- Exploiting the Synthetic Potential of Sesquiterpene Cyclases for Generating Unnatural Terpenoids
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The substrate flexibility of eight purified sesquiterpene cyclases was evaluated using six new heteroatom-modified farnesyl pyrophosphates, and the formation of six new heteroatom-modified macrocyclic and tricyclic sesquiterpenoids is described. GC-O analysis revealed that tricyclic tetrahydrofuran exhibits an ethereal, peppery, and camphor-like olfactoric scent.
- Oberhauser, Clara,Harms, Vanessa,Seidel, Katja,Schr?der, Benjamin,Ekramzadeh, Kimia,Beutel, Sascha,Winkler, Sven,Lauterbach, Lukas,Dickschat, Jeroen S.,Kirschning, Andreas
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p. 11802 - 11806
(2018/09/10)
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- The formal total synthesis of FR252921-An immunosuppressant
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The formal total synthesis of FR252921 is described. The key steps include the preparation of three fragments starting from 1,4-butanediol, (R)-malic acid, and prenol, respectively, followed by two consecutive peptide couplings of the three fragments. Other key steps involve an allene-type rearrangement or enyne isomerization to install the triene moiety, a Seebach methylation, a Julia olefination to construct the trisubstituted diene unit, and an enzymatic resolution strategy to generate the C-18 stereocenter.
- Yadav,Sengupta, Sandip
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p. 376 - 388
(2013/03/13)
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- Stereoselective alkene isomerization over one position
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Although controlling both the position of the double bond and E:Z selectivity in alkene isomerization is difficult, 1 is a very efficient catalyst for selective mono-isomerization of a variety of multifunctional alkenes to afford >99.5% E-products. Many reactions are complete within 10 min at room temperature. Even sensitive enols and enamides susceptible to further reaction can be generated. Catalyst loadings in the 0.01-0.1 mol% range can be employed. E-to-Z isomerization of the product from diallyl ether was only -6 times as fast as its formation, showing the extremely high kinetic selectivity of 1.
- Larsen, Casey R.,Grotjahn, Douglas B.
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supporting information; experimental part
p. 10357 - 10360
(2012/08/08)
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- Total synthesis and biological evaluation of methylgerambullone
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First total synthesis of methylgerambullone (MGB, 1) isolated from Glycosmis angustifolia was completed via a convergent route. The effect of MGB on the contractile responses of the isolated guinea-pig ileum induced by acetylcholine was investigated. As a result, it showed a potent relaxation rate (78.66 ± 4.30% at 100 mg/L) in a concentration-dependent manner on longitudinal smooth muscle contraction of isolated guinea-pig ileum induced by 1 μM acetylcholine.
- Moon, Jong Taik,Ha, Sung Hoon,Lee, So Hyung,Kwon, Tae Hui,Oh, Chun Rim,Kim, Young Deuk,Kim, Jungahn,Choo, Dong Joon,Lee, Jae Yeol
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scheme or table
p. 52 - 55
(2010/04/24)
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- IspG converts an epoxide substrate analogue to (E)-4-hydroxy-3-methylbut-2- enyl diphosphate: Implications for IspG catalysis in isoprenoid biosynthesis
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(Chemical Equation Presented) IspG is an intriguing enzyme in bacteria, parasite, and plant isoprenoid biosynthesis, and its catalytic mechanism remains elusive. We report here the synthesis of (2R,3R)-4-hydroxy-3-methyl-2,3- epoxybutanyl diphosphate (Epoxy-HMBPP), a proposed intermediate in one of the frequently cited mechanistic models. We have also demonstrated that this epoxide analogue is a catalytically competent IspG substrate. This study represents the first mechanistic study of this important enzyme.
- Nyland II, Rodney L.,Xiao, Youli,Liu, Pinghua,Freel Meyers, Caren L.
