Asymmetric Synthesis of Crispine A: Constructing Tetrahydroisoquinoline Scaffolds Using Pummerer Cyclizations

For the first time, a concise, linear and stereoselective synthesis of both enantiomers of the natural product crispine A has been achieved in six steps with an overall yield of 20%, starting from commercially available veratraldehyde. Asymmetric Keck allylation and trifluoroacetic anhydride-mediated Pummerer cyclization were the key transformations used to construct the tetrahydroisoquinoline core structure.