The 1,2,4-trisubstituted pyrrole (4), which is readily prepared from pyrrole itself, undergoes double- barrelled Heck cyclizations to give, inter alia, compounds (3) and (17) for which crystal structures have been determined. Product (3) constitutes the core associated with several key members, e.g. (1) and (2), of the lamellarin class of marine alkaloid.