N-Acylated amino acid methyl esters from marine Roseobacter group bacteria

• Hilke Bruns,
• Lisa Ziesche,
• Nargis Khakin Taniwal,
• Laura Wolter,
• Thorsten Brinkhoff,
• Jennifer Herrmann,
• Rolf Müller and
• Stefan Schulz

Beilstein J. Org. Chem. 2018, 14, 2964–2973, doi:10.3762/bjoc.14.276

• them have been characterized so far [14][15][16][17][18]. Such signalling compounds as well as many other unknown metabolites often occur in small amounts, which renders trace detecting methods like GC/MS a suitable approach for their detection and structure elucidation, provided their polarity falls

Protein–protein interactions in bacteria: a promising and challenging avenue towards the discovery of new antibiotics

• Laura Carro

Beilstein J. Org. Chem. 2018, 14, 2881–2896, doi:10.3762/bjoc.14.267

• identification requires detailed structure elucidation, which in the end makes the design of an effective PPI modulator both difficult and challenging [19][20][21][22]. PPI modulation can be achieved through two opposite but complementary approaches: stabilization or inhibition (Figure 1). Although so far the

Herpetopanone, a diterpene from Herpetosiphon aurantiacus discovered by isotope labeling

• Xinli Pan,
• Nicole Domin,
• Sebastian Schieferdecker,
• Hirokazu Kage,
• Martin Roth and
• Markus Nett

Beilstein J. Org. Chem. 2017, 13, 2458–2465, doi:10.3762/bjoc.13.242

• pathway. After large-scale fermentation of H. aurantiacus 114-95T, the putative diterpene was isolated in sufficient quantity to enable NMR-based structure elucidation. The compound, for which the name herpetopanone is proposed, features a rare octahydro-1H-indenyl skeleton. Herpetopanone bears

• . Although the elemental composition does not necessarily exclude a polyketide origin, it perfectly matches a diterpene comprising four intact isoprene units. To obtain sufficient material for structure elucidation, the fermentation of H. aurantiacus 114-95T was repeated on a 50 L scale in VNY medium

• assignment of several other protons and the readout of their coupling constants was challenging due to severe signal overlapping. A TOCSY spectrum suggested that, with the exception of four methyl groups (CH3-1, CH3-3, CH3-13, CH3-20), all protons were part of the same spin system. Structure elucidation

Enzymatic separation of epimeric 4-C-hydroxymethylated furanosugars: Synthesis of bicyclic nucleosides

• Neha Rana,
• Manish Kumar,
• Vinod Khatri,
• Jyotirmoy Maity and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2017, 13, 2078–2086, doi:10.3762/bjoc.13.205

• concentrated under reduced pressure to afford a colourless oil. The two products formed in the reaction had different polarity and were easily separated by column chromatography over silica gel in quantitative yields. The structure elucidation of the two products revealed that Novozyme®-435 exhibited exclusive

18-Hydroxydolabella-3,7-diene synthase – a diterpene synthase from Chitinophaga pinensis

• Jeroen S. Dickschat,
• Jan Rinkel,
• Patrick Rabe,
• Arman Beyraghdar Kashkooli and
• Harro J. Bouwmeester

Beilstein J. Org. Chem. 2017, 13, 1770–1780, doi:10.3762/bjoc.13.171

• , revealing that the expression of one and the same terpene synthase in different heterologous hosts may yield different terpene products. Keywords: biosynthesis; Chitinophaga pinensis; Nicotiana benthamiana; structure elucidation; terpenes; Introduction Terpene synthases convert a handful of simple linear

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

A new member of the fusaricidin family – structure elucidation and synthesis of fusaricidin E

• Marcel Reimann,
• Louis P. Sandjo,
• Luis Antelo,
• Eckhard Thines,
• Isabella Siepe and
• Till Opatz

Beilstein J. Org. Chem. 2017, 13, 1430–1438, doi:10.3762/bjoc.13.140

• BASF SE, 67056 Ludwigshafen, Germany 10.3762/bjoc.13.140 Abstract Two hitherto unknown fusaricidins were obtained from fermentation broths of three Paenibacillus strains. After structure elucidation based on tandem mass spectrometry and NMR spectroscopy, fusaricidin E was synthesized to confirm the

• structure and the suggested stereochemistry. The synthesis was based on a new strategy which includes an efficient access to the 15-guanidino-3-hydroxypentadecanoyl (GHPD) side chain from erucamide. Keywords: cyclodepsipeptides; fusaricidins; lipopeptides; structure elucidation; total synthesis

