The marine sponge Agelas citrina as a source of the new pyrrole–imidazole alkaloids citrinamines A–D and N-methylagelongine

• Christine Cychon,
• Ellen Lichte and
• Matthias Köck

Beilstein J. Org. Chem. 2015, 11, 2029–2037, doi:10.3762/bjoc.11.220

• (10) [8][9][10] (Figure 1). Additionally, five new compounds, four with a dimeric PIA structure (1–4) and the N-methyl analogue (5) of the bromopyrrole alkaloid agelongine (12) [11], were isolated. Herein, we describe the isolation and structure elucidation of citrinamines A (1), B (2), and N

• at carbon C-9 in citrinamines C (3) and D (4) may be attributed to the utilization of MeOH as solvent for the extraction of the sponge. To verify the structure elucidation of citrinamines C (3) and D (4), further extraction of sponge tissue of Agelas citrina is necessary to obtain pure material. The

• scheme. The MeOH/CH2Cl2 extract of the sample was partitioned between n-hexane, n-BuOH, and H2O. The n-BuOH soluble fraction was further purified by size exclusion chromatography (Sephadex LH-20) and preparative reversed-phase HPLC yielding five new compounds (1–5). The isolation and structure

Synthesis of constrained analogues of tryptophan

• Elisabetta Rossi,
• Valentina Pirovano,
• Marco Negrato,
• Giorgio Abbiati and
• Monica Dell’Acqua

Beilstein J. Org. Chem. 2015, 11, 1997–2006, doi:10.3762/bjoc.11.216

• compounds embodying constrained analogues of tryptophan. Structure elucidation of diastereoisomeric tetrahydrocarbazoles 3a and 3’a via NMR experiments. Planned Diels–Alder reactions for the synthesis of tetrahydrocarbazoles as constrained analogues of tryptophan. Synthesis of unprotected tryptophan

Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

• Louis P. Sandjo,
• Victor Kuete and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183

• also interact with DNA [41]. Review Chemistry Structure elucidation: 13C NMR data The difficulty of NMR data assignment could be related to the presence of a high number of quaternary carbons in tetra- to octaheterocycles of these alkaloids. For example, up to eleven quaternary carbons may be involved

• (compounds 12–15) if the CH3 group is bound to an uncharged nitrogen atom [50]. Rings A–C (Table 6) rarely contain functional groups and the hydrogen chemical shifts (compounds 12–14, 17, and 19) can be used as a starting point for structure elucidation. 2D Long range correlations maps (HMBC) can easily lead

• of the A ring when the B ring is not aromatic. The compilation of this NMR data could be used as a library for a database prediction and could also save time with respect to structure elucidation of related natural congeners. Earlier, successful synthetic figures have also been presented as well as

Structure and conformational analysis of spiroketals from 6-O-methyl-9(E)-hydroxyiminoerythronolide A

• Ana Čikoš,
• Irena Ćaleta,
• Dinko Žiher,
• Mark B. Vine,
• Ivaylo J. Elenkov,
• Marko Dukši,
• Dubravka Gembarovski,
• Marina Ilijaš,
• Snježana Dragojević,
• Ivica Malnar and
• Sulejman Alihodžić

Beilstein J. Org. Chem. 2015, 11, 1447–1457, doi:10.3762/bjoc.11.157

• to isolate and fully characterise the products. Structure elucidation of compound 2 Analysis of HMBC spectra, as well as chemical shift comparison with the parent compound 1 [39], showed that the 9-C-signal of 2 exhibits a large upfield shift to 107.1 ppm (168.1 ppm in 1), as well as intense HMBC

• unchanged. Structure elucidation of compound 3 The main feature of compound 3 is the appearance of a double bond between 10-C and 11-C, as evidenced by the signal in the 1H NMR spectrum at 5.65 ppm and relevant HMBC correlations. The initial 3D structure of the compound was generated from the previously

• , antiperiplanar and one weak, synclinal) suggest an axial orientation of 8-H and equatorial position of 8-Me. Similar to 2, the six-membered tetrahydropyran assumes an anomerically non-stabilised chair conformation with the larger 6-methoxy substituent in the axial position. Structure elucidation of compound 4

A novel and widespread class of ketosynthase is responsible for the head-to-head condensation of two acyl moieties in bacterial pyrone biosynthesis

• Darko Kresovic,
• Florence Schempp,
• Zakaria Cheikh-Ali and
• Helge B. Bode

Beilstein J. Org. Chem. 2015, 11, 1412–1417, doi:10.3762/bjoc.11.152

• their isolation followed by NMR-based structure elucidation (Table S5, Supporting Information File 1) we could confirm that Pseudomonas sp. GM30 is producing pseudopyronine A (9), B (10) and the new derivative C (11) all differing in the chain length of the eastern acyl moiety. As heterologous

