysine

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

• flash chromatography using Merck silica gel 60 (70–200 mesh). Thin-layer chromatography was performed with 0.2 mm pre-coated polyester sheets (Polygram SIL (G/UV254), Macherey-Nagel). NMR spectra were obtained on either a Bruker DRX-400 (400 MHz) or an AV III-400 (400 MHz) spectrometer and were

Homochiral BINOL-based macrocycles with π-electron-rich, electron-withdrawing or extended spacing units as receptors for C₆₀

• Marco Caricato,
• Silvia Díez González,
• Idoia Arandia Ariño and
• Dario Pasini

Beilstein J. Org. Chem. 2014, 10, 1308–1316, doi:10.3762/bjoc.10.132

• commercially available plates. Flash chromatography was carried out by using silica gel (pore size 60 Å, 230–400 mesh). 1H and 13C NMR spectra were recorded from solutions in CDCl3 on 200 or 300 MHz spectrometer with the solvent residual proton signal or tetramethylsilane as a standard. The UV–vis

• dry CH2Cl2 under stirring and N2. The solution is stirred overnight, and then H2O (10 mL) is added. The aqueous phase is extracted with CH2Cl2 (3×), the organic phase is washed with H2O (3×) and dried (MgSO4). The products are then purified by flash chromatography. Macrocycles (R,R)-3b and (R,R,R)-4b

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

• Bruker GPX (400 MHz). GC was performed on a Shimadzu GC-2014 and GC–MS was performed on a Shimadzu QP-2010S. Chemical shifts are reported in ppm relative to CDCl3 (1H: 7.26 and 13C: 77.0). Flash chromatography was performed on silica gel (230–400 mesh). General procedure for direct arylations The aryl

Stereocontrolled synthesis of 5-azaspiro[2.3]hexane derivatives as conformationally “frozen” analogues of L-glutamic acid

• Beatrice Bechi,
• David Amantini,
• Cristina Tintori,
• Maurizio Botta and
• Romano di Fabio

Beilstein J. Org. Chem. 2014, 10, 1114–1120, doi:10.3762/bjoc.10.110

• optimized by replacing step c) CH2N2 (diazomethane) with TMSCHN2 (trimethylsilyl diazomethane). This intermediate was transformed into intermediate 17 by a Horner–Wadsworth–Emmons reaction [23][24], thereby obtaining 17 as the single E-isomer in 68% yield after purification by flash chromatography (Scheme 3

• initial attempts afforded compound 18 in 50% average yield, but also resulted in significant amounts of the undesired byproduct 19 (ratio 18:19 = 4:1 by 1H NMR), a compound difficult to separate by flash chromatography from product 18. Therefore, a thorough optimization of the reaction conditions was

• mixture at 70–90 °C for 2 h, the olefin derivative 18 was isolated in 58% yield after purification by flash chromatography. Notably, under these reaction conditions no formation of the byproduct 19 was observed. After successfully obtaining terminal olefin 18, the efforts were then focused on the

cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• solution of saturated NaHCO3 (100 mL), and after stirring for 10 min both phases were separated. The aqueous phase was extracted with EtOAc (3 × 50 mL), the combined organic layers were dried (Na2SO4) and evaporated. The residue after flash chromatography (CHCl3/acetone/HCO2H, 97:3:1, twice) yielded title

Visible light mediated intermolecular [3 + 2] annulation of cyclopropylanilines with alkynes

• Theresa H. Nguyen,
• Soumitra Maity and
• Nan Zheng

Beilstein J. Org. Chem. 2014, 10, 975–980, doi:10.3762/bjoc.10.96

• (18 watts) positioned 8 cm from the test tube. After the reaction was complete as monitored by TLC, the mixture was diluted with diethyl ether and filtered through a short pad of silica gel. The filtrate was concentrated in vacuum and purified by silica gel flash chromatography to afford the desired

Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles

• Zong Guan,
• Jan C. Namyslo,
• Martin H. H. Drafz,
• Martin Nieger and
• Andreas Schmidt

Beilstein J. Org. Chem. 2014, 10, 832–840, doi:10.3762/bjoc.10.79

• groups. Heating of the carbene dimer results in the formation of novel quinazolines. Experimental General considerations: All reactions for the dimerisation and the rearrangement were carried out under an atmosphere of nitrogen in oven-dried glassware. Flash-chromatography was performed with silica gel

Domino reactions of 2H-azirines with acylketenes from furan-2,3-diones: Competition between the formation of ortho-fused and bridged heterocyclic systems

