Stereocontrolled access to the most highly condensed pentalenolactone antibiotic. From cycloheptatriene to pentalenolactone P methyl ester

Paquette, Leo A.; Kang, Ho Jung; Sup, Choon

doi:10.1021/ja00045a008

Cited by 36 publications

(22 citation statements)

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“…NMR: Bruker AM 360 and Varian Gemini 200 BB; UV/Vis: PerkinϪ Elmer Model 554; IR nujol mull, KBr cells, FT-IR 1720X (PerkinϪElmer); EI-MS: 70 eV, Finnigan MAT 311 A; elemental analysis: Heraeus CHN-O-Rapid, Institut für Anorganische und Angewandte Chemie, Universität Hamburg. Formylferrocene, formylruthenocene, [17] chloromethylcycloheptatriene, [16] BaMnO 4, [18] 2-bromo-5-cyclohepta-2Ј,4Ј,6Ј-trien-1-ylthiophene (16), [22] 2-cycloheptatrienyl-2Ј,5-bithiophene (19) [26] and 2-formyl-5-cycloheptatrienylthiophene (22) [30] were synthesised according to literature procedures.…”

Section: Methodsmentioning

confidence: 99%

“…Since deprotonated phosphonates are known to react more stereoselectively than phosphoranes in the formation of E-olefins, [15] (cycloheptatrienylmethyl)diethylphosphonate (6) was prepared in a Michaelis-Arbuzov reaction from 1-chloromethyl-1,3,5-cycloheptatriene. [16] For n ϭ 1 the phosphonate 6 underwent a Wittig-Horner-Wadsworth-Emmons (WHWE) reaction in the presence of NaH with the formyl metallocene (M ϭ Fe: 7a; M ϭ Ru: 7b [17] ) to form the neutral compounds 8a and 8b (Scheme 4, i). The elongation of the olefinic bridge (Scheme 4, iiϪvii) could be performed by the reaction of the formyl metallocenes 7a and 7b with (ethoxycarbonylmethyl)diethylphosphonate in a WHWE reaction.…”

Section: Complexes With Olefinic Linkersmentioning

confidence: 99%

“…Lithium-bromine exchange and subsequent nucleophilic addition to the tropylium cation led to the formation of 2-bromo-5-cycloheptatrienylthiophene (16). [23] Compound 16 was allowed to react with ferrocenyl zinc chloride [24] in a cross-coupling reaction [25] affording a mixture of isomers A, B and C of the monothiophene species 17 (Scheme 5).…”

Section: Complexes With Olefinic Linkersmentioning

confidence: 99%

“…(Cyclohepta-1,3,5-trien-1-ylmethyl)diethylphosphonate (6): 1-Chloromethyl-1,3,5-cycloheptatriene [16] (10.0 g, 71 mmol) was stirred in triethylphosphite (13.4 mL, 78 mmol) at 166°C for 8 h. After cooling, the reaction mixture was distilled at 2 ϫ 10 Ϫ2 mbar. Unreacted 1-chloromethylcyclohepa-1,3,5-triene was recovered at 30°C, and the product 6 obtained at 80°C as a yellow oil.…”

Section: Bmentioning

confidence: 99%

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Second Harmonic Generation and Two-Photon Fluorescence as Nonlinear Optical Properties of Dipolar Mononuclear Sesquifulvalene Complexes

Wong¹,

Meyer‐Friedrichsen²,

Farrell³

et al. 2000

Eur. J. Inorg. Chem.

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Section: Methodsmentioning

confidence: 99%

Section: Complexes With Olefinic Linkersmentioning

confidence: 99%

Section: Complexes With Olefinic Linkersmentioning

confidence: 99%

Section: Bmentioning

confidence: 99%

See 2 more Smart Citations

Second Harmonic Generation and Two-Photon Fluorescence as Nonlinear Optical Properties of Dipolar Mononuclear Sesquifulvalene Complexes

Wong¹,

Meyer‐Friedrichsen²,

Farrell³

et al. 2000

Eur. J. Inorg. Chem.

