View source for Kaurane

{{Multiple image
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| image1 = kaurane IUPAC.png
|   caption1 = IUPAC
| image2 = kaurane CAS.png
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| footer = The two different structures referred to as '''kaurane'''.
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'''Kaurane''' is a defined [[parent hydride]] used in the [[IUPAC]] [[nomenclature of natural products]] and also, distinctly, in [[CAS nomenclature]]. It is a [[diterpene]] with a rigid four-ring structure and six [[Chirality|chiral centres]].

==Ambiguity between IUPAC and CAS==
[[File:Kaurane numbered.png|thumb|right|250px|The conventional numbering of kaurane: for the numbering of the methyl groups at C-18 and C-19, see text.]]
The stereochemistry of the six chiral centres is defined by convention: however, IUPAC and CAS use different opposite [[enantiomer]]s, which also leads to a slight difference in numbering between the two systems. IUPAC conventional kaurane has (5''S'',8''S'',9''S'',10''S'',13''S'',15''R'')-stereochemistry, and is drawn with the five-membered ring receding into the plane of the image.<ref name="IUPAC">{{IUPAC natural products 1999}}.</ref> CAS conventional kaurane has (5''R'',8''R'',9''R'',10''R'',13''R'',15''S'')-stereochemistry, and is drawn with the five-membered ring protruding from the plane of the image.<ref name="CAS">{{citation | contribution = 57817-89-7 – Kaur-16-en-18-oic acid, 13-&#91;(2-''O''-β-<small>D</small>-glucopyranosyl-β-<small>D</small>-glucopyranosyl)oxy&#93;-, β-<small>D</small>-glucopyranosyl ester, (4α)- | url = http://www.commonchemistry.org/ChemicalDetail.aspx?ref=57817-89-7 | title = Common Chemistry | publisher = Chemical Abstracts Service | accessdate = 2009-09-05}}.</ref> For the two methyl groups attached to carbon-4, the two number systems are identical (but see below): the methyl group receding into the plane of the image is numbered carbon-18 and the one protruding from the plane of the image is numbered carbon-19.<ref name="Errata">{{citation | title = Revised Section F: Natural Products and Related Compounds (IUPAC Recommendations 1999): Corrections and modifications (2004) | journal = Pure Appl. Chem. | volume = 76 | issue = 6 | pages = 1283–92 | doi = 10.1351/pac200476061283}}.</ref><ref group="note">Note that the numbering on the structural diagrams in the appendix to the [http://media.iupac.org/publications/pac/1999/pdf/7104x0587.pdf original version of the IUPAC Recommendations 1999] is [http://media.iupac.org/publications/pac/2004/pdf/7606x1283.pdf ''incorrect''].</ref>

