Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres

• Myriam Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262

• isomers had to be separated by flash chromatography. In 2014, Sano and co-workers reported a selective synthesis of Xaa-ψ[CF=C]-Pro with a new cyclopentanone derivative 20 bearing a bulky 2-(4-methyl-2,6,7-trioxabicyclo[2.2.2]octan-1-yl) group (OBO), which favoured the formation of the (E)-isomer in the

• starting from the commercially available protected chiral hydroxyl ester 75. Reduction to the aldehyde followed by coupling with bromodifluoropropene gave two diastereoisomers 76a and 76b separable by flash chromatography. Then, the copper-catalyzed defluorinative allylic alkylation using Grignard reagents

• -alkylation on the γ,γ-difluoro-α,β-unsaturated δ-lactam 86. Unfortunately, the α-alkylation provided a mixture of diastereoisomers 87a and 87b which was separable by flash chromatography. The dipeptide isostere 88 was finally obtained after the opening of the lactam 87b in acidic conditions and N-Boc

An efficient synthesis of a C₁₂-higher sugar aminoalditol

• Łukasz Szyszka,
• Anna Osuch-Kwiatkowska,
• Mykhaylo A. Potopnyk and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2017, 13, 2146–2152, doi:10.3762/bjoc.13.213

• phases were separated, and the aqueous layer was extracted with CH2Cl2 (3 × 20 mL). The combined organic solutions were washed with water (30 mL) and brine (30 mL), dried, concentrated, and the crude material was purified by flash chromatography (hexanes/ethyl acetate 5:1 to 2:1) to afford 13 (0.19 g

Iodoarene-catalyzed cyclizations of N-propargylamides and β-amidoketones: synthesis of 2-oxazolines

• Somaia Kamouka and
• Wesley J. Moran

Beilstein J. Org. Chem. 2017, 13, 1823–1827, doi:10.3762/bjoc.13.177

• mixture extracted with CH2Cl2. The organic layers were combined and dried with MgSO4, filtered and concentrated under vacuum. The product was purified by flash chromatography (9:1 petroleum ether/EtOAc) to provide oxazoline 6. See Supporting Information File 1 for full experimental details. Examples of

An efficient Pd–NHC catalyst system in situ generated from Na₂PdCl₄ and PEG-functionalized imidazolium salts for Mizoroki–Heck reactions in water

• Nan Sun,
• Meng Chen,
• Liqun Jin,
• Wei Zhao,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 1735–1744, doi:10.3762/bjoc.13.168

• extracted with MTBE (5 mL × 2) and the organic layers combined, dried over anhydrous Na2SO4, and concentrated under vacuum. Finally, the resulted residual were purified by flash chromatography on silica to afford the desired cross-coupling alkene products. The purity of the obtained products was confirmed

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Effect of uridine protecting groups on the diastereoselectivity of uridine-derived aldehyde 5’-alkynylation

• Raja Ben Othman,
• Mickaël J. Fer,
• Laurent Le Corre,
• Sandrine Calvet-Vitale and
• Christine Gravier-Pelletier

Beilstein J. Org. Chem. 2017, 13, 1533–1541, doi:10.3762/bjoc.13.153

• ) and allyl bromide (1.5 equiv). The suspension was stirred at 50 °C for 12 h, filtered and concentrated in vacuo. The resulting residue was submitted to flash chromatography (elution conditions mentioned below) to afford the corresponding N-allyl compound. General procedure for the oxidation of uridine

• h. The reaction was then quenched by addition of a saturated aqueous solution of NH4Cl (40 mL) and THF was removed in vacuo. The aqueous phase was extracted with EtOAc and the combined organic layers were dried over Na2SO4, filtered and concentrated in vacuo. The crude foam was purified by flash

• chromatography. C-5’ configuration of nucleoside derivatives and related biological activity. 1H NMR of (5’R)-16 and (5’S)-16 and of a (5’R)/(5’S)-16 mixture. 1H NMR of (5’R)-17 and (5’S)-17 and example of configuration determination for a pure isolated compound with unknown configuration. Hypothetical Cram

