Total Synthesis of (+)‐Azaspiracid‐1. Part I: Synthesis of the Fully Elaborated ABCD Aldehyde

Has aspirations: The total synthesis of (+)-azaspiracid-1 has been realized. The ABCD fragment was synthesized in 20 linear steps and 16 % overall yield through the enantioselective syntheses of the AB sulfone and the CD aldehyde, their coupling by a sulfone anion addition, and a thermodynamically controlled bis(spiroketalization) event. The E, FG, and HI ring fragments were synthesized enantioselectively and then coupled by using aldol methodology. Finally, a complex addition of the anion of the anomeric EFGHI sulfone to the ABCD aldehyde completed the synthesis in 26 linear steps and 2.7 % yield.