Stereoselective Synthesis Using Diastereotopic Groups

Hoffmann, Reinhard W.

doi:10.1055/s-2004-831169

Cited by 36 publications

(21 citation statements)

References 59 publications

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“…The selectivity achieved in the reaction of this substrate suggests, however, that similar selectivities might be achievable in a diastereotopos-differentiating reaction. [23] In order to study this phenomenon a limited set of 1,3-divinyl-2-cyclopentyl tetronates 8 was synthesized in unoptimized reaction sequences (Scheme 3) and subjected to the conditions of the [2 + 2]-photocycloaddition (Scheme 4). Diacetate 19 was available as side product of the nucleophilic epoxide ringopening of epoxide 12.…”

Section: Preparation Of Key Intermediate 5 and Photocycloaddition Expmentioning

confidence: 99%

Total Synthesis of Punctaporonin C by a Regio‐ and Stereoselective [2+2]‐Photocycloaddition

Fleck

Bach

2010

Chemistry A European J

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The unique sesquiterpene punctaporonin C was synthesized starting from commercially available 7-tert-butoxynorbornadiene in a linear sequence of 29 steps and with an overall yield of 0.65%. Key step of the synthesis was an intramolecular [2+2]-photocycloaddition, in which the two vinylic double bonds in a 1,3-divinyl-2-cyclopentyl tetronate were differentiated by reaction with the photoexcited tetronate. The reaction gave regio- and diastereoselective access to the tricyclic core skeleton of punctaporonin C in 63% yield. Additional studies related to the tetronate [2+2]-photocycloaddition revealed that even diastereotopic vinylic double bonds in a 1,3-divinyl-2-cyclopentyl tetronate can be differentiated (d.r. up to 78:22). In the further course of the total synthesis the complete tetracyclic oxatetracyclo[6.3.2.0(1, 4).0(5, 12)]tridecane skeleton of punctaporonin C was established by an intramolecular aldol reaction, closing a seven-membered oxepane ring. The nucleophilic methyl ketone employed in this step was generated by Wacker oxidation of the vinylic double bond, which was not involved in the [2+2]-photocycloaddition. Several reactions employed in the synthetic sequence required adaptation to the rigid skeleton of punctaporonin C, for example, the reduction of a mesylate, the alkylation of a cyclobutane carboxylate, or the methyl addition to a prostereogenic carbonyl group.

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Section: Preparation Of Key Intermediate 5 and Photocycloaddition Expmentioning

confidence: 99%

Total Synthesis of Punctaporonin C by a Regio‐ and Stereoselective [2+2]‐Photocycloaddition

Fleck

Bach

2010

Chemistry A European J

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“…As outlined in figure 2, trienes might be Cssymmetric and contain two enantiotopic vinyl moieties, pseudo-C2-symmetric or C1-symmetric (both containing two diastereotopic vinyl groups). Thus, the olefin metathesis step may become a group selective reaction [35,36] in all three cases and this stereochemical problem needs to be addressed. …”

Section: Synthesis Of Heterocycles By Rcm Of Trienesmentioning

confidence: 99%

"Ring Closing Metathesis of Substrates Containing more than two C-Cdouble Bonds: Rapid Access to Functionalized Heterocycles"

Schmidt¹,

Hermanns

2006

COC

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In most cases where ring closing metathesis is applied to the synthesis of heterocycles, α,ω-dienes are used as precursors. If substrates containing more than two double bonds are subjected to a metathesis reaction, carba-or heterocycles bearing additional exocyclic alkene functionality result, or multiple ring closing processes occur. This offers interesting and potentially very useful synthetic perspectives. On the other hand, selectivity problems need to be addressed as the cyclization of substrates with more than two double bonds available for olefin metathesis may result in constitutional isomers or stereoisomers. This review highlights problems and opportunities evolving from ring closing metathesis of tri-, tetra-, and polyenes as a strategy for the selective synthesis of functionalized heterocycles. The chapter on RCM of trienes is subdivided according to the symmetry of the metathesis precursor. The following two chapters deal with the double or multiple RCM of tetra-or polyenes. These processes are further classified according to the preferred cyclization mode. Finally, the application of cascade or domino metathesis reactions to the synthesis of heterocycles will be discussed. These processes can be classified into those where exclusively C-C-double bonds take part in the metathesis reaction, and those where one or more C-C-triple bonds are involved.

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“…The same group described two different approaches to the tetracyclic core of the aspidosperma alkaloids by a double oxidative amination and double conjugate addition process [29]. Treating the cyclohexadiene 48 with Pd(OAc) 2 and O 2 in DMSO provided the tetracyclic compound 49 as a single isomer in 75% yield. On the other hand, the allylic oxidation using Pd/C-t-BuOOH and subsequent double 1,4-addition in the presence of DBU led to 50 in 54% yield (Scheme 17).…”

Section: Miscellaneous Reactionsmentioning

confidence: 99%

“…A broad range of reactions have been developed for the desymmetrization of cyclohexadienes, and synthetic applications to natural product synthesis have been reported. The reviews on the desymmetrization of dienes before 2005 have already been reported [1][2][3][4]. We will then highlight the recent reports for the desymmetrization of dienes by diastereotopic group differentiating reactions in a stereoselective manner and its applications (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…A remaining olefin unit in the reaction products could be used for further transformations. Substrate-based asymmetric inductions from the latent stereogenic centers, namely, diastereotopic group differentiating reactions during the asymmetric syntheses have been explored [2]. In particular, substituted 1,4-cyclohexadienes have a great potential for the desymmetrization reactions [3,4].…”

Section: Introductionmentioning

confidence: 99%

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Diastereoselective Desymmetrization of Symmetric Dienes and its Synthetic Application

Nakahara

Fujioka

2010

Symmetry

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Abstract:The desymmetrization of symmetric compounds is a useful approach to obtain chiral building blocks. Readily available precursors with a prochiral unit could be converted into complex molecules with multiple stereogenic centers in a single step. In this review, recent advances in the desymmetrization of symmetric dienes in the diastereotopic group differentiating reaction and its synthetic application are presented.

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Stereoselective Synthesis Using Diastereotopic Groups

Cited by 36 publications

References 59 publications

Total Synthesis of Punctaporonin C by a Regio‐ and Stereoselective [2+2]‐Photocycloaddition

Total Synthesis of Punctaporonin C by a Regio‐ and Stereoselective [2+2]‐Photocycloaddition

"Ring Closing Metathesis of Substrates Containing more than two C-Cdouble Bonds: Rapid Access to Functionalized Heterocycles"

Diastereoselective Desymmetrization of Symmetric Dienes and its Synthetic Application

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