New depsidones and isoindolinones from the mangrove endophytic fungus Meyerozyma guilliermondii (HZ-Y₂) isolated from the South China Sea

• Senhua Chen,
• Zhaoming Liu,
• Yayue Liu,
• Yongjun Lu,
• Lei He and
• Zhigang She

Beilstein J. Org. Chem. 2015, 11, 1187–1193, doi:10.3762/bjoc.11.133

• ). In the bioactivity assay, all depsidones showed strong α-glucosidase inhibitory activity with IC50 values ranging from 2.1 to 13.3 μM. Details of the isolation, structure elucidation, and biological activity of these compounds are reported herein. Results and Discussion Botryorhodine E (1) was

Synthesis of modified cyclic and acyclic dextrins and comparison of their complexation ability

• Kata Tuza,
• László Jicsinszky,
• Tamás Sohajda,
• István Puskás and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2014, 10, 2836–2843, doi:10.3762/bjoc.10.301

• shows similarity to a typical CD-drug interaction. Based on the promising results of the preliminary complexation studies with some model drugs, modified cyclodextrins and the corresponding acyclodextrins were synthesized (Scheme 1) in order to compare their complexation behavior. The structure

• elucidation of the O-benzyl intermediary products and the final HP-maltooligomers was performed by NMR (see Supporting Information File 1). Both proton and carbon assignments are based on the DEPT-ed-HSQC spectra. The NMR spectra confirm the complete 1-O-benzylation at the glycosidic oxygen (Figures S1–S6

Specific DNA duplex formation at an artificial lipid bilayer: fluorescence microscopy after Sybr Green I staining

• Emma Werz and
• Helmut Rosemeyer

Beilstein J. Org. Chem. 2014, 10, 2307–2321, doi:10.3762/bjoc.10.240

• ], 2. for the development of analytical techniques for the detection of nucleic acids [15][16][17], 3. for structure elucidation of complex aggregates formed by such natural nanostructures [5][6] and 4. for cell-surface engineering [18]. In a preceding manuscript [19] we reported the lipid bilayer

A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry

• J. Alexander Willms,
• Rita Beel,
• Martin L. Schmidt,
• Christian Mundt and
• Marianne Engeser

Beilstein J. Org. Chem. 2014, 10, 2027–2037, doi:10.3762/bjoc.10.211

• spectrometric means for structure elucidation, collision-induced dissociation (CID) experiments have been perfomed. The results for R = Et are shown in Figure 5. All four mass-selected ions [IIa]+/[IIb]+ and [IIIa]+/[IIIb]+ show a very strong propensity to expel CO2 which even happens during the ESI process via

A tandem Mannich addition–palladium catalyzed ring-closing route toward 4-substituted-3(2H)-furanones

• Jubi John,
• Eliza Târcoveanu,
• Peter G. Jones and
• Henning Hopf

Beilstein J. Org. Chem. 2014, 10, 1462–1470, doi:10.3762/bjoc.10.150

• obtained from these two substrates in good yields (Figure 2). We also tried a reaction with N-Boc protected imine under optimized conditions and the corresponding furanone was obtained in good yield (Figure 2, compound 14). The structure elucidation of the furanone products 3, and 5–14 was accomplished by

Heronapyrrole D: A case of co-inspiration of natural product biosynthesis, total synthesis and biodiscovery

• Jens Schmidt,
• Zeinab Khalil,
• Robert J. Capon and
• Christian B. W. Stark

Beilstein J. Org. Chem. 2014, 10, 1228–1232, doi:10.3762/bjoc.10.121

• quantity available was insufficient for in depth structure elucidation. Fortunately, analytical HPLC–DAD comparisons between natural and synthetic samples of heronapyrrole D (see the Supporting Information File 1), together with optical rotation measurements [natural [α]D22 +7.5 (c 0.003, MeOH); synthetic

cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• -glucopyranoside 6''-gallate, Figure 6) was subjected to both, basic and acidic hydrolysis during its structure elucidation. However, under these conditions four stereoisomers of the original aglycon (2R,3R)-taxifolin were formed. Base-catalyzed isomerization of another taxifolin glycoside, (2R,3R)-2,3

Structure elucidation of female-specific volatiles released by the parasitoid wasp Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)

