Compounds of the formula
where n is an integer from 1 to 12, R and R₁ are the same or different and are hydrogen or C₁ to C₆ linear or branched alkyl as well as their physiologically active salts and amides thereof and the enantiomers, mixtures and racemates are disclosed. Intermediates useful in preparing the above compounds are also disclosed as are processes for preparing these compounds.