Synthesis and biological evaluation of (-)-6-O-desmethylcryptopleurine and analogs

(-)-Cryptopleurine 1 is one of the most potent anti-proliferative member of the phenanthroquinolizidine class of alkaloids. We report here the synthesis of (-)-6-O-desmethylcryptopleurine (-)-2 and (-)-6-O-desmethyl-(15R)-hydroxycryptopleurine (-)-4 in their enantiomerically enriched form through a convergent synthetic route, where the chirality is introduced by the use of commercially available (R)-methyl piperidine-2-carboxylate hydrochloride 17. Anti-proliferative activities of these compounds were evaluated on a panel of four cancer cell lines, revealing that compounds (-)-2 and (-)-4 are potent cytotoxic compared to cryptopleurine.