Highly Efficient Stereoconservative Amidation and Deamidation of α-Amino Acids
作者:Deepak M. Shendage、Roland Fröhlich、Günter Haufe
DOI:10.1021/ol048771l
日期:2004.10.1
[reaction: see text] An overall stereoconservative protection and deprotection method of amino and carboxyl groups is presented. N-Phthaloyl N'-alkyl secondary amides of alpha-amino acids can be generated from corresponding N-phthaloyl amino acids by coupling reaction of N-alkylamines using mixed anhydride method. These secondary amides can be transformed by thermal rearrangement of intermediate nitrosoamides
The Vinylfluoro Group as an Acetonyl Cation Equivalent: Stereoselective Synthesis of 6-Substituted 4-Hydroxy Pipecolic Acid Derivatives
作者:Nirupam Purkayastha、Deepak M. Shendage、Roland Fröhlich、Günter Haufe
DOI:10.1021/jo901872a
日期:2010.1.1
An unprecedented cascade of reactions after acid-catalyzed hydrolysis of tert-butyl (2S,5S)-2-tert-butyl-5-(2-fluoroallyl)-3-methyl-4-oxoimidazolidine-1-carboxylate 3a leading to pipecolic acid derivative 5 is presented. The vinylfluoro group is shown to be all acetonyl cation equivalent under acidic conditions. Interestingly, vinylchloro and vinylbromo groups do not show Such transformation under the same conditions. The pipecolic acid derivative 5 produced in this way is further used to synthesize (2R,4R,6S)-6-tert-butyl-4-hydroxypiperidine2-carboxylic acid 9.