SYNTHESIS OF SOME RACEMIC GAMMA-FLUORO-ALPHA-AMINO ACIDS

Versatile three-step procedures for syntheses of seven racemic gamma-f luoro-alpha-amino acids are described. Alkylation of tert-butyl N-(dip henylmethylene)glycinate with 1-bromo-2-fluoroalkanes gave N-protected aminoacid esters both in anhydrous medium using lithium-diisopropylam ide as base at low temperature or in a two phase system of 50% aqueous sodium hydroxide and methylene chloride with triethylbenzylammonium c hloride as the phase transfer catalyst at room temperature. Subsequent two-step deprotection with citric acid and hydrochloric acid gave the title compounds in 13-33% overall yields.