Enantioselective synthesis and absolute configuration of (−)-pulo'upone by asymmetric intramolecular diels-alder reaction

Oppolzer, Wolfgang; Dupuis, Dominique; Poli, Giovanni; Raynham, Tony; Bérnardinelli, Gerald

doi:10.1016/s0040-4039(00)82216-9

Cited by 68 publications

(26 citation statements)

References 36 publications

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“…In some syntheses a Lewis acid and a covalently bound chiral auxiliary are used to improve the diastereo-and enantioselectivities of the IMDA cycloaddition. For example, Oppolzer, [20] Takano, [21] and Evans [22] used different covalently bound auxiliaries in their natural product syntheses. Furthermore, Evans has used asymmetric copper catalysts in IMDA during the preparation of isopulo'upone.…”

Section: Resultsmentioning

confidence: 99%

Preparation of Bicyclo[4.3.0]nonanes by an Organocatalytic Intramolecular Diels–Alder Reaction

Selkälä

Koskinen

2005

Eur J Org Chem

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Section: Resultsmentioning

confidence: 99%

Preparation of Bicyclo[4.3.0]nonanes by an Organocatalytic Intramolecular Diels–Alder Reaction

Selkälä

Koskinen

2005

Eur J Org Chem

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“…Although Oppolzer´s work [14] gives an example of introducing a chloroacetyl group into Oppolzer´s sultam, his approach requires the application of non-standard conditions (n-BuLi as a base in THF at -78°C) and because of this we decided to try to apply our ZnCl 2 technique.…”

Section: Discussionmentioning

confidence: 99%

A New Routine for the Synthesis of N-substituted-N-(sulfonyl) bromoacetamides with ZnCl2 as a Catalyst

Trávníček

Potáček

1999

Molecules

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“…Sub- (1) with different views of the crystal structure. For the synthesis of the eastern fragment, TBDPS-protected Roche aldehyde 34 was subjected to a HWE olefination with phosphonate 35 (19) to afford the corresponding N-enoyl sultam 36. Subsequent to ␣-alkylation with methyl iodide by using Oppolzer's 1,4-addition͞enolate-trapping protocol (20), reductive removal of the auxiliary afforded primary alcohol 37 in good yield and diastereoselectivity (78%, 97:3).…”

Section: Third-generation Approachmentioning

confidence: 99%

Toward the synthesis of the carbacylic ansa antibiotic kendomycin

Mulzer

Pichlmair

Green

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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The convergent synthesis of a benzofuran analog of the carbacyclic ansa compound kendomycin has been achieved by assembling three major fragments by means of epoxide opening and directed ortho lithiation. The crucial tetrahydropyran ring was formed by a highly stereoselective cationic cyclization. Analysis of all synthesized tetrahydropyran-arene compounds reveals a hindered sp 2 -sp 3 rotation, which results in rotational isomers or atropisomers affecting macrocyclization reactions. The latter could only be achieved by means of Horner-Wadsworth-Emmons olefination.O rganic compounds derived from nature have been an abundant source of drugs and drug leads and have provided a rich array of interesting synthetic targets. Among various selection criteria, novel and complex structural features combined with interesting biological activities might be the most important ones to promote a molecule to a target for natural product synthesis. Kendomycin (1), a novel streptomyces metabolite, which was presented at a meeting in 1999, consummately meets all the requirements and thus was selected as a target for our research one year later. Originally, 1 had been published as (Ϫ)-TAN 2162 in the patent literature as a potent endothelin receptor antagonist and antiosteoporotic compound (1-3). With its reisolation from a different streptomyces strain, the absolute configuration of 1 has been determined. Additionally, the biosynthetic pathway and further antibiotic and cytotoxic activities have been reported (4, 5). The structure of 1 (Fig. 1) features an aliphatic ansa chain that is attached by carbons C5 and C18 to a quinone methide core. Thus, 1 is one of the very few ansa-carbon natural products that have been isolated so far. Likewise, the quinone methide structure, which can be regarded as a 1,6-oxidation product of the corresponding benzofuran, has no precedence in natural product chemistry.Particular attention should be devoted to the fully substituted tetrahydropyran ring, which is, combined with the quinone methide, a sterically encumbered region in the molecule, possibly prone to atropisomeric phenomena. In this contribution we give a progress report on our total synthesis of kendomycin (6-8). First-Generation ApproachOur initial synthetic plan (Fig. 2) focused on a ring-closing metathesis (RCM) macrocyclization of the seco intermediates 2 or 3. It was obvious that the formation of the quinone methide chromophore should be deferred to the end of the synthesis, envisaging either an oxidation of the corresponding benzofuran or a 1,6-elimination. Key intermediates 2 and 3 were to be assembled either by a Heck coupling of alkene 4 and arylbromide 5 or an epoxide opening reaction of 5 with epoxide 6. The tetrahydropyran ring should be formed by an intramolecular hetero-Michael addition of enone 7, which should be derived from a Horner-Wadsworth-Emmons (HWE) olefination of aldehyde 8 with ␤-ketophosphonate 9.As outlined in Fig. 3, the stereotetrad of the tetrahydropyran ring was constructed by aldol addition methodology and...

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Enantioselective synthesis and absolute configuration of (−)-pulo'upone by asymmetric intramolecular diels-alder reaction

Cited by 68 publications

References 36 publications

Preparation of Bicyclo[4.3.0]nonanes by an Organocatalytic Intramolecular Diels–Alder Reaction

Preparation of Bicyclo[4.3.0]nonanes by an Organocatalytic Intramolecular Diels–Alder Reaction

A New Routine for the Synthesis of N-substituted-N-(sulfonyl) bromoacetamides with ZnCl2 as a Catalyst

Toward the synthesis of the carbacylic ansa antibiotic kendomycin

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