The synthesis of optically active Hagemann's esters was investigated. The starting materials in this approach were enamino esters (R,Z)-8, prepared through the condensation of keto ester 6 with (R)-1-phenylethylamine 7. Michael addition reaction of the enamino esters (R,Z)-8 with methyl vinyl ketone gave the expected adducts 10 with good e.e.s of 93-96%. Subsequent annulation of the adducts furnished optically active Hagemann's esters. (C) 2001 Elsevier Science ltd. All rights reserved.
Barta, Nancy S.; Brode, Adam; Stille, John R., Journal of the American Chemical Society, 1994, vol. 116, # 14, p. 6201 - 6206
作者:Barta, Nancy S.、Brode, Adam、Stille, John R.
DOI:——
日期:——
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.
The synthesis of optically active Hagemann's esters was investigated. The starting materials in this approach were enamino esters (R,Z)-8, prepared through the condensation of keto ester 6 with (R)-1-phenylethylamine 7. Michael addition reaction of the enamino esters (R,Z)-8 with methyl vinyl ketone gave the expected adducts 10 with good e.e.s of 93-96%. Subsequent annulation of the adducts furnished optically active Hagemann's esters. (C) 2001 Elsevier Science ltd. All rights reserved.
An Enantioselective Total Synthesis of (+)- and (−)-Saudin. Determination of the Absolute Configuration
作者:Robert K. Boeckman,、Maria del Rosario Rico Ferreira、Lorna H. Mitchell、Pengcheng Shao
DOI:10.1021/ja017194i
日期:2002.1.1
A short efficient enantioselective synthesis of both (+)- and (-)-saudin, a naturally occurring hypoglycemic diterpene, is described. This synthesis establishes the absoluteconfiguration of natural (-)-saudin for the first time. The key steps include the enantioselective construction of a dimethyl Hagemann's ester by an asymmetric Michael reaction and establishment of the key 1,3 disposed quaternary