3.3.4. Others

A chemical investigation of the fermentation of *Penicillium* sp. GD6, associated with the Chinese mangrove *Bruguiera gymnorrhiza*, resulted in the isolation of an unusual pyrrolizidine alkaloid, penibruguieramine A (**133**) (Figure 36), characterized by an unprecedented 1-alkenyl-2-methyl-8-hydroxymethyl pyrrolizidin-3-one skeleton [115] (Scheme 27).

**Figure 36.** Structure of compound **133**.

**Scheme 27.** Proposed biosynthetic pathway for compound **133** [115].

Talaramide A (**134**) (Figure 37) is the second example of an alkaloid with a unique oxidized tricyclic system resembling a bird cage, which was obtained from the mangrove endophytic fungus *Talaromyces* sp [116]. The first example was rubrobramide, obtained from the fungus *Cladobotryum ubrobrunnes*cens [117]. **134** was a PKS-NRPS hybrid metabolite derived from acetyl acid, malonic acid, and *L*-leucine. A series of polymerizations, cyclizations, rearrangements, and redox reactions finally afforded the unique oxidized tricyclic skeleton of **134** (Scheme 28).

**Figure 37.** Structures of compound **134** and rubrobramide.

**Scheme 28.** Proposed biosynthetic pathway for compound **134** [116].
