Unconventional application of the Mitsunobu reaction: Selective flavonolignan dehydration yielding hydnocarpins

• Guozheng Huang,
• Simon Schramm,
• Jörg Heilmann,
• David Biedermann,
• Vladimír Křen and
• Michael Decker

Beilstein J. Org. Chem. 2016, 12, 662–669, doi:10.3762/bjoc.12.66

• combine the structural moieties of flavonoids and phenylpropanoids (lignans). Among the group of flavonolignans, the medicinally most important ones can be found in Silybum marianum (L.) Gaertn., the milk thistle. The phenolic secondary metabolites of this plant have been intensively studied due to their

Antibiotics from predatory bacteria

• Juliane Korp,
• María S. Vela Gurovic and
• Markus Nett

Beilstein J. Org. Chem. 2016, 12, 594–607, doi:10.3762/bjoc.12.58

• known secondary metabolites of M. xanthus DK1622 show a wide range of biological activities and can hence be expected to fulfill different ecological functions. The yellow DKxanthenes, for instance, play a crucial role in spore maturation during fruiting body formation [63]. They were also shown to

• completely ignored in the field. It is therefore no surprise that to date only three classes of secondary metabolites have been reported from this genus (Figure 6). Siphonazole and its O-methyl derivative were the first natural products to be isolated from a Herpetosiphon strain [125]. The two compounds

• metabolites from the H. aurantiacus type strain 114-95T led to the discovery of auriculamide (22) [127]. This natural product is composed of a 2-hydroxy-3-methylvalerate and a 2-amino-1-(3-chloro-4-hydroxyphenyl)pentan-3-one residue. A retrobiosynthetic analysis allowed the assignment of the gene cluster

Biosynthesis of α-pyrones

• Till F. Schäberle

Beilstein J. Org. Chem. 2016, 12, 571–588, doi:10.3762/bjoc.12.56

• Till F. Schaberle Institute for Pharmaceutical Biology, University of Bonn, Nußallee 6, 53115 Bonn, Germany 10.3762/bjoc.12.56 Abstract The α-pyrone moiety is a structural feature found in a huge variety of biologically active metabolites. In recent times new insights into additional biosynthetic

• ]. These toxic fungi-derived metabolites are often pathogenic to plants, and are therefore called phytotoxins. Phytotoxins are divided into host-specific and host non-specific toxins, whereby the here named Alternaria-derived dibenzo-α-pyrones 17, 18, and 19 represent host-specific phytotoxins [26

• , production by a fungus and modification of the metabolites by plant enzymes is also possible. Further α-pyrone plant secondary metabolites are ellagitannins and ellagic acid (22) [27] (Figure 4). These metabolites are important constituents of different foods, e.g., berries, nuts, medicinal plants and

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

• , Universitetsparken 15, Building 3, 1st floor, 2100 Copenhagen East, Denmark 10.3762/bjoc.12.34 Abstract Here we review discoveries of secondary metabolites from microbes associated with insects. We mainly focus on natural products, where the ecological role has been at least partially elucidated, and/or the

• species [12][13][14][15][16][17]. As a response to these threats, many insects have evolved defensive strategies, including mechanical and behavioral defense, complex immune systems, and the use of bioactive secondary metabolites produced by residing mutualists [12][13][14][15][16][17][24][25][26]. The

• occurrence of these metabolites in often subinhibitory concentrations indicates that they might not primarily function as antimicrobials. Rather they work as signaling molecules leading to modulation of gene expression in the target organism, to alteration in factors contributing to the virulence or

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• trained staff and are therefore unsuitable for field implementation. An appealing approach to overcome these drawbacks relies on the use of CD-based chemosensors. Apart from detection, the main concern in any event of exposure remains the fast degradation of NOPs into less toxic metabolites by rapid

Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen

• Hans Sterckx,
• Johan De Houwer,
• Carl Mensch,
• Wouter Herrebout,
• Kourosch Abbaspour Tehrani and
• Bert U. W. Maes

