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3
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84888877969
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The biosynthetic origins of diterpenes can be complex. Class I terpene cyclases catalyse the formation of a reactive cationic intermediate via pyrophosphate ionization as is typical of mono- and sesquiterpene biosynthesis. Class II diterpene synthases use protonation of an alkene to initiate cyclisation. Some enzymes combine both these functions, with pyrophosphate ionization followed by a protonation step or vice versa. For reviews see
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J. Shinozaki M. Shibuya Y. Ebizuka K. Masuda Biosci., Biotechnol., Biochem. 2013 77 2278 2282
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Shinozaki, J.1
Shibuya, M.2
Ebizuka, Y.3
Masuda, K.4
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5
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0000502773
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in, ed. D. E. Cane, Elsevier Science, Oxford, ch. 2.08, Enzyme-induced conformational control of the fates of cationic intermediates in terpene biosynthesis has recently been proposed by Tantillo in his seminal studies of the bisabolyl cation: see
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J. MacMillan and M. H. Beale, in Comprehensive Natural Products Chemistry, ed., D. E. Cane, Elsevier Science, Oxford, 1999, vol. 2, ch. 2.08, pp. 217-243
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(1999)
Comprehensive Natural Products Chemistry
, vol.2
, pp. 217-243
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MacMillan, J.1
Beale, M.H.2
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9
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25844476888
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Briza Publications, Pretoria, South Africa
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B. van Wyk, M. Wink, Medicinal Plants of the World, Briza Publications, Pretoria, South Africa, 2004
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(2004)
Medicinal Plants of the World
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Van Wyk, B.1
Wink, M.2
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16
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84941723329
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Jpn. Kokai Tokkyo Koho JP 2012206962) albeit with differing, apparently erroneous stereochemistry of the Δ17(18) double bond 8 PCM
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H. Takikawa and M. Sugiyama, Jpn. Kokai Tokkyo Koho JP 2012206962, 2012
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(2012)
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Takikawa, H.1
Sugiyama, M.2
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20
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79959190033
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Quantum mechanical calculations were performed in Gaussian 09:, Gaussian, Inc., Wallingford CT
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Quantum mechanical calculations were performed in Gaussian 09: M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery Jr, J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, N. J. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski and D. J. Fox, Gaussian 09, Revision D.01, Gaussian, Inc., Wallingford CT, 2013
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(2013)
Gaussian 09, Revision D.01
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Frisch, M.J.1
Trucks, G.W.2
Schlegel, H.B.3
Scuseria, G.E.4
Robb, M.A.5
Cheeseman, J.R.6
Scalmani, G.7
Barone, V.8
Mennucci, B.9
Petersson, G.A.10
Nakatsuji, H.11
Caricato, M.12
Li, X.13
Hratchian, H.P.14
Izmaylov, A.F.15
Bloino, J.16
Zheng, G.17
Sonnenberg, J.L.18
Hada, M.19
Ehara, M.20
Toyota, K.21
Fukuda, R.22
Hasegawa, J.23
Ishida, M.24
Nakajima, T.25
Honda, Y.26
Kitao, O.27
Nakai, H.28
Vreven, T.29
Montgomery, J.A.30
Peralta, J.E.31
Ogliaro, F.32
Bearpark, M.33
Heyd, J.J.34
Brothers, E.35
Kudin, K.N.36
Staroverov, V.N.37
Kobayashi, R.38
Normand, J.39
Raghavachari, K.40
Rendell, A.41
Burant, J.C.42
Iyengar, S.S.43
Tomasi, J.44
Cossi, M.45
Rega, N.46
Millam, N.J.47
Klene, M.48
Knox, J.E.49
Cross, J.B.50
Bakken, V.51
Adamo, C.52
Jaramillo, J.53
Gomperts, R.54
Stratmann, R.E.55
Yazyev, O.56
Austin, A.J.57
Cammi, R.58
Pomelli, C.59
Ochterski, J.W.60
Martin, R.L.61
Morokuma, K.62
Zakrzewski, V.G.63
Voth, G.A.64
Salvador, P.65
Dannenberg, J.J.66
Dapprich, S.67
Daniels, A.D.68
Farkas, Ö.69
Foresman, J.B.70
Ortiz, J.V.71
Cioslowski, J.72
Fox, D.J.73
more..
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23
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77956630251
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ESI This has also been suggested in the case of the sesterterpene ophiobolin F
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S. G. Smith J. M. Goodman J. Am. Chem. Soc. 2010 132 12946 12959
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J. Am. Chem. Soc.
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Smith, S.G.1
Goodman, J.M.2
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26
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0034683034
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Class II diterpene synthases are also known to utilise alkene protonation to initiate biosynthesis. 3 Although 1-4 possess a Z configured C-17 alkene which might arise from 2Z-geranylfarnesol, we chose to show the 2E-geranylfarnesol as the precursor as previous work with the squalene-hopene cyclase had shown it to be a much better precursor of cyclized products. 2 However, either the 2E or 2Z isomer could lead to the same cationic intermediates (C, Scheme 1) via cyclisation. Indeed, the precursor may be the (pyro)phosphate ester of geranylfarnesol as this would not be expected to significantly affect the chemistry shown and would provide a strong interaction with the cyclase active site For reviews of quantum mechanical studies of terpene biosynthetic pathways, see
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K. U. Wendt G. E. Schulz G. E. E. J. Corey D. R. Liu Angew. Chem., Int. Ed. 2000 39 2812 2833
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(2000)
Angew. Chem., Int. Ed.
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Wendt, K.U.1
Schulz, G.E.2
Corey, G.E.E.J.3
Liu, D.R.4
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28
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84887788807
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Interconversion between the twist-boat and chair conformers of β- C entails significant molecular motions, especially of the C-17 methyl and C-18 hydroxymethyl groups. Steric and hydrogen-bonding interactions between these groups and active-site residues could disfavor twist-boat → chair conversion relative to hydride migration. While the initial 1,2-hydride shift leading from β- C to β- D is computed to be uphill by 4.5 kcal mol-1, the next step in the cascade is significantly downhill, thereby limiting reversion of β- D back to β- C. That is, the intermediate derived from 1,2-methyl migration from C-13 to C-18 in β- D is 9.3 kcal mol-1 lower in energy than the twist-boat form of β- C (see the ESI)
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D. J. Tantillo Nat. Prod. Rep. 2013 30 1079 1086
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(2013)
Nat. Prod. Rep.
, vol.30
, pp. 1079-1086
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Tantillo, D.J.1
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