Structural revisions of some non-adjacent bis-tetrahydrofuran annonaceous acetogenins.

The relative stereochemistries of bullatalicin [1] and bullatalicinone [2] were partially reassigned based on COSY and relayed COSY spectra. The structures of annonins VIII [3], IV [4], and XVI [5] were revised and concluded as bullatalicin [1], bullatanocin [6], and squamostatin A [7], respectively