Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products – serie
Visar alla böcker i serien Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products. Handla med fri frakt och snabb leverans.
120 produkter
120 produkter
Del 87 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Progress in the Chemistry of Organic Natural Products
Inbunden, Engelska, 2003
1 082 kr
Skickas inom 10-15 vardagar
Del 88 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products 88
Inbunden, Engelska, 2006
1 619 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister" after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series' inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Del 89 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products
Inbunden, Engelska, 2008
1 082 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister" after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series' inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Del 90 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Epothilones: An Outstanding Family of Anti-Tumor Agents
From Soil to the Clinic
Inbunden, Engelska, 2008
1 667 kr
Skickas inom 10-15 vardagar
Epothilones have received unusual attention over the past ten years. They are novel antitumor drugs which very much like their predecessor paclitaxel (Taxol) act via microtubule stabilization. In comparison to paclitaxel and a number of alternative drugs with a similar mode of bioaction (e.g. laulimalide, eleutherobin, peluroside, discodermolide) the epothilones have significant advantages, above all very high activity in the nanomolar range and low susceptibility towards multidrug resistance. Epothilone B and several derivatives thereof are in phase I-III clinical trials; one of them (ixabepilone, BMS) is already on the market, others are supposed to appear on the market in the near future. All naturally occurring epothilones have been isolated from Sorangium cellulosum; their antitumor action is traced back to the stabilization of microtubules. In consequence, the formation of the mitototic spindle is prohibited and the cell undergoes apoptosis.
Inbunden, Engelska, 1964
1 082 kr
Skickas inom 10-15 vardagar
Inbunden, Engelska, 1972
1 619 kr
Skickas inom 10-15 vardagar
Eine grosse Anzahl heterocyclischer Naturstoffe leitet sich vom Ring- system des Piperidins (1) ab. Als Substituenten einfach oder mehrfach substituierter Piperidinbasen finden sich Methyl-, Carboxyl-, Hydroxyl- und Aminogruppen sowie aliphatische Seitenketten unterschiedlicher Lange. Die Substitution erfolgt bevorzugt an den C-Atomen 2, 3 und 6 sowie am Heteroatom. In zahlreichen Fallen ist der Piperidinring in a- oder ss-Stellung direkt oder uber eine C-Brucke mit einem weiteren Heterocyclus verbunden, z. B. einem Piperidin-, Piperidein-, Pyridin-, Indol-, Chinolizidin- oder Furanrest. Daruber hinaus kann der Piperidin- ring zum 2,6-Dioxopiperidin (Glutarimid) oxydiert oder zum Pipendein dehydriert sein. Wahrend Naturstoffe mit Pyridinstruktur im Tier- und Pflanzenreich weit verbreitet sind und einzelnen von ihnen wie NAD oder Pyridoxal- phosphat als Coenzymen des Primarstoffwechsels besondere Bedeutung zukommt, handelt es sich bei den naturlichen Piperidinverbindungen im allgemeinen um sekundare Pflanzenstoffe (vgl. I8, I9I). Dabei sind einige wie z. B. die Pipecolinsaure (7) sporadisch auf verschiedene Pflanzen- familien verteilt.Andere Piperidinbasen wie die Conium- oder Piper- Alkaloide weisen dagegen eine ausgesprochene Artspezifitat auf. Im Gegensatz zu den meisten Pyridinalkaloiden finden sich die Piperidin- basen oft mit strukturell andersartig gebauten Alkaloiden vom Chino- lizidin- oder Trepantyp vergesellschaftet, was in den meisten Fallen durch eine enge biogenetische Verwandtschaft bedingt sein durfte.
Inbunden, Engelska, 1976
2 156 kr
Skickas inom 10-15 vardagar
Del 36 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Fortschritte der Chemie Organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products
Inbunden, Engelska, 1979
1 082 kr
Skickas inom 10-15 vardagar
This volume is part of a series, inaugurated in 1938, now referred to simply as "Zechmeister" after its founder, L. Zechmeister. It contains contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a reconized authority in his field, and provides a comprehensive and up-to-date review of the topic in question. This title looks at the chemistry of organic natural products. It is addressed to biologists, technologists and chemists alike. The series can be used by the expert as a source of information and literature citations, and by the non-expert as a means of orientation in a rapidly developing discipline.
