Stereoselective synthesis of tricyclic guanidine systems: confirmation of the stereochemistry of batzelladine F left-hand tricyclic guanidine portion

The stereoselective synthetic methods for anti- and syn-fused tricyclic guanidine compounds 4a and 4b were developed based on a successive 1,3-dipolar cycloaddition. Through these synthetic studies, the stereochemistry of the left-hand tricyclic guanidine unit of batzelladine F (3) was confirmed as a syn-fused one, which is identical with the structure reported by the Murphy and Snider groups.