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• W2143136608 abstract "Stereochemistry of Ring Opening of Aziridinones (α-Lactams) The chiral, non-racemic aziridinone (R)-4 (e.e. 92%) reacts with magnesium halides to afford the α-halo amides (S)-3a (e.e. 88.8%), (S)-3b (e.e. 89.0%), and (S)-3c (e.e. 88.2%) in high yields. Acid-catalysed hydrolysis of (R)-4 in aqueous acetone yields 74% of the α-hydroxy amide (S)-3d (e.e. 88.0%). Methanolysis of (R)-4 in [D4]methanol at 60°C followed the first-order rate law with k = 1.53 ṁ 10–5 s–1 yielding quantitatively a 82:18 mixture of the α-methoxy amide (S)-3e (e.e. 89%) and the α-amino ester (R)-14 (e.e. 87%). The latter is obtained exclusively (e.e. 87%) when (R)-4 reacts with sodium methoxide and methanol in ether while only the former is formed (e.e. 88.2%) by slow methanolysis in the presence of a catalytic amount of 4-toluenesulfonic acid. The absolute configurations of the major enantiomers derived from (R)-4 are based on the retention on a Chirasil-L-Val capillary gas chromatography column, CD spectra, and the comparison with authentic samples of (S)-3a, obtained from (S)-tert-leucine [(S)-1] and (S)-3d. The results demonstrate that the N – C(3) bond of the aziridinone (R)-4 is cleaved by nucleophiles with a high degree of stereospecificity and inversion of configuration. This stereochemical course is at variance with that inferred from the methanolysis of the similar aziridinone (R)-7. – Treatment of (R)-4 in [D4]methanol with one equivalent of 3-chloroperbenzoic acid (15) containing 5% of 3-chlorobenzoic acid (16) affords carbon monoxide and the racemic oxaziridine 18 in quantitative yield, which is also obtained from the imine 19 in a very fast reaction. The acid 16 effects slow decomposition of (R,S)-4 into carbon monoxide and imine 19, probably by general acid catalysis. The stereochemical result obtained from (R)-4 as well as the reaction conditions and differences in rate for formation and epoxidation of 19 suggest that in the peracid oxidation of an aziridinone the sequence of events consists of a rate-limiting, acid-catalysed decomposition into carbon monoxide and an imine, followed by very fast epoxidation of the latter. The previous mechanism, invoking as intermediates alleged aziridinone N-oxides, e.g. 17, is not supported by the present study." @default.
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• W2143136608 date "1991-09-01" @default.
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• W2143136608 title "Stereochemie der Ringöffnung von Aziridinonen (α-Lactamen)" @default.
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• W2143136608 doi "https://doi.org/10.1002/cber.19911240937" @default.
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