Depolymerization and De–N–Acetylation of Glycosaminoglycuronans by the Action of Alkali in the Presence of Sodium Borohydride

Publisher Website
Google Scholar
Abstract
Depolymerization of Ch–4–S, Ch–6–S, HA and HP was observed by gel filtration after treatment with 2–10 N NaOH or Ba(OH)2 in the presence of NaBH4 at 80–83° for 1–5 hr. Depolymerized products were isolated after these treatments. 4–Deoxy–α–L–threo–4–enohexopyranosyluronic acid residue as the nonreducing end group was demonstrated by the H–1 and H–4 proton signals in the NMR spectra and by the absorption at 225–230 nm. L–Gulonic acid, which was produced from D–glucuronic acid by the action of NaBH4, was detected as the reducing end group in the depolymerized products of Ch–6–S, but no hexosaminitol was detected. De–N–acetylation to the extent of 34–50% occurred after treatment with 2. 5 N NaOH in the presence of NaBH4, and almost complete de–N–acetylation accompanied by considerable destruction was observed with Ch–4–S and Ch–6–S after treatment with 5. 5–10. 0 N NaOH. A reaction mechanism is proposed for the depolymerization of glycosaminoglycuronans by the action of alkali.