Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• . Analysis of data combination from ovicidal activity, mass spectrometry, and metabolomics using HPLC-diode array detector-MS (HPLC-DAD-MS), partial least squares regression analysis (PLS-DA), and a correlation map (univariate correlation analyses) enabled the prediction of compounds that have a positive

Isolation and characterization of new phenolic siderophores with antimicrobial properties from Pseudomonas sp. UIAU-6B

• Emmanuel T. Oluwabusola,
• Olusoji O. Adebisi,
• Fernando Reyes,
• Kojo S. Acquah,
• Mercedes De La Cruz,
• Larry L. Mweetwa,
• Joy E. Rajakulendran,
• Digby F. Warner,
• Deng Hai,
• Rainer Ebel and
• Marcel Jaspars

Beilstein J. Org. Chem. 2021, 17, 2390–2398, doi:10.3762/bjoc.17.156

• presence of interesting aromatic compounds and led to a decision to undertake large-scale fermentation. The total crude extract (8.2 g) was subsequently subjected to a combination of fractionations (Kupchan partition and MPLC), and purification by reversed-phase semipreparative HPLC to obtain five new

• compounds 1–5 was assigned as ʟ, based on the derivatization with Marfey’s reagent of compound 2 and 4 hydrolysates, which represented the two distinctive structural scaffolds and chemical shifts followed by HPLC analysis of the derivatized amino acid residuals in the hydrolysate and threonine standards

• -deuterated solvent peak (3.31 and 49.1 ppm for CD3OD). The multiplicities of 13C NMR were determined by an edited heteronuclear single quantum coherence (HSQC) experiment. HRESIMS spectra were obtained using a Thermo Instruments MS system (LTQ XL/LTQ Orbitrap Discovery) coupled to a thermo instruments HPLC

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• (Scheme 23). The small amount of exo,cis-isomers 67Ba/67Bc was only detected by HPLC analysis of the crude reaction mixture. Takacs et al. observed the rapid cyclization of salicylamide-derived amidal auxiliary derivatives 68 and 70 in presence of 1.5 equiv of a 1:1 mixture of Hg(OAc)2/Hg(TFA)2 resulting

Phenolic constituents from twigs of Aleurites fordii and their biological activities

• Kyoung Jin Park,
• Won Se Suh,
• Da Hye Yoon,
• Chung Sub Kim,
• Sun Yeou Kim and
• Kang Ro Lee

Beilstein J. Org. Chem. 2021, 17, 2329–2339, doi:10.3762/bjoc.17.151

• SYNAPT G2 mass spectrometer and semipreparative HPLC was conducted using a Gilson 306 pump with a Shodex refractive index detector and a Phenomenex Luna 10 μm column (250 × 10 mm). Silica gel 60 (Merck, Darmstadt, 70–230 mesh, and 230–400 mesh) and RP-C18 silica gel (Merck, 230–400 mesh) were used for

• –C6). Fraction C1 (2.0 g) was subjected to RP-C18 silica gel chromatography, eluting with gradient solvent system (30 → 100% aq. MeOH) to yield four subfractions (C2A–C2D). Fraction C2C (210 mg) was purified by semipreparative HPLC (2 mL/min, 50% aq. MeOH) to yield compounds 17 (5 mg) and 19 (6 mg

• ). Fraction C3 (5.2 g) was subjected to RP-C18 silica gel chromatography, eluting with gradient solvent system (30 → 100% aq. MeOH) to yield five subfractions (C3A–C3E). Fraction C3B (554 mg) was subjected to repeated RP-C18 silica gel chromatography and further purified by semipreparative HPLC (50% aq. MeOH

Base-free enantioselective S_N2 alkylation of 2-oxindoles via bifunctional phase-transfer catalysis

• Mili Litvajova,
• Emiliano Sorrentino,
• Brendan Twamley and
• Stephen J. Connon

Beilstein J. Org. Chem. 2021, 17, 2287–2294, doi:10.3762/bjoc.17.146

• of biological interest, as evidenced by the facile preparation of the (S)-enantiomer of a potent CRTH2 receptor antagonist. The importance of the 3,3-spirooxindole core and its access through enantioselective enolate alkylation. Substrate scope. aIsolated yield. bDetermined by CSP-HPLC. cValue in

Nomimicins B–D, new tetronate-class polyketides from a marine-derived actinomycete of the genus Actinomadura