• Armin Tröger,
• Teris A. van Beek,
• Martinus E. Huigens,
• Isabel M. M. S. Silva,
• Maarten A. Posthumus and
• Wittko Francke

Beilstein J. Org. Chem. 2014, 10, 767–773, doi:10.3762/bjoc.10.72

• -diene and (2E,4E,6S,8S,10S)-4,6,8,10-tetramethyltrideca-2,4-dien-1-ol or their enantiomers as sex specific volatiles. The structures were assigned on the basis of GC–MS investigations using synthetic reference compounds. Keywords: natural products; structure elucidation; sex specific; Trichogramma

New sesquiterpene hydroquinones from the Caribbean sponge Aka coralliphagum

• Qun Göthel and
• Matthias Köck

Beilstein J. Org. Chem. 2014, 10, 613–621, doi:10.3762/bjoc.10.52

• ; natural products; NMR; sesquiterpene hydroquinone; structure elucidation; Introduction Aka coralliphagum (Siphonodictyon coralliphagum) is known to have four distinct morphological forms: forma typica, f. tubulosa, f. obruta, and f. incrustans [1]. This sponge has the ability to burrow into live coral

• compounds. Results and Discussion The aqueous n-BuOH extract from Aka coralliphagum was subjected to solvent partitioning, followed by gel chromatography and reversed phase (C18) HPLC to yield siphonodictyals E1–E4 (1–4) and cyclosiphonodictyol A (5) (Figure 1). The structure elucidation was based on 1D and

Total synthesis and cytotoxicity of the marine natural product malevamide D and a photoreactive analog

• Werner Telle,
• Gerhard Kelter,
• Heinz-Herbert Fiebig,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2014, 10, 316–322, doi:10.3762/bjoc.10.29

• , Scheme 2). However, after treatment of dipeptide 15 with secondary amine 16 (0.43 equiv) and DEPC (17, 2.5 equiv), the only isolable product was oxazolylphosphate 18 (35%) without any amide formation occurring. The structure elucidation of 18 required C–P coupling constant analysis, which showed doublet

Tanzawaic acids I–L: Four new polyketides from Penicillium sp. IBWF104-06

• Louis P. Sandjo,
• Eckhard Thines,
• Till Opatz and
• Anja Schüffler

Beilstein J. Org. Chem. 2014, 10, 251–258, doi:10.3762/bjoc.10.20

• same trans-decalinpentanoic acid skeleton as tanzawaic acids A–H. One of the new compounds was found to inhibit the conidial germination in the rice blast fungus Magnaporthe oryzae at concentrations of 25 μg/mL. Keywords: arohynapene; natural products; polyketides; structure elucidation; tanzawaic

• Discussion Structure elucidation. Compound 1 has the molecular formula C18H26O4 determined on the basis of NMR and HRMS-ESI data which gave a pseudo-molecular ion at m/z 329.1744 (calcd for [M + Na]+: 329.1729). This composition accounted for six double bond equivalents. The NMR spectra of 1 (Table 1 and

Plakilactones G and H from a marine sponge. Stereochemical determination of highly flexible systems by quantitative NMR-derived interproton distances combined with quantum mechanical calculations of ¹³C chemical shifts

• Simone Di Micco,
• Angela Zampella,
• Maria Valeria D’Auria,
• Carmen Festa,
• Simona De Marino,
• Raffaele Riccio,
• Craig P. Butts and
• Giuseppe Bifulco

Beilstein J. Org. Chem. 2013, 9, 2940–2949, doi:10.3762/bjoc.9.331

• the four diastereoisomers 2a,b,e,f endowed with the epoxide moiety in a trans-configuration, by comparing the experimental vs the calculated distances (Table 3). In Table 3 only a subset of all values was used for the stereochemical structure elucidation, more specifically, the values where DFT

Synthesis and determination of the absolute configuration of (−)-(5R,6Z)-dendrolasin-5-acetate from the nudibranch Hypselodoris jacksoni

• I. Wayan Mudianta,
• Victoria L. Challinor,
• Anne E. Winters,
• Karen L. Cheney,
• James J. De Voss and
• Mary J. Garson

Beilstein J. Org. Chem. 2013, 9, 2925–2933, doi:10.3762/bjoc.9.329

• methoxyphenylacetic acid (MPA) derivative. Results and Discussion Isolation and structure elucidation of natural product 1 Eight individuals of H. jacksoni were collected by SCUBA from two locations in SE Queensland. Owing to their small size (21–40 mm), the specimens were not examined individually. Extraction into

Studies toward bivalent κ opioids derived from salvinorin A: heteromethylation of the furan ring reduces affinity

