An efficient synthesis of new diastereomeric enantiopure 1-aminocyclopentane-1,2,4-tricarboxylic acids

Novel 1-aminocyclopentane-1,2,4-tricarboxylic acids I and II contg. the glutamic acid skeleton were prepd. as two diastereomers characterized by having the carbonyl groups in positions two and four cis to each other and trans with respect to the 1-carboxylic group and as all cis relationship, resp. The reaction sequences, i.e., Diels-Alder reaction to give norbornene cycloadducts, oxidative cleavage of the double bond of the cycloadducts, ensured the proper stereochem. of both diastereomers. Each diastereomer was prepd. in enantiopure form starting from exo- and endo-2-amino-norbornene-2-carboxylic acid derivs. III and IV (R1= 8-(-)-phenylmenthyl) obtained through a very efficient asym. synthesis