A convergent approach to midpacamide and dispacamide pyrrole-imidazole marine alkaloids

A two-step synthesis of the N-acylated alpha -azido-omega -aminovalerate. a common intermediate for the synthesis of midpacamide and dispacamide, is d escribed. This intermediate undergoes cyclization through the corresponding alpha -ureido ester derivative to give the 3-methylhydantoin ring present in midpacamide, whereas the reaction with triphenylphosphine. tosyl isocyan ate and ammonia followed by cyclization of the resulting guanidine derivati ve provides the 2-aminoimidazole ring present in dispacamide. (C) 2001 Else vier Science Ltd. All rights reserved.