Synthesis of oligonucleotides on a soluble support

• Harri Lönnberg

Beilstein J. Org. Chem. 2017, 13, 1368–1387, doi:10.3762/bjoc.13.134

• precipitation from water and one flash chromatography (Scheme 11). Detritylation was carried out with HCl in a 2:5 (v/v) mixture of MeOH and DCM. The acid was neutralized with pyridine, the mixture concentrated to oil and subjected to flash column chromatography on silica gel. For subsequent coupling, the

• desired commercial block was used in 50% excess and DCI as an activator. After standard I2 oxidation, the support-bound material was precipitated from water. The precipitation was quantitative, but some reagents and byproducts, above all DCI, coprecipitated with the support. The flash chromatography after

An improved preparation of phorbol from croton oil

• Alberto Pagani,
• Simone Gaeta,
• Andrei I. Savchenko,
• Craig M. Williams and
• Giovanni Appendino

Beilstein J. Org. Chem. 2017, 13, 1361–1367, doi:10.3762/bjoc.13.133

• purification of a crude mixture of ethanol solvates of phorboids by reverse-phase preparative flash chromatography or by countercurrent chromatography were developed [15][16][17]. The recovery of the triesters could be improved by first treating croton oil with acidic methanol to selectively remove the 20-acyl

Aqueous semisynthesis of C-glycoside glycamines from agarose

• Juliana C. Cunico Dallagnol,
• Alexandre Orsato,
• Diogo R. B. Ducatti,
• Miguel D. Noseda,
• Maria Eugênia R. Duarte and
• Alan G. Gonçalves

Beilstein J. Org. Chem. 2017, 13, 1222–1229, doi:10.3762/bjoc.13.121

• in warm MeOH (50 mL), filtered through a borosilicate sintered funnel and dried under reduced pressure. Finally the crude was submitted to flash chromatography (Silica Gel 60, Eluent: MeOH/2 M NH4OH 6:1) to give the pure glycamine. Physical data and spectral assignments Compound 3: [α]D: −23.0 (c 1.0

Phosphorus pentasulfide mediated conversion of organic thiocyanates to thiols

• Chandra Kant Maurya,
• Avik Mazumder and
• Pradeep Kumar Gupta

Beilstein J. Org. Chem. 2017, 13, 1184–1188, doi:10.3762/bjoc.13.117

• water (10 mL), extracted with ethyl acetate (3 × 10 mL), the organic phase was dried over sodium sulfate and evaporated under reduced pressure to get the crude product which was purified by flash chromatography (hexane–ethyl acetate) to get the pure thiol. 3-Phenoxypropylthiol (7) Oil (1.43 g, 85%). IR

Regioselective (thio)carbamoylation of 2,7-di-tert-butylpyrene at the 1-position with iso(thio)cyanates

• Anna Wrona-Piotrowicz,
• Marzena Witalewska,
• Janusz Zakrzewski and
• Anna Makal

Beilstein J. Org. Chem. 2017, 13, 1032–1038, doi:10.3762/bjoc.13.102

• evaporated. The products were isolated by flash chromatography (eluent: CH2Cl2). 2,7-Di-tert-butyl-N-ethylpyrene-1-carboxamide (3a). White solid (293 mg, 76%). Mp 258–259 °C; 1H NMR (600 MHz, CDCl3) δ 8.26 (s, 1H), 8.20 (d, J = 1.8 Hz, 1H), 8.18 (d, J = 1.8 Hz, 1H), 8.03 (m, 3H), 7.98 (d, J = 9.0 Hz, 1H

• anhydride (278 μL, 2 mmol) in CH2Cl2 (20 mL). The reaction mixture was warmed to room temperature and stirred for 2 h. After this time the reaction mixture was poured into ice-water (50 mL) and extracted several times with CH2Cl2. The combined extracts were dried over anhydrous Na2SO4 and evaporated. Flash

• chromatography (eluent: CH2Cl2) afforded the product. Yellow solid. (310 mg, 87%). Mp 121–122 °C; 1H NMR (600 MHz, CDCl3) δ 9.23 (d, J = 1.8 Hz, 1H), 8.59 (s, 1H), 8.29 (d, J = 1.2 Hz, 1H), 8.28 (d, J = 1.8 Hz, 1H), 8.24 (d, J = 1.2 Hz, 1H), 8.05 (d, J = 9.0 Hz, 1H), 8.01 (d, J = 9.0 Hz, 1H), 2.94 (s, 3H), 1.60

