Total Synthesis and Structural Revision of (±)-Mauritamide B

Mauritamide B (<b>1a</b>) is a taurine-connected cyclic guanidino-bromopyrrole alkaloid originally isolated from the marine sponge <i>Agelas linnaei</i>. To date, the total synthesis of taurine-connected guanidino-bromopyrrole alkaloids, including this compound, has not yet been reported. Herein, a total synthesis of (±)-mauritamide B (<b>1b</b>) was achieved by oxidation of 2-aminoimidazole of dihydro-sventrin (<b>10</b>) using activated carbon and air in the presence of taurine. The synthetic precursor of <b>10</b>, 4-(3-aminopropyl)-2-aminoimidazole (<b>22</b>), was synthesized via our original route. The NMR data of the obtained product agreed with that reported for mauritamide B (<b>1a</b>). However, a detailed analysis of the NMR data of synthetic (±)-mauritamide B (<b>1b</b>) including ¹H-¹⁵N HSQC spectrum revealed the need for a structural revision of the reported structure for mauritamide B (<b>1b</b>).