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

• but provides a new insight into the structural/biosynthetic diversity in microbial secondary metabolites. Finally, it should be noted that the R-enantiomer-rich anteisoalkyl group is extremely rare: only two ceramides, each from the dinoflagellate Coolia monotis [33] and the sponge Ephydatia syriaca

Automated high-content imaging for cellular uptake, from the Schmuck cation to the latest cyclic oligochalcogenides

• Rémi Martinent,
• Javier López-Andarias,
• Dimitri Moreau,
• Yangyang Cheng,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2020, 16, 2007–2016, doi:10.3762/bjoc.16.167

• an endosomal pathway. The low pKa value of the four GCP moieties could result in an improved buffering capacity, which could facilitate endosomal escape by the proton-sponge effect [28]. Significant inhibition of DNA transfection by bafilomycin (a macrolide antibiotic that can block the endosomal

Antibacterial scalarane from Doriprismatica stellata nudibranchs (Gastropoda, Nudibranchia), egg ribbons, and their dietary sponge Spongia cf. agaricina (Demospongiae, Dictyoceratida)

• Cora Hertzer,
• Stefan Kehraus,
• Nils Böhringer,
• Fontje Kaligis,
• Robert Bara,
• Dirk Erpenbeck,
• Gert Wörheide,
• Till F. Schäberle,
• Heike Wägele and
• Gabriele M. König

Beilstein J. Org. Chem. 2020, 16, 1596–1605, doi:10.3762/bjoc.16.132

• (Chromodorididae, Doridoidea) nudibranchs, their egg ribbons, and the associated dietary sponge Spongia cf. agaricina (Demospongiae, Porifera) led to the isolation of the structurally new scalarane-type sesterterpene 12-deacetoxy-4-demethyl-11,24-diacetoxy-3,4-methylenedeoxoscalarin, with an unprecedented position

• defend themselves with toxic or deterrent molecules [1][2][3][4][5][6][7][8]. Sponges (Porifera), for example, represent one of the main sources of marine bioactive natural products, due to their impressive chemical armoury [4]. These specialized metabolites can be produced either by the sponge itself or

• , and sesquiterpenoids, or scalarane-type sesquiterpenoids and sesterterpenoids from their sponge prey [23][37][38][39][40][41][42][43][44][45]. However, confusion in the chemotaxonomy of Chromodorididae arose by multiple changes in the species names, including splitting and synonymizations, and the

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• ruptured surface obtained [46]. SEM micrographs also allow the determination of different types of pores. The group of Okman showed SEM investigations on activated carbons prepared from grape seeds by activation with KOH. The sponge-like surface of the activated carbon indicates a microporous structure [56

Towards the total synthesis of chondrochloren A: synthesis of the (Z)-enamide fragment

• Jan Geldsetzer and
• Markus Kalesse

Beilstein J. Org. Chem. 2020, 16, 670–673, doi:10.3762/bjoc.16.64

• -dichloro-1,1,3,3-tetraisopropyldisiloxane, TBSOTf = tert-butyldimethylsilyl trifluoromethanesulfonate, proton sponge = 1,8-bis(N,N-dimethylamino)naphthalene. Synthesis of (Z)-bromide 4 using a palladium-catalyzed, stereoselective dehalogenation [21][22][23][24]. TBSOTf = tert-butyldimethylsilyl

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

• Qiao Lin,
• Shiling Zhang and
• Bin Li

Beilstein J. Org. Chem. 2020, 16, 492–501, doi:10.3762/bjoc.16.44

• has not been reported. Thiazolidinone derivatives are important moieties in functional materials and natural products [12][13][14], such as latrunculin that has been obtained from the sponge Cacospongia mycofijiensis [15]. Convenient syntheses of thiazolidinone derivatives are highly attractive to

Two antibacterial and PPARα/γ-agonistic unsaturated keto fatty acids from a coral-associated actinomycete of the genus Micrococcus

• Amit Raj Sharma,
• Enjuro Harunari,
• Naoya Oku,
• Nobuyasu Matsuura,
• Agus Trianto and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 297–304, doi:10.3762/bjoc.16.29

• natural products have been isolated from sponge-associated Micrococcus, including glycosylated glycerolipid [13][14], cyclic peptide [15], xanthone glycoside [16], and halogenated diphenyl ether [14]. Until now, however, no natural products are known from coral-associated Micrococcus. As a part of our

Two new aromatic polyketides from a sponge-derived Fusarium

• Mada Triandala Sibero,
• Tao Zhou,
• Keisuke Fukaya,
• Daisuke Urabe,
• Ocky K. Karna Radjasa,
• Agus Sabdono,
• Agus Trianto and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2019, 15, 2941–2947, doi:10.3762/bjoc.15.289

• program from marine fungi, two new aromatic polyketides karimunones A (1) and B (2) and five known compounds (3–7) were isolated from sponge-associated Fusarium sp. KJMT.FP.4.3 which was collected from an Indonesian sponge Xestospongia sp. The structures of these compounds were determined by the analysis

• polyketide; Fusarium; marine fungus; secondary metabolite; sponge; Introduction Marine organisms have been known as a potential source of prospective bioactive compounds, and sponges are particularly emphasized as the most promising source among all marine invertebrates [1][2]. However, the collection of

• structurally unique secondary metabolites with various biological activities [8][9]. Specifically, sponge-associated fungi are attracting substantial attention because of their high capability of producing a wide range of bioactive compounds [5][10][11]. As a tropical country, Indonesia is known as the second

Isolation and biosynthesis of an unsaturated fatty acid with unusual methylation pattern from a coral-associated bacterium Microbulbifer sp.

