Enantioselective Michael Reactions of Chiral Secondary Enaminoesters with 2-Substituted Nitroethylenes. Syntheses of <i>trans,trans</i>-2,4-Disubstituted Pyrrolidine-3-carboxylates
作者:Gilbert Revial、Sethy Lim、Bernard Viossat、Pascale Lemoine、Alain Tomas、Arthur F. Duprat、Michel Pfau
DOI:10.1021/jo000206i
日期:2000.7.1
The Michael reaction of chiral 3-substituted secondary enaminoesters with 2-substituted nitroethylenes leads to (Z)-adducts, with good to excellent diastereoselectivity. The nitro group of these adducts was catalytically reduced to give, after cyclization and chiral amine elimination, pyrrolines or pyrrolidines after further reduction. In particular, the syntheses of ethyl (2R,3S,4S)-2,4-dimethylp
Stereoselective Reduction of Enantiopure β-Enamino Esters by Hydride: A Convenient Synthesis of Both Enantiopure β-Amino Esters
作者:Cristina Cimarelli、Gianni Palmieri
DOI:10.1021/jo960107y
日期:1996.1.1
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.