Difference between revisions of "Kaurane"

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'''Kaurane''' is a [[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]].
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{{Multiple image
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| footer = The two different structures referred to as '''kaurane'''.
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'''Kaurane''' is a defined [[fundamental parent structure]] 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]].
  
The stereochemistry of the six chiral centres is defined by convention: however, IUPAC and CAS use different conventional stereochemistry, 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''S'',8''R'',9''S'',10''S'',13''R'',15''R'')-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> Carbon-19 (one of the two methyl groups attached to carbon-4) is on the same side of the molecule as the five-membered ring in both systems: hence it is receding into the plane of the image in IUPAC nomenclature and protruding from the plane of the image in CAS nomenclature.
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==Ambiguity between IUPAC and CAS==
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[[File:Kaurane numbered.png|thumb|right|217px|The conventional numbering of kaurane: for the numbering of the methyl groups at C-18 and C-19, see text.]]
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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">{{IUPAC natural products errata 2004}}.</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>
  
The name ''ent''-kaurane is sometimes used to refer to the CAS conventional kaurane and so to distinguish it from the IUPAC stereochemistry. It is also possible to explicitly specify the stereochemistry at carbons 8 and 13, giving:
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===''ent''-Kaurane===
*(8''S'',13''S'')-kaurane (IUPAC conventional)
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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>
*(8''R'',13''R'')-kaurane (CAS conventional)
 
  
==References==
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==Occurence==
{{reflist}}
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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>
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==Notes and references==
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===Notes===
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{{reflist|group=note}}
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===References===
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{{reflist|2}}
  
 
==Further reading==
 
==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-kappa B by Directly Targeting the DNA-binding Activity of p50 and Blocks the Expression of Antiapoptotic NF-kappa B Target Genes | journal = J. Biol. Chem. | volume = 277 | issue = 21 | pages = 18411–20 | doi = 10.1074/jbc.M201368200}}.
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*{{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 | 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}}.
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*{{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 | 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}}.
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*{{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}}.
*{{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 | 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 = 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 | 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 = 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}}.
 
*{{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}}.
 
*{{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}}.
 
  
 
==External links==
 
==External links==
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[[Category:Diterpenes]]
 
[[Category:Diterpenes]]
[[Category:Nomenclature of natural products]]
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[[Category:Kaurane terpenoids|*]]
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[[Category:Nomenclature of terpenes and terpenoids]]
  
 
{{CC-BY-3.0}}
 
{{CC-BY-3.0}}

Latest revision as of 05:40, 11 March 2010

IUPAC
CAS
The two different structures referred to as kaurane.

Kaurane is a defined fundamental parent structure 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 chiral centres.

Ambiguity between IUPAC and CAS

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 enantiomers, which also leads to a slight difference in numbering between the two systems. IUPAC conventional kaurane has (5S,8S,9S,10S,13S,15R)-stereochemistry, and is drawn with the five-membered ring receding into the plane of the image.[1] CAS conventional kaurane has (5R,8R,9R,10R,13R,15S)-stereochemistry, and is drawn with the five-membered ring protruding from the plane of the image.[2] 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.[3][note 1]

ent-Kaurane

The name ent-kaurane is sometimes used to refer to the CAS conventional kaurane,[4] and so to distinguish it from the IUPAC stereochemistry, in particular by the International Union of Biochemistry and Molecular Biology (IUBMB).[5] 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 (4S)-configuration, is kaur-16-en-18-oic acid in CAS nomenclature but ent-kaur-16-en-19-oic acid in IUBMB nomenclature.[2][5][note 2]

Occurence

Kaurane diterpenes have been extracted from a variety of plant species,[4][6] in particular Stevia sp., the source of the steviol glycosides stevioside and rebaudioside-A that have been used as artificial sweetners.[7] They are intermediates in gibberellin biosynthesis, leading to a group of important plant hormones (gibberellins):[8] gibberellin A12 is biosynthesized from ent-kaurene by six successive oxidations catalyzed by ent-kaurene oxidase (EC 1.14.13.78) and ent-kaurenoic acid oxidase (EC 1.14.13.79).[5] The ent-kaurane skeleton is also found in veatchine and other Garrya alkaloids.[9]

Notes and references

Notes

  1. Note that the numbering on the structural diagrams in the appendix to the original version of the IUPAC Recommendations 1999 is incorrect.
  2. 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 2004 errata to the IUPAC Recommendations 1999.