• (Figure 1). Thus, an assumed stereoisomer (containing D-allo-Ile) of the new fusaricidin member was synthesized based on analogy to known members of the series and compared to the natural product [8]. Results and Discussion Isolation and structure elucidation The Paenibacillus strain was cultivated on

New tricks of well-known aminoazoles in isocyanide-based multicomponent reactions and antibacterial activity of the compounds synthesized

• Maryna V. Murlykina,
• Maryna N. Kornet,
• Sergey M. Desenko,
• Svetlana V. Shishkina,
• Oleg V. Shishkin,
• Aleksander A. Brazhko,
• Vladimir I. Musatov,
• Erik V. Van der Eycken and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2017, 13, 1050–1063, doi:10.3762/bjoc.13.104

• -amino-5-methylisoxazole (7) according to the elaborated procedures (Table 1, methods A or B) as well as under other conditions were not successful. Structure elucidation The purity and structures of the heterocycles obtained were established by means of mass spectrometry (including HRMS), NMR

Cycloheximide congeners produced by Streptomyces sp. SC0581 and photoinduced interconversion between (E)- and (Z)-2,3-dehydroanhydrocycloheximides

• Li Yang,
• Ping Wu,
• Jinghua Xue,
• Huitong Tan,
• Zheng Zhang and
• Xiaoyi Wei

Beilstein J. Org. Chem. 2017, 13, 1039–1049, doi:10.3762/bjoc.13.103

• . Results and Discussion Structure elucidation The molecular formula of compound 1 was established as C15H21NO4 based on the HRESI(+)-MS ion at m/z 302.1357 [M + Na]+ (calcd 302.1363). Its 1H and 13C NMR spectral data (Table 1), in combination with the HSQC spectrum, indicated the presence of a conjugated

• findings suggested that these cycloheximide derivatives possibly exert the antifungal and cytotoxic activities via a similar mode of action. Conclusion Three new (1–3) and three known (4–6) cycloheximide congeners were obtained from the cultures of Streptomyces sp. SC0581. The structure elucidation of the

Novel β-cyclodextrin–eosin conjugates

• Gábor Benkovics,
• Damien Afonso,
• András Darcsi,
• Szabolcs Béni,
• Sabrina Conoci,
• Éva Fenyvesi,
• Lajos Szente,
• Milo Malanga and
• Salvatore Sortino

Beilstein J. Org. Chem. 2017, 13, 543–551, doi:10.3762/bjoc.13.52

• standard nitration conditions to obtain the desired dye eosin B (4) (Figure 1). The NMR spectra showing the structure elucidation of the free dyes eosin Y (2) and eosin B (4) are shown in Supporting Information File 1, Figures S3–S7 and Figures S15–S19, respectively. Synthesis of eosin Y–β-CD and eosin B–β

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

• feeding deterrence under laboratory conditions at concentration levels below natural abundance in the sea slug bodies. Herein we report on the secondary metabolome of a single specimen of P. longicirrum, including the structure elucidation of the new metabolites 1, 5, 9, 14 and 15, and show the fish

• tentative. It can, however be stated that the P. longicirrum specimen investigated in this study either belongs to a different chemotype or has different food preference than the one investigated by Coll and co-workers [13]. Detailed chemical investigation of P. longicirrum including structure elucidation

Polyketide stereocontrol: a study in chemical biology

• Kira J. Weissman

Beilstein J. Org. Chem. 2017, 13, 348–371, doi:10.3762/bjoc.13.39

• ][32][33][34][35][36][37], in combination with structure elucidation at high resolution of AT5 from the DEBS PKS, which was solved in the presence of acetate (Figure 7) [38]. For example, extender unit-specific ATs contain positively charged residues in the active site (R667 and H745, DEBS AT5

• stereochemistry by site-directed mutagenesis awaits identification of further stereochemical determinants in ER active sites. Bioinformatics-guided structure elucidation The strong correlations between certain sequence motifs present in PKS domains and the stereochemistry of the resulting polyketide chains has

• ‘Caffrey’ motifs are present (for example, the LDD motif indicative of B-type KRs, with the second D being most diagnostic, particularly for trans-AT PKSs) and therefore these predictions can be an important complement to full structure elucidation. On the other hand, some KRs possess sequence features of

Supramolecular frameworks based on [60]fullerene hexakisadducts

• Andreas Kraft,
• Johannes Stangl,
• Ana-Maria Krause,
• Klaus Müller-Buschbaum and
• Florian Beuerle

