A new semisynthetic pyrrolizidine alkaloid, 9-0-[(f)-2-hydroxy-2-phenylbutyryl] retronecine N- oxide (2a), was synthesized and found to be more active than indicine N-oxide (1) on which it was modeled. 9-0-[(5)-(+)-2-hydroxy-2-phenylbutyryl] retronecine (5) and its diastereomer, 9-0-[(R)-(-)-2-hydroxy-2-phenylbutyryl] retronecine (61, were prepared, and their detailed 'Hnmr spectra are presented. Conformational analyses of these molecules in solution are ...