• Alexander F. Khlebnikov,
• Mikhail S. Novikov,
• Viktoriia V. Pakalnis,
• Roman O. Iakovenko and
• Dmitry S. Yufit

Beilstein J. Org. Chem. 2014, 10, 784–793, doi:10.3762/bjoc.10.74

• -diones 2a–c and 3-aryl-2H-azirines 1a–c. A mixture of azirine 1 (1 mmol) and furane-2,3-dione 2 (1 mmol) in anhydrous benzene (5 mL) was refluxed for 0.5–1 h. The solvent was removed in vacuum, and the residue was purified by flash chromatography on silica (eluent petroleum ether/ethyl acetate, 1:1

A novel family of (1-aminoalkyl)(trifluoromethyl)- and -(difluoromethyl)phosphinic acids – analogues of α-amino acids

• Natalia V. Pavlenko,
• Tatiana I. Oos,
• Yurii L. Yagupolskii,
• Igor I. Gerus,
• Uwe Doeller and
• Lothar Willms

Beilstein J. Org. Chem. 2014, 10, 722–731, doi:10.3762/bjoc.10.66

• acetaminomethylenemalonate have been used to prepare the title compounds. Experimental All reactions with P–H compounds were performed under an argon atmosphere. Flash chromatography was carried out using Merck silica gel 60 (230–400 mesh ASTM) and Aldrich ion-exchange resin Dowex WX-50. The NMR spectra were recorded on

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

• Peter H. Huy,
• Julia C. Westphal and
• Ari M. P. Koskinen

Beilstein J. Org. Chem. 2014, 10, 369–383, doi:10.3762/bjoc.10.35

• hydrogen and subsequent Boc-protection in one pot, the diastereomers cis- and trans-16c were easily separated by flash chromatography. Thereby, we found it advantageous to perform the hydrogenolysis in the presence of HCl to protonate the released amine and then induce Boc protection after neutralisation

Synthesis of the B-seco limonoid core scaffold

• Hanna Bruss,
• Hannah Schuster,
• Rémi Martinez,
• Markus Kaiser,
• Andrey P. Antonchick and
• Herbert Waldmann

Beilstein J. Org. Chem. 2014, 10, 194–208, doi:10.3762/bjoc.10.15

• regioselective opening [60][61] leading to the β-hydroxyketone that was temporarily masked as a TES ether. Reduction of ketone 85 with NaBH4 resulted in the formation of two diastereomeric alcohols in 2:1 ratio. To our delight flash chromatography permitted smooth separation of the two compounds. nOe studies

One-pot synthesis of cyanohydrin derivatives from alkyl bromides via incorporation of two one-carbon components by consecutive radical/ionic reactions

• Shuhei Sumino,
• Akira Fusano,
• Hiroyuki Okai,
• Takahide Fukuyama and
• Ilhyong Ryu

Beilstein J. Org. Chem. 2014, 10, 150–154, doi:10.3762/bjoc.10.12

• h. After cooling to room temperature, the reaction mixture was concentrated and purified by silica gel flash chromatography (hexane/EtOAc 97:3) to afford 3a (95.3 mg, 79%). 1H NMR (CDCl3, 500 MHz) δ 5.18 (t, J = 6.8 Hz, 1H), 4.4–4.2 (m, 2H), 2.0–1.9 (m, 2H), 1.6–1.5 (m, 2H), 1.4–1.2 (m, 13H), 0.88

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• (10 mol %) and azobisisobutyronitrile (AIBN, 8 mol %) in air under irradiation for two days. The product was purified by flash chromatography to obtain a mixture of cis and trans isomers, whose ratio depends primarily on the nature of the substituent in cyclopropanes 26a–e [240]. The oxidation of

Synthesis and determination of the absolute configuration of (−)-(5R,6Z)-dendrolasin-5-acetate from the nudibranch Hypselodoris jacksoni

• I. Wayan Mudianta,
• Victoria L. Challinor,
• Anne E. Winters,
• Karen L. Cheney,
• James J. De Voss and
• Mary J. Garson

Beilstein J. Org. Chem. 2013, 9, 2925–2933, doi:10.3762/bjoc.9.329

• acetone followed by partitioning into diethyl ether gave an extract which was fractionated first by normal phase (NP) flash chromatography and then by preparative NP HPLC to give (+)-agassizin, (−)-furodysinin, (−)-euryfuran, (−)-dehydroherbadysidolide, (+)-pallescensone, and the new sesquiterpene 1