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

• apparatus for 4.0 hours. The yield of the crude extract (2.70 g) was 26% based on the dry-leaves weight. The extract components were partially separated by gradient flash chromatography using silica gel 60 (0.040–0.063 mm) as absorbent and 5–80% of acetone in petroleum ether as eluent, followed by a washing

Total synthesis of TMG-chitotriomycin based on an automated electrochemical assembly of a disaccharide building block

• Yuta Isoda,
• Norihiko Sasaki,
• Kei Kitamura,
• Shuji Takahashi,
• Sujit Manmode,
• Naoko Takeda-Okuda,
• Jun-ichi Tamura,
• Toshiki Nokami and
• Toshiyuki Itoh

Beilstein J. Org. Chem. 2017, 13, 919–924, doi:10.3762/bjoc.13.93

• silica gel F254 plates (thickness 0.25 mm). Flash chromatography was carried out on a column of silica gel (Kanto Chem. Co., Silica Gel N, spherical, neutral). Gel permeation chromatography (GPC) was carried out on a Japan Analytical Industry LC-918 equipped with JAIGEL-2H using CHCl3 as eluent. All

A practical and efficient approach to imidazo[1,2-a]pyridine-fused isoquinolines through the post-GBB transformation strategy

• Taofeng Shao,
• Zhiming Gong,
• Tianyi Su,
• Wei Hao and
• Chao Che

Beilstein J. Org. Chem. 2017, 13, 817–824, doi:10.3762/bjoc.13.82

• under vacuum and the resulting residue was purified by flash chromatography (hexane/ethyl acetate 8:1) to afford GBB adduct 4a (90% yield). Typical procedure for the Au-catalyzed cyclization reaction. To a solution of the GBB adduct 4 (0.2 mmol) in 2 mL of acetonitrile was added Au(JohnPhos)Cl (0.02

• mmol) and the resulting mixture was stirred under inert atmosphere at reflux temperature for 24 h. Then, the solvent was removed under vacuum and the residue purified by flash chromatography (hexane/ethyl acetate 5:1) to afford the desired product 6. Representative bioactive imidazo[1,2-a]pyridine and

Synthesis of ribavirin 2’-Me-C-nucleoside analogues

• Fanny Cosson,
• Aline Faroux,
• Jean-Pierre Baltaze,
• Jonathan Farjon,
• Régis Guillot,
• Jacques Uziel and
• Nadège Lubin-Germain

Beilstein J. Org. Chem. 2017, 13, 755–761, doi:10.3762/bjoc.13.74

• at 0 °C. Then the mixture was stirred for 12 h at rt and concentrated in vacuum. The residue was purified by flash chromatography (EtOAc/cyclohexane, 3:7 to 1:0) affording the mixture of the corresponding 1-benzyl-4-(2’,3’-O-isopropylidene-2’-C-methyl-β-D-ribofuranosyl)-1,2,3-triazole-5-carboxamide

• for C19H22O5, 330.1467; found, 330.1478. The mixture of carboxamides and palladium chloride (23 mg, 0.13 mmol) in ethanol (10 mL) was hydrogenated with H2 at 4 bar for 48 h. After filtration over Celite and concentration in vacuum, the crude was purified by flash chromatography (cyclohexane/EtOAc 2:8

• mL) with palladium chloride (9.1 mg, 0.05 mmol) under 4 bar pressure of hydrogen for 24 h. After filtration over Celite and concentration in vacuum, the crude was purified by flash chromatography (pure EtOAc to EtOAc/MeOH 1:1) to afford 3 as a white solid (0.03 g, 45%) that was lyophilized. [α]D25

Ultrasound-promoted organocatalytic enamine–azide [3 + 2] cycloaddition reactions for the synthesis of ((arylselanyl)phenyl-1H-1,2,3-triazol-4-yl)ketones

• Gabriel P. Costa,
• Natália Seus,
• Juliano A. Roehrs,
• Raquel G. Jacob,
• Ricardo F. Schumacher,
• Thiago Barcellos,
• Rafael Luque and
• Diego Alves

