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

Identification of volatiles from six marine Celeribacter strains

• Anuj Kumar Chhalodia,
• Jan Rinkel,
• Dorota Konvalinkova,
• Jörn Petersen and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 420–430, doi:10.3762/bjoc.17.38

• between the sulfur and an ester oxygen. This phenomenon was first described in supramolecular structures by Gleiter [59] and later also used to explain the outcome of organocatalytic reactions [60]. The pure stereoisomers of 42 were isolated by preparative HPLC, for which the best separation was achieved

• spectra were recorded on a Bruker α spectrometer equipped with a diamond-ATR probe, and qualitative signal intensities are reported by w (weak), m (medium), and s (strong). HPLC purification of compound 42 was performed on an Azura HPLC system (Knauer, Berlin, Germany) equipped with a UV–vis detector MWL

• chromatography (cyclohexane/ethyl acetate 99:1) gave a mixture of stereoisomers (Z)-42 and (E)-42 as pale yellow oil (96 mg, 0.65 mmol, 92%, dr 94:6 by 1H NMR). The product mixture was separated by preparative HPLC to give pure (Z)-42 (73 mg, 0.50 mmol, 70%) and (E)-42 (6 mg, 0.04 mmol, 6%). (Z)-42. Rf 0.74

1,2,3-Triazoles as leaving groups: S_NAr reactions of 2,6-bistriazolylpurines with O- and C-nucleophiles

• Dace Cīrule,
• Irina Novosjolova,
• Ērika Bizdēna and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 410–419, doi:10.3762/bjoc.17.37

• used in the reactions were dried with standard drying agents and freshly distilled prior to use. Commercial reagents were used as received. IR spectra were recorded in KBr tablets with a Perkin–Elmer Spectrum BX FTIR spectrometer (4000–450 cm−1). Wavelengths are given in cm−1. For HPLC analysis an

• DMF (0.5 mL) was added and the reaction mixture was stirred for 15 min at rt, controlled by HPLC. Then toluene or ethyl acetate (25 mL) was added to the mixture and it was extracted with 5% LiCl solution (3 × 5 mL). The organic phase was dried over anhydrous Na2SO4, filtered and evaporated. Silica gel

• column chromatography (DCM/MeCN 10:1) gave the product as colourless amorphous solid. Yield 115 mg, 83%. Rf = 0.80 (DCM/MeCN 5:1); HPLC: tR = 7.68 min, purity 98%; IR (KBr) ν (cm−1): 3075, 2965, 2930, 2870, 1745, 1605, 1435, 1415, 1350, 1330, 1245, 1235, 1070; 1H NMR (300 MHz, CDCl3) δ 8.70 (s, 1H, H-C

Synthesis of legonmycins A and B, C(7a)-hydroxylated bacterial pyrrolizidines

• Wilfred J. M. Lewis,
• David M. Shaw and
• Jeremy Robertson

Beilstein J. Org. Chem. 2021, 17, 334–342, doi:10.3762/bjoc.17.31

• configurationally unstable in aqueous solution. Chiral HPLC analysis of samples of pyrrolizixenamide A isolated from culture clearly indicated racemic specimens but also revealed the presence of the two C(7a)-hydroxylated derivatives whose presence in the mixture became enriched during purification. Taken together

Regioselective chemoenzymatic syntheses of ferulate conjugates as chromogenic substrates for feruloyl esterases

• Olga Gherbovet,
• Fernando Ferreira,
• Apolline Clément,
• Mélanie Ragon,
• Julien Durand,
• Sophie Bozonnet,
• Michael J. O'Donohue and
• Régis Fauré

Beilstein J. Org. Chem. 2021, 17, 325–333, doi:10.3762/bjoc.17.30

• lignocellulosic matrix. Moreover, Faes are useful tools to obtain commercially relevant ferulic acid, which represents up to 3 wt % of plant the cell wall dry weight [8]. So far, the detection and characterization of Faes has mainly relied on either the use of HPLC or on UV–visible spectrophotometry, using

¹⁹F NMR as a tool in chemical biology

• Diana Gimenez,
• Aoife Phelan,
• Cormac D. Murphy and
• Steven L. Cobb

Beilstein J. Org. Chem. 2021, 17, 293–318, doi:10.3762/bjoc.17.28

• convenient technique to study a range of factors that might influence the plasma and metabolic stability of the lead compounds, proving itself as a valuable alternative to more challenging conventional HPLC or 1H NMR analyses. It is also worth noting that recent investigations within the Dalvit group have

1,2,3-Triazoles as leaving groups in S_NAr–Arbuzov reactions: synthesis of C6-phosphonated purine derivatives

