Expedient synthesis of (+)-lycopalhine A

Two amino acids play a key role in the first total synthesis of lycopalhine A. l-glutamic acid serves as a convenient chiral starting material for the 13-step synthesis, and l-proline promotes an unusual 5-endo-trig Mannich cyclization that generates the central pyrrolidine ring of the Lycopodium alkaloid. The bicyclo[3.3.0]octanol moiety of the molecule is formed through an intramolecular aldol addition that may occur spontaneously in nature. Just Another Mannich Monday: By using l-glutamate and l-proline as a starting material and catalyst, respectively, the complex alkaloid lycopalhine A was assembled in only 13 steps. The synthesis features not only an unusual Mannich reaction but also a biomimetic aldol addition that completes the intricate carbon skeleton of the natural product.