Regioselective, rhodium-catalyzed hydroformylation of olefinic pyrrolidine derivatives was utilized as a key step in the formal syntheses of the indolizidine alkaloids (+/-)-167B, 2, and (+/-)-209D, 3, and the ant venom pyrrolizidine alkaloid (3S,5R,8S)-3-heptyl-5-methylpyrrolizidine, 4.