Inbunden, Engelska, 1996
1 082 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister” after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series’ inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Inbunden, Engelska, 1997
1 619 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister” after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series’ inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Inbunden, Engelska, 1997
1 815 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as 'Zechmeister' after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series' inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances, ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Del 72 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products
Inbunden, Engelska, 1997
1 619 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister” after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series’ inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Inbunden, Engelska, 1997
1 889 kr
Skickas inom 10-15 vardagar
The Leguminosae is an economically important family in the Dicotyledonae with many cultivated species, e. g. , beans and peas. The family also contains many well-known medicinal plants. It is composed of 17,000 or more species that constitute nearly one twelfth of the world's flowering plants (1). Traditionally the family has been divided into three subfamilies, Caesalpinioideae, Mimosoideae and Papilionoi- deae, which are sometimes recognized as separate families Caesalpinia- ceae, Mimosaceae and Papilionaceae. The International Code of Botanical Nomenclature permits alternative nomenclatures, the family names being replaced by Fabaceae, Fabales and Faboideae, and this usage will be common (2). Licorice (liquorice, kanzoh in Japanese, gancao in Chinese) is the name applied to the roots and stolons of some Glycyrrhiza species (Fabaceae) and has been used by human beings for at least 4000 years. The earliest written reference to the use of licorice is contained in the Codex Hammurabi dating from 2100 B. C. , and the subsequent history in the West has been described in the earlier reviews (3-6).In the Far East, references to the effectiveness of licorice are contained in the "Shen Nong Ben Cao Jing", the first Chinese dispensatory whose original anonymous volumes probably appeared by the end of the third century (7, 8).
Inbunden, Engelska, 1998
2 016 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister" after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series'inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Inbunden, Engelska, 1998
1 614 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister” after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series’ inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Del 76 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products
Inbunden, Engelska, 1998
1 082 kr
Skickas inom 10-15 vardagar
In order to make further progress in elucidating the mechanism of NOS catalysis it will be essential to throw light on the interaction between the enzyme and its substrate. An understanding of the catalytic site will also assist the development of therapeutically important NOS inhibitors. In particular. it will be useful to uncover any differences that exist between the substrate binding sites of the three NOS isozymes which might be exploited for the development of isoform selective NOS inhibitors. A comparison of NOS to other Arg-binding proteins has shown no significant sequence homology (159). Moreover, the lack of a 3D structure and absence of significant sequence homology between the NOS oxygenase domain and known cytochromes P450 has made it difficult to identify residues and construct a model of the distal heme pocket responsible for substrate binding. However, a number of groups are currently working towards crystallisation of the separate NOS reductase and oxygenase domains of the three isoforms for X-ray diffraction studies; the first X-ray structure is likely to be forthcoming within a matter of months. * The results of these studies are expected to resolve many of the uncertainties surrounding the structure of the NOS catalytic site. Preliminary X-ray diffraction analysis of CPR from rat liver has already been reported by MASTERS et al. (524) and the future emergence of a detailed structure for this protein should throw light on the structure and function of the NOS reductase domain.
Fortschritte der Chemie organischer Naturstoffe
Progress in the Chemistry of Organic Natural Products
Inbunden, Engelska, 1999
1 114 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister" after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Inbunden, Engelska, 1999
1 619 kr
Skickas inom 10-15 vardagar
It was in 1979 when GROVE et al. isolated from pollen of rape (Brassica nap us) a highly active plant growth promoter, named it brassinolide and elucidated its structure as (22R,23R,24S)-2
Inbunden, Engelska, 2000
1 082 kr
Skickas inom 10-15 vardagar
Inbunden, Engelska, 2000
1 082 kr
Skickas inom 10-15 vardagar
Glycosmis is a clearly defined genus within the tribe Clauseneae of the Aurantioideae subfamily of the family Rutaceae comprising about 40 species (1). Its range of distribution is centered in south and southeast Asia (India, Sri Lanka, Myanmar, Thailand, Malaysia, Indonesia) and extends to south China and Taiwan as well as to New Guinea and north Australia. Exceptions are only cultivated species like the Chinese G. parvijiora (Sims) Little, formerly called G. citrifolia (Willd. ) Lindley, which became naturalized in tropical America and Africa (Angola) (1). The shrubs or small trees are unarmed and possess pinnate or simple leaves with translucent punctate glands emitting an aromatic odor when crushed. The axillary inflorescences are usually dispersed closed panicles with small white flowers. The fruits are mostly pink, reddish or white berries of about I cm in diameter with only one or two seeds. The genus name Glycosmis originates from the sweet smell of the flowers and the sweet taste of the fleshy pericarp of the fruits. A good field and herbarium character of the genus is that the buds of new leaves are usually covered with short rusty-red hairs.In spite of the good delimitation of Glycosmis from the other closely related Clauseneae genera Clausena, Micromelum, Murraya, and Merrillia and the already existing subrevisionary treatment by Stone (1), there are still many unresolved taxonomic problems at the species level.
Inbunden, Engelska, 2001
2 076 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister” after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series’ inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Fortschritte der Chemie organischer Naturstoffe
Progress in the Chemistry of Organic Natural Products
Inbunden, Engelska, 2002
2 156 kr
Skickas inom 10-15 vardagar
This work on the progress in the chemistry of organic natural products offers examination on topics such as: the naturally occuring coumarins; variations of ring-attached five-carbon units found in coumarins; and variations of five carbon units attached to carbon and oxygen in coumarins.