• Thomas A. Munro,
• Wei Xu,
• Douglas M. Ho,
• Lee-Yuan Liu-Chen and
• Bruce M. Cohen

Beilstein J. Org. Chem. 2013, 9, 2916–2924, doi:10.3762/bjoc.9.328

• after heating overnight at reflux. As an alternative linker attachment point, (2-hydroxyethoxy)methyl ether 6 was prepared from the known methylthiomethyl ether 7 using a slight modification of previous conditions (Scheme 2) [24]. Structure elucidation The molecular formula of 2 and 3 was established by

SF002-96-1, a new drimane sesquiterpene lactone from an Aspergillus species, inhibits survivin expression

• Silke Felix,
• Louis P. Sandjo,
• Till Opatz and
• Gerhard Erkel

Beilstein J. Org. Chem. 2013, 9, 2866–2876, doi:10.3762/bjoc.9.323

• µM (1.3 µg/mL). Moreover, it also reduced mRNA levels and protein synthesis of survivin and triggered apoptosis. Keywords: apoptosis; inhibitor; natural products; secondary metabolite; structure elucidation; survivin; Introduction Survivin, a member of the inhibitor of apoptosis (IAP) protein

• transiently transfected Colo 320 cells. In the current study, the fermentation, structure elucidation, and some biological properties of the compound are described. Results and Discussion Identification and structure elucidation SF002-96-1 was obtained by a bio-guided isolation procedure as a colourless oil

[²H₂₆]-1-epi-Cubenol, a completely deuterated natural product from Streptomyces griseus

• Christian A. Citron and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 2841–2845, doi:10.3762/bjoc.9.319

• to slow down all metabolic processes in living organisms. Potential applications of completely labelled compounds from natural sources in structure elucidation, biosynthetic or pharmacokinetic investigations are discussed. Keywords: biosynthesis; deuterium; labelling; natural products; Streptomyces

Halogenated volatiles from the fungus Geniculosporium and the actinomycete Streptomyces chartreusis

• Tao Wang,
• Patrick Rabe,
• Christian A. Citron and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 2767–2777, doi:10.3762/bjoc.9.311

• structure elucidation all possible constitutional isomers for X and Y were obtained by synthesis or from commercial suppliers. Comparison of mass spectra and GC retention times rigorously established the structures of the two chlorinated volatiles. Chlorinated volatiles are not very widespread, but

The myxocoumarins A and B from Stigmatella aurantiaca strain MYX-030

• Tobias A. M. Gulder,
• Snežana Neff,
• Traugott Schüz,
• Tammo Winkler,
• René Gees and
• Bettina Böhlendorf

Beilstein J. Org. Chem. 2013, 9, 2579–2585, doi:10.3762/bjoc.9.293

• The myxobacterial strain Stigmatella aurantiaca MYX-030 was selected as promising source for the discovery of new biologically active natural products by our screening methodology. The isolation, structure elucidation and initial biological evaluation of the myxocoumarins derived from this strain are

• described in this work. These compounds comprise an unusual structural framework and exhibit remarkable antifungal properties. Keywords: antifungal activity; myxobacteria; natural products; Stigmatella aurantiaca; structure elucidation; Introduction Despite declining interest of most big R&D-driven

• ) in relation to the non-treated control. Structures of epothilone A (1), soraphen A1α (2), pyrrolnitrin (3), fenpiclonil (4), myxothiazol A (5), and aurachin A (6). HMBC interactions used for the structure elucidation of myxocoumarin A (7). Chemical structure of myxocoumarin B (9). Postulated

Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C₂-symmetric building block: a strategy for the synthesis of decanolide natural products

• Bernd Schmidt and
• Oliver Kunz

Beilstein J. Org. Chem. 2013, 9, 2544–2555, doi:10.3762/bjoc.9.289

• structure elucidation and for correcting erroneous assignments. In particular if ex-chiral pool starting materials with well established absolute configurations are used, such as D-mannitol-derived 1 or L-tartrate-derived ent-1, highly reliable structural assignments become possible. Two decanolides, for

Flexible synthesis of anthracycline aglycone mimics via domino carbopalladation reactions

• Markus Leibeling and
• Daniel B. Werz

Beilstein J. Org. Chem. 2013, 9, 2194–2201, doi:10.3762/bjoc.9.258

• have been isolated from bacteria of the order Streptomycetales. The group of Brockmann, who first found anthracyclines in 1963, described them as red to orange dyes [2]. Their structure elucidation revealed a linear fourfold annulated ring system including two benzene units (A-ring and C-ring). The