Total synthesis of (+)-demethoxycardinalin 3.

The total synthesis of (+)-demethoxycardinalin 3 is described. The synthetic strategy features the synthesis of dimeric Fischer carbene and its use in a bidirectional Dötz benzannulation reaction to set the dimeric structure of the cardinalins. The oxa-Pictet-Spengler reaction was used to construct the pyran rings. The synthesis is completed in seven steps and an overall yield of 7%.