Oxazolinyloxiranyllithium-Mediated Stereoselective Synthesis of α-Epoxy-β-amino Acids

Luisi, Renzo; Capriati, Vito; Degennaro, Leonardo; Florio, Saverio

doi:10.1021/ol034927q

Cited by 34 publications

(22 citation statements)

References 18 publications

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“…Synthesis of spirocyclic systems 218 [R = Ph, 4-ClC 6 H 4 , 4-MeOC 6 H 4 , CH 3 (CH 2 ) 6 , etc.] containing oxazolidine fragments was the subject of a series of publications [8,[242][243][244] were then used to obtain optically active and racemic amino acids [244]. Dihydrooxazoles 219 turned out to be convenient starting compounds (Scheme 127).…”

Section: Five-membered Oxaza Heterocyclic Compoundsmentioning

confidence: 99%

“…Dihydrooxazoles 219 turned out to be convenient starting compounds (Scheme 127). Attack by nitrone on the oxirane ring in substrate 220 led to the formation of trioxadiazadispiroundecanes 221 [242,243] (Scheme 128). The mechanism of analogous transformation of oxirane 222 is shown in Scheme 129.…”

Section: Five-membered Oxaza Heterocyclic Compoundsmentioning

confidence: 99%

“…The mechanism of analogous transformation of oxirane 222 is shown in Scheme 129. The final products in the above reactions were acyloxiranes 223 and oxirane-containing amino acids 224 [243] or rare epoxy lactones 225 [245] (Scheme 130). Such reactions are also typical of aziridines 226 [246] 227 structurally related to epoxide 220 was synthesized [247] from chiral Garner aldehyde 4 [R 2 B = (+)-lpc 2 B or 9-BBN; Scheme 132].…”

Section: Five-membered Oxaza Heterocyclic Compoundsmentioning

confidence: 99%

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Five-membered oxaza heterocyclic compounds on the basis of epoxides and aziridines

2011

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Section: Five-membered Oxaza Heterocyclic Compoundsmentioning

confidence: 99%

Section: Five-membered Oxaza Heterocyclic Compoundsmentioning

confidence: 99%

Section: Five-membered Oxaza Heterocyclic Compoundsmentioning

confidence: 99%

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Five-membered oxaza heterocyclic compounds on the basis of epoxides and aziridines

2011

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“…The a-lithiated O-protected propargyl alcohol 34 was prepared by deprotonation with n-BuLi and used in the synthesis of a cyclic enediyne related to maduropeptin chromophor [28]. Lithiated epoxides [29] of general structure II (X = O, n = 0) were first postulated as intermediates by Cope, and many of them act as carbenoid species: they can undergo (a) b-elimination to give an enolate, (b) a-ring opening followed by , which reacted with nitrones to give, after hydrolysis and catalytic hydrogenation, a-epoxy-b-aminoacids [32]. Oxyranyllithium 37 was prepared by lithiation a to the silicon with n-BuLi in ether at ±116 C with retention of the configuration of the oxirane [33].…”

Section: Introductionmentioning

confidence: 99%

Polyfunctional Lithium Organometallics for Organic Synthesis

Yus¹,

Foubelo²

2005

Handbook of Functionalized Organometallics

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Multifunctional organic molecules can be achieved by reacting functionalized organolithium compounds [1] with electrophilic reagents, this fact makes these intermediates of relevant interest in synthetic organic chemistry [2]. Another remarkable fact concerning organolithium compounds, compared with other organometallic compounds is that they can be prepared following a great number of different methodologies [3]: hydrogen±lithium exchange (deprotonation), halogen±lithium exchange, transmetallation reactions, carbon±heteroatom bond cleavage and carbolithiation of multiple carbon±carbon bonds. However, the highly ionic character of the carbon±lithium bond [4] makes these compounds extremely reactive and also unstable, so the synthetic processes should be carried out in some cases under very mild reaction conditions.Regarding the stability of functionalized organolithium compounds, it depends mainly on three factors, the most important one being the compatibility of the functional group with the carbon±lithium bond, so in some cases the functionality should be protected. The hybridization of the carbon atom bonded to the lithium atom is also important, so sp derivatives are more stable than the corresponding sp 2 and these are more stable than the sp 3 ones as it happens to the corresponding carbanions. Finally, the relative position of the functionality and the carbanionic center is also relevant, probably the b-functionalized derivatives being the most unstable species due to the existence of two consecutive carbon atoms with opposite polarities, the b-elimination process to give an olefin is extremely favored. Stabilized organolithium compounds, such as lithium enolate intermediates [5], a-organolithium compounds bearing electron-withdrawing groups (RSO, RSO 2 , CN, NO 2 , etc.) and heteroatoms such as sulfur [6], selenium and phosphorus as well as functionalized aryllithium compounds will not be consider in depth in this chapter due to the limited length of this review.The following study is ordered based on the relative position of the functionality and the carbanionic center, as well as on the hybridization of that center.

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“…Lithiation/electrophile trapping of oxazolinylepoxide 202 provided access to acyloxiranes 205 [72], while deprotonation/electrophile trapping of oxazolinylepoxide 206 with nitrones gave access to enantiopure a-epoxy-bamino acids 208 (Scheme 5.48)[73].Lithiation/electrophile trapping of enantiopure epoxide 209 stereoselectively gave epoxide 211; further elaboration via a metalated epoxide gave spirocyclic epoxide 212, which after treatment with acid gave epoxylactone 213 as a single diastereomer (Scheme 5.49)[74]. benzothiazolyl and benzotriazolyl units have been employed as heteroaromatic anion-stabilizing groups for metalated epoxides (Scheme 5.47) [71].…”

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confidence: 99%

Metalated Epoxides and Aziridines in Synthesis

Hodgson

Bray

2006

Aziridines and Epoxides in Organic Synthesis

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The chemistry of epoxides and aziridines is dominated by reactions that involve cleavage of the strained heterocyclic ring by nucleophiles (see Chapters 7 and 12). However, a less well known aspect of the chemistry of epoxides and aziridines is that which occurs upon reaction with a strong base. Abstraction of a b-proton may occur, resulting in the formation of allylic alcohols or amines, a process termed belimination [1a]. However, the b-hydrogens are not usually the most acidic; due to the electron-withdrawing effect of the oxygen/nitrogen and the acidifying nature of the three-membered ring, removal of an a-proton can occur to give an a-metalated epoxide (oxiranyl anion) or aziridine (aziridinyl anion) 1 (Scheme 5.1).The chemistry of a-metalated epoxides and aziridines (the a prefix will from now on not be included but should be assumed) has been reviewed previously [1], but in this chapter it is our intention to focus on those reactions involving them that are useful in synthesis, rather than just of pedagogical interest. Beginning with metalated epoxides, since the greater amount of work has involved them, we intend to present carefully chosen examples of their behavior that delineate the diverse nature of their chemistry. We will then move on to metalated aziridines, the chemistry of which, it will become apparent, closely mirrors that of their epoxide cousins.

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Oxazolinyloxiranyllithium-Mediated Stereoselective Synthesis of α-Epoxy-β-amino Acids

Cited by 34 publications

References 18 publications

Five-membered oxaza heterocyclic compounds on the basis of epoxides and aziridines

Five-membered oxaza heterocyclic compounds on the basis of epoxides and aziridines

Polyfunctional Lithium Organometallics for Organic Synthesis

Metalated Epoxides and Aziridines in Synthesis

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