Tenacibactins K–M, cytotoxic siderophores from a coral-associated gliding bacterium of the genus Tenacibaculum

• Yasuhiro Igarashi,
• Yiwei Ge,
• Tao Zhou,
• Amit Raj Sharma,
• Enjuro Harunari,
• Naoya Oku and
• Agus Trianto

Beilstein J. Org. Chem. 2022, 18, 110–119, doi:10.3762/bjoc.18.12

• 50275, Central Java, Indonesia 10.3762/bjoc.18.12 Abstract HPLC/DAD-based chemical investigation of a coral-associated gliding bacterium of the genus Tenacibaculum yielded three desferrioxamine-class siderophores, designated tenacibactins K (1), L (2), and M (3). Their chemical structures, comprising

• three different seawater-based media, and butanolic extracts of the fermented cultures were subjected to HPLC/DAD analysis, which detected several unknown metabolites not present in our in-house UV database, showing UV end-absorption in the culture extract of A11M seawater medium. Purification of these

• reaction monitoring (MRM) mode with the parameter setting “isCID = 0” and “Collision = 45”. An Agilent HP1200 HPLC system equipped with a diode array detector was used for analysis and purification. The absorbance of microtitre plate wells was read on a Thermo Scientific Multiskan Sky microplate reader

Regioselective synthesis of methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates as new amino acid-like building blocks

• Jolita Bruzgulienė,
• Greta Račkauskienė,
• Aurimas Bieliauskas,
• Vaida Milišiūnaitė,
• Miglė Dagilienė,
• Gita Matulevičiūtė,
• Vytas Martynaitis,
• Sonata Krikštolaitytė,
• Frank A. Sløk and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2022, 18, 102–109, doi:10.3762/bjoc.18.11

• blocks was developed. Regioisomeric methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates were prepared by the reaction of β-enamino ketoesters (including azetidine, pyrrolidine or piperidine enamines) with hydroxylamine hydrochloride. Unambiguous structural assignments were based on chiral HPLC

• hydroxylamine hydrochloride in methanol (Scheme 1). Synthesized compounds 4b–g exhibited optical activity, and the corresponding (R)- or (S)-enantiomers rotated the plane of plane-polarized light in opposite directions. The enantiomeric purity of chiral compounds 4b–g was assessed via chiral HPLC analysis of

Bifunctional thiourea-catalyzed asymmetric [3 + 2] annulation reactions of 2-isothiocyanato-1-indanones with barbiturate-based olefins

• Jiang-Song Zhai and
• Da-Ming Du

Beilstein J. Org. Chem. 2022, 18, 25–36, doi:10.3762/bjoc.18.3

• an Agilent 6520 Accurate-Mass Q-TOF MS system equipped with an electrospray ionization (ESI) source. Optical rotations were measured with a Krüss P8000 polarimeter at the indicated concentration with the units of g/100 mL. Enantiomeric excesses were determined by chiral HPLC analysis using an Agilent

• excess (ee) values were determined by HPLC analysis. Substrate scope of barbiturate-based olefins. The reactions were carried out with 1a (0.12 mmol), 2 (0.10 mmol) and catalyst C4 (5 mol %) in solvent (1.0 mL) at room temperature for 12–40 h. The yields refer to isolated products after column

• chromatography. The diastereoisomeric ratios (dr values) were determined by 1H NMR spectroscopy and the enantiomeric excess (ee) values were determined by HPLC analysis. Gram-scale synthesis of 3ah. Further transformation of 3ah. One-pot three-component reaction. Proposed reaction mechanism. Optimization of the

The enzyme mechanism of patchoulol synthase

• Houchao Xu,
• Bernd Goldfuss,
• Gregor Schnakenburg and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 13–24, doi:10.3762/bjoc.18.2

• . Acknowledgements We thank Andreas Schneider for HPLC purifications and the computing centre of the University of Cologne (RRZK), providing CPU time on the DFG-funded supercomputer CHEOPS. Funding This work was funded by the DFG (DI1536/7-2).

