NOVELTY - Synthesis of antiinfluenza virus medicine includes reacting ethyl acetoacetate and cyclopropylamine; reacting ethyl 3-(cyclopropylamino)-2-butenoate with 1,4-benzoquinone in potassium hydroxide; reacting 1-cyclopropyl-2-methyl-5-acetoxy-1H-indole-3-carboxylic acid ethyl ester with bromine; reacting 1-cyclopropyl-2-(bromomethyl)-5-acetoxy-6-bromo-1H-indole-3-carboxylic acid ethyl ester with thiophenol in potassium hydroxide; and reacting 1-cyclopropyl-2-(bromomethyl)-5-acetoxy-6-bromo-1H-indole-3-carboxylic acid ethyl ester with amine compound in potassium carbonate.    USE - Method for synthesizing antiinfluenza virus medicine.    ADVANTAGE - The method is simple. The product has high effect, small toxic effect, and small side effect.    DETAILED DESCRIPTION - Synthesis of antiinfluenza virus medicine comprises:    (A) reacting ethyl acetoacetate and cyclopropylamine to obtain ethyl 3-(cyclopropylamino)-2-butenoate;    (B) reacting obtained product with 1,4-benzoquinone in potassium hydroxide to obtain 1-cyclopropyl-2-methyl-5-hydroxy-1H-indole-3-carboxylic acid ethyl ester;    (C) reacting obtained product with acetyl chloride to obtain 1-cyclopropyl-2-methyl-5-acetoxy-1H-indole-3-carboxylic acid ethyl ester;    (D) reacting obtained product with bromine to obtain 1-cyclopropyl-2-(bromomethyl)-5-acetoxy-6-bromo-1H-indole-3-carboxylic acid ethyl ester;    (E) reacting obtained product with thiophenol compound in potassium hydroxide to obtain 1-cyclopropyl-2-(thiomethyl-substitutedphenyl)-5-hydroxy-6-bromo-1H-indole-3-carboxylic acid ethyl ester of formula (I);    (F) reacting compound (I) with dimethylamine in formaldehyde to obtain 1-cyclopropyl-2-(thiomethyl-substitutedphenyl)-4-(dimethylaminomethyl)-5-hydroxy-6-bromo-1H-indole-3-carboxylic acid ethyl ester of formula (II);    (G) reacting 1-cyclopropyl-2-(bromomethyl)-5-acetoxy-6-bromo-1H-indole-3-carboxylic acid ethyl ester with amine compound of formula HNR2R3 in potassium carbonate to obtain 1-cyclopropyl-2-(disubstituted-amino)-5-acetoxy-6-bromo-1H-indole-3-carboxylic acid ethyl ester of formula (III);    (H) reacting obtained product with potassium hydroxide to obtain 1-cyclopropyl-2-(disubstituted-amino)-5-hydroxy-6-bromo-1H-indole-3-carboxylic acid ethyl ester of formula (IV); and    (I) reacting obtained product with dimethylamine in formaldehyde to obtain 1-cyclopropyl-2-(disubstituted-amino)-4-(dimethylaminomethyl)-5-hydroxy-6-bromo-1H-indole-3-carboxylic acid ethyl ester of formula (V).    N.B: R1-R3 are not defined.