Thionyl Chloride → HCID 86738944, compound

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Reaction Steps

The starting material for the preparation of the intermediates III-A and III-B is methyl 2,3,6-trideoxy-4-C-methyl-3-trifluoroacetamido-α-L-lyxo hexopyranoside (VII), a known compound described in British patent application No. 2034707. Treatment of this compound (VII) in anhydrous benzene with thionyl chloride, followed by aqueous sodium bicarbonate gives methyl 2,3,4,6-tetradeoxy-4-C-methylene-3-trifluoroacetamido-α-L-threohexopyranoside (VIII). Catalytic hydrogenation of compound VIII proceeds stereoselectively giving methyl 2,3,4,6-tetradeoxy-4-C-methyl-3-trifluoroacetamido-α-L-arabino-hexopyranoside (XI). Mild acid hydrolysis of compounds VIII and XI gives the corresponding hexopyranoses IX and XII which by treatment with trifluoroacetic anhydride are transformed into the corresponding 1-0-trifluoroacetates X and XIII. Treatment of these intermediates with dry hydrogen chloride in anhydrous diethyl ether leads to the 1-chloroderivatives III-A and III-B, respectively. The foregoing sequence of transformations is shown in the scheme below: ##STR3## For the preparation of the 1-chloroderivative III-C, the key intermediate XVI is obtained by either of two different routes. Oxidation of compound VIII with meta-chloroperbenzoic acid in 1,2-dichloroethane gives compound XVI, which may alternatively be obtained by treatment with diazomethane of methyl 2,3,6-trideoxy-3-trifluoroacetamido-α-L-threo-hexopyranosid-4-ulose (XV), a known compound described in U.S. Pat. No. 4,039,663, as shown below: ##STR4## Azidolysis of methyl 2,3,6-trideoxy-4-C-hydroxymethyl-4,4'-anhydro-3-trifluoroacetamido-α-L-lyxo-hexopyranoside (XVI) gives the azido compound XVII. Catalytic hydrogenation thereof, followed by N-trifluoroacetylation affords compound XVIII, which on mild acid hydrolysis gives XIX. Subsequent 0-trifluoroacetylation thereof, followed by treatment with dry hydrogen chloride in anhydrous diethyl ether gives the 1-chloroderivative III-C.

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