Lamellarin Structures: Fused Ring Systems and Substitutions

The majority of isolated lamellarins exhibit a fused 14-phenyl-6H-[1]benzopyrano[4 0 ,3 0 :4,5]pyrrolo[2,1-a] isoquinolin-6-one ring framework, which serves as a common scaffold and is referred to as type I lamellarins (Fig. 1). The aromatic A-, E-, and F-rings of type I lamellarins are heavily substituted with hydroxy and methoxy groups. The 5,6-bond on ring D may be saturated (type Ia) or unsaturated (type Ib). Some lamellarins have a simpler non-fused 3,4-diarylpyrrole-2-carboxylate structure and are classified as type II lamellarins. Certain fused lamellarins have been discovered as water-soluble sulfate esters.