*4.2. Glycosylated Pyrroles*

In 2016, the known synthetic product jaspamycin (**473**) [355], which is used as a tool compound for the investigation of Parkinson's disease, was isolated from a marine sponge *Jaspis splendens* and was therefore reported for the first time as a naturally occurring metabolite (Figure 64) [356]. The full stereochemistry of the attached sugar was identical to that of the synthetic product.

**Figure 64.** Sugar-substituted marine pyrrole alkaloids **473**–**474**.

Another marine pyrrole alkaloid, neopetroside B (**474**), contains a rare *<sup>N</sup>*-glycosylpyridinium moiety and was isolated from a *Neopetrosia* sp. sponge in 2015 (Figure 64) [357]. The absolute configuration of compound **474** was determined by comparison with a similar congener from the same work, the sugar unit of which was cleaved off, followed by the synthesis of acetylated (+)-2-octyl glycosides. Comparison of these compounds with

authentic samples according to the procedure of Leontein then revealed the D-configuration of the sugar unit [357,358].

In 2016, two new pyrrole oligoglycosides, plancipyrrosides A (**475**) and B (**476**) were isolated from the Vietnamese starfish *Acanthaster planci* (Figure 65) [359]. The absolute configuration was determined by comparison with the previously confirmed absolute configurations of the hydrolyzed sugar moieties. Plancipyrroside B (**476**) exhibits a stronger inhibitory effect on lipopolysaccharide-induced nitric oxide production in RAW 264.7 cells (5.94 μM ± 0.34 μM) than plancipyrroside A (16.61 μM ± 1.85 μM) [359].

**Figure 65.** Oligosaccharide-substituted pyrroles **475** and **476** from a marine starfish *Acanthaster planci*.

The sugar-containing pyrrole alkaloids, phallusialides A–E (**477**–**481**) were discovered in a marine bacterium of the genus *Micromonospora* in 2019 (Figure 66) [360]. The relative and absolute configurations of compounds **477**–**481** were determined by ROESY correlations and ECD spectroscopy. While phallusialide A (**477**) and B (**478**) displayed moderate to weak antibacterial activity (MIC values between 32 μg/mL and 64 μg/mL), phallusialides C–E (**479**–**481**) failed to show any detectable activity in the same assay (MIC values > 256 μg/mL). The authors speculated that the lack of halogenation at the pyrrole core of compound **479** and the additional sugar moieties in compounds **480** and **481** were responsible for the inactivity [360].

**Figure 66.** A new group of phallusialides A–D (**477**–**481**) discovered from a marine bacterium.