Beilstein J. Org. Chem. 2016, 12, 144–153, doi:10.3762/bjoc.12.16

• drug Mefloquine. The oxidation method can also be used to prepare metabolites of APIs which is illustrated for the natural product papaverine. ICP–MS analysis of the purified reaction products revealed that the base metal impurity was well below the regulatory limit. Keywords: base metal; benzylic

• earlier and can also be achieved in an enantioselective manner [41]. Human metabolism can produce metabolites of pharmaceuticals that possess completely different properties such as for instance biological activity, toxicity and clearance rates. Rapid identification and synthesis of potential drug

• metabolites is therefore of great importance to facilitate the drug discovery process [42]. For this purpose chemoselective oxidation protocols are a valuable tool since they can provide us with metabolites typically generated by cytochrome P450 enzymes. Bearing this in mind we attempted to oxygenate the

Physical properties and biological activities of hesperetin and naringenin in complex with methylated β-cyclodextrin

• Waratchada Sangpheak,
• Jintawee Kicuntod,
• Roswitha Schuster,
• Thanyada Rungrotmongkol,
• Peter Wolschann,
• Nawee Kungwan,
• Helmut Viernstein,
• Monika Mueller and
• Piamsook Pongsawasdi

Beilstein J. Org. Chem. 2015, 11, 2763–2773, doi:10.3762/bjoc.11.297

• three different cancer cell lines. The overall results suggested that solubilities and bioactivities of both flavanones were increased by complexation with methylated β-CDs. Keywords: binding energy; bioactivity; cyclodextrins; hesperetin; naringenin; Introduction Flavonoids are secondary metabolites

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• related metabolites. Selected members from the four different subclasses of the Xenia diterpenoid family, the xenicins, xeniolides, xeniaphyllanes and xeniaethers, are presented. The synthetic strategies are discussed with an emphasis on the individual key reactions for the construction of the uncommon

• a large group of structurally diverse secondary metabolites. Among these natural products, Xenia diterpenoids or xenicanes represent a unique family with intriguing structural features and diverse biological activities. Many xenicanes display significant cytotoxic and antibacterial activity and are

• therefore of great interest for drug discovery, especially for their application as anticancer agents [1]. Marine soft corals of the genus Xenia (order Alcyonacea, family Xeniidae) are known to be rich in xenicane diterpenoids. The first reported member of these metabolites was xenicin (1), isolated from

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

• understanding of biosynthesis. As demonstrated in this article, the usage of isotopes is not at all old-fashioned, but continues to give important insights into biosynthetic pathways of secondary metabolites. This review with 85 cited references is structured by separate discussions of compounds from different

• reductase [16], aflatoxin B1 (2) [17] and the potent antifungal agent amphotericin B (3) [18], which affects membrane integrity. The products of polyketide synthases (PKS) belong to the first secondary metabolites that were investigated using isotopically labeled compounds [19]. Feeding experiments using

Biocatalysis for the application of CO₂ as a chemical feedstock

• Apostolos Alissandratos and
• Christopher J. Easton

Beilstein J. Org. Chem. 2015, 11, 2370–2387, doi:10.3762/bjoc.11.259

• current oxidative technologies that rely on diminishing natural fossil-fuel deposits. Enzymes that catalyse CO2 fixation steps in carbon assimilation pathways are promising catalysts for the sustainable transformation of this safe and renewable feedstock into central metabolites. These may be further

• , and in oxygen-deficiency zones [50]. Reductive tricarboxylic acid cycle The tricarboxylic acid (TCA) cycle is used by all aerobic organisms to generate NADH through the oxidation of small organic metabolites. For pyruvate (11), isocitrate (7) and 2-oxoglutarate (6), oxidation occurs together with a

• fixation A large number of enzymes use CO2 (or HCO3−) as a substrate without taking part in autotrophic pathways [26]. These are predominantly found in assimilatory pathways where small organic molecules are used as carbon sources, and anaplerosis through which intermediate metabolites in central pathways

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

• products; NMR spectroscopy; Introduction Bromotyrosine-derived alkaloids are unique brominated metabolites which were isolated mainly from marine sponges of the order Verongida. For more than 50 years, bromotyrosine alkaloids raised the interests of synthetic and natural products chemists due to their

