SYNTHESIS OF MODIFIED PARTIAL STRUCTURES OF THE BACTERIAL-CELL WALL .2. RETARDED METABOLISM OF LIPOPEPTIDES BY INSERTION OF ALPHA-SUBSTITUTED ALPHA-AMINO-ACIDS

The synthesis of the lipopeptide 1, which exhibits both immunological activity (induction of the colony stimulating factor (CSF)) and stabil ity against metabolic degradation, has been described. A detailed inve stigation of the course of the ene reaction between the dipeptide 21 a nd butyl glyoxylate enabled us to use this type of pericyclic reaction for the establishment of the essential pentenoic acid side chain in 2 3. The required amino acid 15 was obtained by enzymatic hydrolysis of the corresponding rac-ester 19. The absolute configuration of 1 was as signed by oxidative cleavage of the double bond in 24 and 25 followed by comparison of the degradation products with authentic samples.