Synthesis of Tricycles Based on 1,6-Anhydro-β-D-hexopyranoses Fused with Morpholine. 3,10,12-Trioxa-6-azatricyclo[7.2.1.02,7]dodecanes

The key step of the synthetic route was opening of the oxirane ring in 1,6:3,4-dianhydro-2-O-tosyl-β-D-galactopyranose (1) with 2-chloroethanol to give 1,6-anhydro-4-O-(2-chloroethyl)-2-O-tosyl-β-D-glucopyranose (2), which was converted in four steps into 4-O-(2-aminoethyl)-1,6:2,3-dianhydro-β-D-mannopyranose (6). The latter compound underwent intramolecular cyclisation to afford the fused morpholine derivative 3-amino-1,6-anhydro-3-deoxy-3-N,4-O-ethylene-β-D-altropyranose (7) which gave the corresponding quaternary ammonium salt 11 by N-methylation. Acid cleavage of the 1,6-anhydro bond in 7 gave 3-acetamido-3-deoxy-3-N,4-O-ethylene-D-altropyranose (9).