Asymmetric Phase-Transfer Catalyzed Glycolate Alkylation, Investigation of the Scope, and Application to the Synthesis of (−)-Ragaglitazar

Andrus, Merritt B.; Hicken, Erik J.; Stephens, Jeffrey C.; Bedke, D. Karl

doi:10.1021/jo051568z

Cited by 45 publications

(17 citation statements)

References 27 publications

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“…The use of chiral ammonium salts as catalysts (Fig XII.11) levobupivacaine [110], and ragaglitazar [111] (Fig XII.12). The highly enantioselective syntheses of kurasoin A and B reported by Andrus and co-workers are illustrative examples of phase transfer catalysis utility.…”

Section: Xii5 Phase Transfer Catalysis In Target Molecule Synthesismentioning

confidence: 99%

Organocatalysis in Total Synthesis

Marqués‐López¹,

Herrera²

2013

Comprehensive Enantioselective Organocatalysis

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Section: Xii5 Phase Transfer Catalysis In Target Molecule Synthesismentioning

confidence: 99%

Organocatalysis in Total Synthesis

Marqués‐López¹,

Herrera²

2013

Comprehensive Enantioselective Organocatalysis

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“…Under PTC conditions, acidic substrates such as phenylketone derivatives can be used to create chiral stereogenic centers. Andrus demonstrated asymmetric glycolate alkylation with up to 90% ee using various electrophiles and its application to the synthesis of (-)-ragaglitazar in six steps (Scheme 3.16) [37][38][39].…”

Section: Asymmetric Alkylationmentioning

confidence: 99%

Cinchona‐Derived Chiral Phase‐Transfer Catalysts for Other Asymmetric Synthesis

Arai

2008

Asymmetric Phase Transfer Catalysis

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Phase-transfer catalysis has been recognized as one of the most powerful synthetic tools for establishing practical protocols because it offers several advantages, such as operational simplicity, mild conditions with aqueous media, suitability for large-scale reaction, and an environmentally benign nature. Since the pioneering studies on asymmetric alkylation promoted by chiral phase-transfer catalysts (PTCs) [1,2], this research area has served as an attractive area for the pursuit of green chemistry, and many types of chiral quaternary ammonium salts for various asymmetric phasetransfer catalyses have been developed over the past few decades [3,4]. For example, two-center organocatalysis using bis-ammonium salts derived from tartrate represents a new concept in asymmetric PTC chemistry [5].In particular, it is not only the cinchona alkaloids that are suitable chiral sources for asymmetric organocatalysis [6], but also the corresponding ammonium salts. Indeed, the latter are particularly useful for chiral PTCs because: (1) both pseudo enantiomers of the starting amines are inexpensive and available commercially; (2) various quaternary ammonium salts can be easily prepared by the use of alkyl halides in a single step; and (3) the olefin and hydroxyl functions are beneficial for further modification of the catalyst. In this chapter, the details of recent progress on asymmetric phase-transfer catalysis are described, with special focus on cinchonaderived ammonium salts, except for asymmetric alkylation in a-amino acid synthesis. Asymmetric Darzens ReactionThe Darzens reaction is a fundamental reaction, the products of which are extremely useful for the synthesis of other molecules. Despite these advantages, the reaction Asymmetric Phase Transfer Catalysis. Edited by Keiji Maruoka

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“…[a] spite of some precedented studies in this field with a-het-A C H T U N G T R E N N U N G eroatom-containing carbonyl compounds, [16] only a small number of examples were found in which induction of stereochemistry was realized by a group on an a-heteroatom. [17] Thus, our result clearly and successfully emphasized the importance of this substrate system.…”

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confidence: 99%

Diastereoselective Alkylation of Glycinates by Assistance of Intramolecular Potassium⋅⋅⋅Fluorine Interactions

Yamazaki

Kawashita

Kitazume

et al. 2009

Chemistry A European J

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Stereoselective synthesis of a-amino acid derivatives with natural as well as unnatural structural features has constituted an important field in synthetic organic chemistry.[1] Various types of glycinates have been employed thus far as convenient key substrates for the preparation of such target molecules with exerting effective steric bias usually to esters or amides [1d] or with utilizing appropriate chiral catalysts.[2]During our continuing study to clarify the role of fluorine atoms in organic reactions, we have reported [3] that, as shown in Scheme 1, an excellent level of diastereoselectivity (up to 95:5) was attained for the alkylation of a-alkoxyesters by various types of electrophiles; in all of these reactions, the intramolecular interaction of fluorine with a metal has played a pivotal role. This process can be realized by conformationally fixing the enolate through formation of a bicyclo [3.3.0]-type structure. This would allow the appropriate electrophiles to approach exclusively from the re-face of the enolate as a result of preferable participation of the pro-R lone pair of the carbonyl a-oxygen and the auxiliary covers the opposite face. In this communication, we would like to describe our extension of this strategy to glycinates (3); this, like the previous a-alkoxy ester examples shown in Scheme 1, successfully demonstrated the significant importance of intramolecular metal···F chelation for attainment of excellent diastereoselectivity.Preparation of the starting materials (3) was carried out from the readily available fluorinated acetophenones (1, Scheme 2). To this end, treatment of the benzylimine of 1 d (n = 3) [4] with DBU efficiently catalyzed isomerization through a [1,3] proton shift as reported by Soloshonok et al. [4,5] Product 2 d was furnished upon hydrolytic workup. On the other hand, syntheses of 2 b (n = 1) and 2 c (n = 2) were initiated by the similar imine process from the corresponding ketones (1 b, n = 1 and 1 c, n = 2, respectively) [6] , and their NaBH 4 -mediated reduction followed by regiose- [a] Prof.

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Asymmetric Phase-Transfer Catalyzed Glycolate Alkylation, Investigation of the Scope, and Application to the Synthesis of (−)-Ragaglitazar

Cited by 45 publications

References 27 publications

Organocatalysis in Total Synthesis

Organocatalysis in Total Synthesis

Cinchona‐Derived Chiral Phase‐Transfer Catalysts for Other Asymmetric Synthesis

Diastereoselective Alkylation of Glycinates by Assistance of Intramolecular Potassium⋅⋅⋅Fluorine Interactions

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