Structure Characterization, Biomimetic Total Synthesis, and Optical Purity of Two New Pyrrolidine Alkaloids, Pandamarilactonine-A and -B, Isolated from Pandanus amaryllifolius Roxb

Two new alkaloids, both possessing a pyrrolidinyl α,β-unsaturated γ-lactone residue and a γ-alkylidene α,β-unsaturated γ-lactone residue, were isolated from a tropical medicinal plant, Pandanus amaryllifolius Roxb. Their structures were deduced by spectroscopic analysis including the new NMR technique PFG J-HMBC 2D spectroscopy and then confirmed by biomimetic total synthesis. It was found that one diastereoisomer, pandamarilactonine-A (1), comprised a mixture enriched with (+)-enantiomer, while another diastereomeric isomer, pandamarilactonine-B (2), occurred as a racemate.