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“…110 Thus, the acetophenone-sensitized ODPM rearrangement of 109 gives 110 in 76% yield. Compound 110 was transformed in several steps into the -diketone 111, a key intermediate in the synthesis of cedrol (112,Scheme 27). 110a A photochemical approach to [3.3.3]propellanes by the ODPM rearrangement has allowed the synthesis of the sesquiterpene hydrocarbon (()-modhephene (113).…”

Section: F the Odpm Rearrangement Of Bridged Cyclic γ-Unsaturated Kmentioning

confidence: 99%

Synthetic Aspects of the Di-π-methane Rearrangement

1996

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Formal Asymmetric Synthesis of Pentalenolactone E and Pentalenolactone F-1. Retrosynthesis and π-Facial Differentiation in Palladium-Catalyzed and Dipolar [3 + 2]-Cycloaddition Reactions of Bicyclic Alkenes: Evidence for Electrostatic Control of Stereoselectivity

Rosenstock

Gais²,

Herrmann

et al. 1998

Eur. J. Org. Chem.

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A successful new strategy for the asymmetric synthesis of pentalenolactone E (2a) and pentalenolactone F (2b) has been developed. This strategy involves the assembly of ring A of 2a and 2b through a Binger‐type Pd‐catalyzed [3 + 2]‐cycloaddition reaction of diquinene 7 with the diphenyl‐substituted methylenecyclopropane 18. Diquinene 7 is available in an enantiomerically pure state in 8 steps from diester 8 by using a pig liver esterase catalyzed enantioselective hydrolysis as the key step. Unexpected facial selectivities of 1,3‐dipolar and Pd‐catalyzed [3 + 2]‐cycloaddition reactions as well Michael reactions of 7 have been observed. Thus, 7 reacted with CH2N2 with a stereoselectivity of 98% or greater in favour of reaction at the concave side, with formation of the cisoid triquinane 27. A Trost‐type Pd‐catalyzed reaction of 7 with 11 gave the transoid triquinane 6 and the cisoid triquinane 12 in ratios of 1:1.7 to 1:5.3 depending on the polarity of the solvent. Binger‐type Pd‐catalyzed cycloaddition reactions of 7 with methylenecyclopropane (13) in toluene afforded a mixture of 6 and 12 in a ratio of 1:7. In the Pd‐catalyzed reaction of 7 with the phenyl‐substituted methylenecyclopropanes 14a/b the cisoid triquinane 15 was obtained with a selectivity of 6.7:1 or above. Pd‐catalyzed reactions of 7 with the disubstituted methylenecyclopropanes 16 and 18 gave, however, the transoid triquinanes 17 and 19, respectively, with selectivities of 23:1 and 7:1, respectively. Nakamura‐type cycloaddition of 7 to the methylenecyclopropanone ketal 20 led to the quantitative formation of the transoid triquinane 21a and the cisoid triquinane 22a in a ratio of 1:2. The structures of cycloadducts 12, 15, 19 and 27 were determined by X‐ray analyses. The π‐facial differentiation may be ascribed mainly to a stabilization of the concave transition states by an electrostatic interaction between the lactone carbonyl group and the nucleophilic reagents. The stereoselectivity model proposed has been substantiated by a study of the analogous cycloaddition reactions of diquinenes 29a−c, which exhibited only a low π‐facial stereoselectivity, and by an X‐ray structure analysis of 7, which revealed a slight concave pyramidalization of the double bond. X‐ray structure analysis and NMR spectroscopy of diquinane 28a showed the 5E‐conformation, in which the hydroxy group occupies the pseudoaxial position, to be the more stable one. According to force‐field calculations, the 5E‐conformation seems to be stabilized by an intramolecular electrostatic interaction between the hydroxylic oxygen atom and the lactone carbonyl group, corresponding to the initial step of an intermolecular nucleophilic attack at the carbonyl group. The O−C1 distance and the O−C1−O angle found in the crystal structure of 28a support this notion.

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Stereocontrolled access to the most highly condensed pentalenolactone antibiotic. From cycloheptatriene to pentalenolactone P methyl ester

Cited by 36 publications

References 1 publication

Second Harmonic Generation and Two-Photon Fluorescence as Nonlinear Optical Properties of Dipolar Mononuclear Sesquifulvalene Complexes

Second Harmonic Generation and Two-Photon Fluorescence as Nonlinear Optical Properties of Dipolar Mononuclear Sesquifulvalene Complexes

Synthetic Aspects of the Di-π-methane Rearrangement

Formal Asymmetric Synthesis of Pentalenolactone E and Pentalenolactone F-1. Retrosynthesis and π-Facial Differentiation in Palladium-Catalyzed and Dipolar [3 + 2]-Cycloaddition Reactions of Bicyclic Alkenes: Evidence for Electrostatic Control of Stereoselectivity

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