N-Acetylgalactosamine 4,6-bissulfate in rat urine. I. Isolation, identification and chemical synthesis

By starting with 4 1 of rat urine, it was possible to obtain a sulfate ester of hexosamine in crystalline form. A series of identification procedures including chemical analyses, enzymatic digestion, proton magnetic resonance spectroscopy and infrared spectroscopy showed that this substance is 2-acetamido-2-deoxy-D-galactose 4,6-bissulfate. The trivial name for this compound is N-acetylgalactosamine 4,6-bissulfate; Quantitation by isotopic techniques indicated the urine possessed an average concentration of 8 muM N-acetylgalactosamine 4,6-bissulfate. Further extension of these studies necessitated the chemical synthesis of N-acetylgalactosamine 4,6-bissulfate and related compounds to be used for references or as biological substrates. Direct sulfation of N-acetylgalactosamine was attempted first, and strong preference for attack on the primary hydroxyl group (position 6) was found for chlorosulfonic acid. Thus, the reaction with 2.2 molar equivalents of the sulfating agent gave N-acetylgalactosamine 6-sulfate and its derivatives bearing a second sulfate at either position 1 (minor) or position 3 (major). The lack of sulfation at position 4 could be attributed to steric effects of the sulfate group preferentially attached to position 6. Another experiment in which UDP-N-acetylgalactosamine 4-sulfate was used in place of the free sugar led to the formation of a bissulfated sugar-nucleotide which, on subsequent hydrolysis with mild acid, afforded N-acetylgalactosamine 4,6-bissulfate, the same compound as that obtained from rat urine.