A mixture of trans 3-amino-2,5-dihydroxy-1,2,3,4-tetrahydronaphthalene and trans 3-amino-2,8-dihydroxy-1,2,3,4-tetrahydronaphthalene (278 mg, prepared in the manner disclosed in GB 1442851) was dissolved at room temperature with stirring under argon in N,N-dimethylformamide (2 mL) along with 5-chloroindole-2-carboxylic acid (315 mg), 1-hydroxy-7-azabenzotriazole (230 mg), and 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride (330 mg). After 3 days the reaction mixture was purified without work-up by reverse phase preparative HPLC to provide the two isomers as off-white solids, trans 3-(5-chloroindole-2-carbonylamino)-2,5-dihydroxy-1,2,3,4-tetrahydronaphthalene, Example 2 (eluted first, 130 mg) and trans 3-(5-chloroindole-2-carbonylamino)-2,8-dihydroxy-1,2,3,4-tetrahydronaphthalene, Example 3 (eluted second, 104 mg). HPLC/MS for both isomers [M+H]+, 357; [M−H]−, 355.
