Synthesis of pyrrolizidine oximes 222 and 236: Novel alkaloids of a dendrobatid poison frog

Article abstract of DOI:10.1016/S0040-4020(01)80634-7

The structures of two novel spiropentanopyrrolizidine oxime alkaloids, namely 2',3',5',6',7',7a'-hexahydro-2,2-dimethylspiro[cyclopentane-1,1'-[1H]- pyrrolizine]-7'-oxime (1) and 2',3',5',6',7',7a'-hexahydro-2,2-dimethylspiro-[cyclopentane-1,1'-[1H] -pyrrolizine-7'-oxime-O-methyl ether (2) have been confirmed by synthesis. The route involved synthesis of nitropolyzonamine (4), a known millipede alkaloid, from 2,2-dimethylcyclopentanone in 6 steps. After conversion of 4 to the ketone 6, the oxime 1 and O-methyl oxime 2 were obtained. The relative stereochemistry of synthetic nitropolyzonamine was confirmed by x-ray crystallography.