Short and Efficient Enantioselective Synthesis of cis and trans Pyrrolidine-2,5-dicarboxylic Acids

Article abstract of DOI:10.1016/S0040-4039(00)74065-2

N-BOC-ethyl pyroglutamate 1 undergoes nucleophilic ring opening with lithium methyl p-tolylsulfinyl anion delivering the p-tolylketosulfoxide 2.Treatment of 2 with TFA gave rise to a mixture of thioesters 3a,3b.The hydrolysis of 3b afforded the (2S,5S) pyrrolidine-2,5-dicarboxylic acid 5, a constituent of the red alga Schizymenia dubyi.Under Pummerer reaction conditions (TFAA/Pyr), 2 yielded the 5-oxo-L-pipecolic acid derivative 6. Key words: Pyroglutamate; Regioselective Reactions; lithium methyl p-tolylsulfinyl anion; 5-carboxy-L-proline; 5-oxo-L-pipecolic acid; Pummerer Reaction.