Stereoselective Reduction of Enantiopure β-Enamino Esters by Hydride: A Convenient Synthesis of Both Enantiopure β-Amino Esters
摘要:
The reduction of enantiopure beta-enamino esters 1 with sodium triacetoxyborohydride in acetic acid is described. This occurs with good diastereo- and enantioselectivity to yield beta-amino esters 2 and 3 (after hydrogenolysis of the N-chiral group). A model is reported for the origin of the stereoselectivity through an enol ester-diacetoxyborohydride 6, which affords the intramolecular reduction. By choosing the appropriate chiral amine, this procedure allows a straightforward preparation of both the enantiopure beta-amino esters and derivatives with known biological activity, using readily available starting materials and inexpensive reagents and conditions.