Studies directed towards the synthesis of stevastelins—a macrolactonization approach to stevastelin B

A synthetic approach towards the cyclic depsipeptide immunosuppressant stevastelin B, based on the stereoselective synthesis of its propionate-derived fatty acid segment 6 that was coupled with the tripeptide 7 leading to the advanced stage acyclic intermediate 5, is described. In spite of our best efforts, the crucial macrolactonization reaction was not successful.