Enamino Ester Reduction: A Short Enantioselective Route to Pyrrolizidine and Indolizidine Alkaloids. Synthesis of (+)-Laburnine, (+)-Tashiromine, and (−)-Isoretronecanol
over Pd/C gave rise to the higher diastereoselectivity and mainly afforded the unexpected anti addition product (e.d. 84%). The scope of these reductions has been extended to the synthesis of three pyrrolizidine or indolizidine alkaloids: (+)-tashiromine, (+)-laburnine, and (-)-isoretronecanol. Syntheses of these natural products, starting from chiral beta-enamino diesters, were achieved in a short and