Peptide stapling by late-stage Suzuki–Miyaura cross-coupling

• Hendrik Gruß,
• Rebecca C. Feiner,
• Ridhiwan Mseya,
• David C. Schröder,
• Michał Jewgiński,
• Kristian M. Müller,
• Rafał Latajka,
• Antoine Marion and
• Norbert Sewald

Beilstein J. Org. Chem. 2022, 18, 1–12, doi:10.3762/bjoc.18.1

• peptides P2 to P4 with complete conversion (Scheme 2B). LC–MS analyses revealed broadened or two signals for peptides P1 to P4, which were inseparable by preparative RP-HPLC purification (see Supporting Information File 1). The presence of more than one isomer may be due to the co-existence of

• + 4-position with 4-(2-carboxyethyl)phenylboronic acid followed by on-resin SMC (Scheme 2B). LC–MS analysis revealed two isobaric peaks indicating two isomers, which were largely separable by preparative HPLC with the less polar isomer P5.2 being the major one. The secondary structures of both isomers

Unsaturated fatty acids and a prenylated tryptophan derivative from a rare actinomycete of the genus Couchioplanes

• Shun Saito,
• Kanji Indo,
• Naoya Oku,
• Hisayuki Komaki,
• Masashi Kawasaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2939–2949, doi:10.3762/bjoc.17.203

• .17.203 Abstract A genome mining survey combined with metabolome analysis of publicly available strains identified Couchioplanes sp. RD010705, a strain belonging to an underexplored genus of rare actinomycetes, as a producer of new metabolites. HPLC-DAD-guided fractionation of its fermentation extracts

• -octadienoic acid (5), and one prenylated tryptophan derivative, 6-(3,3-dimethylallyl)-N-acetyl-ʟ-tryptophan (6). The enantiomer ratio of 4 was determined to be approximately S/R = 56:44 by a recursive application of Trost’s chiral anisotropy analysis and chiral HPLC analysis of its methyl ester. Compounds 1–5

• date [25], leaving room for exploration. Four strains of the same genus, available at the NBRC’s culture collection [20], were fermented and their metabolites were analyzed by HPLC-DAD, which detected several prominent peaks from the culture extracts of strain RD010705. Fractionation and purification

A photochemical C=C cleavage process: toward access to backbone N-formyl peptides

• Haopei Wang and
• Zachary T. Ball

Beilstein J. Org. Chem. 2021, 17, 2932–2938, doi:10.3762/bjoc.17.202

• , byproducts or transiently stable intermediates were sometimes indicated by HPLC and/or NMR of these photocleavage reactions [16][17]. These observations prompted a more detailed study of the components present during photocleavage reactions of small-molecule models, leading to the identification of the N

• aqueous photocleavage in the presence of triethylamine, and the resulting reaction mixture was purified by reversed-phase HPLC (Figure 2). We isolated a nitroso product 3, in addition to two other major identifiable components of the crude reaction: quinoline N-oxide (4) and quinolinone (5). The compounds

First total synthesis of hoshinoamide A

• Haipin Zhou,
• Zihan Rui,
• Yiming Yang,
• Shengtao Xu,
• Yutian Shao and
• Long Liu

Beilstein J. Org. Chem. 2021, 17, 2924–2931, doi:10.3762/bjoc.17.201

• yield when HATU/DIPEA as the coupling reagent was used (Table 1, entry 2). Only trace product could be detected with EEDQ (Table 1, entry 4). Further screening did not give better results (Table 1, entries 5 and 6). The purity of tripeptide 7 was determined by HPLC and no racemization was observed

• and detection at 220 nm. Preparative reverse-phase HPLC was performed by using Thermo Scientific Ultimate 3000 equipped with a Thermo Hypersil Gold (5 µm, 150 × 21.2 mm) column adpoting the following buffer systems: A: 0.1% TFA in water. B: 0.1% TFA in MeCN using a 10–90–90–10 vol % MeCN gradient (10

• /H2O (10 mL, 50:50:50 v/v/v). The reaction mixture was stirred for 3 h, and then concentrated in vacuo. The crude peptide was precipitated using cold Et2O and centrifuged at 7000 rpm to give a white solid. This solid was further purified by RP-HPLC through protocols described in the general method

Highly stereocontrolled total synthesis of racemic codonopsinol B through isoxazolidine-4,5-diol vinylation

• Lukáš Ďurina,
• Anna Ďurinová,
• František Trejtnar,
• Ľuboš Janotka,
• Lucia Messingerová,
• Jana Doháňošová,
• Ján Moncol and
• Róbert Fischer

Beilstein J. Org. Chem. 2021, 17, 2781–2786, doi:10.3762/bjoc.17.188

• 1 and 2. Acknowledgements The authors thank to Dr. Vladimír Mastihuba for HPLC measurements. Funding This work was supported by the Slovak Grant Agency for Science VEGA (project nos. 1/0552/18, 2/0057/18), and Charles University Research Programme Progres (grant no. Q42).