3-Pyridinols and 5-pyrimidinols: Tailor-made for use in synergistic radical-trapping co-antioxidant systems

• Luca Valgimigli,
• Daniele Bartolomei,
• Riccardo Amorati,
• Evan Haidasz,
• Jason J. Hanthorn,
• Susheel J. Nara,
• Johan Brinkhorst and
• Derek A. Pratt

Beilstein J. Org. Chem. 2013, 9, 2781–2792, doi:10.3762/bjoc.9.313

• removed by filtration through a pad of celite and the filtrate was concentrated under reduced pressure. The crude residue obtained was subjected to flash chromatography on silica gel (eluent: ethyl acetate/hexanes) and the product isolated in quantitative yield. 1H NMR (CDCl3) δ 2.15 (s, 6H), 2.43 (s, 6H

• % Pd/C and the resulting black suspension was stirred at room temperature under an atmosphere of H2 (1 atm) overnight. The catalyst was removed by filtration through a pad of celite and the filtrate was concentrated under reduced pressure. The crude residue obtained was subjected to flash

• chromatography on silica gel (eluent: ethyl acetate/hexanes) and the product isolated in quantitative yield. 1H NMR (CDCl3) δ 9.32 (br s, 1H, exchanges with D2O), 7.75 (s, 1H), 7.25 (d, J = 8.6 Hz, 1H), 6.56 (d, 8.6 Hz, 1H), 3.84 (s, 3H); 13C NMR (CDCl3) δ 54.2, 111.0, 128.7, 132.3, 148.2, 158.3; HRMS (EI+) m/z

Total synthesis of the endogenous inflammation resolving lipid resolvin D2 using a common lynchpin

• John Li,
• May May Leong,
• Alastair Stewart and
• Mark A. Rizzacasa

Beilstein J. Org. Chem. 2013, 9, 2762–2766, doi:10.3762/bjoc.9.310

• with triphenylphosphine. Treatment of the salt 6 with n-BuLi gave the ylide and condensation with the aldehyde 7 afforded the desired E-enyne 11 along with the Z-isomer in a ratio of 2.2:1 which were easily separated by flash chromatography (Scheme 3). The minor Z-isomer could also provide novel

One-pot cross-enyne metathesis (CEYM)–Diels–Alder reaction of gem-difluoropropargylic alkynes

• Santos Fustero,
• Paula Bello,
• Javier Miró,
• María Sánchez-Roselló,
• Günter Haufe and
• Carlos del Pozo

Beilstein J. Org. Chem. 2013, 9, 2688–2695, doi:10.3762/bjoc.9.305

• mixture and was allowed to react for two additional hours. Flash chromatography of the crude product afforded the desired tandem derivative 3a in 60% overall yield (Scheme 2). Next, the one-pot protocol was extended to other starting difluoropropargylic alkynes and dienophiles, affording a new family of

• reaction mixture was purified by flash chromatography in hexanes/ethyl acetate (3:1). N-Benzyl-2,2-difluoro-3-methylenepent-4-enamide (2a). Following the procedure described above and before adding the dienophile, the crude mixture was subjected to flash chromatography affording 41 mg of 2a (70% yield) as

Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate

• James A. B. Laurenson,
• John A. Parkinson,
• Jonathan M. Percy,
• Giuseppe Rinaudo and
• Ricard Roig

Beilstein J. Org. Chem. 2013, 9, 2660–2668, doi:10.3762/bjoc.9.301

• oxidation (catalytic osmium tetroxide, NMO aqueous t-BuOH, 83%) of 25 to avoid ambiguity, and converted to the dibenzoate 29c (not shown, 80%) as described above. The dibenzoates were purified by flash chromatography then examined by chiral HPLC (Chiralcel OD, 2% iPrOH in hexane). The separation of the

Gold(I)-catalyzed domino cyclization for the synthesis of polyaromatic heterocycles

• Mathieu Morin,
• Patrick Levesque and
• Louis Barriault

Beilstein J. Org. Chem. 2013, 9, 2625–2628, doi:10.3762/bjoc.9.297

• equipped with a magnetic stirrer was added the silyl enol ether 11 (0.101 mmol) followed by nitromethane (1 mL) and [L1AuNCMe][SbF6] (0.005 mmol). After stirring overnight, the reaction mixture was concentrated in vacuo and the crude mixture was purified by flash chromatography (1–5% ethyl acetate/hexanes