[Asymmetric synthesis with unlimited stereoselectivity--the synthesis of isomer-free peptide derivatives by stereoselective four-component condensation (author's transl)].

: The development of methods for the synthesis of peptides by stereoselective four-component condensations led to new ways to prepare pure chiral chemical compounds with high yield by asymmetric syntheses. A scheme of asymmetric syntheses is described, which begins with a productively stereoselective synthesis affording a high yield of the desired product, accompanied by a minor amount of a diastereomeric byproduct. This is converted into an easily removable non-isomeric compound by a subsequent reaction with unlimited destructive stereoselectivity which is due to non-linear effects. In general, only small losses of the main product occur during the latter step. The efficiency of such asymmetric syntheses is enhanced by the use of chiral templates which can be recycled. As an illustration we describe the synthesis of a stereoisomer-free tetravaline derivative by a productively stereoselective four-component condensation, followed by conversion of the contaminating diastereoisomer into an easy to remove non-isomeric compound by destructively stereoselective partial acidolysis which yields the main product in 73% and with a purity of greater than 99.98%.