• Kārlis-Ēriks Kriķis,
• Irina Novosjolova,
• Anatoly Mishnev and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 193–202, doi:10.3762/bjoc.17.19

• conversion of starting material 6d was monitored by HPLC, and after completion, product 4d was precipitated from the reaction mixture by hexane. For entries 1 and 3 in Table 2, an extra purification step by silica gel column chromatography was required. For compound 4d, the optimal reaction conditions were 2

• compounds were monitored by HPLC and TLC analysis using silica gel 60 F254 aluminum plates (Merck). Visualization was accomplished by UV light. Column chromatography was performed on silica gel (60 Å, 40−63 μm, ROCC). The yield of the products refers to chromatographically and spectroscopically homogeneous

• 1H,13C-HSQC 2D NMR experiments for representative products of each compound class. Crystallographic diffraction data were collected with a NoniusKappa CCD diffractometer (Mo Kα, λ = 0.71073 Å) equipped with a low-temperature Oxford Cryosystems Cryostream Plus device. HPLC analysis was performed using

Supramolecular polymerization of sulfated dendritic peptide amphiphiles into multivalent L-selectin binders

• David Straßburger,
• Svenja Herziger,
• Katharina Huth,
• Moritz Urschbach,
• Rainer Haag and
• Pol Besenius

Beilstein J. Org. Chem. 2021, 17, 97–104, doi:10.3762/bjoc.17.10

• purified by RP-HPLC and separated from impurities, like disubstituted byproduct, to finally afford 5 in 68% yield. Subsequently, an azide functionality was easily introduced using azidoacetic acid NHS ester to obtain compound 6. In the next step, the solubilizing side-arm 4 was attached twice to the

• copper-catalyzed azide–alkyne cycloaddition (Scheme 2). The reaction took place in degassed DMSO at 50 °C with CuSO4 pentahydrate, sodium ascorbate and tris(benzyltriazolylmethyl)amine (TBTA) as chelating species. HPLC-monitoring of the reaction showed a full conversion after three days and the crude

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• precursor (−)-75 was 97.6%, determined by HPLC. The overall yield for this synthesis was 13.4% and specific rotation [α]D25 −13.0 (c 0.73, CHCl3) {lit. [α]D −13 (CHCl3), [17]}. Spino synthesis – 2009 Spino et al. synthesized both (−)-adaline (1) and (+)-euphococcinine (2) [53]. The main features in this

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• band gaps (by ≈0.5 eV). In cases of pyrazine and pyridine-fused analogs, differences are not so noticeable. Experimental The synthetic procedures, HPLC, X-ray studies and spectra (1H and 13C NMR) of all new compounds can be found in Supporting Information File 1. Molecular structure of carbazole-based

• ]helicenes 10. Supporting Information Supporting Information File 76: Experimental procedures and analytical data, copies of 1H and 13C NMR spectra of all new compounds, X-ray data for 9c and 10a–c, HPLC spectra of helicenes 10a–c, UV–vis and fluorescence spectra of 10a–c. Acknowledgements The authors

Chemical constituents of Chaenomeles sinensis twigs and their biological activity

• Joon Min Cha,
• Dong Hyun Kim,
• Lalita Subedi,
• Zahra Khan,
• Sang Un Choi,
• Sun Yeou Kim and
• Chung Sub Kim

Beilstein J. Org. Chem. 2020, 16, 3078–3085, doi:10.3762/bjoc.16.257

• data were acquired on a Waters SYNAPT G2 (Milford, MA, USA). The HPLC–DAD–MS data were measured using an Agilent 1260 Infinity HPLC system (Agilent, Santa Clara, CA, USA) with a Kinetex C18 5 μm column (250 mm length × 4.6 mm i.d.; Phenomenex, Torrance, CA, USA). Purification was achieved using a semi

• -preparative HPLC system equipped with a Gilson 306 pump (Middleton, WI, USA), a Shodex refractive index detector (New York, NY, USA), a Luna C18 10 µm column (250 mm length × 10 mm i.d.; Phenomenex, Torrance, CA, USA), and an Apollo Silica 5 μm column (250 mm length × 10 mm i.d.; Apollo, Manchester, UK) at a

• g) was chromatographed on an RP-C18 silica gel column (90% aqueous MeOH) to yield 12 subfractions (H3-1–H3-12), and compound 11 (5 mg) was obtained from subfraction H3-12 (50 mg) by semi-preparative normal-phase HPLC (hexanes/EtOAc 8:1). The CHCl3-soluble fraction (15 g) was subjected to passage

