Improved Preparation of β‐<scp>d</scp>‐ManNAc‐(1→4)‐<scp>d</scp>‐Glc and β‐<scp>d</scp>‐TalNAc‐(1→4)‐<scp>d</scp>‐Glc Disaccharides and Evaluation of Their Activating Properties on the Natural Killer Cells NKR‐P1 and CD69 Receptors
The synthetic access of either beta-D-ManNAc-(1-->4)-D-Glc (5) is beta-d-TalNAc-(1-->4)-D-Glc (6) disaccharides has been effectively improved with respect to previous syntheses (J. Carbohydr. Chem. 2000, 19, 79-91 and 2004, 23, 179-190), optimizing the preparation of suitably protected 4-O-(2-acetamido-2-deoxy-3,4-O-isopropylidene-beta-D-talopyranosyl)-2,3:5,6-di-O-isopropylidene-aldehydo-D-glucose dimethyl acetal derivatives obtained by complete stereoselective LiAlH4 reduction of new 2'-oximino precursors derived from lactose. The affinity of the disaccharides 5 and 6 toward the natural killer cell NKR-P1 and CD69 receptors has been evaluated and discussed.
Stereoselective entry into the d-GalNAc series starting from the d-Gal one: a new access to N-acetyl-d-galactosamine and derivatives thereof
A new stereoselective preparation of N-aceyl-D-galactosamine (1b) starting from the known p-methoxyphenyl 3,4-O-isopropylidene-6-O-(1-methoxy-1-methylethyl)-beta-D-galactopyranoside (10) is described using a simple strategy based on (a) epimerization at C-2 of 10 via oxidation-reduction to give the talo derivative 11, (b) amination with configurational inversion at C-2 of 11 via a S(N)2-type reaction