Unambiguous structural and nuclear magnetic resonance spectral characterization of two triterpenoids of Maprouneaguianensis by two-dimensional nuclear magnetic resonance spectroscopy

It is shown that 1H–13C shift-correlated two-dimensional spectra obtained for polarization transfer via two-bond and three-bond 13C–1H coupling can, in conjunction with related experiments, be used to assign unambiguously the molecular skeletons of two of the less common triterpenes, moretenone and 3-acetylaleuritolic acid. It is concluded that this is a technique of considerable generality for assigning structures of triterpenes and is more reliable than alternative approaches such as mass spectral fragmentation patterns. It has the additional benefit of simultaneously providing reliable 13C and 1H spectral assignments for these compounds.