===''ent''-Kaurane===
The name ''ent''-kaurane is sometimes used to refer to the CAS conventional kaurane,<ref name="ent">{{citation | first1 = Fumihiro | last1 = Nagashima | first2 = Hironao | last2 = Tanaka | first3 = Shigeru | last3 = Takaoka | first4 = Yoshinori | last4 = Asakawa | title = ''Ent''-kaurane-type diterpenoids from the liverwort ''Jungermannia exsertifolia'' ssp. ''cordifolia'' | journal = Phytochemistry | volume = 41 | issue = 4 | year = 1996 | pages = 1129–41 | doi = 10.1016/0031-9422(95)00755-5}}. {{citation | first1 = Francisco Javier | last1 = Arriaga-Giner | first2 = Angel | last2 = Rumbero | first3 = Eckhard | last3 = Wollenweber | title = 16α,19-Diacetoxy-''ent''-kaurane, a New Natural Diterpene from the Exudate of ''Ozothamnus scutellifolius'' (Asteraceae) | journal = Z. Naturforsch. C | volume = 54 | pages = 602–4 | year = 1999}}. {{citation | title = ''Ent''-kaurane Diterpenoid Glycosides from the Leaves of ''Cussonia racemosa'', a Malagasy Endemic Plant | first1 = Liva Rakotondraibe Romuald | last1 = Harinantenaina | first2 = Ryoji | last2 = Kasai | first3 = Kazuo | last3 = Yamasaki | journal = Chem. Pharm. Bull. | year = 2002 | volume = 50 | issue = 2 | pages = 268–71 | doi = 10.1248/cpb.50.268}}. {{citation | title = Three New Cytotoxic ''ent''-Kaurane Diterpenoids from ''Isodon weisiensis'' C. Y. Wu | first1 = Lan | last1 = Ding | first2 = Zhang-Jing | last2 = Zhang | first3 = Guo-An | last3 = Liu | first4 = Dong-Juan | last4 = Yang | first5 = Guo-Cong | last5 = Guo | first6 = Han | last6 = Wang | first7 = Kun | last7 = Sun | journal = Helv. Chim. Acta | volume = 88 | issue = 9 | year = 2005 | pages = 2502–7 | doi = 10.1002/hlca.200590185}}. {{citation | first1 = Ronan | last1 = Batista | first2 = Pablo A. | last2 = García | first3 = Maria A. | last3 = Castro | first4 = José M. Miguel | last4 = del Corral | first5 = Arturo | last5 = San Feliciano | first6 = Alaíde B. | last6 = de Oliveira | title = New oxidized ''ent''-kaurane and ''ent''-norkaurane derivatives from kaurenoic acid | journal = J. Braz. Chem. Soc. | volume = 18 | issue = 3 | year = 2007 | pages = 622–27 | doi =  10.1590/S0103-50532007000300020}}. {{citation | last1 = Zhao | first1 = Yong | last2 = Pu | first2 = Jian-Xin | last3 = Huang | first3 = Sheng-Xiong | last4 = Ding | first4 = Li-Sheng | last5 = Wu | first5 = Ying-Li | last6 = Li | first6 = Xian | last7 = Yang | first7 = Li-Bin | last8 = Xiao | first8 = Wei-Lie | last9 = Chen | first9 = Guo-Qiang | last10 = Sun | first10 = Han-Dong | title = ''ent''-Kaurane diterpenoids from ''Isodon pharicus'' | journal = J. Nat. Prod. | year = 2009 | volume = 72 | issue = 6 | pages = 988–93 | doi = 10.1021/np9000366 | pmid = 19425589}}.</ref> and so to distinguish it from the IUPAC stereochemistry, in particular by the [[International Union of Biochemistry and Molecular Biology]] (IUBMB).<ref name="EC">{{citation | url = http://www.chem.qmul.ac.uk/iubmb/enzyme/EC4/2/3/19.html | contribution = EC&nbsp;4.2.3.19 – ''ent''-kaurene synthase | title = IUBMB Enzyme Nomenclature | accessdate = 2009-09-18}}. {{citation | url = http://www.chem.qmul.ac.uk/iubmb/enzyme/EC1/14/13/78.html | contribution = EC&nbsp;1.14.13.78 – ''ent''-kaurene oxidase | title = IUBMB Enzyme Nomenclature | accessdate = 2009-09-05}}. {{citation | url = http://www.chem.qmul.ac.uk/iubmb/enzyme/EC1/14/13/79.html | contribution = EC&nbsp;1.14.13.79 – ''ent''-kaurenoic acid oxidase | title = IUBMB Enzyme Nomenclature | accessdate = 2009-09-05}}.</ref> This is the structure of the cyclic skeleton of all naturally occurring kaurane terpenes. However, the numbering system is distinct between CAS nomenclature and IUBMB nomenclature: the metabolic intermediate [[kaurenoic acid]], which has the (4''S'')-configuration, is kaur-16-en-18-oic acid in CAS nomenclature but ''ent''-kaur-16-en-19-oic acid in IUBMB nomenclature.<ref name="CAS"/><ref name="EC"/><ref group="note">The reason for this difference is that the ''ent'' nomenclature operation reverses the configuration of every chiral centre in the molecule, and so maps C-19 onto C-18 and vice versa. This is clarified in the [http://media.iupac.org/publications/pac/2004/pdf/7606x1283.pdf 2004 errata to the IUPAC Recommendations 1999].</ref>

