Intellectual curiosity has always been one of the major driving forces leading to new advances in chemistry. At the onset of the 20th century, the fact that biaryls could be optically active even if lacking asymmetrically substituted carbon atoms arose interest, hinting at a novel type of stereomerism. It took quite a while (and some bizarre explanations)1 until in 1922 Christie and Kenner2 first correctly recognized that the phenomenon was the consequence of a hindered rotation about the aryl-aryl single bondshence termed atropisomerism by Kuhn. Still, no particular attention was initially paid to this class of stereoisomers until enantiomerically pure biaryls, such as BINAP (1),3 were found to be excellent ligands in asymmetric catalysis and until the chiral biaryl unit was recognized as the decisive structural element of many natural products (Figure 1).4,5 With the modern screening techniques and the bioassayguided search for novel compounds, the number of isolated axially chiral natural biaryls is steadily increasing.4 This class of secondary metabolites is characterized by a broad structural diversity, reaching from relatively simple molecules like the C2-symmetric biphenyl 2, which solely contains the element of axial chirality,6 to more complex compounds, like, e.g., the dimeric naphthylisoquinoline alkaloids michellamine A [(P,P)-3] and its axial epimer (i.e., its atropodiastereomer), michellamine B [(P,M)-3],7,8 which possess even three biaryl axes, of which the two outer ones are stereogenic, while * To whom correspondence should be addressed. E-mail: bringmann@ chemie.uni-wuerzburg.de; breuning@chemie.uni-wuerzburg.de. † These authors contributed equally to this work. ‡ Present address: Institute of Organic Chemistry, RWTH Aachen, Landoltweg 1, 52074 Aachen, Germany. § Present address: Kekulé Institute of Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk Str. 1, 53121 Bonn, Germany. Gerhard Bringmann was born in 1951 and studied chemistry in Gie en and Münster, Germany. After his Ph.D. with Prof. B. Franck in 1978 and postdoctoral studies with Prof. Sir D. H. R. Barton in Gif-sur-Yvette (France), he passed his habilitation at the University of Münster in 1984. In 1986, he received offers for full professorships of Organic Chemistry at the Universities of Vienna and Würzburg, of which he accepted the latter in 1987. In 1998, he was offered the position of director at the Leibniz Institute of Plant Biochemistry in Halle, which he declined. His research interests focus on the field of analytical, synthetic, and computational natural product chemistry, i.e., on axially chiral biaryls. He received several prizes and awards, among them the Otto-Klung Award in chemistry (1988), the Prize for Good Teaching of the Free State of Bavaria (1999), the Adolf-Windaus Medal (2006), the Honorary Doctorate of the University of Kinshasa (2006), the Paul-J.-Scheuer Award (2007), and the Honorary Guest Professorship of Peking University (2008). Chem. Rev. 2011, 111, 563–639 563

Atroposelective total synthesis of axially chiral biaryl natural products.

Saponins occur widely in plant species and exhibit a range of biological properties, both beneficial and deleterious. This review, which covers the literature to mid 1986, is concerned with their occurrence in plants and their effects when consumed by animals and man. After a short discussion on the nature, occurrence, and biosynthesis of saponins, during which the distinction between steroidal and triterpenoid saponins is made, the structures of saponins which have been identified in a variety of plants used as human foods, animal feedingstuffs, herbs, and flavorings are described. Many of these compounds have been characterized only during the last 2 decades, and modern techniques of isolation, purification, and structural elucidation are discussed. Particular consideration is given to mild chemical and enzymatic methods of hydrolysis and to recent developments in the application of NMR and soft ionization MS techniques to structural elucidation. Methods currently used for the quantitative analysis of saponins, sapogenols, and glycoalkaloids are critically considered; advances in the use of newer methods being emphasized. The levels of saponins in a variety of foods and food plants are discussed in the context of the methods used and factors affecting these levels, including genetic origin, agronomic, and processing variables, are indicated. Critical consideration is given to the biological effects of saponins in food which are very varied and dependent upon both the amount and chemical structure of the individual compounds. The properties considered include membranolytic effects, toxic and fungitoxic effects, adverse effects on animal growth and performance, and the important hypocholesterolemic effect. A final section deals briefly with the pharmacological effects of saponins from ginseng, since use of this plant is increasing in certain sections of western society as well as being traditional in the Orient.

