The nuclear magnetic resonance and mass spectra of derivatives of cycloserine

Abstract

On the basis of NMR spectral data, it is shown that acetylation of the 3-isoxazolidone ring of N-acetylcycloserine occurs on nitrogen whereas sulfonylation occurs on the carbonyl oxygen. The change in conformation (dihedral angles) resulting from introduction of a double bond into the heterocyclic ring is reflected in a consistent displacement of the parameters of the ABX system. Variation in the site of acylation is considered explicable in terms of kinetic vs. thermodynamic control. The mass spectra of various derivatives of cycloserine are shown to be compatible with the assigned structures. Some unusual modes of fragmentation of the 4-amino-3-isoxazolidone system are discussed.