Synthesis of Aristotelia-Type Alkaloids.. Part IV. Synthesis of (±)-aristoserratine

A convergent diastereoselective synthesis of racemic aristoserratine ((±)- 24 ) via an intramolecular iminium-ion cyclization is described. The pivotal imine (±)- 19 was prepared by condensation of the two building blocks (± )-trans-8-amino-3-(2,6-difluorobenzyloxy)-1-p-menthene ((±)- 11 ) and N-(p-methoxybenzenesulfonyl)-3-indo-leacetaldehyde ( 18 ) which were synthesized from (±)-trans-1-p-menthene-3,8-diol ((±)- 7 ) and 3-indoleacetic acid, respectively. On the route to the target (±)- 24 , two previously unknown indole alkaloids have been characterized, namely (±)-‘anti’-hobartin-15-ol ((±)- 22 ) and (±)-‘anti’-aristotelin-15-ol ((±)- 23 ).