The application of vinylogous iminium salt derivatives to an efficient synthesis of the pyrrole containing alkaloids Rigidin and Rigidin E

Studies directed on the synthesis of the pyrrole containing marine natural products Rigidin and Rigidin E via vinylogous iminium salts are described. The successful strategy relies on the formation of a 2,4-disubstituted pyrrole from a vinamidinium salt followed by acylation at the 5-position of pyrrole. Halogenation and aminocarbonylation at the 3-position of pyrrole followed by hydrolysis of the ester group at C-2 and subsequent Curtius rearrangement generates the pyrrolopyrimidine skeleton. A final deprotection step completes the synthesis of Rigidin and Rigidin E.