• Zhiwei Zhang,
• Tao Zhou,
• Taehui Yang,
• Keisuke Fukaya,
• Enjuro Harunari,
• Shun Saito,
• Katsuhisa Yamada,
• Chiaki Imada,
• Daisuke Urabe and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2194–2202, doi:10.3762/bjoc.17.141

• medium, and the whole culture broth was extracted with 1-butanol. The extract was subjected to silica gel and ODS column chromatography, and the final purification was achieved by reversed-phase HPLC to yield two new spirotetronate polyketides, nomimicins B (1) and C (2), along with a known compound

• give 0.23 g of brown oil that was further purified by preparative HPLC (Cosmosil 5C18-ARII, 10 × 250 mm, 4 mL/min, UV detection at 254 nm) with 73% MeCN in 0.1% HCO2H solution to yield nomimicin A (4, 33 mg, tR 21.5 min). Fractions 5 (2:1) and 6 (1:1) were combined and concentrated to provide 0.48 g of

• brown oil that was then fractionated by ODS column chromatography with a gradient of MeCN + 0.1% HCO2H solution (2:8, 3:7, 4:6, 5:5, 6:4, 7:3, and 8:2, v/v). The ODS fraction 6 (7:3) was concentrated to afford 0.22 g of semipure material. Final purification was achieved by preparative HPLC (Cosmosil

Enantioenriched α-substituted glutamates/pyroglutamates via enantioselective cyclopropenimine-catalyzed Michael addition of amino ester imines

• Zara M. Seibel,
• Jeffrey S. Bandar and
• Tristan H. Lambert

Beilstein J. Org. Chem. 2021, 17, 2077–2084, doi:10.3762/bjoc.17.134

• additions to methyl acrylate. Supporting Information Supporting Information File 314: Experimental details, characterization data, spectra, and HPLC traces. Acknowledgements We thank the Leighton group (Columbia University) for use of their instrumentation. Funding Financial support for this work was

Cascade intramolecular Prins/Friedel–Crafts cyclization for the synthesis of 4-aryltetralin-2-ols and 5-aryltetrahydro-5H-benzo[7]annulen-7-ols

• Jie Zheng,
• Shuyu Meng and
• Quanrui Wang

Beilstein J. Org. Chem. 2021, 17, 1481–1489, doi:10.3762/bjoc.17.104

• diastereoselectivity (cis/trans ratio = 1:99). The preferential formation of the trans-configured products for furan nucleophiles may be due to the fact that the addition of furan is reversible leading to equilibration to the more stable trans product. To test this hypothesis, we monitored the reaction by HPLC (Table

• mixture of 13a (1.40 mmol), nucleophile (1.47 mmol), BF3·Et2O (1.54 mmol) in anhydr. CH2Cl2 (6 mL) was stirred at 0 °C for 2 h. aIsolated yield by chromatography; bisolated by preparative HPLC. Reaction of aldehydes 13b–h with veratrole or furan. Reaction conditions: a mixture of 13b–h (1.40 mmol

Organocatalytic asymmetric Michael/acyl transfer reaction between α-nitroketones and 4-arylidenepyrrolidine-2,3-diones

• Chandrakanta Parida and
• Subhas Chandra Pan

Beilstein J. Org. Chem. 2021, 17, 1447–1452, doi:10.3762/bjoc.17.100

• 2 (0.1 mmol), 10 mol % VII in 0.6 mL 1,2-dichloroethane were reacted at 25 °C for 12 hours. Yields correspond to isolated yields after silica gel column chromatography and ees were determined by chiral HPLC. Catalyst screening and optimization of the reaction conditions. Scope of α-nitroketones 2 in

Analogs of the carotane antibiotic fulvoferruginin from submerged cultures of a Thai Marasmius sp.

• Birthe Sandargo,
• Leon Kaysan,
• Rémy B. Teponno,
• Christian Richter,
• Benjarong Thongbai,
• Frank Surup and
• Marc Stadler

Beilstein J. Org. Chem. 2021, 17, 1385–1391, doi:10.3762/bjoc.17.97

• characterization. Results Structure elucidation of the secondary metabolites 2–6 Preparative HPLC of the supernatant crude extract of a submerged cultivation of Marasmius sp. strain MFLUCC 14-0681 in ZM½ media led to the isolation of six carotane sesquiterpenoids, fulvoferruginins A–F (1–6, Figure 1). The first