Beilstein J. Org. Chem. 2017, 13, 1–9, doi:10.3762/bjoc.13.1

• . Keywords: fullerenes; hexakisadducts; hydrogen bonding; porous materials; structure elucidation; Introduction The utilization of confined nanospace in rigid frameworks [1], which are derived from small molecular precursors under dynamic conditions, has emerged as a novel design paradigm for functional

O-Alkylated heavy atom carbohydrate probes for protein X-ray crystallography: Studies towards the synthesis of methyl 2-O-methyl-L-selenofucopyranoside

• Roman Sommer,
• Dirk Hauck,
• Annabelle Varrot,
• Anne Imberty,
• Markus Künzler and
• Alexander Titz

Beilstein J. Org. Chem. 2016, 12, 2828–2833, doi:10.3762/bjoc.12.282

• was available for molecular replacement and the protein contains only one methionine and no cysteine residues, which is insufficient to consider incorporation of selenomethionine in the protein for the structure elucidation. Its carbohydrate-binding specificity was determined and a preference for O

Identification, synthesis and mass spectrometry of a macrolide from the African reed frog Hyperolius cinnamomeoventris

• Markus Menke,
• Pardha Saradhi Peram,
• Iris Starnberger,
• Walter Hödl,
• Gregory F.M. Jongsma,
• David C. Blackburn,
• Mark-Oliver Rödel,
• Miguel Vences and
• Stefan Schulz

Beilstein J. Org. Chem. 2016, 12, 2731–2738, doi:10.3762/bjoc.12.269

• several isomers, helpful for the structure elucidation of natural compounds, e.g., in chemical ecology or fragrance research. The mass spectral fragmentation of macrolides differs markedly from that of open-chain esters, because initial bond cleavage often does not lead to the release of an uncharged

Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis

• Darcy J. Atkinson,
• Briar J. Naysmith,
• Daniel P. Furkert and
• Margaret A. Brimble

Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226

• B Enduracidin A (7) and B (8) were first isolated from Streptomyces fungicidicus B 5477 from a soil sample collected in Nishinomiya, Japan (Figure 2) [1]. Detailed reports of the isolation procedures, in vivo and in vitro antimicrobial activity, physical properties and structure elucidation have

New furoisocoumarins and isocoumarins from the mangrove endophytic fungus Aspergillus sp. 085242

• Ze’en Xiao,
• Senhua Chen,
• Runlin Cai,
• Shao’e Lin,
• Kui Hong and
• Zhigang She

Beilstein J. Org. Chem. 2016, 12, 2077–2085, doi:10.3762/bjoc.12.196

• known compounds (3, 4, 7–9) (Figure 1). Details of the isolation, structure elucidation, and biological activity of these compounds are reported herein. Results and Discussion The mangrove endophytic fungus Aspergillus sp. 085242 was cultured on solid rice medium with saline water for four weeks. The

Mechanistic investigations on six bacterial terpene cyclases

• Patrick Rabe,
• Thomas Schmitz and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 1839–1850, doi:10.3762/bjoc.12.173

• terpene cyclases were characterised by one- and two-dimensional NMR spectroscopic methods, allowing for a full structure elucidation. The absolute configurations of four terpenes were determined based on their optical rotary powers. Incubation experiments with 13C-labelled isotopomers of FPP in buffers

• containing water or deuterium oxide allowed for detailed insights into the cyclisation mechanisms of the bacterial terpene cyclases. Keywords: absolute configuration; biosynthesis; enzyme mechanisms; structure elucidation; terpenes; Introduction Terpenes are structurally fascinating natural products with

• cyclases, purification and full structure elucidation of their products by NMR and determination of optical rotary powers. Furthermore, the enzyme mechanisms of the investigated terpene cyclases were studied by isotopic labelling experiments [34] similar to recently reported investigations on other

The EIMS fragmentation mechanisms of the sesquiterpenes corvol ethers A and B, epi-cubebol and isodauc-8-en-11-ol

• Patrick Rabe and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 1380–1394, doi:10.3762/bjoc.12.132

• standard. Furthermore, various high quality databases containing the EI mass spectra and retention indices of thousands of compounds are available that assist in automated compound identification [2][3]. If unknown compounds are detected in natural extracts, their structure elucidation by GC–MS is more

Marine-derived myxobacteria of the suborder Nannocystineae: An underexplored source of structurally intriguing and biologically active metabolites

• Antonio Dávila-Céspedes,
• Peter Hufendiek,
• Max Crüsemann,
• Till F. Schäberle and
• Gabriele M. König

