Stereoselective Synthesis of Aza Analogues of Isoaltholactone and Goniothalesdiol - New Applications of the Heck-Matsuda Reaction

The stereoselective synthesis of nitrogen analogues of biologically active isoaltholactone and goniothalesdiol are described. The successful strategy employed a Heck–Matsuda reaction between a chiral endocyclic enecarbamate bearing an ester functionality and arenediazonium tetrafluoroborates in a divergent approach at an early stage of the synthesis. Several aspects related to this critical arylation reaction are discussed to highlight structural features that affect the outcome of the arylation process. The synthesis of (–)‐aza‐isoaltholactone 6 was successfully accomplished in nine steps from the starting enecarbamate. We also performed the synthesis of the new fully substituted pyrrolidine (–)‐(2R,3R,4S,5S)‐1‐(tert‐butoxycarbonyl)‐3,4‐dihydroxy‐5‐phenylpyrrolidin‐2‐ylacrylic acid 28, which is a potential advanced intermediate in the route to aza‐altholactone. Moreover, the synthesis of a new nitrogen analogue of goniothalesdiol (+)‐33 was accomplished from the protected dihydroxypyrrolidine (–)‐27, obtained from an attempted synthesis of aza‐altholactone. The total synthesis of the nitrogen analogues of biologically active isoaltolactone and goniothalesdiol are described, which use a key Heck reaction of chiral endocyclic enecarbamates with arenediazonium tetrafluoroborates in a divergent approach.