Synthesis of chiral spiro 3-oxazolin-5-one 3-oxides (chiral nitrones) via a nitrosoketene intermediate and their asymmetric 1,3-dipolar cycloaddition reactions leading to the EPC synthesis of modified amino acids

Katagiri, Nobuya; Okada, Makoto; Mori­shita, Yohei; Kaneko, Chikara

doi:10.1016/s0040-4020(97)00284-6

Cited by 37 publications

(21 citation statements)

References 20 publications

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“…Regarding the latter, the use of N- benzyl hydroxylamine (Scheme 4) is representative of several variations which were explored and found to either resist cycloaddition or give large amounts of oxazole side-products via dehydration of the intermediate nitrone (i.e., 18 ) 29,30. Eventually a more satisfactory solution that allowed advancement of the N -methylhydroxylamine adducts was implemented ( vide infra ) 23,24,31,25,26…”

Section: Resultsmentioning

confidence: 99%

Welwitindolinone C synthetic studies. Construction of the welwitindolinone carbon skeleton via a transannular nitrone cycloaddition

et al. 2010

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Section: Resultsmentioning

confidence: 99%

Welwitindolinone C synthetic studies. Construction of the welwitindolinone carbon skeleton via a transannular nitrone cycloaddition

et al. 2010

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“…The activity of 5a$(þ)-10-CSA was subsequently studied in a variety of solvents (6 h, rt 14 Whilst no effort was made to re-isolate the catalyst at the end of the reaction 1 H NMR spectral analysis of the crude reaction products showed resonance signals attributable to the parent bicycle 5a so confirming the stability of the catalyst to the reaction conditions. There is little precedent for the existence of iminium ions of isoxazolidine frameworks; aside from sporadic mention as transient intermediates 19,20 to the best of our knowledge the benzisoxazolium trifluoroacetate 10, Fig. 3, is the only claimed stable cation.…”

Section: Resultsmentioning

confidence: 99%

NH-Isoxazolo-bicycles; new molecular scaffolds for organocatalysis

Doyle

Heaney

2011

Tetrahedron

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a b s t r a c tA new scaffold for organocatalysis of the DielseAlder reaction is disclosed; an isoxazolidine ring forms the core of the catalyst and its activity is enhanced by judicious fusion of a second five-membered heterocycle to the c-edge. The catalyst performance is improved by the incorporation of an endo-cyclic electron withdrawing group adjacent to the fusion point. The organic core is effective only in the presence of an acid co-catalyst and whilst the two-component system shows potential as an enantioselective catalyst it is demonstrated that stereocontrol is a feature of the organic core and is fully independent of the choice of co-catalyst.

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“…15,16 This column separated the (2S,1ЈR) stereoisomer (2) from its (2S,1ЈS) epimer (3) and from the coeluting (2R,1ЈS) and (2R,1ЈR) stereoisomers (Fig. 3).…”

Section: Resultsmentioning

confidence: 99%

“…Recently, a fully stereoselective synthetic method leading to the (2S,1ЈS) isomer was described. 15,16 The (2S,1ЈR) isomer, although detected in plant isolates, 1,8,9 has not yet been characterized as a pure compound. The inhibitory activity of 2-(cyclopent-2Ј-enyl)glycine was reported to be associated with this stereoisomer.…”

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confidence: 99%

Synthesis of epimers of L-cyclopentenylglycine using enzymatic resolution

2000

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Both epimers of the naturally occurring nonproteinogenic amino acid L-cyclopentenylglycine, (2S,1'S)- and (2S, 1'R)-2-(cyclopent-2'-enyl)glycine, were obtained via a procedure involving condensation of 3-chlorocyclopentene with diethyl acetylaminomalonate, deethoxycarbonylation, chromatographic separation of the resulting two pairs of enantiomers, and enzymatic resolution of the racemates employing enantioselective hydrolysis of the ethyl ester group with alpha-chymotrypsin. The method was used for preparation of (13)C-labeled compounds of interest for biosynthetic tracer experiments. Enantiomeric purity of the products was determined by chiral HPLC on a Crownpak CR(+) column. The biologically active (2S,1'R) isomer was obtained as a pure compound and characterized for the first time. The (2R,1'R) and (2R,1'S) isomers were obtained as N-acetyl ethyl ester derivatives.

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Synthesis of chiral spiro 3-oxazolin-5-one 3-oxides (chiral nitrones) via a nitrosoketene intermediate and their asymmetric 1,3-dipolar cycloaddition reactions leading to the EPC synthesis of modified amino acids

Cited by 37 publications

References 20 publications

Welwitindolinone C synthetic studies. Construction of the welwitindolinone carbon skeleton via a transannular nitrone cycloaddition

Welwitindolinone C synthetic studies. Construction of the welwitindolinone carbon skeleton via a transannular nitrone cycloaddition

NH-Isoxazolo-bicycles; new molecular scaffolds for organocatalysis

Synthesis of epimers of L-cyclopentenylglycine using enzymatic resolution

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