Streptocarbazoles A and B, Two Novel Indolocarbazoles from the Marine-Derived Actinomycete Strain <i>Streptomyces</i> sp. FMA

Streptocarbazoles A (<b>1</b>) and B (<b>2</b>), two novel indolocarbazoles featuring unprecedented cyclic <i>N</i>-glycosidic linkages between 1,3-carbon atoms of the glycosyl moiety and two indole nitrogen atoms of the indolocarbazole core, were isolated from the marine-derived actinomycetes strain <i>Streptomyces</i> sp. FMA. Their structures were established by spectroscopic methods, CD spectra, and ECD quantum mechanical calculations. Compound <b>1</b> was cytotoxic on HL-60 and A-549 cell lines and could arrest the cell cycle of Hela cells at the G₂/M phase