Preparation of 2-amino-1,6-anhydro-2-deoxy-β-D-mannopyranose by intramolecular substitution of the tosyloxy group in sterically hindered position of 1,6-anhydro-2-O-p-tolylsulfonyl-β-D-glucopyranose

1,6 : 3,4-Dianhydro-2-O-p-tolylsulfonyl-β-D-galactopyranose (I) was converted to 1,6-anhydro-4-O-benzyl-2-O-p-tolylsulfonyl-β-D-glucopyranose (II) and then reacted with benzylisocyanate to give 3-O-(N-benzylcarbamoyl) derivative III. The cyclization of this substance under the effect of potassium tert-butoxide in tert-butanol gave 3-benzyl-(1,6-anhydro-4-O-benzyl-2,3-dideoxy-β-D-mannopyrano) [2,3-d]oxazolidin-2-one (IV) which was hydrolysed to 1,6-anhydro-4-O-benzyl-2-benzylamino-2-deoxy-β-D-mannopyranose (VIII). Catalytic debenzylation of VIII on palladium on charcoal in the presence of hydrochloric acid gave the hydrochloride of 2-amino-1,6-anhydro-2-deoxy-β-D-mannopyranose (IX), which was acetylated to triacetate XI. Depending on the conditions during catalytic debenzylation of the oxazolidine derivative IV either O-debenzylated derivative VI alone was obtained, or the completely debenzylated oxazolidine derivative VII.