SYNTHESIS OF α-AMINO ACIDS WITH β,γ-UNSATURATED SIDE CHAINS

Article abstract of DOI:10.1016/S0040-4020(01)86051-8

α-Amino acids with allenyl, vinyl and acetylenic side chains can be synthesized using non-enolate based strategies.The ester enolate-Claisen rearrangement applied to propargylic esters of N-protected α-amino acids is of limited utility since only poor yields of allenic product are obtained with the N-Boc glycine esters, the system which give the most reproducible results.However, α-allenyl-α-amino acids that are fully functionalized on the α-carbon are available through the agency of 4-allenyl-2-phenyloxazolones 4 ( obtained from propargyl esters of N-benzoyl protected amino acids via cyclization and Claisen rearrangement ) provided that Meerwein's reagent is used to facilitate hydrolysis of the benzamide function in 5.A variety of α-substituted glycinates, including those with α-vinyl and α-acetylenic functions, can be prepared using a two step sequence involving condensation of the cationic glycine synthon 22 with various organomagnesium reagents, followed by hydrolysis.