Beilstein J. Org. Chem. 2017, 13, 694–702, doi:10.3762/bjoc.13.68

• developing agents. Baker silica gel (particle size 0.040–0.063 mm) was used for flash chromatography. A Cole Parmer-ultrasonic processor Model CPX 130, with a maximum power of 130 W, operating at an amplitude of 40% and a frequency of 20 kHz was used. The temperature of the reaction was monitored using an

Secondary metabolome and its defensive role in the aeolidoidean Phyllodesmium longicirrum, (Gastropoda, Heterobranchia, Nudibranchia)

• Alexander Bogdanov,
• Cora Hertzer,
• Stefan Kehraus,
• Samuel Nietzer,
• Sven Rohde,
• Peter J. Schupp,
• Heike Wägele and
• Gabriele M. König

Beilstein J. Org. Chem. 2017, 13, 502–519, doi:10.3762/bjoc.13.50

• Thermo Scientific Qexactive mass spectrometer with HESI source, Phenomenex Kinetex C18 column (150 mm × 4.6 mm, 2.6 µm, 100 Å). A Grace Reveleris X2 system equipped with 12 g Reveleris C18 column was used for flash chromatography. HPLC was performed either on a Merck Hitachi HPLC system equipped with a L

Highly reactive, liquid diacrylamides via synergistic combination of spatially arranged curing moieties

• Maximilian Maier,
• Magnus S. Schmidt,
• Markus Ringwald and
• Christoph P. Fik

Beilstein J. Org. Chem. 2017, 13, 372–383, doi:10.3762/bjoc.13.40

• rt. Then, the THF was evaporated, ethyl acetate was added and the resulting mixture was washed 3 times with 2 N HCl and once with water. The organic layer was dried (Na2SO4), the solvent was evaporated and the residue was purified by flash chromatography. N,N'-Diacryloyl-N,N'-diallyl-1,4-but-2

Continuous-flow synthesis of highly functionalized imidazo-oxadiazoles facilitated by microfluidic extraction

• Ananda Herath and
• Nicholas D. P. Cosford

Beilstein J. Org. Chem. 2017, 13, 239–246, doi:10.3762/bjoc.13.26

• flash chromatography (SiO2) to afford the desired product (CombiFlash® Rf, 12 g flash column). The solvent gradient was 90% hexane to 50% ethyl acetate over 15 min at a flow rate of 15 mL/min. General procedure for the continuous flow synthesis of imidazo[1,2-a]pyridin-2-yl-1,2,4-oxadiazoles (Table 3

• residue was purified via automated flash chromatography (SiO2) to afford the desired product (CombiFlash® Rf, 12g flash column). The solvent gradient was 90% hexane to 50% ethyl acetate over 15 min at a flow rate of 15 mL/min. In-flask (batch) preparation of imidazo[1,2-a]pyridin-2-yl-1,2,4-oxadiazoles

Efficient access to β-vinylporphyrin derivatives via palladium cross coupling of β-bromoporphyrins with N-tosylhydrazones

• Vinicius R. Campos,
• Ana T. P. C. Gomes,
• Anna C. Cunha,
• Maria da Graça P. M. S. Neves,
• Vitor F. Ferreira and
• José A. S. Cavaleiro

Beilstein J. Org. Chem. 2017, 13, 195–202, doi:10.3762/bjoc.13.22

• spectra were recorded on an UV-2501 PC Shimadzu spectrophotometer using CHCl3 as solvent. Flash chromatography was carried out using silica gel (230–400 mesh) and preparative thin-layer chromatography was carried out on 20 × 20 cm glass plates coated with silica gel (1 mm thick). The reactions were

A postsynthetically 2’-“clickable” uridine with arabino configuration and its application for fluorescent labeling and imaging of DNA

• Heidi-Kristin Walter,
• Bettina Olshausen,
• Ute Schepers and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2017, 13, 127–137, doi:10.3762/bjoc.13.16

• by flash chromatography (SiO2, 0 → 50% EtOAc in CH2Cl2). 1.78 g (3.66 mmol, 89%) of 4 as a colorless solid were obtained. Spectral data were in accordance with the literature [32]. Synthesis of 5. Under argon atmosphere 4 (1.02 g, 2.10 mmol) was dissolved in dry THF (20 mL) and cooled to 0 °C with an

Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates

• Matthias C. Letzel,
• Hans J. Schäfer and
• Roland Fröhlich

Beilstein J. Org. Chem. 2017, 13, 33–42, doi:10.3762/bjoc.13.5

• of triethylamine, whereby the menthyl esters 7–12 were obtained in good yield after flash chromatography as a mixture of two diastereomers (Scheme 1). The benzyl menthyl malonates 7–12 were hydrogenated under atmospheric pressure to afford the free carboxylic acids 13a/b–18a/b in high yield and

• extracted with ether (5 × 20 mL). The combined organic layers were washed with saturated sodium hydrogen carbonate (2 × 20 mL) and dried over MgSO4. After evaporation of the solvent in the vacuum the product was purified by flash chromatography. Homo-coupling reaction: 1.6 mmol of the auxiliary modified

• with methylene chloride (4 × 20 mL). The combined organic layers were washed successively with 2 N HCl (3 × 20 mL), saturated sodium hydrogen carbonate (2 × 20 mL) and brine (20 mL) and dried (MgSO4). After evaporation of the solvent the product was purified by flash chromatography. General procedure

Synthesis of spiro[isoindole-1,5’-isoxazolidin]-3(2H)-ones as potential inhibitors of the MDM2-p53 interaction

• Salvatore V. Giofrè,
• Santa Cirmi,
• Raffaella Mancuso,
• Francesco Nicolò,
• Giuseppe Lanza,
• Laura Legnani,
• Agata Campisi,
• Maria A. Chiacchio,
• Michele Navarra,
• Bartolo Gabriele and
• Roberto Romeo

Beilstein J. Org. Chem. 2016, 12, 2793–2807, doi:10.3762/bjoc.12.278

• reported in ppm relative to CDCl3 (7.26 ppm). Merck silica gel 60-F254 precoated aluminum plates have been used for thin-layer chromatographic separations. Flash chromatography was performed on Merck silica gel (200–400 mesh). Preparative separations were carried out by a MPLC Büchi C-601 by using Merck

• irradiated under microwave conditions at 200 W, 110 °C, for 4 h (CEM Discover Microwave reactor). The removal of the solvent in vacuo afforded a crude material which, after flash chromatography purification by using as eluent a mixture of chloroform/cyclohexane/ethyl acetate 5:3:2, gave compounds 6a and 7a

Chromium(II)-catalyzed enantioselective arylation of ketones

• Gang Wang,
• Shutao Sun,
• Ying Mao,
• Zhiyu Xie and
• Lei Liu

Beilstein J. Org. Chem. 2016, 12, 2771–2775, doi:10.3762/bjoc.12.275

• ) were added successively and the mixture was stirred at indicated temperature for 24 h. After that, the mixture was filtered through a short pad of celite and purified by flash chromatography using silica gel or alumina (200–300 mesh) to give the product 2. Scope of the catalytic enantioselective Cr

Facile synthesis of a 3-deazaadenosine phosphoramidite for RNA solid-phase synthesis

• Elisabeth Mairhofer,
• Elisabeth Fuchs and
• Ronald Micura

Beilstein J. Org. Chem. 2016, 12, 2556–2562, doi:10.3762/bjoc.12.250

• purified by flash chromatography (1% methanol in dichloromethane + 1.5% triethylamine, size: 18.0 × 2.5 cm, 23 g silica gel). Yield: 823.7 mg (63%) of compound 4 as beige foam. TLC (10% methanol in dichloromethane): Rf = 0.52; 1H NMR (300 MHz, DMSO-d6) δ 4.80–4.70 (m, 2H, H-C(5’)), 4.84–4.86 (t, J = 3.7 Hz

• ), dried over Na2SO4 and evaporated. The crude product was purified by flash chromatography (1% methanol in dichloromethane + 1.5% triethylamine, size: 18.0 × 2.0 cm, 21 g silica gel). Yield: 212 mg (40%) of compound 6 as white foam. TLC (10% methanol in dichloromethane): Rf = 0.32; 1H NMR (300 MHz, DMSO

• through celite and partitioned between dichloromethane and 5% aqueous sodium bicarbonate solution (10 mL each). The organic layer was washed twice with 5% aqueous sodium bicarbonate solution (2 × 10 mL), dried over Na2SO4 and evaporated. The regioisomers were separated by flash chromatography (toluene