Synthesis of the retro-inverso peptide analogues of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP)

Two novel retro-inverso analogues of a conformationally restricted carbocyc lic muramyl dipeptide (MDP) derivative N-(2-methyl-3-oxo-3,4-dihydro-2H-1,4 -benzoxazine-2-carbonyl)-L-alanyl-D-isoglutamine were prepared and tested i n a immunorestoration test in mice. Both retro-inverso MDP analogues did no t enhance non-specific resistance to experimental fungal infection in immun osuppressed animals, suggesting that the intact amide bond is essential for the immunorestorating activity in this type of rigidified carbocyclic MDP analogues.