New antiinfective and human 5-HT2 receptor binding natural and semisynthetic compounds from the Jamaican sponge Smenospongia aurea

In addition to the sesquiterpene-phenol aureols (1), 6′-chloroaureol (2), and aureol acetate (3), eight indole alkaloids including the new N-3′-ethylaplysinopsin (9) have been isolated from the Jamaican sponge Smenospongia aurea. Makaluvamine O (10), a new member of the pyrroloiminoquinone class, was also isolated. The structures were characterized by spectroscopic methods, and two new derivatives of aureol were prepared to optimize the biological activity. Aureol N,N-dimethyl thiocarbamate (1a) and 6-bromoaplysinopsin (7) exhibit significant antimalarial and antimycobacterial activity in vitro. Compound 6 showed activity against the Plasmodium enzyme plasmepsin II. The 6-bromo-2′-de-N-methylaplysinopsin (6), 6-bromoaplysinopsin (7), and N-3′-ethylaplysinopsin (9) displaced high-affinity [³H] antagonist ligands from cloned human serotonin 5-HT₂ receptor subtypes, whereas the other compounds tested did not. Remarkably, the 6-bromo-2′-de-N-methylaplysinopsin (6) showed a >40-fold selectivity for the 5-HT_2C subtype over the 5-HT_2A subtype.