• structure resembling that of the carotane sesquiterpenoid fulvoferruginin (1, [8]) with the only difference being a tertiary methyl group at C-14 (δC/H 8.7/1.20), instead of an olefin. Compound 2 was therefore named fulvoferruginin B. Subsequently, a minor peak following 2 in the HPLC chromatogram was

• distinct. Considering other rDNA regions currently leads to more questions than answers regarding the phylogeny and clearly shows the need for further taxonomic re-evaluation. Experimental General experimental procedures An Agilent 1200 series HPLC-UV system (Santa Clara, CA, USA) with an ESI-TOF-MS (MaXis

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• mixing elements, reactor residence coils, heating/cooling segments and additional downstream components such as phase separators, quenching stages and crystallisers. A typical flow reactor will comprise two or more pumps (isocratic/peristaltic/syringe) that feed an HPLC manifold (into which samples may

• introduced to the reactor alongside cyclohexanone (65) in a single flow stream. A simple HPLC pump, mild heating (50 °C) and a residence time of 25 minutes was all that was required to give the β-hydroxy ketone 66 with >95% conversion, with modest diastereomeric ratio (dr) of 3:1 and high ee (82%). In the

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

Synthesis of 10-O-aryl-substituted berberine derivatives by Chan–Evans–Lam coupling and investigation of their DNA-binding properties

• Peter Jonas Wickhorst,
• Mathilda Blachnik,
• Denisa Lagumdzija and
• Heiko Ihmels

Beilstein J. Org. Chem. 2021, 17, 991–1000, doi:10.3762/bjoc.17.81

• buffer solution. Oligodeoxyribonucleotides (HPLC purified) d[A(GGGTAA)3GGG] (22AG), F21T [fluo-G3(TTAG3)3-tamra; fluo = fluorescein, tamra = tetramethylrhodamine], Fa2T [fluo-(ACAG3TGT)2-tamra], FmycT [fluo-TGAG3TG3TAG3TG3TA-tamra] and FkitT [fluo-AG3AG3CGCTG3AG2AG3-tamra] were purchased from Biomers.net

Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• donors in liquid SO2. Reactions were carried out at 30 °C for mannosyl fluoride α-15 and glucosyl fluoride α-16; at 60 °C for glucosyl fluoride β-16. Anomeric ratios were determined by HPLC analysis. 2-Deoxy glycosyl fluoride α-19 as a glycosyl donor in liquid SO2. Screening of conditions for

Enhanced target cell specificity and uptake of lipid nanoparticles using RNA aptamers and peptides

• Roslyn M. Ray,
• Anders Højgaard Hansen,
• Maria Taskova,
• Bernhard Jandl,
• Jonas Hansen,
• Citra Soemardy,
• Kevin V. Morris and
• Kira Astakhova

Beilstein J. Org. Chem. 2021, 17, 891–907, doi:10.3762/bjoc.17.75

• , ≥99.8%), citric acid monohydrate, sodium chloride, Na2HPO4, and KH2PO4 were purchased from Sigma-Aldrich (Germany). RNA and DNA oligonucleotides The RNA aptamers and Cy5 DNA oligonucleotides were synthesized and purified using ion-paired and ion-exchange HPLC at the RNA/DNA synthesis core at City of

Synthesis of bis(aryloxy)fluoromethanes using a heterodihalocarbene strategy

• Carl Recsei and
• Yaniv Barda

Beilstein J. Org. Chem. 2021, 17, 813–818, doi:10.3762/bjoc.17.70

• ); (b) AcCl, HCl, Et2O, rt, 24 h, 70%; (c) KHF2, neat, 105–110 °C, 60%. Attempted synthesis of 4. Reagents and conditions: (a) Ca(OH)2, 1,4-dioxane/water, reflux, 72 h, 5% (by HPLC integration); (b) ClF2CO2Na, K2CO3, DMF, 95 °C, 4 h, 7 (4%), 8 (19%). Synthesis of 10. Reagents and conditions: (a

Chiral isothiourea-catalyzed kinetic resolution of 4-hydroxy[2.2]paracyclophane

• David Weinzierl and
• Mario Waser

Beilstein J. Org. Chem. 2021, 17, 800–804, doi:10.3762/bjoc.17.68

• -resolution mass spectra were obtained using a Thermo Fisher Scientific LTQ Orbitrap XL with an Ion Max API Source. Analyses were made in the positive ionization mode if not otherwise stated. HPLC was performed using a Thermo Scientific Dionex Ultimate 3000 system with diode array detector with a CHIRAL ART

