New muramyl dipeptide (MDP) mimics without the carbohydrate moiety as potential adjuvant candidates for a therapeutic hepatitis B vaccine (HBV).

A series of new muramyl dipeptide (MDP) mimics were designed and synthesized via a solid-phase synthetic route. Their adjuvant activities were evaluated ex vivo for investigation of the synergism of the S(28-39) peptide, which is an MHC class I binding epitope of recombinant hepatitis B surface antigen (HBsAg) for both humans and mice. Several compounds without the carbohydrate moiety exerted better adjuvanticity than the MDP-C that has been reported by our laboratory previously. A primary screening test revealed that compounds 6, 14 and 16 exhibited stronger adjuvanticity compared with other MDP mimics.