| Abstract
| - Various chiral pyrrolidine tetrasubstituted β-enamino esters were reduced catalytically or chemicallywith good to moderate diastereoselectivity owing to a chiral induction originated from (S)-α-methylbenzylamine. With endocyclic double bond compounds, the best result was obtained usingPtO2 as hydrogenation catalyst and led to a major syn addition product (e.d. 90%). In the case ofexocyclic double bond compounds, hydrogenation over Pd/C gave rise to the higher diastereoselectivity and mainly afforded the unexpected anti addition product (e.d. 84%). The scope of thesereductions has been extended to the synthesis of three pyrrolizidine or indolizidine alkaloids: (+)-tashiromine, (+)-laburnine, and (−)-isoretronecanol. Syntheses of these natural products, startingfrom chiral β-enamino diesters, were achieved in a short and convenient manner, leading toenantiopure compounds in good overall yields.
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