Stereoselective Syntheses of (+)‐Broussonetine D and (+)‐Australine via a Functionalized Pyrrolidine from an Extended Chiral 1,3‐Oxazine

The asymmetric syntheses of (+)‐broussonetine D and (+)‐australine have been achieved via a functionalized pyrrolidine obtained from an extended chiral 1,3‐oxazine. The key steps include pyrrolidine formation by oxazine cleavage and diastereoselective allylation to a pyrrolidine aldehyde. (+)‐Broussonetine D and (+)‐australine were synthesized from anti,syn,syn‐oxazine, in six steps, with an overall yield of 22.2 %, and in seven steps, with an overall yield of 33.2 %. The asymmetric syntheses of (+)‐broussonetine D (6 steps, 22.2 % yield) and (+)‐australine (7 steps, 33.2 % yield) have been performed via a functionalized pyrrolidine from an anti,syn,syn‐oxazine using olefin cross metathesis and stereoselective allylation.