The minimal active
principle, N-acetylmuramyl-L-alanyl-D-isoglutamine*
(MDP), of complete Freund's adjuvant was studied in dry dimethyl sulfoxide
solutions by 1H n.m.r. at 400 MHz. All resonances except those of
the non-anomeric CH protons of the sugar ring were
assigned. The α/β anomeric ratio was found to be
the same (2 : 1) as reported for the equilibrated aqueous solutions from which
the dimethyl sulfoxide solutions were prepared. The present findings indicate
that MDP adopts a substantially structured conformation in dimethyl sulfoxide
solutions.
Anomeric ratio and dihedral angles of α,β-iodo-methyl-D-ribofuranose