GlycoBioinformatics

• Kiyoko F. Aoki-Kinoshita,
• Frédérique Lisacek,
• Niclas Karlsson,
• Daniel Kolarich and
• Nicolle H. Packer

Beilstein J. Org. Chem. 2021, 17, 2726–2728, doi:10.3762/bjoc.17.184

• knowledge. Most structural data at this stage is generated by analytical approaches, such as mass spectrometry (MS), high-pressure liquid chromatography (HPLC), and capillary electrophoresis (CE). The articles by Phung et al. [9] and by Lippold et al. [10] suggest ways of combining and customising available

The ethoxycarbonyl group as both activating and protective group in N-acyl-Pictet–Spengler reactions using methoxystyrenes. A short approach to racemic 1-benzyltetrahydroisoquinoline alkaloids

• Marco Keller,
• Karl Sauvageot-Witzku,
• Franz Geisslinger,
• Nicole Urban,
• Michael Schaefer,
• Karin Bartel and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2716–2725, doi:10.3762/bjoc.17.183

• methods All chemicals used were of analytical grade and were obtained from abcr (Karlsruhe, Germany), Fischer Scientific (Schwerte, Germany), Merck, Darmstadt, Germany, TCI (Eschborn, Germany) or Th. Geyer (Renningen, Germany). HPLC grade and dry solvents were purchased from VWR (Darmstadt, Germany) or

• determined by the open tube capillary method on a Büchi melting point B-540 apparatus and are uncorrected. HPLC purities were determined using an HP Agilent 1100 HPLC with a diode array detector and an Agilent Zorbax Eclipse plus C18 column (150 × 4.6 mm; 5 µm) with methanol/water in different proportions

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

• THF and phosphate-buffered saline (PBS). The reaction used 64 and 3q as starting materials and was stereocontrolled efficiently, providing an enantiomeric excess of about >99%. The subsequent N-glycosylation further provided enantiopure lamivudine (1). Hu et al. [60] explained that chiral HPLC and

• a cis/trans ratio of 1.3:1 for the nucleoside intermediate 79a. Further, the nucleoside intermediate 79a was deprotected using a type of basic resin. This gave the cis-diastereomer 3TC (1), which was purified by chiral HPLC, resulting in an ee value of 70% (Scheme 28). Further developments in the

• could have been due to an in situ chelation process. The level of selectivity was determined by HPLC to be >300:1 in favor of the β-configured cis-isomers (racemic mixture of 80a and 80b) [30]. Further, the desilylation using tetrabutylammonium fluoride (TBAF) gave racemic (±)-BCH-189 (1c). Chu et al

Solvent-free synthesis of enantioenriched β-silyl nitroalkanes under organocatalytic conditions

• Akhil K. Dubey and
• Raghunath Chowdhury

Beilstein J. Org. Chem. 2021, 17, 2642–2649, doi:10.3762/bjoc.17.177

• conditions: 1 (0.2 mmol), 2 (0.5 mmol), catalyst VII (0.01 mmol, 5 mol %) at 30 °C. aIsolated yield of 3 after column chromatography. bConversion in % of the starting material 1 is given in parentheses, determined by 1H NMR analysis of the crude reaction mixture. cDetermined by HPLC using a chiral stationary

• reaction mixture. cDetermined by HPLC using chiral stationary phase. Organocatalytic 1,4-conjuagte addition of nitromethane (2) to enone 3o. Preparative scale synthesis of 3c and ent-3d. Catalysts screening and optimization of reaction conditions.a Supporting Information Supporting Information File 366

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• reaction conditions for solvent-free Michael additions.a Michael addition of aldehyde 6a–c to nitroalkenes 7a and 7b.a Supporting Information Supporting information contains characterization data for Michael adducts, pictures of NMR spectra, pictures of HPLC chromatograms, and DFT computational details

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