Proline Derived Bicyclic Derivatives through Metal Catalysed Cyclisations of Allenes: Synthesis of Longamide B, Stylisine D and their Derivatives

Annulations of allene‐substituted proline derivatives promoted by transition metals have been investigated as a general way to access bicyclic structures with a bridgehead nitrogen. Two processes, Pd‐ and Ag‐catalysed cyclisations, have been employed complementary to control the substitution pattern of the product. The investigated methodologies afforded the bicyclic derivatives in comparable yields, while Ag‐catalysis showed higher level of diastereoselectivity. Both processes have been utilized in the synthesis of naturally occurring pyrroles longamide B, stylisine D and their derivatives. Annulations of allene‐substituted proline derivatives promoted by transition metals provide access to bromopyrrole alkaloids. Two processes, Pd‐ and Ag‐catalysed cyclizations, have been studied and used complementary to control the substitution pattern of the bicyclic products. The methodology has been applied in the synthesis of longamide B stylisine D and their derivatives