Asymmetric cyclization via tandem conjugate addition by using metal amide reagents. Importance of the folded orientation of two enoate moieties
作者:Naomi Shida、Tadao Uyehara、Yoshinori Yamamoto
DOI:10.1021/jo00045a003
日期:1992.9
Di-(-)-menthylnona-2,7-diene-1,9-dioate (1) is converted to (-)-menthyl 3(S)-(N-benzylamino)-2(S)-(-)-menthoxycarbonyl)-1(S)-cyclohexane-1-acetate (2) with high diastereoselectivity upon treatment with the amide cuprate or zincate reagent Bn(TMS)NML(n) in the presence of ZnCl2. The folded orientation of the two enoate moieties in 1 is essential for this high asymmetric cyclization via tandem conjugate addition.
Lobocyclamide B from <i>Lyngbya confervoides</i>. Configuration and Asymmetric Synthesis of β-Hydroxy-α-amino Acids by (−)-Sparteine-Mediated Aldol Addition
作者:John B. MacMillan、Tadeusz F. Molinski
DOI:10.1021/ol025876k
日期:2002.5.1
the first reported occurrence of gamma-hydroxythreonine in a natural peptide. Optically active beta-hydroxy-alpha-amino acids required for configurational analysis of the title compound were prepared using a novel (-)-sparteine-mediated asymmetric aldol addition of N-(diphenylmethylene)glycine tert-butyl ester to aldehydes. The method is general for aliphatic and aryl aldehydes and notable for operational