Three novel bis(indole) alkaloids from a stony coral, Tubastraea sp.

Marine Bi-, Bis-, and Trisindole Alkaloids

“…123 Compounds 187 and 188 were isolated from a shallow-water Panamanian sponge (Boca del Toro) Smenospongia cerebriformis together with the two analogs dictazolines A and B (201 and 202) 124 (Figure 1.16). EI-MS analysis of 201 also yielded a prevalent peak corresponding to a retro DielsAlder aplysinopsin unit 124 similar to that observed by Mancini et al 122 Unlike the optically inactive other members of this series previously reported by Mancini et al 122 and Iwagawa et al, 120,121 both 201 and 202 were optically active. 124 Further investigation of the S. cerebriformis extract yielded three more dictazolines C-E (203-205) (Figure 1.16), along with two new cyclobutyl analogs dictazoles A and B (206 and 207) 125 (Figure 1.19).…”

“…hard coral collected from the Odomari area, Kagoshima prefecture 120 (Figure 1.16 by a tetrahydrocarbazole core structure, functionalized with two modified spiroimidazoles and a second indole moiety. 120 NOESY NMR experiments determined the orientation of the two spiro junctions and placed the indole almost perpendicular to the carbazole. 120 Takemura and coworkers 120 hypothesized that the biosynthesis of these compounds occurs via a Diels-Alder reaction between two aplysinopsin subunits (190) 120 (Figure 1.17).…”

“…120 NOESY NMR experiments determined the orientation of the two spiro junctions and placed the indole almost perpendicular to the carbazole. 120 Takemura and coworkers 120 hypothesized that the biosynthesis of these compounds occurs via a Diels-Alder reaction between two aplysinopsin subunits (190) 120 (Figure 1.17). Initially, Takemura and coworkers reported 187-189 as being optically active but in a later report retracted this finding, 121 citing a dysfunctional polarimeter and further suggesting the possibility that 187-189 may be either artifacts formed during isolation or a naturally occurring mixture of enantiomers in almost equal ratios.…”

Discovery of Novel, Potent and Selective Glycine Receptor Modulators from Southern Australian Sponges

“…From several marine taxa such as sponge [140][141][142][143] , scleractinian coral [144][145][146][147] , anemone 148 and mollusc 149 , dozen monomeric aplysinopsins have been reported featuring a diverse pattern of bromination and methylation as well as different levels of oxidation and geometry (E vs. Z) 146,149 . Monomeric aplysinopsins are known to exert a range of biological activities particularly as anticancer and antidepressant agents [150][151][152] , inspiring numerous total syntheses [153][154][155][156] .…”

“…More recently, the discovery of asymmetric and symmetric dimers has generated renewed interest in this structure class. Asymmetric dimers were originally thought to be derived from Diels Alder cycloaddition 146,147 of two monomers but the most recent discovery of symmetric aplysinopsins 157 prompted consideration of an alternate biosynthetic hypothesis, a cyclobutane rearrangement. In addition to their cryptic biogenetic origin and intriguing structures, almost nothing is known about biological activity of the dimeric aplysinopsins.…”