Synthesis of the Marine Natural ProductNα-(4-Bromopyrrolyl-2-carbonyl)-l-homoarginine, a Putative BiogeneticPrecursor of the Pyrrole−Imidazole Alkaloids
Lysine is proposed as an alternative biosynthetic precursor of the pyrrole−imidazole alkaloids frequentlyfound in marine sponges. As a putative key intermediate, the natural product Nα-(4-bromopyrrolyl-2-carbonyl)-l-homoarginine (1) from the sponge Agelas wiedenmayeri was synthesized in the solid phasestarting from Fmoc/Pmc-protected l-homoarginine and in solution starting from readily available l-lysinemethyl ester.