References

  1. Revised Section F: Natural Products and Related Compounds (IUPAC Recommendations 1999). Pure Appl. Chem., 71 (4), 587–643. DOI: 10.1351/pac199971040587.
  2. 2.0 2.1 57817-89-7 – Kaur-16-en-18-oic acid, 13-[(2-O-β-D-glucopyranosyl-β-D-glucopyranosyl)oxy]-, β-D-glucopyranosyl ester, (4α)-. In Common Chemistry; Chemical Abstracts Service, <http://www.commonchemistry.org/ChemicalDetail.aspx?ref=57817-89-7>. (accessed 5 September 2009).
  3. Revised Section F: Natural products and related compounds (IUPAC Recommendations 1999). Corrections and modifications (2004). Pure Appl. Chem., 76 (6), 1283–92. DOI: 10.1351/pac200476061283.
  4. 4.0 4.1 Nagashima, Fumihiro; Tanaka, Hironao; Takaoka, Shigeru; Asakawa, Yoshinori Ent-kaurane-type diterpenoids from the liverwort Jungermannia exsertifolia ssp. cordifolia. Phytochemistry 1996, 41 (4), 1129–41. DOI: 10.1016/0031-9422(95)00755-5. Arriaga-Giner, Francisco Javier; Rumbero, Angel; Wollenweber, Eckhard 16α,19-Diacetoxy-ent-kaurane, a New Natural Diterpene from the Exudate of Ozothamnus scutellifolius (Asteraceae). Z. Naturforsch. C 1999, 54, 602–4. Harinantenaina, Liva Rakotondraibe Romuald; Kasai, Ryoji; Yamasaki, Kazuo Ent-kaurane Diterpenoid Glycosides from the Leaves of Cussonia racemosa, a Malagasy Endemic Plant. Chem. Pharm. Bull. 2002, 50 (2), 268–71. DOI: 10.1248/cpb.50.268. Ding, Lan; Zhang, Zhang-Jing; Liu, Guo-An; Yang, Dong-Juan; Guo, Guo-Cong; Wang, Han; Sun, Kun Three New Cytotoxic ent-Kaurane Diterpenoids from Isodon weisiensis C. Y. Wu. Helv. Chim. Acta 2005, 88 (9), 2502–7. DOI: 10.1002/hlca.200590185. Batista, Ronan; García, Pablo A.; Castro, Maria A.; del Corral, José M. Miguel; San Feliciano, Arturo; de Oliveira, Alaíde B. New oxidized ent-kaurane and ent-norkaurane derivatives from kaurenoic acid. J. Braz. Chem. Soc. 2007, 18 (3), 622–27. DOI: 10.1590/S0103-50532007000300020. Zhao, Yong; Pu, Jian-Xin; Huang, Sheng-Xiong; Ding, Li-Sheng; Wu, Ying-Li; Li, Xian; Yang, Li-Bin; Xiao, Wei-Lie, et al. ent-Kaurane diterpenoids from Isodon pharicus. J. Nat. Prod. 2009, 72 (6), 988–93. PMID 19425589. DOI: 10.1021/np9000366.
  5. 5.0 5.1 5.2 EC 4.2.3.19 – ent-kaurene synthase. In IUBMB Enzyme Nomenclature, <http://www.chem.qmul.ac.uk/iubmb/enzyme/EC4/2/3/19.html>. (accessed 18 September 2009). EC 1.14.13.78 – ent-kaurene oxidase. In IUBMB Enzyme Nomenclature, <http://www.chem.qmul.ac.uk/iubmb/enzyme/EC1/14/13/78.html>. (accessed 5 September 2009). EC 1.14.13.79 – ent-kaurenoic acid oxidase. In IUBMB Enzyme Nomenclature, <http://www.chem.qmul.ac.uk/iubmb/enzyme/EC1/14/13/79.html>. (accessed 5 September 2009).
  6. Nagashima, Fumihiro; Kondoh, Masuo; Uematsu, Toshinari; Nishiyama, Akiko; Saito, Sayaka; Sato, Masao; Asakawa, Yoshinori Cytotoxic and apoptosis-inducing ent-kaurane-type diterpenoids from the Japanese liverwort Jungermannia truncata nees. Chem. Pharm. Bull. 2002, 50 (6), 808–13. DOI: 10.1248/cpb.50.808. Bruno, Maurizio; Piozzi, Franco; Arnold, Nelly Apostolides; Başer, K. Hüsnü Can; Tabanca, Nurhayat; Kirimer, Neşe Kaurane Diterpenoids from Three Sideritis Species. Turk. J. Chem. 2005, 29 (1), 61–64, <http://journals.tubitak.gov.tr/chem/issues/kim-05-29-1/kim-29-1-7-0402-1.pdf>. Kim, Ki Hyun; Choi, Sang Un; Lee, Kang Ro Diterpene glycosides from the seeds of Pharbitis nil. J. Nat. Prod. 2009, 72 (6), 1121–27. PMID 19435339. DOI: 10.1021/np900101t.
  7. Jaitak, Vikas; Bikram Singh, Bandna; Kaul, V. K. An efficient microwave-assisted extraction process of stevioside and rebaudioside-A from Stevia rebaudiana (Bertoni). Phytochem. Anal. 2009, 20 (3), 240–45. PMID 19358287. DOI: 10.1002/pca.1120.
  8. Brandle, J. E.; Telmer, P. G. Steviol glycoside biosynthesis. Phytochemistry 2007, 68 (14), 1855–63. DOI: 10.1016/j.phytochem.2007.02.010.
  9. Pelletier, S. William; Mody, Naresh V. The Chemistry of C20-Diterpenoid Alkaloids. In The Alkaloids: Chemistry and Pharmacology; Manske, R. H. F.; Rodrigo, R. G. A., Eds.; Academic Press: New York, 1981; Vol. 18, pp 102–21. ISBN 0-12-469518-3.

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