Formulation of vaccine adjuvant muramyldipeptides (MDP). 1. Characterization of amorphous and crystalline forms of a muramyldipeptide analogue.

A relatively nonhygroscopic crystalline form of the glycopeptide, N-acetylmuramyl-L-alpha-aminobutyryl-D-isoglutamine (I), containing approximately one molecule of water was prepared from amorphous material. The crystalline material, consisting of a mixture of the alpha and beta anomers, exhibited better physical and chemical stability than the lyophilized amorphous material. The alpha/beta-anomer ratios of I in both the crystalline and the amorphous state were approximately equal but different from that in solution.