Del 85 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products 85
Inbunden, Engelska, 2002
1 114 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister” after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series’ inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Del 86 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products 86
Inbunden, Engelska, 2003
1 114 kr
Skickas inom 10-15 vardagar
Del 91 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Naturally Occurring Organohalogen Compounds - A Comprehensive Update
Inbunden, Engelska, 2009
3 554 kr
Skickas inom 10-15 vardagar
Despite the long association of organohalogen compounds with human activities, nature is the producer of nearly 5,000 halogen-containing chemicals. Once dismissed as accidents of nature or isolation artifacts, organohalogen compounds represent an important and ever growing class of natural products, in many cases exhibiting exceptional biological activity. Since the last comprehensive review in 1996 (Vol. 68, this series), there have been discovered an additional 2,500 organochlorine, organobromine, and other organohalogen compounds. These natural organohalogens are biosynthesized by bacteria, fungi, lichen, plants, marine organisms of all types, insects, and higher animals including humans. These compounds are also formed abiogenically, as in volcanoes, forest fires, and other geothermal events.In some instances, natural organohalogens are precisely the same chemicals that man synthesizes for industrial use, and some of the quantities of these natural chemicals far exceed the quantities emitted by man.
Del 92 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products, Vol. 92
Inbunden, Engelska, 2010
2 221 kr
Skickas inom 10-15 vardagar
Resin glycosides are part of a very extensive family of secondary metabolites known as glycolipids or lipo-oligosaccharides and are constituents of complex resins (glycoresins) (1) unique to the morning glory family, Convolvulaceae (2). These active principles are responsible for the drastic purgative action of all the important Convolvulaceous species used in traditional medicine throughout the world since ancient times. Several commercial purgative crude drugs can be prepared from the roots of different species of Mexican morning glories. Their incorporation as therapeutic agents in Europe is an outstanding example of the assimilation of botanical drugs from the Americas as substitutes for traditional Old World remedies (3). Even though phytochemical investigations on the constituents of these drugs were initiated during the second half of the nineteenth century, the structure of their active ingredients still remains poorly known for some examples of these purgative roots. During the last two decades, the higher resolution c- abilities of modern analytical isolation techniques used in conjunction with pow- ful spectroscopic methods have facilitated the elucidation of the active principles of these relevant herbal products. This chapter describes the ethnobotanical information associated with the p- gative morning glory species and how traditional usages were instrumental in plant selection for chemical studies. The advantages and limitations of available analy- cal techniques for the isolation, puri?cation, and structure characterization of the individual constituents of these complex glycoconjugates are also discussed.
Häftad, Engelska, 2010
1 619 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister" after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series' inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Del 89 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products
Häftad, Engelska, 2010
1 114 kr
Skickas inom 10-15 vardagar
The volumes of this classic series, now referred to simply as "Zechmeister" after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series' inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.
Del 90 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Epothilones: An Outstanding Family of Anti-Tumor Agents
From Soil to the Clinic
Häftad, Engelska, 2010
1 667 kr
Skickas inom 10-15 vardagar
Epothilones have received unusual attention over the past ten years. They are novel antitumor drugs which very much like their predecessor paclitaxel (Taxol) act via microtubule stabilization. In comparison to paclitaxel and a number of alternative drugs with a similar mode of bioaction (e.g. laulimalide, eleutherobin, peluroside, discodermolide) the epothilones have significant advantages, above all very high activity in the nanomolar range and low susceptibility towards multidrug resistance. Epothilone B and several derivatives thereof are in phase I-III clinical trials; one of them (ixabepilone, BMS) is already on the market, others are supposed to appear on the market in the near future. All naturally occurring epothilones have been isolated from Sorangium cellulosum; their antitumor action is traced back to the stabilization of microtubules. In consequence, the formation of the mitototic spindle is prohibited and the cell undergoes apoptosis.
Del 93 - Fortschritte der Chemie organischer Naturstoffe Progress in the Chemistry of Organic Natural Products
Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products, Vol. 93
Inbunden, Engelska, 2010
2 156 kr
Skickas inom 10-15 vardagar
Lignans, by convention, are a group of natural products that are formed by linking two phenylpropanoid units (C C units) by oxidative coupling. Most importantly, in 6 3 a lignan, two (C C units) are bound through the central carbon of their side chains, 6 3 0 i. e. the 8 and 8 positions (1, 2). The occurrence of C C -dimers, linked at sites other 6 3 0 than the 8–8 positions, is also known and these compounds have been termed neolignans (3, 4). As these two groups of compounds have close structural as well as biosynthetic relationships, they are often associated together and incorporated under the general term “lignan” (5). The diverse structural categorization of true lignans and of a few neolignans is presented in Fig. 1. Through the years, several review articles or books covering different facets of lignans, including their ch- istry (6, 7), biogenesis (8), synthesis (9), and biological activities (10) have been published. Enduring research for the investigation of secondary metabolites of plants has evidenced some compounds that are biogenetically related to true lignans or neolignans but bear some features not discerned in conventional lignans. These compounds or groups of compounds have been termed as “non-conventional lignans”, and include coumarinolignans, ?avonolignans, and stilbenolignans. The non-conventional lignans, like the conventional ones, have two C C units linked 6 3 together but have additional structural features to place them also under the category of coumarins, ?avonoids, or stilbenes.