Ester-Enolate Claisen Rearrangement of α-Amino Acid Derivatives

Article abstract of DOI:10.1021/jo00141a024

With the standard procedure for the Ireland-Claisen rearrangement, using 2 equiv of base, allylic esters of N-acyl α-amino acids are converted to the rearranged γ,δ-unsaturated α-amino acids in moderate to good yield and diastereoselectivity.Moderate variation, but not reversal, of stereoselectivity is seen on using different solvents or conditions.Variation in the substituents on the amino group, α-position, and allylic alcohol moiety was also studied.For each case in which the stereochemistry of the rearranged product was proven, it was consistent with predominant formation of the E enolate (enolate oxygen and anionic acylamido substituent cis).The rearrangement was also apllied successfully to the synthesis of highly hindered amino acids and to cyclo-alkenyl-substituted analogues.In a number of instances, comparison was made with an alternative rearrangement procedure involving an oxazole intermediate.