Novel regio- and stereoselective O-6-desulfation of the glucosamine moiety of heparin with N-methylpyrrolidinone–water or N,N-dimethylformamide–water mixtures11Abbreviations: I, α-l-idopyranosyluronic acid residue; A, 2-deoxy-2-sulfamido-α-d-glucopyranosyl residue. [A-6(OS)] refers to the 6-O-sulfo group of the 2-amino-2-deoxy-α-d-glucopyranosyl moiety, and [I-2(OS)] refers to the 2-O-sulfo group of the α-l-idopyranosyl-uronic acid moiety.