Synthesis and antiproliferative activity of conjugates of adenosine with muramyl dipeptide and nor-muramyl dipeptide derivatives.

We synthesized a series of MDP(D,D) and nor-MDP(D,D) derivatives conjugated with adenosine through a spacer as potential immunosuppressants. New conjugates 8a-k were evaluated on two leukemia cell lines (Jurkat and L1210) and PBMC from healthy donors. The conjugates 8a-k and MDP(D,D)/nor-MDP(D,D) derivatives 7e, f, i, j were active against L1210 cell line. Unconjugated nor-MDP(D,D) had better antiproliferative properties, but the conjugates 8b, f, g had the highest values of selectivity index. Both cell lines as well as PBMC were resistant to analogs 11a, b with the 6-aminohexanoic linker.