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

• fascinating example of a large variety of secondary metabolites produced exclusively by marine sponges. To date, more than 150 PIAs have been isolated mainly from various species of the families Agelasidae, Axinellidae, Dyctionellidae, and Hymeniacidonidae and some of them show promising biological activities

• which could be an alternative origin of these metabolites. The molecular formula of citrinamine B (2) was established by HR–ESIMS (m/z 740.0337, [M + H]+, monoisotopic) and the pseudomolecular ion peaks at m/z = 740/742/744 (1:2:1) to be C24H28Br2N11O5S. The 1D 1H and 13C NMR spectra of 2 were similar

Synthesis, antimicrobial and cytotoxicity evaluation of new cholesterol congeners

• Mohamed Ramadan El Sayed Aly,
• Hosam Ali Saad and
• Shams Hashim Abdel-Hafez

Beilstein J. Org. Chem. 2015, 11, 1922–1932, doi:10.3762/bjoc.11.208

• cholesterol (oxysterol) metabolites contributes to the prognosis of major chronic diseases. Cholesterol is completely absent in prokaryotic organisms [1][2][3]. Cholesterol gives eukaryotic membranes sufficient mechanical stiffness against cationic selective antimicrobials (CSAs) such as antimicrobial

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• ethylene (24) under high dilution conditions to deliver the tetracyclic compound 49 in 62% yield (Scheme 7). To assemble 5-F2-isoprostanes, lipid oxidation metabolites, various functionalized cyclobutene derivatives were subjected to a RRM sequence [12]. Cyclobutene derivative 50 in the presence of the

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

• on pyridoacridine-related metabolites as one biologically interesting group of alkaloids identified from marine sources. They are produced by marine sponges, ascidians and tunicates, and they are structurally comprised of four to eight fused rings including heterocycles. Acridine, acridone

• structures is further discussed. Moreover, the biosynthetic pathways of some of these metabolites have been shown since they could inspire biomimetic synthesis. The synthesis routes used to prepare members of these marine alkaloids (as well as their analogues), which are synthesized for biological purposes

• metabolites. It is well known that these chemicals play specific roles for their host with respect to communication [1], sexual attraction [2] and defense [3]. Marine biodiversity has provided around three thousand new chemicals, the most predominant of which are associated with polyketides, peptides

Synthesis and spectroscopic properties of β-triazoloporphyrin–xanthone dyads

• Dileep Kumar Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2015, 11, 1434–1440, doi:10.3762/bjoc.11.155

• diporphyrin analogues [20][28][29][30]. Xanthene-9H-ones are an important class of oxygen-containing heterocycles and are mainly found as secondary metabolites in higher plants and microorganisms. The naturally occurring and synthetic xanthones possess diverse pharmacological activities [31][32][33][34

A new and efficient procedure for the synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones

• Marcelo Isidoro P. Reis,
• Vinícius R. Campos,
• Jackson A. L. C. Resende,
• Fernando C. Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2015, 11, 1235–1240, doi:10.3762/bjoc.11.137

• ]quinazoline; microwave; naphthoquinone; 1,3-quinazoline; 1,3,5-triazinane; Introduction Quinones represent a diverse family of naturally occurring secondary metabolites [1][2][3]. Interest in these substances has intensified in recent years due to their pharmacological importance [4]. Heterocycle-fused

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

• ; Meyerozyma guilliermondii; Introduction Depsidones are characterized by the presence of cyclic diaryl ethers with an ester link joining the two aromatic rings [1][2]. They have been isolated mainly from various lichens [3][4][5] and other fungi [6][7][8][9][10][11]. These metabolites displayed a wide range

Electrosynthesis and electrochemistry

• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2015, 11, 949–950, doi:10.3762/bjoc.11.105

• molecules. Such electro-oxidative treatment generates potential metabolites that can be then biologically studied [10]. The combination of electrosynthesis with other powerful techniques, such as ultrasonic treatment and flow microcells, will push the electrosynthetic applications beyond current limits [11

