Studies toward the total synthesis of eletefine: an efficient construction of the AB ring system

Cody, Jeremy A.; Ahmed, I.; Tusch, Douglas J.

doi:10.1016/j.tetlet.2010.08.058

Cited by 8 publications

(5 citation statements)

References 13 publications

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“… 26 Conversion to the acid chloride was followed by coupling with secondary amine 42 , prepared in excellent yield by treatment of bromoacetal with excess methylamine. The resulting tertiary amide 43 underwent clean Pomeranz–Fritsch-like cyclization/aromatization 27 to provide isoquinolone 44 . Attempted oxidative demethylation of 44 with ceric ammonium nitrate (CAN) gave an intractable mixture of products; hence, stepwise demethylation then oxidation was pursued.…”

Section: Results and Discussionmentioning

confidence: 99%

“…26 Conversion to the acid chloride was followed by coupling with secondary amine 42, prepared in excellent yield by treatment of bromoacetal with excess methylamine. The resulting tertiary amide 43 underwent clean Pomeranz− Fritsch-like cyclization/aromatization 27 products; hence, stepwise demethylation then oxidation was pursued. A short treatment with molten pyridinium chloride 28,29 (to avoid N-demethylation) provided monomethyl ether 45 in moderate yield, but again, CAN-mediated oxidative demethylation of this phenol was unsuccessful.…”

Section: ■ Introductionmentioning

confidence: 99%

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Toward the Total Synthesis of Alpkinidine: Synthesis of Haloquinone CE Ring System Synthons and Attempted Nucleophilic Bisannulation

et al. 2022

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Model chemistry involving the bisannulation of 2,3-dichloro-1,4-naphthoquinone with the ester enolate derived from ethyl o -nitrophenylacetic acid, which rapid assembled the ABCD ring system of a pentacyclic pyrroloacridine, has been applied to the attempted synthesis of the marine natural product alpkinidine. The reaction of ethyl o -nitrophenylacetic acid with 6,7-dichloro-2-methylisoquinoline-1,5,8(2 H )-trione, required to extend the model strategy to alpkinidine, was unfruitful, giving only complex mixtures. Efforts to direct the regiochemistry of the key Michael substitution step using 6-bromo-2-methylisoquinoline-1,5,8(2 H )-trione afforded an adduct sharing the complete carbon skeleton of alpkinidine, but this could not be elaborated to the natural product.

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Section: Results and Discussionmentioning

confidence: 99%

“…26 Conversion to the acid chloride was followed by coupling with secondary amine 42, prepared in excellent yield by treatment of bromoacetal with excess methylamine. The resulting tertiary amide 43 underwent clean Pomeranz− Fritsch-like cyclization/aromatization 27 products; hence, stepwise demethylation then oxidation was pursued. A short treatment with molten pyridinium chloride 28,29 (to avoid N-demethylation) provided monomethyl ether 45 in moderate yield, but again, CAN-mediated oxidative demethylation of this phenol was unsuccessful.…”

Section: ■ Introductionmentioning

confidence: 99%

Toward the Total Synthesis of Alpkinidine: Synthesis of Haloquinone CE Ring System Synthons and Attempted Nucleophilic Bisannulation

et al. 2022

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“…Having explored the effect of oxygen substitution on OSEs,t welve oxo-bridged natural products that have been proposed in the literature were evaluated (i.e., 19-29, Figure 3). [20][21][22][23][24][25][26][27][28][29][30] Thec alculated OSEs were observed to range from À13.9 to 32.1 kcal mol À1 .O nly hugonianene A( 29)h ad an OSE value greater than 30 kcal mol À1 ,that is,diagnostic for unstable.F or the remaining NPs,t he OSE analysis raised no red flags for suspect structural assignments.T his was not Figure 2. Calculated OSEs (OPLS_2005, kcal mol À1 )ofparent oxobridged alkenes corresponding to known isolable skeletons.…”

Section: In Memory Of Paul Von Raguø Schleyer and Julius Bredtmentioning

confidence: 99%

Reassignments and Corroborations of Oxo‐Bridged Natural Products Directed by OSE and DU8+ NMR Computation

2019

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Structural misassignments of natural products are prevalent in the literature.Developing methods and theoretical concepts to assist those undertaking structural elucidation is therefore of paramount importance,s uch that biologists and synthetic chemists avoid pursuing phantom chemical entities. Herein described is astrategy for predicting the isolabilities of oxygen-substituted bridgehead natural products based on calculations of olefin strain energies,N MR chemical shifts and coupling constants (DU8 +). This approachp rovides corroborating evidence for the structures of certain bridgehead alkene natural products while leading to the reassignment of several other structures.

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“…18 Therefore, an intramolecular Pomeranz-Fritsch type condensation was applied. 19 Required acetal 7 was obtained in three steps from commercial 2,3-dihydroxybenzoic acid (4). After quantitative methylation and saponification of intermediate ester (98%, 2 steps), derived benzoic acid 5 was amidated with amino acetal 6 in the presence of EDCI 6 in moderate yield (55%), which could not be improved by other methods, such as CDI/DMAP or intermediate acid chloride formation.…”

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confidence: 99%

Dihydroxylation Studies of Isoquinolinones: Synthesis of the EF-Ring of Lysolipin I

Heinemann¹,

Voigt²,

Menche³

2021

Synthesis

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Inspired by the potent polycyclic xanthone antibiotic Lysolipin I, a general study on asymmetric dihydroxylation reactions of variously substituted isoquinolinones was performed. Different isoquinolinones were efficiently prepared, either by a Pomeranz-Fritsch type condensation or a Curtius rearrangement. Under a broad variety of conventional oxygenation procedures they proved very unreactive. However, either by suitable substitution of the appending aromatic ring or more forcing conditions a dihydroxylation could finally be performed, which allowed for synthesis of the EF-ring of Lysolipin I.

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Studies toward the total synthesis of eletefine: an efficient construction of the AB ring system

Cited by 8 publications

References 13 publications

Toward the Total Synthesis of Alpkinidine: Synthesis of Haloquinone CE Ring System Synthons and Attempted Nucleophilic Bisannulation

Toward the Total Synthesis of Alpkinidine: Synthesis of Haloquinone CE Ring System Synthons and Attempted Nucleophilic Bisannulation

Reassignments and Corroborations of Oxo‐Bridged Natural Products Directed by OSE and DU8+ NMR Computation

Dihydroxylation Studies of Isoquinolinones: Synthesis of the EF-Ring of Lysolipin I

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