Baculiferins A–O, O-sulfated pyrrole alkaloids with anti-HIV-1 activity, from the Chinese marine sponge Iotrochota baculifera

Fifteen new DOPA-derived pyrrole alkaloids, named baculiferins A–O (2–16), were isolated from the Chinese marine sponge Iotrochota baculifera, together with the known alkaloids purpurone (1) and ningalin A (17). Most of the new compounds contain one to three O-sulfate units. Their structures were determined by extensive spectroscopic analysis including 1H and 13C NMR (COSY, HMQC, HMBC) and ESIMS data. A possible pathway for the biosynthetic origin of the isolated alkaloids is proposed, in which DOPA is assumed to be a joint biogenetic precursor. Baculiferins C, E–H, and K–N (4, 6–9, 12–15) were found to be potent inhibitors against the HIV-1 IIIB virus in both, MT4 and MAGI cells. Additional bioassay revealed that baculiferins could dramatically bind to the HIV-1 target proteins Vif, APOBEC3G, and gp41, for which structure–activity relationships are discussed.