Total Synthesis of the Pyrrole Alkaloids Strychnuxinal and Strychnuxin

The first asymmetric total syntheses of the fused-pyrrole alkaloids strychnuxinal and strychnuxin have been achieved in 6 and 7 steps, respectively, starting from commercially available (+/-)-4-chlorostyrene oxide. Key steps in the synthetic route include a regioselective epoxide opening, a reductive etherification sequence to form the central 1,4-oxazine ring, and a late-stage phenol synthesis using a mild palladium-catalyzed coupling reaction. Notably, the optimized synthetic sequence presented avoids the use of traditional protecting groups. Total synthesis of these two structurally related natural products confirmed both their constitution (via NMR and X-ray crystallography) and their absolute configuration (via optical rotation).