Andreas Speicher

• Saarland University

A polyprenyl side chain could be introduced into the heterocyclic quinoline moiety through Suzuki‐Miyaura coupling of the corresponding quinoline‐N‐oxide with a polyprenyl boronic acid. This tool could be utilized for the synthesis of the natural product Aurachin B from the myxobacterium Stigmatella aurantiaca. This prenylated quinoline could then...

A target-focused library of small molecules, containing a set of quinones, quinolones, coumarins, flavonoids and other diverse drugs was screened to identify potential inhibitors of the cytochrome bd-I oxidase from Escherichia coli by means of an electrochemical assay based on the immobilization of the proteins on gold nanoparticles. As primary hit...

The Cover Feature shows a chiral sulfinyl auxiliary in the ortho‐position of a biaryl axis inducing a C–H activated atroposelective macrocyclization with final transformation to the configurationally stable natural Isoriccardin C. More information can be found in the Communication by S. Choppin, A. Speicher et al.

Macrocyclization is typically the key step in syntheses of cyclophane‐type natural products. Considering compounds with axially chiral biaryl moieties, the control of atroposelectivity is essential for biological activity and is synthetically challenging. Herein we report on atroposelective macrocyclization involving an oxidative Heck type process...

The macrocyclization uses to be the key step in the syntheses of cyclophane type natural products. Considering cyclophanes with axially chiral biaryl moieties, the control of atroposelectivity is ‐ referring to synthesis and biological activities ‐ essential and challenging. We report on an atroposelective approach involving Heck cyclization, allow...

The macrocyclization uses to be the key step in the syntheses of cyclophane type natural products. Considering cyclophanes with axially chiral biaryl moieties, the control of atroposelectivity is ‐ referring to synthesis and biological activities ‐ essential and challenging. We report on an atroposelective approach involving Heck cyclization, allow...

Natural macrocyclic bis(bibenzyls) exhibiting configurationally stable axially chiral biaryls are of high interest from a structural as well as from a synthetic point of view. An enantiopure sulfinyl auxiliary controlling an atropo-diastereoselective biaryl Suzuki coupling reaction has been investigated and promising results for the preparation of...

The target compounds are synthesized via Conrad—Limpach cyclization.

An unusual tetrahydrochromeno[4,3-b]indole type analogue of medicarpin has been isolated from the roots of the Black Locust and subsequently has been synthesized together with an aromatic derivative which shows considerable biological activity against a range of significant targets.

Isoplagiochin C 1 was prepared for the first time in enantiopure form from synthetic racemic material, using a novel stereochemical concept. This macrocyclic bisbibenzyl contains two biaryl axes. Of these, axis A is configurationally stable by its fixation within the macrocyclic framework, while axis B is stereochemically unstable. By diesterificat...

Macrocyclic bisbibenzyls are intriguing natural products that are obtained from liverworts. Recently, they have received growing interest due to the discovery of novel representatives and because of their antitumoral and antifungal activities. Depending on the individual coupling type, these structures can possess one or two biaryl axes, which, wit...

The Heck protocol was applied for the first time to the atroposelective synthesis of macrocyclic natural products. As ring closure to bis(bibenzyls) of the isoplagiochin type leads to a configurationally stable biaryl axis in the molecule, cyclization could be conducted atroposelectively in the presence of a chiral BINAP ligand.

The yeast-to-hypha transition plays a crucial role in the pathogenesis of C. albicans. Farnesol, a quorum sensing molecule (QSM) secreted by the fungal itself, could prevent the formation of hyphae and subsequently lead to the defect of biofilm formation. The DPP3, encoding phosphatase, is a key gene in regulating farnesol synthesis. In this study,...

Recently, remarkable microtubule inhibitor and anti-tumor activities of the bis(bibenzyl) marchantin C--isolated from liverworts like Marchantia polymorpha since 1983--were found. In this paper we describe the efficient total synthesis of this subtype of bis(bibenzylic) compounds with two biarylether connections. Two selectively methylated derivati...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Macrocyclic bis(bibenzyl) compounds are natural products from liverworts and are of growing interest due to recent reports on new isolated compounds and on their remarkable biological activities. We report here on a flexible and general approach to the total set of nine bis(bibenzyl) compounds of the riccardin and plagiochin type derived from perro...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Recently, remarkable microtubule inhibitor and anti-tumor activities of the bisbibenzyl marchantin C—isolated from liverworts like Marchantia polymorpha since 1983—were found. In this Letter we describe the first and efficient total synthesis of this subtype of bisbibenzylic compounds with two biarylether connections. The structure was confirmed by...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Macrocycles of the bisbibenzyl-type are natural products that are found exclusively in bryophytes (liverworts). The molecular framework of the subtype “isoplagiochin” is of substantial structural interest because of the chirality of the entire molecule, which arises from two biaryl axes in combination with two helical two-carbon units in a cyclic a...

Recently, a bisbibenzyl named plagiochin E showing remarkable antifungal and antitumor activities was isolated from Marchantia polymorpha, a liverwort. The total synthesis of the proposed structure for plagiochin E and of two structurally and biosynthetically related bisbibenzyls and comparison of the NMR data of the synthetic compounds with those...

We describe a route for the polymer supported total synthesis of the cyclic bisbibenzyls of the isoplagiochin type found in liverworts. TentaGel® resins were used as solid support for a sequence involving Suzuki, Wittig and hydrogenation protocols. The polymer linked intermediates could be characterized by HR-MAS NMR. This route is to be extended t...