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supporting information; experimental part
p. 17734 - 17735
(2010/04/01)
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- Extensive isomerization of alkenes using a bifunctional catalyst: An alkene zipper
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Catalyzed movement of alkene double bonds up to 30 positions has been accomplished using a catalyst featuring a cationic CpRu fragment and bifunctional imidazolylphosphine. The basic nitrogen of the latter is thought to deprotonate coordinated alkene intermediates reversibly, facilitating isomerization between terminal and (E)-alkenes and accelerating conversions by factors of up to 1 × 104. Copyright
- Grotjahn, Douglas B.,Larsen, Casey R.,Gustafson, Jeffery L.,Nair, Reji,Sharma, Abhinandini
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p. 9592 - 9593
(2008/03/11)
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- Hydrazines and azides via the metal-catalyzed hydrohydrazination and hydroazidation of olefins
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The discovery, study, and implementation of the Co- and Mn-catalyzed hydrohydrazination and hydroazidation reactions of olefins are reported. These reactions are equivalent to direct hydroaminations of C-C double bonds with protected hydrazines or hydrazoic acid but are based on a different concept in which the H and the N atoms come from two different reagents, a silane and an oxidizing nitrogen source (azodicarboxylate or sulfonyl azide). The hydrohydrazination reaction using di-tert-butyl azodicarboxylate is characterized by its ease of use, large functional group tolerance, and broad scope, including mono-, di-, tri-, and tetrasubstituted olefins. Key to the development of the hydroazidation reaction was the use of sulfonyl azides as nitrogen sources and the activating effect of tert-butyl hydroperoxide. The reaction was found to be efficient for the functionalization of mono-, di-, and trisubstituted olefins, and only a few functional groups are not tolerated. The alkyl azides obtained are versatile intermediates and can be transformed to the free amines or triazoles without isolation of the azides. Preliminary mechanistic investigations suggest a rate-limiting hydrocobaltation of the alkene, followed by an amination reaction. Radical intermediates cannot be ruled out and may be involved.
- Waser, Jerome,Gaspar, Boris,Nambu, Hisanori,Carreira, Erick M.
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p. 11693 - 11712
(2007/10/03)
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- Cobalt-catalyzed hydroazidation of olefins: Convenient access to alkyl azides
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Conversion of olefins to azides was achieved with high Markovnikov selectivity for a broad range of alkenes using 6 mol % Co(BF4)·6H2O and ligand 1, with 3 equiv of TsN3 as nitrogen source and simple silanes (PhSiH3, TMDSO). Copyright
- Waser, Jerome,Nambu, Hisanori,Carreira, Erick M.
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p. 8294 - 8295
(2007/10/03)
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- Intramolecular Formal oxa-[3 + 3] Cycloaddition Approach to the ABD System of Phomactin A
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(Equation Presented) The ABD-ring of phomactin A was synthesized using an intramolecular formal oxa-[3 + 3] cycloaddion of an α,β-unsaturated iminium salt tethered to a 1,3-diketone. This represents the first time that the 12-membered ring has been formed
- Cole, Kevin P.,Hsung, Richard P.
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p. 4843 - 4846
(2007/10/03)
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- An efficient total synthesis of (2E,4E,7R)-farnesa-2,4,10-triene from (R)-(+)-citronellal
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(2E,4E,7R)-farnesa-2,4,10-triene(Caparratriene) (1), a novel sesquiterpene hydrocarbon with significant growth inhibitory activity against CEM leukemia cells, was first synthesized from (R)-(+)-citronellal (2) by employing titanium-induced intermolecular
- Li, Jing,Liu, Zuosheng,Lan, Jiong,Li, Yulin
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p. 259 - 262
(2007/10/03)
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- Natural and unnatural terpenoid precursors of insect juvenile hormone
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The biosynthesis of insect juvenile hormone (JH) is due, in part, to the precise head-to-tail coupling of allylic and homoallylic diphosphate substrates, as catalyzed by one or more prenyltransferases. To better understand this enzyme's role in JH production, homodimethylallyl diphosphate and both the natural and unnatural homologs of geranyl diphosphate have been prepared as potential substrates for insect prenyltransferase. These latter materials were constructed in a convergent manner by olefination of the corresponding trisnoraldehydes obtained from either terminal oxidative cleavage of geraniol or higher-order cuprate conjugate addition to acrolein. To aid in characterizing the nature of the terpenoid skeletons formed from our in vitro studies, homologous derivatives of farnesol were also prepared by anion coupling of the geranyl derivatives to either C5 or C6 allylic bromides. The preparation of these materials and the results of incubations with larval corpora allata homogenates of the lepidopteran Manduca sexta are described.
- Sen, Stephanie E.,Ewing, Gregory J.
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p. 3529 - 3536
(2007/10/03)
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- First total synthesis of (+)-caparratriene
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Caparratriene (1), a new sesquiterpene hydrocarbon with significant growth inhibitory activity against CEM leukemia cells, was first synthesized starting from (R)-(+)-citronellal through 3 steps in an overall yield of 17.5%. The absolute configuration at
- Li, Jing,Liu, Zuosheng,Lan, Jiong,Li, Yulin
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p. 229 - 230
(2007/10/03)
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- Lewis Acid-Promoted Selective Rearrangement of Trisubstituted Epoxides to Aldehydes or Ketones
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Rearrangement of trisubstituted epoxides has been effected under the influence of various Lewis acids.Among these, methylaluminum bis(4-bromo-2,6-di-tert-butylphenoxide) (MABR) can be selectively rearranged from trisubstituted epoxides to aldehydes, while
- Maruoka, Keiji,Murase, Noriaki,Bureau, Ronan,Ooi, Takashi,Yamamoto, Hisashi
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p. 3663 - 3672
(2007/10/02)
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