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Conformational Studies of N3-Substituted [1,3,4]-Oxadiazinan-2-ones

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journal contribution
posted on 19.11.2002, 00:00 by David M. Casper, Jennifer R. Blackburn, Christopher D. Maroules, Tana Brady, Joel M. Esken, Gregory M. Ferrence, Jean M. Standard, Shawn R. Hitchcock
Pseudoephedrine-based [1,3,4]-oxadiazinan-2-ones acylated at the N3-position with either acetyl (2a), propionyl (2b), or phenylacetyl (2c) substituents are known to undergo conformational changes that are observable by 13C NMR spectroscopy. The conformational properties of new [1,3,4]-oxadiazinan-2-one derivatives 2dk are examined by X-ray crystallography and variable-temperature 13C NMR spectroscopy and further evaluated by semiempirical AM1 calculations. The collected data reveal that the conformational changes of the overall ring system are dependent upon the stereoelectronic factors of the N3-substituent.