An access to various sulfation patterns in dermatan sulfate: chemical syntheses of sulfoforms of trisaccharide methyl glycosides
2002
Barroca, N. | Jacquinet, J.C.
The syntheses are reported for the first time of alpha-L-IdopA2SO3-(1 to 3)-beta-D-GalpNAc4SO3-(1 to 4)-alpha-L-IdopA2SO3-(1 to OMe), its disulfated analogue alpha-L-IdopA2SO3-(1 to 3)-beta-D-GalpNAc-(1 to 4)-alpha-L-IdopA2SO3-(1 to OMe), and of (beta-D-GalpNAc4SO3-(1 to 4)-alpha-L-IdopA2SO3-(1 to 3)-(beta-D-GalpNAc4SO3-(1 to OMe), which represent structural fragments of dermatan sulfate, unavailable directly by chemical or enzymatic degradation of the glycosaminoglycan polymer. These molecules were readily obtained from a pair of key disaccharide intermediates, in which the relative difference of stability of the D-GalNAc 4-hydroxy protecting groups (acetate or pivalate) toward saponification conditions allowed access to various sulfoforms from a common precursor. For the preparation of these blocks, the 4-O-pivaloyl-D-galacto moiety was readily obtained through a one-pot stereospecific intramolecular nucleophilic displacement on an easily available 3-O-pivaloyl-D-gluco precursor, and the L-IdoA moiety through selective radical oxidation at C-6 of a L-ido 4,6-diol derivative with oxoammonium salts.
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