Reactions of the Cyclic Tautomer of 3-Indoleacetamides. : Synthesis of N_b-Methyl-4,5,6-tribromo-3-indoleacetamide

概要

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The cyclic tautomer (5) of N_b-methyl-3-indoleacetamide (4) has been prepared by dissolving 4 in phosphoric acid. The bromination of 5 with 1 or 2 mol of N-bromosuccinimide (NBS) or 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TABCO) gave the 5-bromo- (8) and the 5,7-dibromo (9) derivatives. On the other hand, the 5-bromo derivative (11) was the major product of the bromination of the N-acetyl cyclic tautomer (6) even with 2 mol of NBS. The 5-nitro derivative (17) was obtained in excellent yield by the nitration of 6 with ammonium nitrate in trifluoroacetic anhydride (TFAA). Reduction of 17 followed by bromination gave the 4,6-dibromo derivative (19), which gave the tribromide (20) in the Sandmeyer reaction. The 4,5,6-tribromo-3-indoleacetamide (7), which is the indole moiety of a marine indole alkaloid, chartelline A, was obtained by the ring opening of 20. Furthermore, the oxidation of 5 with lead tetraacetate followed by acetylation gave the 5-acetoxy derivative (22). The selective hydrolysis and bromination of 22 gave the 4,6-dibromo-5-hydroxy derivative (24).
社団法人日本薬学会の論文
1990-10-25