Cycloaddition of chiral nitrones. Asymmetric synthesis of isoxazolidines

Bełżecki, C.; Panfil, Irma

doi:10.1021/jo01322a005

Cited by 64 publications

(19 citation statements)

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“…With AcOEt/MeOH 9:l (500 ml) as eluent 335 mg (43 Yo) of 7 were obtained as a colourless syrup4). ,6 t8.9-di-0-isopropylidene-a-o-mann0-4-nonosulo-4,7-furanose Noxide (7). Rf0.21 (AcOEt/CH,OH 9:l); [a]:: = +42.2" (c = I, CHCI,).…”

Section: Experimental Partmentioning

confidence: 99%

“…This may be due to a stronger interaction of the nitrone HOMO with the LUMO of the acrylate than with the LUMO of the methacrylate [4] [5]. The lower regioselectivity found in the cycloaddition of acrylate (see also [6] [7]) corresponds well with this explanation, which implies that HOMO-controlled cycloadditions would favour a 'syn' attack. This may be compared to the opposite face selectivity in Diels-Alder additions (with normal electron demand) of alkoxyalkyl-substituted dienes and dienophiles : a preferred 'anti' mode of addition of alkoxyalkyl-substituted dienophiles has been implied [8], a case analogous to a LUMO-controlled cycloaddition of a N-alkoxyalkyl-nitrone.…”

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confidence: 96%

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Diastereoselectivity in the Reaction of N‐Glycosyl‐nitrones: 1,3‐Dipolar Cycloaddition and Addition of Phosphite Anion

Bernet

Krawczyk

Vasella

1985

Helvetica Chimica Acta

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The direction of approach of dibenzyl phosphite on the one hand and of dipolarophiles on the other hand to the spironitrone 7 was examined. The nitrone 7 was prepared from the lactone 3. The nucleophilic addition of dibenzyl phosphite gave 8 as a single adduct (86%). Its structure was established by X-ray analysis. From the cycloaddition of methyl methacrylate, the products 9a, 9b, l l a , and l l b (83:2:7.5:7.5, 81 %) were isolated. The structure of the main adduct 9a was established by an X-ray analysis of a derivative of it, and the structures of the other adducts were deduced from their NMR spectra. The cycloaddition of 7 and methyl acrylate gave the adducts 10a, lob, 12a, 13a, 13b, and 14a (27:10:54:1:2:6,87%). The structures of these compounds were deduced from their NMR spectra. The results are discussed in relation to prior hypothesis.1. Introduction. -The nucleophilic addition of dialkyl phosphite anions to (2)-Calkyl-N-(2,3 : 5,6-di-0 -isopropylidene-cc -D-mannofuran0syl)nitrones 1 gives the (1 S ) -Nglycosyl-N-hydroxyaminophosphonates 2 with a diastereoselectivity of about 90 % [ 11 (Scheme I ) . A high diastereoselectivity had been predicted, based on the analogy between a LUMO-controlled 1,3-dipolar cycloaddition of N-glycosyl-nitrones and the addition of nucleophiles to it [ 11.

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Section: Experimental Partmentioning

confidence: 99%

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confidence: 96%

Diastereoselectivity in the Reaction of N‐Glycosyl‐nitrones: 1,3‐Dipolar Cycloaddition and Addition of Phosphite Anion

Bernet

Krawczyk

Vasella

1985

Helvetica Chimica Acta

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“…4, which showed correlations between H-2 and C-7, H-7 and C-2, H-7 and C-9, H-8 and C-1, H-8 and C-1 0 , H-9 and C-2 0 , H-9 and C-6 0 , and H-9 and C-7, disclosed the plane structure of 3. Concerning the absolute configuration of 1,3-diphenyl-1-propanols, several reports have been published [12][13][14][15][16], and the [a] D of R isomers are all positive while the S isomers are negative. Therefore, it was deduced that 3 might have R configuration.…”

Section: Resultsmentioning

confidence: 99%

Chemical studies on the roots of Uvaria welwitschii

et al. 2011

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A chemical investigation of the chloroform extract of the roots of Uvaria welwitschii (Annonaceae), an African traditional medicine taken for stomach ache, led to the isolation of eight new compounds, named welwitschins A-H (1-8), together with five known compounds (9-13). The structural elucidation by spectroscopic studies of the compounds isolated is described. All new compounds were flavonoids having a 2-hydroxy-3,4,6-trimethoxyphenyl moiety in the A-ring, and unsubstituted phenyl in the B-ring. Four of them (1-4) were monomeric flavonoids while the others (5-8) were dimeric flavonoids. The cytotoxicity of the isolated compounds against human promyelocytic leukemia HL-60 cells was investigated.

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“…These results are consistent with previous studies on 1,3-dipolar cycloaddition reaction of nitrone. [1][2][3][42][43][44][45][46][47][48][49][50] The formation and the ratio of two stereoisomers can be explained on the basis of both electronic and steric factors as follows. Aldonitrones such as 1a have been known to be stable in Z-configuration.…”

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confidence: 99%

“…Aldonitrones such as 1a have been known to be stable in Z-configuration. [1][2][3][42][43][44][45][46][47][48][49][50]52) Monosubstituted alkenes such as 2C-M have been known to have relatively high HOMO and to undergo exclusively a dipole-LUMO/dipolarophile-HOMO controlled reaction with the Z-aldonitrone (1a) (see Chart 7). [1][2][3] Though the reaction proceeds with high regioselectivity, the stereoselectivity of the reaction was poor one.…”

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confidence: 99%

The Effects of Lewis Acid on the 1,3-Dipolar Cycloaddition Reaction of C-Arylaldonitrones with Alkenes.

Shimizu

Ishizaki

Nitada

2002

CHEMICAL & PHARMACEUTICAL BULLETIN

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Absence of Lewis AcidThe reaction of N-benzyl-C-phenylnitrone (1a) with a variety of mono-and 1,1-disubstituted alkenes (2A-P) was carried out under various conditions and the results ware * To whom correspondence should be addressed. The regio-and stereoselectivity of the 1,3-dipolar cycloaddition reactions of C-aryl-N-alkylaldonitrones (1a-e) with some alkenes were found to be affected significantly by the addition of Lewis acid. The rate of the reaction was also affected by adding the Lewis acid. In the reactions using allyl alcohol as a dipolarophile an addition of Lewis acid caused a remarkable acceleration of the reaction and a great change in the stereoselectivity. In the reactions using ethyl acrylate as a dipolarophile the regioselectivity was reversed whether the reaction was performed in the presence or the absence of Lewis acid; i.e. isoxazolidine-5-carboxylates were obtained mainly in the absence of Lewis acid although isoxazolidine-4-carboxylates were obtained mainly in the presence of Lewis acid. When the reaction of C,N-diarylaldonitrones (1k, 1m, 1n) with ethyl acrylate was carried out in the presence of Lewis acid, the cleavage of the N-O bond of the cycloadducts giving g g-aminoalcohols was also observed besides a reverse phenomenon of regioselectivity.

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Cycloaddition of chiral nitrones. Asymmetric synthesis of isoxazolidines

Cited by 64 publications

References 5 publications

Diastereoselectivity in the Reaction of N‐Glycosyl‐nitrones: 1,3‐Dipolar Cycloaddition and Addition of Phosphite Anion

Diastereoselectivity in the Reaction of N‐Glycosyl‐nitrones: 1,3‐Dipolar Cycloaddition and Addition of Phosphite Anion

Chemical studies on the roots of Uvaria welwitschii

The Effects of Lewis Acid on the 1,3-Dipolar Cycloaddition Reaction of C-Arylaldonitrones with Alkenes.

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