5-Indolylidene-2-iminothiazolidin-4-ones - Convenient Starting Compounds for Stereoselective Synthesis of Novel Dispirooxindole Derivatives

A convenient method for the synthesis of novel dispirooxindoles containing 2-iminothiazolidin-4-one moiety has been proposed. The method relies on a 1,3-dipolar cycloaddition of azomethine ylides generated in situ from paraformaldehyde and N-alkyl amino acids including chiral ones to 5-indolylidene-2-iminothiazolidin-4-ones. The method is suitable for preparing enantiomerically pure derivatives.