Synthesis of the furo[2,3-b]chromene ring system of hyperaspindols A and B

• Danielle L. Paterson and
• David Barker

Beilstein J. Org. Chem. 2015, 11, 265–270, doi:10.3762/bjoc.11.29

• hepatitis and depression, and as topical antimicrobials for wounds and snake bites [2][3][4][5]. There is great interest in secondary metabolites produced by plants from the Hypericum genus due to the bioactivity of many compounds that have been isolated from this source. A wide variety of compounds have

Natural phenolic metabolites with anti-angiogenic properties – a review from the chemical point of view

• Qiu Sun,
• Jörg Heilmann and
• Burkhard König

Beilstein J. Org. Chem. 2015, 11, 249–264, doi:10.3762/bjoc.11.28

• natural metabolites available from plants, phenolic compounds play a particularly important role in human health as they occur in significant amounts in many fruits, vegetables and medicinal plants. In this review natural phenolic compounds of plant origin with significant anti-angiogenic properties are

• options with antibodies and VEGF receptor inhibitors showed several clinical limitations, making the search for further clinically relevant targets and other drugs necessary to combat tumor-related angiogenesis. Secondary natural metabolites have also been identified as attractive candidates for the

• polyphenols was previously considered as unspecific, more recently, observations of a specific interference with biological mechanisms at the molecular level have significantly increased. Especially in the fields of anti-inflammatory activity, chemoprevention and cytoprotection, natural phenolic metabolites

Cathodic reductive coupling of methyl cinnamate on boron-doped diamond electrodes and synthesis of new neolignan-type products

• Taiki Kojima,
• Rika Obata,
• Tsuyoshi Saito,
• Yasuaki Einaga and
• Shigeru Nishiyama

Beilstein J. Org. Chem. 2015, 11, 200–203, doi:10.3762/bjoc.11.21

• -type products were synthesized from the hydrodimer. Keywords: boron-doped diamond (BDD) electrode; cathodic reduction; electrochemistry; electrosynthesis; neolignan; Introduction Numerous lignans and neolignans were found as secondary plant metabolites, and many of them are known to exhibit

A carbohydrate approach for the formal total synthesis of (−)-aspergillide C

• Pabbaraja Srihari,
• Namballa Hari Krishna,
• Ydhyam Sridhar and
• Ahmed Kamal

Beilstein J. Org. Chem. 2014, 10, 3122–3126, doi:10.3762/bjoc.10.329

• rings) are unexpected, novel, secondary metabolites, isolated from the marine-derived fungus Aspergillus ostianus strain 01F313 in bromine-modified 1/2PD culture medium [1][2][3][4]. Interestingly, these compounds show cytotoxicity against mouse lymphocytic leukemia cells (L1210) with LD50 values of 2.1

Trogopterins A–C: Three new neolignans from feces of Trogopterus xanthipes

• Soyoon Baek,
• Xuikui Xia,
• Byung Sun Min,
• Chanil Park and
• Sang Hee Shim

Beilstein J. Org. Chem. 2014, 10, 2955–2962, doi:10.3762/bjoc.10.313

• with IC50 values of 34.77–45.68 μM. Keywords: cytotoxic activity; neolignans; Trogopterus xanthipes; Introduction Chemical studies of natural products including ones derived from plants and microorganisms have led to the isolation of numerous novel metabolites with biological activities [1][2]. As a

Thermal and oxidative stability of the Ocimum basilicum L. essential oil/β-cyclodextrin supramolecular system

• Daniel I. Hădărugă,
• Nicoleta G. Hădărugă,
• Corina I. Costescu,
• Ioan David and
• Alexandra T. Gruia

Beilstein J. Org. Chem. 2014, 10, 2809–2820, doi:10.3762/bjoc.10.298

• to these aspects, such as diepoxidation of limonene to the carcinogenic diepoxylimonene or oxidation of other terpenes (e.g., pinene) to harmful oxidized derivatives [14][26][27], the degradation of safrole to carcinogenic metabolites [28], or the formation of oxygentated derivatives of limonene