Synthesis of 1-Amino-2,2-dialkylcyclopropanecarboxylic Acids via Base-Induced Cyclization of .gamma.-Chloro-.alpha.-imino Esters
作者:Marc Boeykens、Norbert De Kimpe、Kourosch Abbaspour Tehrani
DOI:10.1021/jo00102a022
日期:1994.11
beta-Chloro ketones were oxidatively transformed into alpha-keto carboxylic esters and condensed with primary amines in the presence of titanium(IV) chloride. Base-induced cyclization of the resulting gamma-chloro-alpha-imino esters, incorporating suitable N-substituents, led directly to 1-amino-2,2-dialkyl- cyclopropanecarboxylic ester derivatives via a 1,5-dehydrochlorination process. Syntheses of different N- and/or carboxyl-protected geminally (gem) dialkylated cyclopropane amino acids were developed, while access to the free alpha-amino acids is also given. The methodology used was further extended by reduction of the gamma-chloro-alpha-imino esters to functionalized gamma-chloro-alpha-amino esters,prior to ring closure, affording N-alkyl-gem-dialkyl-1-aminocyclopropanecarboxylic acid derivatives.