Synthesis of Naphthoquinone‐ and Pyrrolo[2,1‐a]isoquinoline‐Fused Heterocycles and Tridemethoxy Lamellarin D

Synthesis of two lamellarin derivatives, that is, naphthoquinone‐fused pyrrolo[2,1‐a]isoquinoline and tridemethoxy lamellarin D was reported. The former was synthesized by Lewis acid‐catalyzed oxidative cyclization of 6,7‐dimethoxynaphthalene‐1,4‐dione and papaverine to form the pentacyclic scaffold. The latter was prepared via base‐mediated Grob coupling of 1‐methylisoquinoline and 7‐methoxy‐3‐nitrocoumarin as a key step to construct the lamellarin skeleton. A naphthoquinone‐fused pyrrolo[2,1‐a]isoquinoline derivative was prepared by Lewis acid‐catalyzed oxidative cyclization of 6,7‐dimethoxynaphthalene‐1,4‐dione and papaverine to form the pentacyclic scaffold, whereas tridemethoxy lamellarin D was synthesized via base‐mediated Grob coupling of 1‐methylisoquinoline and 7‐methoxy‐3‐nitrocoumarin as a key step to construct the lamellarin skeleton.