| Abstract
| - 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 changesthat are observable by 13C NMR spectroscopy. The conformational properties of new [1,3,4]-oxadiazinan-2-one derivatives 2d−k are examined by X-ray crystallography and variable-temperature 13C NMR spectroscopy and further evaluated by semiempirical AM1 calculations. Thecollected data reveal that the conformational changes of the overall ring system are dependentupon the stereoelectronic factors of the N3-substituent.
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