合成路线1

Reaction of L-aspartic acid (I) with trifluoroacetic acid and trifluoroacetic anhydride afforded N-trifluoroacetyl-L-aspartic anhydride (II). Then, Friedel-Crafts acylation of 1,3-difluorobenzene (III) with this anhydride in the presence of AlCl3 gave ketone (IV). The reduction of the carbonyl group of (IV) was effected by catalytic hydrogenation in the presence of Pearlman's catalyst, and the resulting phenylbutyric acid (V) was converted to acid chloride on treatment with PCl5 in cold dichloromethane, and subsequently cyclized by addition of AlCl3 to yield tetralone (VI). Hydrogenolysis of (VI) in the presence of Pearlman's catalyst gave tetrahydronaphthalene (VII), and further hydrolysis of trifluoroacetamide with LiOH yielded (S)-5,7-difluoro-1,2,3,4-tetrahydronaphthalen-2-yl amine (VIII). Imidazole ring was then constructed by treatment of this amine with 1,3-dihydroxyacetone (IX) and potassium thiocyanate in acidic medium, and the hydroxyl group of the resulting X was substituted by a formamido group by either heating in formamide at 175 C or with ammonium formate. Finally, formamide (XI) was hydrolyzed in refluxing isopropanolic HCl.