Synthesis and properties of chiral N,N-maleoyl derivatives and Diels-Alder reactions with cyclopentadiene

Maleyl amino acid derivatives were prepared from maleic anhydride and cyclized by reaction with ZnCl2 and hexamethyldisilazane yielding maleoyl derivatives. These derivatives were used as dienophiles in cycloadditions with cyclopentadiene. The isolated norbornene derivatives resulted from an endo addition, and might be interpreted as analogues of thalidomide. For comparing the properties of compounds prepared by this route, some reference compounds were synthesized from endo-bicyclo2.2.1]hept-2-ene-5,6-dicarboxylic anhydride and amino acid derivatives. All compounds were characterized by spectroscopic methods, their stereochemistry is discussed, and results were compared with results from calculations.