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

Mauritamide B (1a) is a taurine-connected cyclic guanidino-bromopyrrole alkaloid originally isolated from the marine sponge Agelas linnaei. 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 (1b) was achieved by oxidation of 2-aminoimidazole of dihydro-sventrin (10) using activated carbon and air in the presence of taurine. The synthetic precursor of 10, 4-(3-aminopropyl)-2-aminoimidazole (22), was synthesized via our original route. The NMR data of the obtained product agreed with that reported for mauritamide B (1a). However, a detailed analysis of the NMR data of synthetic (±)-mauritamide B (1b) including 1H–15N HSQC spectrum revealed the need for a structural revision of the reported structure for mauritamide B (1b).