The chemistry and biological significance of saponins in foods and feedingstuffs.

Pharmacology of Schisandra chinensis Bail.: An overview of Russian research and uses in medicine

Schisandra chinensis (Turcz.) Bail. is often referred to as an example of a medicinal plant with use in modern Chinese medicine. However, Schisandra chinensis first gained recognition as an adaptogen in the official medicine of the USSR in the early 1960s, principally as a result of the large number of pharmacological and clinical studies carried out by Russian scientists in the preceding two decades. Schizandra has now secured an established position within the medicine of Russia/USSR as evidenced by the inclusion of the drug in recent editions of the National Pharmacopoeia of the USSR and in the State Register of Drugs. Pharmacological studies on animals have shown that Schizandra increases physical working capacity and affords a stress-protective effect against a broad spectrum of harmful factors including heat shock, skin burn, cooling, frostbite, immobilisation, swimming under load in an atmosphere with decreased air pressure, aseptic inflammation, irradiation, and heavy metal intoxication. The phytoadaptogen exerts an effect on the central nervous, sympathetic, endocrine, immune, respiratory, cardiovascular, gastrointestinal systems, on the development of experimental atherosclerosis, on blood sugar and acid-base balance, and on uterus myotonic activity. Studies on isolated organs, tissues, cells and enzymes have revealed that Schizandra preparations exhibit strong antioxidant activities and affect smooth muscles, arachidonic acid release, biosynthesis of leukotriene B(4) in leukocytes, platelet activating factor activity, carbohydrate-phosphorus metabolism, the formation of heat shock protein and polyamines, tissue respiration and oxygen consumption, and the tolerance of an organism to oxygen intoxication. In healthy subjects, Schizandra increases endurance and accuracy of movement, mental performance and working capacity, and generates alterations in the basal levels of nitric oxide and cortisol in blood and saliva with subsequent effects on the blood cells, vessels and CNS. Numerous clinical trials have demonstrated the efficiency of Schizandra in asthenia, neuralgic and psychiatric (neurosis, psychogenic depression, astheno-depressive states, schizophrenia and alcoholism) disorders, in impaired visual function, hypotension and cardiotonic disorders, in epidemic waves of influenza, in chronic sinusitis, otitis, neuritis and otosclerosis, in pneumonia, radioprotection of the fetoplacental system of pregnant women, allergic dermatitis, acute gastrointestinal diseases, gastric hyper- and hypo-secretion, chronic gastritis, stomach and duodenal ulcers, wound healing and trophic ulcers. This review describes the considerable diversity of pharmacological effects of Schisandra chinensis reported in numerous studies carried out in the former USSR and which have been confirmed over more than 40 years of use of the plant as an official medicinal remedy. Such knowledge can be applied in the expansion of the use of Schizandra in the pharmacotherapy of European and other countries as well as for the further discovery of new drugs based on the lignans that constitute the main secondary metabolites of this plant.

Pharmacology of Schisandra chinensis Bail an overview of Russian research and uses in medicine

Over the past fifty years, hundreds of polyyne compounds have been isolated from nature. These often unstable molecules are found in sources as common as garden vegetables and as obscure as bacterial cultures. Naturally occurring polyynes feature a wide range of structural diversity and display an equally broad array of biological properties. Early synthetic efforts relied primarily on Cu-catalyzed, oxidative acetylenic homo- and heterocoupling reactions to assemble the polyyne framework. The past 25 years, however, have witnessed a renaissance in the field of polyyne natural product synthesis: transition-metal-catalyzed alkynylation reactions and asymmetric transformations have combined to substantially expand access to natural polyynes. This Review recounts these synthetic achievements and also highlights both the natural source(s) and biological relevance for many of these compounds.

Synthesis of Naturally Occurring Polyynes

Two new hydroxystilbene dimers, named scirpusin A (1) and B (12), were isolated from the rhizoma of Scirpus fluviatilis (TORR.) A. GRAY (Cyperaceae) together with two known hydroxystilbenes, resveratrol and 3, 3', 4, 5'-tetrahydroxystilbene, and four known triterpens, betulin, lupeol, betulinaldehyde and betulinic acid. The structures of scirpusin A and B were elucidated to be 1 and 12, respectively, by chemical and spectral evidence.

