23445-02-5Relevant academic research and scientific papers
Divergent Photocyclization/1,4-Sigmatropic Rearrangements for the Synthesis of Sesquiterpenoid Derivatives
Gorobets, Evgueni,Wong, Norman E.,Paton, Robert S.,Derksen, Darren J.
, p. 484 - 487 (2017)
Combined experimental and computational efforts have demonstrated the utility of divergent photocyclization/1,4-sigmatropic rearrangement reactions for developing a general strategy toward the synthesis of cubebane-, spiroaxane-, and guaiane-type sesquiterpenes and related analogues. The configuration of the bridgehead substituent, the choice of solvent, and the wavelength of irradiation all impact diastereoselectivity in this tandem reaction process.
Exploiting the Synthetic Potential of Sesquiterpene Cyclases for Generating Unnatural Terpenoids
Oberhauser, Clara,Harms, Vanessa,Seidel, Katja,Schr?der, Benjamin,Ekramzadeh, Kimia,Beutel, Sascha,Winkler, Sven,Lauterbach, Lukas,Dickschat, Jeroen S.,Kirschning, Andreas
supporting information, p. 11802 - 11806 (2018/09/10)
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.
A multiproduct terpene synthase from medicago truncatula generates cadalane sesquiterpenes via two different mechanisms
Garms, Stefan,Koellner, Tobias G.,Boland, Wilhelm
supporting information; experimental part, p. 5590 - 5600 (2010/11/20)
Terpene synthases are responsible for a large diversity of terpene carbon skeletons found in nature. The multiproduct sesquiterpene synthase MtTPS5 isolated from Medicago truncatula produces 27 products from farnesyl diphosphate (1, FDP). In this paper, we report the reaction steps involved in the formation of these products using incubation experiments with deuterium-containing substrates; we determined the absolute configuration of individual products to establish the stereochemical course of the reaction cascade and the initial conformation of the cycling substrate. Additional labeling experiments conducted with deuterium oxide showed that cadalane sesquiterpenes are mainly produced via the protonation of the neutral intermediate germacrene D (5). These findings provide an alternative route to the general accepted pathway via nerolidyl diphosphate (2, NDP) en route to sesquiterpenes with a cadalane skeleton. Mutational analysis of the enzyme demonstrated that a tyrosine residue is important for the protonation process.
Stereocontrolled syntheses of (-)-cubebol and (-)-10-epicubebol involving intramolecular cyclopropanation of a-lithiated epoxides
Hodgson, David M.,Salik, Saifullah,Fox, David J.
supporting information; experimental part, p. 2157 - 2168 (2010/06/17)
Figure Presented Formylation of (-)-menthone (11) with LDA and HCO 2CH2CF3 avoids loss of configurational integrity at the isopropyl group, giving hydroxymethylenementhone 12. Lithium 2,2,6,6-tetramethylpiperidideinduced intramolecular cyclopropanation of derived unsaturated terminal epoxide 17 (and chlorohydrin 16), efficiently generates a substituted tricyclo[4.4.0.01.5]decan-4-ol 18, which is used in a concise synthesis of (-)-cubebol (1). In contrast, isopropyl group inversion during formylation of menthone with NaOMe and HCO2Et led, by a similar strategy, to syntheses of 7-epicubebol (33) and (from(+)-menthone) of naturally occurring (-)-10-epicubebol (39), confirming the original structural assignment. Computational studies support the origin of the inversion as being rate-determining formylation of cis-enolate 27 from amixture of rapidly interconverting enolates. In the synthesis of 7-epicubebol (33), allylic tertiary C-H insertion is observed as a significant competing reaction in the intramolecular cyclopropanation of unsaturated terminal epoxide 22.
Synthesis of (-)-cubebol by face-selective platinum-, gold-, or coppercatalyzed cycloisomerization: Evidence of chirality transfer and mechanistic insights
Fehr, Charles,Winter, Beat,Magpantay, Iris
experimental part, p. 9773 - 9784 (2010/04/24)
We describe in detail a direct, stereoselective synthesis of (-)-cubebol based on a Pt-, Au-, or Cu-catalyzed cycloisomerization in which control of the configuration of the propargylic center is essential for the facial selectivity. In addition, we show that cycloisomerization reactions of enantioenriched propargyl pivalates occur with substantial chirality transfer. We confirm a mechanism by means of cyclization followed by an [l,2]-acyl migration for the Pt- and the Au-catalyzed cycloisomerization. So far, no evidence supports that the Cu-catalyzed cycloisomerization follows the same reaction course.
Thieme chemistry journal awardees - Where are they now? Synthesis of (-)-cubebol by intramolecular cyclopropanation of a terminal epoxide
Hodgson, David M.,Salik, Saifullah
scheme or table, p. 1730 - 1732 (2009/12/05)
A synthesis of (-)-cubebol from l-menthone is described. The key step involves efficient (90%) and completely stereocontrolled intramolecular cyclopropanation of an unsaturated α-lithiated terminal epoxide. Georg Thieme Verlag Stuttgart.
Platinum- and gold-catalyzed rearrangement reactions of propargyl acetates: Total syntheses of (-)-α-cubebene, (-)-cubebol, sesquicarene and related terpenes
Fuerstner, Alois,Hannen, Peter
, p. 3006 - 3019 (2008/02/04)
Propargyl acetates, in the presence of catalytic amounts of late transition-metal salts such as PtCl2 or AuCl3, represent synthetic equivalents of α-diazoketones. This notion is corroborated by a concise approach to various sesquiterpene natural products starting from readily available substrates. Specifically, (+)-carvomenthone (17) is converted into propargyl acetate (S)-26 by a sequence involving Stille cross-coupling of its kinetic enol triflate 18, regioselective hydroboration/oxidation of the resulting 1,3-diene 19, and addition of an alkynyl cerium reagent to aldehyde 21 thus obtained. Since the latter step was found to be unselective, the configuration of the reacting propargyl acetate was unambiguously set by oxidation followed by diastereoselective transfer hydrogenation by using Noyori's catalyst 25. Compound (5)-26, on treatment with PtCl2 in toluene, converted exclusively to the tricyclic enol acetate 27, which was sap onified to give norcubebone 11 in excellent overall yield. The conversion of this compound into the sesquiterpene alcohol (-)-cubebol (6) was best achieved with MeCeCl2 as the nucleophile, whereas the formation-of the parent hydrocarbon (-)-α-cubebene (4) was effected in excellent yield by recourse to iron-catalyzed cross coupling methodology developed in this laboratory. Since norketone 11 has previously been transformed into (-)-β-cubebene (5) as well as (-)-4-epicubebol 8, our approach constitutes formal total syntheses of these additional natural products as well. Along similar lines, the readily available propargyl acetates 1, 33 and 47 were shown to give access to 2-carene 44, sesquicarene 39, and episesquicarene 51 in excellent overall yields. In this series, however, the cy cloisomerization reaction was best achieved with catalytic amounts of AuCl3 in 1,2-dichloroethane as the solvent. In addition to these preparative results, our data provide some insight into the mechanism of these remarkable skeletal rearrangement reactions. Transformations of this type are likely triggered by initial coordination of the alkyne unit of the substrate to the carbophilic transition-metal cation. Formal attack of the alkene moiety onto the resulting π-complex engenders the formation of an electrophilic cyclopropyl carbene species which subsequently reacts with the adjacent acetate unit to give the final product. The alternative phasing of events, implying initial attack of the acetate (rather than the alkene moiety) onto the metal-alkyne complex, is inconsistent with the stereochemioal data obtained during this total synthesis campaign.
