A remarkably diverse array of biologically active alkaloids, for example, blockers of neuromuscular-type, ganglionic-type, and nicotinic receptor channels, occurs in amphibian skin, and over 500 alkaloids have been isolated to date. The structural diversity and pharmacological activity associated with these alkaloids have stimulated research in numerous synthetic groups. Among them, we achieved the first synthesis of the alkaloids 223A has been accomplished, the proposed structure has been revised, and the relative stereostructure of natural 223A was determined. We have demonstrated the first enantioselective total synthesis of the antipode of structurally unique alkaloid 205B, and the absolute stereochemistry of natural 205B has been determined to be 2aR, 5aR, 6S, 8S, 8aR. Furthermore, we achieved the chiral synthesis of quinolizidine 207I and its absolute stereochemistry was determined to be 1S, 4S, 10S by the GC-coinjection analysis of racemic compound and natural product. Finally, we also achieved the synthesis of both stereoisomers for the alkaloid 223I, and the determination of the ralative stereochemistry of natural 223I using GC-coinjection analysis of these isomers and natural product is now under investigations.
