Diastereoselective synthesis of 5-iminooxazolines and their subsequent transformation to α,α-disubstituted dipeptide esters: a formal [4+1] cycloaddition reaction of cyclohexyl isocyanide and Z-alkyl-α-benzoyl amino-acrylates
作者:Abbas Ali Esmaeili、Shima Shahmansouri、Azizollah Habibi、Ali Reza Fakhari
DOI:10.1016/j.tet.2012.06.073
日期:2012.9
A novel atom economical diastereoselective synthesis of 5-iminooxazolines and their subsequent transformation to α,α-disubstituted dipeptide esters is described. Heating a mixture of cyclohexyl isocyanide and Z-α-benzoyl amino-acrylic acid alkyl esters under solvent-free conditions, afforded 5-iminooxazolines, which, upon specifications provided α,α-disubstituted dipeptide esters in good yield.
A practical and efficient two reaction sequence one-pot process for the synthesis of Z-α-benzoylamino-acrylic acid methyl esters was developed. The process involves a potassium phosphate-catalyzed Erlenmeyerreaction of aromatic aldehydes with hippuric acid followed by an oxazolone ring-opening methanolysis. This process afforded a good overall yield and an excellent product quality via a simple workup