Total assignment of 1H and 13C spectra of kauradien-9(11),16-oic acid with the aid of heteronuclear correlated 2D spectra optimized for geminal and vicinal 13C–1H coupling constants: or what to do when "INADEQUATE" is impossible

It is shown that heteronuclear correlated spectra in which delay times are optimized for geminal and vicinal 13C–1H couplings rather than direct, 13C–1H couplings can be used to assign quaternary carbons in the 13C spectrum of kauradien-9(11),16-oic acid. These spectra in combination with normal heteronuclear correlated spectra plus homonuclear correlated spectra can be used to completely and unambiguously assign the 13C and 1H spectral peaks for the title compound. The main advantage of this approach over the use of 13C–13C connectivity ("INADEQUATE") experiments is sensitivity.