Beilstein J. Org. Chem. 2016, 12, 969–984, doi:10.3762/bjoc.12.96

• . Further investigation led to the isolation and structure elucidation of the bioactive polyketide haliangicin (24, Figure 10), which was the first myxobacterial metabolite of true marine origin. It was found that this molecule comprised a β-methoxyacrylate subunit including a conjugated tetraene moiety [52

• . Structure elucidation was achieved via extensive NMR measurements. The absolute configuration of the chiral centers could be resolved through comparison of the experimental CD spectrum with calculated data. This metabolite showed inhibitory activity towards the bacterium Arthrobacter crystallopoietes with

• production of secondary metabolites [65]. This work led to the isolation and structure elucidation of two compounds of peptidic nature called miuraenamide A (31) and B (32, Figure 13). Two years later, the same research group published the structures of four additional derivatives, named miuraenamides C–F

Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents

• Daniel Wiegmann,
• Stefan Koppermann,
• Marius Wirth,
• Giuliana Niro,
• Kristin Leyerer and
• Christian Ducho

Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77

• which have a uridine-derived core structure in common. Their antibiotic potency is based on the inhibition of MraY, thereby blocking a membrane-associated intracellular step of bacterial cell-wall biosynthesis. The structure elucidation was carried out using one- and two-dimensional NMR experiments as

Elucidation of a masked repeating structure of the O-specific polysaccharide of the halotolerant soil bacteria Azospirillum halopraeferens Au4

• Elena N. Sigida,
• Yuliya P. Fedonenko,
• Alexander S. Shashkov,
• Nikolay P. Arbatsky,
• Evelina L. Zdorovenko,
• Svetlana A. Konnova,
• Vladimir V. Ignatov and
• Yuriy A. Knirel

Beilstein J. Org. Chem. 2016, 12, 636–642, doi:10.3762/bjoc.12.62

• revealed that its reason is a non-stoichiometric side-chain glucosylation and methylation of the main polysaccharide chain but at this stage, a straightforward structure elucidation of the OPS by NMR spectroscopy [16] was complicated. In order to obtain oligosaccharide fragments of the OPS a Smith

• oligosaccharide, selective solvolysis with CF3CO2H was employed. Recently, this method has been successfully used for the structure elucidation of the O-specific polysaccharides of Escherichia coli (e.g. [20]). The reagent was found to cleave selectively the glycosidic linkage of 6-deoxyhexoses (Rha, Fuc

• afforded complementary oligosaccharides, which identification shed light on the nature of the OPS irregularity and, combined with chemical analysis and NMR spectroscopic analysis data, enabled the structure elucidation of the OPS. Chemical modifications of the OPS, such as O-methylation or O-acetylation

Natural products from microbes associated with insects

• Christine Beemelmanns,
• Huijuan Guo,
• Maja Rischer and
• Michael Poulsen

Beilstein J. Org. Chem. 2016, 12, 314–327, doi:10.3762/bjoc.12.34

• light on the ecology and evolution of defensive associations. Keywords: biosynthesis; chemical ecology; natural products; secondary metabolism; structure elucidation; symbiosis; Introduction Although natural products represent the most consistently successful drug leads [1][2], many pharmaceutical

Recent highlights in biosynthesis research using stable isotopes

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2015, 11, 2493–2508, doi:10.3762/bjoc.11.271

• in the structure elucidation of complex polyketide natural products will be discussed. Especially in combination with two-dimensional NMR spectroscopic techniques, several powerful tools are becoming more interesting to natural products research. Production of new compounds in a labeled medium and

• investigated by fermentation in a 15N-labeled medium and analysis of the resulting product with 13C,15N-HMQC [32]. These applications represent helpful additions to the repertoire for structure elucidation of complex natural products, which can be produced under laboratory conditions in sufficient amounts. Non

• high hopes in the treatment of resistant pathogens (Figure 3). Producing an isotopologue of the desired compound by feeding of labeled precursors or growing the producing organism in labeled medium can simplify structure elucidation by giving access to the sum formula by mass spectrometry, which is not

Bromotyrosine-derived alkaloids from the Caribbean sponge Aplysina lacunosa

• Qun Göthel,
• Thanchanok Sirirak and
• Matthias Köck

Beilstein J. Org. Chem. 2015, 11, 2334–2342, doi:10.3762/bjoc.11.254

• , Verongida), three new bromotyrosine-derived alkaloids: 14-debromo-11-deoxyfistularin-3 (1), aplysinin A (2), and aplysinin B (3) (Figure 1), together with 15 known compounds were obtained. In this report we describe the structure elucidation of 1 to 3 and the biological activities of all the isolated