Access to tetrachlorophthalimide-protected ethyl 2-amino-2-deoxy-1-thio-beta-D-glucopyranosides

Ethyl 2-deoxy-2-tetrachlorophthalimido-1-thio-beta-D-glucopyranoside (7) wa s prepared from glucosamine hydrochloride in four steps with a 20-25% overa ll yield. Formation of 1,3,4,6-tetra-O-acetyl-2-deoxy-2-tetrachlorophthalim ido-beta-D-glucopyranoside (5) was found to be crucial for this reaction se quence since the corresponding alpha-1-acetate did not react in Lewis-acid- catalyzed ethylthio glycosidations. Formation of the beta-1-acetate (5) was achieved by treatment of 3,4,6-tri-O-acetyl-2-deoxy-2-tetrachlorophthalimi do-alpha-D-glucopyranosol bromide(4) with acetic acid under silver zeolite promotion. This was necessary because conditions normally used for p-l-acet ate formation were not tolerated by the tetrachlorophthalimido (TCP) group. (C) 1998 Elsevier Science Ltd. All rights reserved.