Bazzanin S, a new chlorinated bisbibenzyl of the isoplagiochin D type, as well as isoplagiochin D itself were isolated from the liverwort Bazzania trilobata. The structure of bazzanin S was elucidated based on extensive NMR spectral evidence and by mass spectrometry. Both macrocyclic compounds, bazzanin S and isoplagiochin D, as well as previously...

Cyclic bisbibenzyls, like isoplagiochins C (1) and D (2), are stereochemically intriguing molecules: Although not equipped with any of the traditional stereogenic elements that render molecules conformationally stable per se, they are sometimes isolated in an optically active form and are thus chiral at room temperature. The paper describes quantum...

structure;heterocyclic compounds

In this paper we report on a efficient and flexible synthetic route towards the total syntheses of the dihydrocoumarine derivatives hydrangenol (1), phyllodulcin (1a) and macrophyllol (6b). The syntheses started with a readily available phosphonium salt 2 and suitable modified benzaldehydes 3/3a/3b resulting in 46 to 61% overall yields in three to...

Chlorinated cyclic bisbibenzyls of the isoplagiochin type are the first verified halometabolites from bryophytes. They could be obtained by in vitro chlorination of isoplagiochin C with chloroperoxidase from Caldariomyces fumago. Furthermore, an enzyme of this type was detected for the first time in bryophytes namely in the liverwort Bazzania trilo...

We established green cell suspension cultures of Marchantia polymorpha, Marchantia plicata, Riccia fluitans and Asterella blumeana. Whole cell biotransformations of the oxidoreductase type were studied using different exogenous substrates. The results show that cell cultures of liverworts can serve as effective tools in bioconversion reactions for...

Chlorinated bisbibenzyls of the isoplagiochin type detected in different bryophyte species were synthesized by an efficient and flexible unit construction system making extensive use of Suzuki and Wittig protocols.

We have prepared green cell suspension cultures of Marchantia polymorpha, Marchantia plicata, Riccia fluitans and Asterella blumeana. Whole cell biotransformations of the hydrolase type were studied using different exogenous substrates resulting in a small to large-scale production of useful homochiral compounds.

Chlorinated bisbibenzyls of the bazzanin type are detected in crude bryophyte plant extracts of Bazzania trilobata from different locations using MALDI-TOF mass spectrometry. These results show that these chlorinated compounds are not artefacts of an incidental occurrence or of the sample preparation but are genuine and produced by the liverwort or...

Chlorinated bis(bibenzyls) of the bazzanine type were detected in crude bryophyte plant extracts of Bazzania trilobata from different locations using laser desorption/ionization time-of-flight (LDI-TOF) mass spectrometry without addition of an additional chemical matrix. The degree of chlorination could be identified by the characteristic isotope p...

Ten halogenated lunularins 16, 17, 26, 27, 30, 31, 36, 37, 42 and 43 as model substances for a new class of halometabolites isolated from bryophytes are prepared by chemical total syntheses according to a Wittig-protocol using halogenated aldehydes and phosphonium salts and/or by an in vitro halogenation of lunularin using potassium halide and hydr...

The cyclic bisbibenzyl systems Marchantin I (3), Riccardin C (4) and Isoplagiochin C (5) representing unique types of bryophyte constituents were prepared by a flexible, efficient and general synthetic approach involving the construction of biphenyl and bibenzyl units using Suzuki and Wittig protocols.

3.4-Dihydroxy-3′-methoxystilbene, the first monomeric stilbene derivative to be discovered in bryophytes was isolated from the neotropic liverwort Marchesina bongardiana. Its structure has been elucidated on the basis of NMR spectral evidence and independent chemical synthesis of this hitherto unknown compound. © 1997 Elsevier Science Ltd. All righ...

Three new carboxylated α-pyrone derivatives, dumortins A-C, and a new flavone glycoside have been isolated from the liverwort, Dumortiera hirsuta, together with the known flavonoids, luteolin, and . The structures of the new α-pyrones were confirmed spectroscopically as 4-(3′,4′-dihydroxy-E-styryl)-6-carboxy-α-pyrone,4-[2-(3′,4′-dihydroxyphenyl)-et...

Efficient total syntheses are described for the racemic sesquiterpenes herbertenolide (2), α-herbertenol (3) and β-herbertenol (4) from Herberta adunca. ent-Herbertenolide [(+)-2] was prepared from enantiopure (-)-ethyl (1R)-1-methyl-2-oxocyclopentanecarboxylate (9) obtained from ethyl 2-oxocyclopentanecarboxylate (19) via reduction with baker's ye...

Efficient and expeditious syntheses are described for rosmarinic acid (1) and its derivatives 2-4, making extensive use of allyl protective groups for both carboxylic acids and phenolic building blocks. (+)(R)-Rosmarinic acid was obtained by a chemoenzymatic resolution of its phenyl lactic acid precursors.

Syntheses of Bryophyte Constituents. 8. Sphagnum Acid and its Degradation ProductsFor Sphagnum acid (1) and its enzymatic degradation product 5-hydroxy-4-(4-hydroxyphenyl)-5H-furan-2-on (2) efficient syntheses on preparative scale were developed. For the (4-hydroxyphenyl)butenolide 2 some characteristic chemical transformations are observed in acid...

An efficient total synthesis of the sesquiterpene ketone taylorione (1) from Mylia taylorii is described starting from readily available hex-5-yn-2-ol (3) and leading to the natural product in its racemic form.