==Occurence==
Kaurane diterpenes have been extracted from a variety of plant species,<ref name="ent"/><ref>{{citation | last1 = Nagashima | first1 = Fumihiro | last2 = Kondoh | first2 = Masuo | last3 = Uematsu | first3 = Toshinari | last4 = Nishiyama | first4 = Akiko | last5 = Saito | first5 = Sayaka | last6 = Sato | first6 = Masao | last7 = Asakawa | first7 = Yoshinori | title = Cytotoxic and apoptosis-inducing ''ent''-kaurane-type diterpenoids from the Japanese liverwort ''Jungermannia truncata'' nees | journal = Chem. Pharm. Bull. | year = 2002 | volume = 50 | issue = 6 | pages = 808–13 | doi = 10.1248/cpb.50.808}}. {{citation | first1 = Maurizio | last1 = Bruno | first2 = Franco | last2 = Piozzi | first3 = Nelly Apostolides | last3 = Arnold | first4 = K. Hüsnü Can | last4 = Başer | first5 = Nurhayat | last5 = Tabanca | first6 = Neşe | last6 = Kirimer | title = Kaurane Diterpenoids from Three ''Sideritis'' Species | url = http://journals.tubitak.gov.tr/chem/issues/kim-05-29-1/kim-29-1-7-0402-1.pdf | journal = Turk. J. Chem. | volume = 29 | issue = 1 | year = 2005 | pages = 61–64}}. {{citation | last1 = Kim | first1 = Ki Hyun | last2 = Choi | first2 = Sang Un | last3 = Lee | first3 = Kang Ro | title = Diterpene glycosides from the seeds of ''Pharbitis nil'' | journal = J. Nat. Prod. | year = 2009 | volume = 72 | issue = 6 | pages = 1121–27 | doi = 10.1021/np900101t | pmid = 19435339}}.</ref> in particular ''Stevia'' sp., the source of the [[steviol glycoside]]s [[stevioside]] and [[rebaudioside-A]] that have been used as [[artificial sweetner]]s.<ref>{{citation | title = An efficient microwave-assisted extraction process of stevioside and rebaudioside-A from ''Stevia rebaudiana'' (Bertoni) | last1 = Jaitak | first1 = Vikas | last2 = Bikram Singh | first2 = Bandna | last3 = Kaul | first3 = V. K. | journal = Phytochem. Anal. | year = 2009 | volume = 20 | issue = 3 | pages = 240–45 | doi = 10.1002/pca.1120 | pmid = 19358287}}.</ref> They are intermediates in [[gibberellin biosynthesis]], leading to a group of important plant hormones ([[gibberellin]]s):<ref>{{citation | last1 = Brandle | first1 = J. E. | last2 = Telmer | first2 = P. G. | title = Steviol glycoside biosynthesis | journal = Phytochemistry | year = 2007 | volume = 68 | issue = 14 | pages = 1855–63 | doi = 10.1016/j.phytochem.2007.02.010}}.</ref> [[Gibberellin A12|gibberellin A<sub>12</sub>]] is [[Biosynthesis|biosynthesized]] from [[Ent-Kaurene|''ent''-kaurene]] by six successive [[oxidation]]s catalyzed by [[Ent-Kaurene oxidase|''ent''-kaurene oxidase]] (EC&nbsp;1.14.13.78) and [[Ent-Kaurenoic acid oxidase|''ent''-kaurenoic acid oxidase]] (EC&nbsp;1.14.13.79).<ref name="EC"/> The ''ent''-kaurane skeleton is also found in [[veatchine]] and other ''Garrya'' [[alkaloid]]s.<ref>{{citation | first1 = S. William | last1 = Pelletier | first2 = Naresh V. | last2 = Mody | contribution = The Chemistry of C<sub>20</sub>-Diterpenoid Alkaloids | title = The Alkaloids: Chemistry and Pharmacology | editor1-first = R. H. F. | editor1-last = Manske | editor2-first = R. G. A. | editor2-last = Rodrigo | volume = 18 | year = 1981 | location = New York | publisher = Academic Press | pages = 102–21 | isbn = 0-12-469518-3}}.</ref>

==Notes and references==
===Notes===
{{reflist|group=note}}

===References===
{{reflist|2}}

==Further reading==
*{{citation | first1 = Jeong-Hyung | last1 = Lee | first2 = Tae Hyeon | last2 = Koo | first3 = Bang Yeon | last3 = Hwang | first4 = Jung Joon | last4 = Lee | title = Kaurane Diterpene, Kamebakaurin, Inhibits NF-κB by Directly Targeting the DNA-binding Activity of p50 and Blocks the Expression of Antiapoptotic NF-κB Target Genes | journal = J. Biol. Chem. | year = 2002 | volume = 277 | issue = 21 | pages = 18411–20 | doi = 10.1074/jbc.M201368200}}.
*{{citation | first = Satoru | last = Masamune | title = Total Syntheses of Diterpenes and Diterpene Alkaloids. II. A Tetracyclic Common Intermediate | journal = J. Am. Chem. Soc. | year = 1964 | volume = 86 | issue = 2 | pages = 288–89 | doi = 10.1021/ja01056a040}}.
*{{citation | journal = Nature Chem. Biol. | volume = 3 | pages = 396–407 | year = 2007 | doi = 10.1038/nchembio.2007.1 | title = Modern synthetic efforts toward biologically active terpenes | first1 = Thomas J. | last1 = Maimone | first2 = Phil S. | last2 = Baran}}.

==External links==
*[http://chemistry.about.com/od/factsstructures/ig/Chemical-Structures---K/Kaurane.-0xj.htm Kaurane Chemical Structure] (shows the IUPAC conventional structure)
*[http://www.find-health-articles.com/msh-diterpenes-kaurane.htm Diterpenes, Kaurane – Research News and Information]

[[Category:Diterpenes]]
[[Category:Kaurane terpenoids|*]]
[[Category:Nomenclature of terpenes and terpenoids]]

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