The constituents of Scirpus fluviatilis(Torr). A. Gray. I. The structures of two new hydroxystilbene dimers, scirpusin A and B.

Three new chromones (8, 9, and 12), named 3'-O-angeloylhamaudol, ledebouriellol, and 4'-O-β-D-glucosyl-5-O-methylvisamminol, respectively, were isolated from the root and rhizoma of Ledebouriella seseloides WOLFF (Umbelliferae), together with five known coumarins (1-5) and six known chromones (6, 7, 10, 11, 13 and 14). The structures of 8, 9, and 12 were elucidated as (3S)-3, 4-dihydro-5-hydroxy-3-(2-methyl-2-butenyl) oxy-2, 2, 8-trimethyl-2H, 6H-benzo [1, 2-b : 5, 4-b'] dipyran-6-one, (3S)-3, 4-dihydro-2, 2-dimethyl-5-hydroxy-8-hydroxymethyl-3-(2-methyl-2-butenyl) oxy-2H, 6H-benzo [1, 2-b : 5, 4-b'] dipyran-6-one, and (2S)-2, 3-dihydro-2-(1-β-D-glucopyranosyloxy-1-methylethyl)-4-methoxy-7-methyl-5H-furo [3, 2-g] [1] benzopyran-5-one, respectively, by chemical and spectral studies.

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The Constituents of Ledebouriella seseloides WOLFF. I. Structures of Three New Chromones

The 13C NMR spectra of thirteen dibenzocyclooctadiene lignans, isolated from the iruits of Schizandra chinensis BAILL (Schizandraceae), were analyzed and their carbon shifts assigned Several important chemical shift trends are described

The constituents of Schizandra chinensis Baill. VI. 13C nuclear magnetic resonance spectroscopy of dibenzocyclooctadiene lignans.

Four new dibenzocyclooctadiene lignans, named (-)-gomisins L1 (6) and L3 (7), (±)-gomisin M1 (8) and (+)-gomisin M2 (9), were isolated from the fruits of Schizandra chinensis BAILL. (Schizandraceae). Their absolute structures were elucidated by means of chemical and spectral studies. The stereostructure of γ-schizandrin (1, dl-form), the plane structure of which had already been suggested by Kochetkov et al. and Liu et al., was also elucidated on the basis of chemical and spectral studies.

The Constituents of Schizandra chinensis BAILL. X. The Structures of γ-Schizandrin and Four New Lignans, (-)-Gomisins L1 and L2, (±)-Gomisin M1 and (+)-Gomisin M2

A new dibenzocyclooctadiene lignan, gomisin R (4), was isolated from the fruits of Schizandra chinensis BAILL. (Schizandraceae) together with wuweizisu C (1)2) and schisantherin D (12).3) The absolute structure of 1, the relative structure of which has been elucidated by Liu et al., was defined by chemical correlation with dimethylgomisin J (2). The absolute structure of 4 was determined by spectral studies and chemical correlation with 1.

The constituents of Schizandra chinensis Baill. XII. Isolation and structure of a new lignan, gomisin R, the absolute structure of wuweizisu C and isolation of schisantherin D.

Itiro Yosioka

Papers

The constituents of Scirpus fluviatilis(Torr). A. Gray. I. The structures of two new hydroxystilbene dimers, scirpusin A and B.

The Constituents of Ledebouriella seseloides WOLFF. I. Structures of Three New Chromones

The constituents of Schizandra chinensis Baill. VI. 13C nuclear magnetic resonance spectroscopy of dibenzocyclooctadiene lignans.

The Constituents of Schizandra chinensis BAILL. X. The Structures of γ-Schizandrin and Four New Lignans, (-)-Gomisins L1 and L2, (±)-Gomisin M1 and (+)-Gomisin M2

The constituents of Schizandra chinensis Baill. XII. Isolation and structure of a new lignan, gomisin R, the absolute structure of wuweizisu C and isolation of schisantherin D.