Controlled decomposition of SF₆ by electrochemical reduction

• Sébastien Bouvet,
• Bruce Pégot,
• Stéphane Sengmany,
• Erwan Le Gall,
• Eric Léonel,
• Anne-Marie Goncalves and
• Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

• controlled decomposition of sulfur hexafluoride was described under electroreduction. The reduction potential was firstly determined and used for preparative studies. The extrapolation on large scale of this methodology is under current development in our laboratory. Experimental Acetonitrile (HPLC grade

Incorporation of a metal-mediated base pair into an ATP aptamer – using silver(I) ions to modulate aptamer function

• Marius H. Heddinga and
• Jens Müller

Beilstein J. Org. Chem. 2020, 16, 2870–2879, doi:10.3762/bjoc.16.236

• hydrogen citrate (Supporting Information File 1, Table S1, Figures S9–S20). The purity was confirmed by means of HPLC chromatography (Figures S21–S32, Supporting Information File 1). Towards this end, a Macherey–Nagel NUCLEODUR C18 HTec column (5 μm, 124 × 4 mm) was used in combination with the following

• ATP, oligonucleotide sequences, MALDI–TOF spectra of the oligonucleotides and HPLC traces to confirm the oligonucleotide purity. Acknowledgements We thank D. Defayay for performing the HPLC analysis of the oligonucleotides.

Dirhamnolipid ester – formation of reverse wormlike micelles in a binary (primerless) system

• David Liese,
• Hans Henning Wenk,
• Xin Lu,
• Jochen Kleinen and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2020, 16, 2820–2830, doi:10.3762/bjoc.16.232

• C12, with a little portion of double bonds (according to HPLC–MS measurements this portion amounts to ca. 4–12%). A novel synthetic route was chosen for the synthesis of the dirhamnolipid esters. In contrast to the previously used methods [26][27][28], our approach is applicable for any desired alkyl

Synthesis and investigation of quadruplex-DNA-binding, 9-O-substituted berberine derivatives

• Jonas Becher,
• Daria V. Berdnikova,
• Heiko Ihmels and
• Christopher Stremmel

Beilstein J. Org. Chem. 2020, 16, 2795–2806, doi:10.3762/bjoc.16.230

• , and FkrasT. 9-(Azidoalkyl)berberine derivatives 3a–e [54] and 9-propargyladenine (2) [53] were synthesized according to published procedures. Stock solutions of the ligands (1.0 mM) were prepared in MeOH (HPLC grade). Buffer solutions were prepared with biochemical grade chemicals in E-Pure water

Nocarimidazoles C and D, antimicrobial alkanoylimidazoles from a coral-derived actinomycete Kocuria sp.: application of ¹J_C,H coupling constants for the unequivocal determination of substituted imidazoles and stereochemical diversity of anteisoalkyl chains in microbial metabolites

• Md. Rokon Ul Karim,
• Enjuro Harunari,
• Amit Raj Sharma,
• Naoya Oku,
• Kazuaki Akasaka,
• Daisuke Urabe,
• Mada Triandala Sibero and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 2719–2727, doi:10.3762/bjoc.16.222

• those of synthetically prepared model imidazoles. The absolute configurations of the anteisoalkanoyl group present in 1, 4, and 5 were determined by low-temperature HPLC analysis of the degradation products labeled with a chiral anthracene reagent, which revealed that 1 is a mixture of the R- and S

• anthracene reagent to yield the esters of (R)- or (S)-2-(anthracene-2,3-dicarboximido)propanol (nat-10-(R)-2A1P, (S)-10-(R)-2A1P, and (S)-10-(S)-2A1P), which were subjected to HPLC analysis for comparison (Figure 4). The retention times of the standard samples were 177 min for (S)-10-(S)-2A1P

• of nocarimidazole B (4) produced by strain TK35-5. The same compound was originally isolated from marine Nocadiopsis, but the absolute configuration was not elucidated. The conversion of 4 into the derivative nat-11-(R)-2A1P, followed by HPLC analysis, revealed that 4 is an enantiomerically pure S

Enzyme-instructed morphological transition of the supramolecular assemblies of branched peptides

• Dongsik Yang,
• Hongjian He and
• Bing Xu

Beilstein J. Org. Chem. 2020, 16, 2709–2718, doi:10.3762/bjoc.16.221

• , we used TFA at room temperature for 2 h to cleave the tert-butyl protecting groups of 1b and 2b. After adding diethyl ether to precipitate the crude peptides, centrifugation, and washing three times, we used reversed-phase HPLC and acetonitrile (containing 0.1% TFA) and double-distilled water