Synthesis and biological activity of anomeric muramoyldipeptide butylglycosides

The synthesis of anomeric butyl glycosides of muramyl dipeptide was reported. alpha-Butyl glycoside of N-acetyl-D-glucosamine was 4,6-O-benzylidenated and the benzylidene derivative was 3-O-alkylated by the Williamson reaction with sodium (S)-2-chloropropionate. The resulting protected alpha-butyl glycoside of muramic acid was then condensed with L-Ala-D-iGln-OBzl by the DCC-HOSu method. Mild acidic hydrolysis and subsequent catalytic hydrogenolysis of the resulting glycopeptide yielded the target alpha-butyl glycoside of N-acetyl-L-alanyl-D-isoglutamine. In the synthesis of beta-butyl glycoside of N-acetylmuramyl-L-alanyl-D-isoglutamine, 2-acetamido- 4,6-di-O-acetyl-2-deoxy-3-O-[(R)-1-(methoxycarbonyl)ethyl]-alpha- D-glucopyranose, a 1-OH derivative of muramic acid, was the key compound. Its interaction with the excess thionyl chloride resulted in the corresponding glycosyl halide, which was condensed with n-butanol according to Helferich. O-Deacetylation, 4,6-isopropylidenation, and subsequent alkaline hydrolysis of the resulting compound gave the protected beta-butyl glycoside of muramic acid. Its activation and condensation with L-Ala-D-iGln-OBzl and the subsequent removal of protective groups were performed in the same manner as the reactions in the synthesis of alpha-butyl glycoside of N-acetyl-L-alanyl-D-isoglutamine. The adjuvant activity of the butyl glycosides to HIV proteins rgp160 and rgp120 and their ability to affect in vitro HIV replication and the proliferation of mouse spleen T-cells were examined. The biological activity of anomeric muramyl dipeptides was shown to depend essentially on the configuration of their anomeric center.