Synthesis of sulfur-35-labeled glycyrrhizic acid glycopeptide with methionine

To carry out pharmacokinetic investigations, we prepared sulfur-35-labeled protected glycyrrhizic acid glycopeptide with methionine by the reaction of pentaacetylglycyrrhizic trichloride with a small excess of [35S]-methionine methyl ester hydrochloride. Melting points were determined on a Boetius microscopic stage. The IR spectra were recorded with a UR-20 spectrograph in mineral oil. The UV spectra were measured with a Specord UV-vis spectrophotometer in ethanol. The specific rotation was determined with a Perkin-Elmer 141 M polarimeter in a 1-dm-long tube. The radioactivity of the 35S-labeled compounds was measured by a scintillation method with an Izokan-300 counter