The Effect of Acid-addition on The ¹H-NMR Spectra of Some Alkaloids A Versatile Tool for Confirmation of Stereochemistry

Abstract

The specific line-broadening effects caused by the addition of a small amount of acid were noted for some 'H-NMR of stemotinine [1] and isostemotinine [2]. The molecular structure of [1] has recently been established by X-ray analysis, we could correlate the line-broadening effect with the stereochemistry of the spiro-lactone moieties of [1] and [2]. Since line-broadening was found to be induced by partial salt formation of the tertiary amino group, it may be widely observed with other alkaloids and may afford a versatile supplementary tool for the stereochemical study of alkaloids.