• ), 35.4 (1C, -CH2), 34.9 (1C, -CH2), 34.0 (1C, -CH2), 32.2 (1C, -CH2); HRMS (ESI) m/z: calcd for [C16H16O + H]+, 225.1274; found, 225.1280, HPLC: YMC Chiral ART Cellulose-SB, n-hexane/iPrOH 3:1, 1 mL/min, 10 °C; tR = 6.4 min [Sp; minor], 7.2 min [Rp; major]. (Sp)-3a: Analytical data match those reported

• (1C, -CH2), 35.0 (1C, -CH2), 34.4 (2C, -CH, -CH2), 31.8 (1C, -CH2), 19.4 (1C, -CH3), 19.1 (1C, -CH3); HRMS (ESI) m/z: calcd for [C20H22O2 + NH4]+, 312.1958; found, 312.1958, HPLC: YMC Chiral ART Cellulose-SB, n-hexane/iPrOH 3:1, 1 mL/min, 10 °C; tR = 7.3 min [Rp; minor], 8.4 min [Sp; major]. Overview

DNA with zwitterionic and negatively charged phosphate modifications: Formation of DNA triplexes, duplexes and cell uptake studies

• Yongdong Su,
• Maitsetseg Bayarjargal,
• Tracy K. Hale and
• Vyacheslav V. Filichev

Beilstein J. Org. Chem. 2021, 17, 749–761, doi:10.3762/bjoc.17.65

• creates a chiral center at the phosphorus atom resulting in a mixture of 2n diastereomers, where n is the number of modified phosphate groups. The reverse-phase (RP) HPLC purification occasionally results in the separation of individual diastereomers (usually for ONs with a single modification), which

• yield was also improved by minimising the handling of the solid support and performing the reaction using a microtube pump to deliver the sulfonyl azide solution onto the column with CPG support. The cleaved and deprotected N+- and Ts-ONs were initially purified using reversed-phase (RP) HPLC. However

• , the separation of ONs with varying numbers of modifications was not ideal as there were only marginal changes in the retention time in RP-HPLC. Therefore, ion-exchange (IE) HPLC was used for purifying these ONs. The substitution of each phosphate with N+ modification, resulted in a shorter retention

β-Lactamase inhibition profile of new amidine-substituted diazabicyclooctanes

• Zafar Iqbal,
• Lijuan Zhai,
• Yuanyu Gao,
• Dong Tang,
• Xueqin Ma,
• Jinbo Ji,
• Jian Sun,
• Jingwen Ji,
• Yuanbai Liu,
• Rui Jiang,
• Yangxiu Mu,
• Lili He,
• Haikang Yang and
• Zhixiang Yang

Beilstein J. Org. Chem. 2021, 17, 711–718, doi:10.3762/bjoc.17.60

• reacted with SO3·pyridine to form sulfonic acid derivatives A1–21 after purification by preparative HPLC. The sodium salts of these compounds were obtained by ion exchange using a column filled with Dowex-50wx Na+ resin using water as the eluent, followed by lyophilization. In case of compound A18, Boc

• deprotection was achieved by using trifluoroacetic acid (TFA) before the preparative HPLC. The synthesis of compounds A22 and A23 was accomplished by an alternative route elaborated in Scheme 5. Coupling of compound 5 and intermediate 2 was achieved by using HATU and DIPEA in a DMF/CH2Cl2 mixture to form the

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• chromatography (HPLC) (methanol/toluene as the eluent) to isolate a reddish-brown powder of methanofullerene 3 in 21% yield (Scheme 4). Similar to photolysis, the thermal rearrangement of kinetic products gives [6,6]-closed isomers that are thermodynamically more stable. After some time, the team of scientists

Synthesis and properties of oligonucleotides modified with an N-methylguanidine-bridged nucleic acid (GuNA[Me]) bearing adenine, guanine, or 5-methylcytosine nucleobases

• Naohiro Horie,
• Takao Yamaguchi,
• Shinji Kumagai and
• Satoshi Obika

Beilstein J. Org. Chem. 2021, 17, 622–629, doi:10.3762/bjoc.17.54

• C18 Cartridge. Subsequently, the desired oligonucleotides were further purified using reversed-phase HPLC with Waters XBridge™ C18 (4.6 × 50 mm analytical and 10 mm × 50 mm preparative) columns, with a linear gradient of MeCN (2.5–5% over 5 min, then 5–7.5% over 20 min) in 0.1 M triethylammonium