• Amit Raj Sharma,
• Enjuro Harunari,
• Tao Zhou,
• Agus Trianto and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2019, 15, 2327–2332, doi:10.3762/bjoc.15.225

• the sponge from which a vast array of natural products has been isolated and symbiotic bacteria are suggested to be responsible for the biosynthesis of such natural products [2]. Although it is well established that corals are associated with diverse microbes, coral-associated bacteria and their

Novel (2-amino-4-arylimidazolyl)propanoic acids and pyrrolo[1,2-c]imidazoles via the domino reactions of 2-amino-4-arylimidazoles with carbonyl and methylene active compounds

• Victoria V. Lipson,
• Tetiana L. Pavlovska,
• Nataliya V. Svetlichnaya,
• Anna A. Poryvai,
• Nikolay Yu. Gorobets,
• Erik V. Van der Eycken,
• Irina S. Konovalova,
• Svetlana V. Shiskina,
• Alexander V. Borisov,
• Vladimir I. Musatov and
• Alexander V. Mazepa

Beilstein J. Org. Chem. 2019, 15, 1032–1045, doi:10.3762/bjoc.15.101

• considered as the analogues of both 3,3’-spirooxindole and 2-aminoimidazole marine sponge alkaloids. Keywords: 2-amino-4-arylimidazole; (2-amino-4-arylimidazolyl)propanoic acid; isatin; Meldrum’s acid; multicomponent reactions; pyrrolo[1,2-c]imidazole; 3,3’-spirooxindoles; Introduction Heterocyclic

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

• Jan Hendrik Lang and
• Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

• endeavour, a new synthesis of the polyketide section present in seragamides and most of jasplakinolides and geodiamolides. We also include the synthesis of the protected tripeptide section of seragamide A (2), even if the macrocycle still remains to be assembled. Seragamide A (2) from the marine sponge

Synthesis and SAR of the antistaphylococcal natural product nematophin from Xenorhabdus nematophila

• Frank Wesche,
• Hélène Adihou,
• Thomas A. Wichelhaus and
• Helge B. Bode

Beilstein J. Org. Chem. 2019, 15, 535–541, doi:10.3762/bjoc.15.47

• moiety itself are required for bioactivity [16]. These findings suggest a specific interaction of this electrophilic moiety with a nucleophile. Such an interaction was previously reported for the macrocyclic peptide cyclotheonamide A, isolated from marine sponge Theonella sp. Cyclotheonamide A is

1,8-Bis(dimethylamino)naphthyl-2-ketimines: Inside vs outside protonation

• A. S. Antonov,
• A. F. Pozharskii,
• P. M. Tolstoy,
• A. Filarowski and
• O. V. Khoroshilova

Beilstein J. Org. Chem. 2018, 14, 2940–2948, doi:10.3762/bjoc.14.273

• has been shown that E-isomers of neutral imines can be stabilised by an intramolecular C=N−H···OMe hydrogen bond with a neighbouring methoxy group. Electron-donating OMe groups dramatically increase the basicity of the imino nitrogen, forcing the latter to abstract a proton from the proton sponge

• rotation of the NH2+ fragment in dications. Keywords: hydrogen bond; imine; NMR; proton sponge; superbase; Introduction It is well known that the extremely high basicity of 1,8-bis(dimethylamino)naphthalene (1, DMAN; pKa = 12.1 in H2O [1][2], 18.62 in MeCN [3], 7.5 in DMSO [4]) and its derivatives

• , leading to the formation of stabilised cations. In our recent work, we observed for the first time that the ortho-ketimino group in 4a can compete with the proton sponge moiety for the proton, which results in the formation of equilibria between the forms 4b (protonated to the proton sponge fragment) and

Stereoselective total synthesis and structural revision of the diacetylenic diol natural products strongylodiols H and I

• Pamarthi Gangadhar,
• Sayini Ramakrishna,
• Ponneri Venkateswarlu and
• Pabbaraja Srihari

Beilstein J. Org. Chem. 2018, 14, 2313–2320, doi:10.3762/bjoc.14.206

• Okinawan marine sponge of the genus Petrosia (Strongylophora). The structural elucidation was accomplished by spectroscopic analyses and chemical reactions. It was found that these strongylodiols were present as an enantiomeric mixture with different ratios after analysis of their corresponding MNA ((R

Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

• Cristina Morar,
• Pedro Lameiras,
• Attila Bende,
• Gabriel Katona,
• Emese Gál and
• Mircea Darabantu

Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145

• protonated site in ionic dendrimers 7b, 8 and 9 could not be attributed accurately either in solution (1H NMR), or in the solid state (IR). Consequently, their proposed cationic structures shown in Figure 1 and Scheme 4 (linker P-1 as piperazin-1-ium moiety) should be seen intuitively, a proton sponge-like

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• architectural extreme are: the ecteinascidins, antitumor tetrahydroisoquinoline alkaloids from the colonial Ascidian Ecteinascidia turbinata as exemplified by ecteinascidin 729 (4) [6]; ulbactins F (5a) and G (5b), two polycyclic thiazoline congeners isolated from a culture extract of a sponge derived

Two new 2-alkylquinolones, inhibitory to the fish skin ulcer pathogen Tenacibaculum maritimum, produced by a rhizobacterium of the genus Burkholderia sp.

• Dandan Li,
• Naoya Oku,
• Atsumi Hasada,
• Masafumi Shimizu and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2018, 14, 1446–1451, doi:10.3762/bjoc.14.122

• [21][22][23][24][25], Gram-positive [26][27] and Gram-negative bacteria [28][29][30], and a marine sponge [31]. Among a variety of substituted 4-quinolones, 2-alkyl-4-quinolones are the most common core in antibiotics [32], which were originally discovered as anti-anthrax metabolites produced by

Volatiles from three genome sequenced fungi from the genus Aspergillus

• Jeroen S. Dickschat,
• Ersin Celik and
• Nelson L. Brock

Beilstein J. Org. Chem. 2018, 14, 900–910, doi:10.3762/bjoc.14.77

• produces small amounts of 19. The biosynthetic byproduct dauca-4(11),8-diene (17) has recently also been described from the sponge isolate Dichotomomyces cejpii [48], but the genome of this fungus is not sequenced and the presence of a closely related TS in this organism is currently unknown. While these

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• . Nakiterpiosin (117) is a marine sponge metabolite which demonstrates a potent cytotoxicity against the P388 leukemic cell line. The photo-variant of the Nazarov cyclization has been applied as one of the steps in the total synthesis of nakiterpiosin (117, Scheme 37) [63]. Starting from substrate 115, 1-indanone

Chromium(II)-catalyzed enantioselective arylation of ketones

• Gang Wang,
• Shutao Sun,
• Ying Mao,
• Zhiyu Xie and
• Lei Liu

Beilstein J. Org. Chem. 2016, 12, 2771–2775, doi:10.3762/bjoc.12.275

• smoothly, providing corresponding tetrahydronaphthalen-1-ols bearing a tertiary alcohol center with good enantioselectivities (up to 97% ee). Experimental General procedure for the chromium(II) catalyzed enantioselective arylation of ketones: The solution of L8 (0.25 equiv, 0.025 mmol), proton sponge (0.25

The direct oxidative diene cyclization and related reactions in natural product synthesis

• Juliane Adrian,
• Leona J. Gross and
• Christian B. W. Stark

Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200

• 30% over three steps (Scheme 4). Additional to the synthesis of Donohoe described above [31], two other total syntheses of (+)-D-chitaric acid have been reported [40][41]. Neodysiherbaine A In 2001, the excitatory amino acid neodysiherbaine A (14) has been found in the marine sponge Dysidea herbacea

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

Modular synthesis of the pyrimidine core of the manzacidins by divergent Tsuji–Trost coupling

• Sebastian Bretzke,
• Stephan Scheeff,
• Felicitas Vollmeyer,
• Friederike Eberhagen,
• Frank Rominger and
• Dirk Menche

Beilstein J. Org. Chem. 2016, 12, 1111–1121, doi:10.3762/bjoc.12.107

• biological activities, several synthetic routes have been reported to access these important substructures [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The manzacidins have first been isolated by the group of Kobayashi from the marine sponge Hymeniacidon sp. in the early nineties of the

• motif into 18, tosylisocyanate in combination with strong bases was required to achieve useful degrees of conversion towards the desired precursor 19. The best results were obtained with BuLi, as previously communicated [31], while weaker bases (NEt3, LHMDS, DBU, proton sponge) and less electron

Towards the total synthesis of keramaphidin B

• Pavol Jakubec,
• Alistair J. M. Farley and
• Darren J. Dixon

Beilstein J. Org. Chem. 2016, 12, 1096–1100, doi:10.3762/bjoc.12.104

• addition; keramaphidin B; nitro-Mannich lactamisation cascade; Introduction Keramaphidin B (1) is a marine alkaloid first isolated by Kobayashi in 1994 from the Okinawan marine sponge Amphimedon sp and has been shown to be cytotoxic against KB human epidermoid carcinoma cells (IC50 0.28 μg/mL) and P388

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

• solvents upon light exposure [62]. The salimyxins represent the third group of compounds, i.e., salimyxin A (29) and B (30). These belong to a subgroup of terpenoids named incisterols, which were first discovered from the sponge Dictyonella incisa [63]. Their biosynthesis presumably involves oxidative