TOTAL ASSIGNMENT OF THE PROTON AND CARBON NMR-SPECTRA OF THE ALKALOID QUINDOLINE - UTILIZATION OF HMQC-TOCSY TO INDIRECTLY ESTABLISH PROTONATED CARBON-PROTONATED CARBON CONNECTIVITIES

The reisolation of the indoloquinoline alkaloid quindoline (also known as norcryptolepine) from Cryptolepis sanguinolenta is reported. The structure was unequivocally confirmed by two-dimensional nmr methods; the proton and carbon spectra were assigned for the first time. Because of congestion in the proton spectrum HMQC-TOCSY was used as an alternative to the more familiar COSY experiment. In addition to establishing proton-proton connectivities, HMQC-TOCSY affords the added benefit of providing, in an indirect sense, connectivity information between protonated carbons.