• acetate buffer (pH 7.0). The purity and structure of the oligonucleotides were confirmed by HPLC and MALDI–TOF mass spectrometry, respectively. UV melting experiments and melting profiles The UV melting experiments were carried out using SHIMADZU UV-1650PC and SHIMADZU UV-1800 spectrometers equipped with

• , and 32P NMR spectra for all new compounds, HPLC charts and MALDI–TOF mass data for all new oligonucleotides, UV melting curves of the duplexes formed between GuNA[Me]-modified oligonucleotides and ssDNAs (or ssRNAs), and CD spectra of ON4/ssRNA and ON4/ssDNA. Funding This work was supported in part

Menthyl esterification allows chiral resolution for the synthesis of artificial glutamate analogs

• Kenji Morokuma,
• Shuntaro Tsukamoto,
• Kyosuke Mori,
• Kei Miyako,
• Ryuichi Sakai,
• Raku Irie and
• Masato Oikawa

Beilstein J. Org. Chem. 2021, 17, 540–550, doi:10.3762/bjoc.17.48

• separation of 20* and 20 was realized by preparative HPLC with a CHIRALPAK IC column to furnish 20* (tR 9.6 min) and 20 (tR 11.8 min) in a 20*/20 ratio of 53:46, for which the stereochemical configuration was computationally and spectroscopically determined as 2S and 2R, respectively, one step later for 21

• ]. Chiral HPLC profiles for the separation of menthyl ester diastereomers 20* and 20. Conditions: 4.6 × 250 mm CHIRALPAK IC column, EtOH/hexane 1:19, 1 mL/min, 40 °C, 254 nm, tR 9.6, 11.8 min. Superimposed structures of the top 5 stable conformers (89.9% total population) generated by CONFLEX (MMFF94S) for

Synthesis and physicochemical evaluation of fluorinated lipopeptide precursors of ligands for microbubble targeting

• Masayori Hagimori,
• Estefanía E. Mendoza-Ortega and
• Marie Pierre Krafft

Beilstein J. Org. Chem. 2021, 17, 511–518, doi:10.3762/bjoc.17.45

• was stepwisely elongated, and eventually conjugated with the (perfluoroalkyl)ethyl acids (Scheme 2). After the cleavage from the resin, the Fmoc groups of the amino acids were removed, and the F-lipopeptides were purified using a dialysis membrane. According to mass spectrometry, FTIR, and HPLC

• (surface tension: 72.1 mN m−1 at 20 °C, resistivity: 18.2 MΩ cm). Mass spectra (MS) and HRMS were performed using a JMS-700 spectrometer (JEOL, Japan). RP-HPLC chromatograms were recorded on a Prominence system (Shimadzu, Japan). FTIR spectra were recorded on IRAffinity-1 (Shimadzu, Japan) spectrometer

• ether. The product was collected by filtration and purified by dialysis using a Tube-O-DIALYZER™ mini dialysis system. The purity of the final products was analyzed by a high-performance liquid chromatography (HPLC) system using a reversed-phase column (COSMOSIL 5C18-AR-II 4.6 × 250 mm) with water and

The synthesis of chiral β-naphthyl-β-sulfanyl ketones via enantioselective sulfa-Michael reaction in the presence of a bifunctional cinchona/sulfonamide organocatalyst

• Deniz Tözendemir and
• Cihangir Tanyeli

Beilstein J. Org. Chem. 2021, 17, 494–503, doi:10.3762/bjoc.17.43

• by chiral HPLC chromatography using Agilent instrument. All new products were further analyzed by LC/MS–HRMS–TOF or MALDI–ESI–TOFMS. Synthesis of organocatalyst 5 A solution of quinineamine 2 (226.40 mg, 0.70 mmol) and triethylamine (107 μL, 0.77 mmol) in CH2Cl2 was added to a screw-capped reaction

• -β-sulfanyl ketonesa. Supporting Information Supporting Information File 44: Copies of 1H and 13C NMR spectra, HPLC chromatograms and characterization data of the products. Funding This study was financially supported by Scientific and Technological Research Council of Turkey (217Z035), and Middle

Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• -Bu) 150, deprotected again with piperidine, and cleaved with TFA and trapping agents. The free phosphonodepsipeptide 151 was obtained in 45% yield after HPLC purification (Scheme 25) [38]. A general and high yielding synthesis of phosphonodepsidipeptides 152 was realized via a Mitsunobu reaction of