The invention discloses L-
leucine derivatives blocking the entrance of H5N1
avian influenza virus, which are 3,4-dyhydroxyl benzoyl
leucine methyl ester and 3,4-dyhydroxyl phenylacetyl
leucine methyl ester. The 3,4-dyhydroxyl benzoyl leucine methyl ester is prepared by condensing 3,4-dyhydroxyl
benzoic acid with L-leucine methyl ester; the 3,4-dyhydroxyl phenylacetyl leucine methyl ester is prepared by taking 3,4-dyhydroxyl
phenylacetic acid as a starting material, treating the 3,4-dyhydroxyl
phenylacetic acid by virtue of dimethyl sulphate and
thionyl chloride sequentially, then condensing the 3,4-dyhydroxyl
phenylacetic acid with L-leucine methyl ester, and then performing
demethylation reaction. The compounds, namely, the 3,4-dyhydroxyl benzoyl leucine methyl ester and the 3,4-dyhydroxyl phenylacetyl leucine methyl ester, disclosed by the invention, have a strong inhibitory activity on Influenza strain A / Vietnam / 1194 / 2004
avian influenza virus, and have a mechanism of acting on the entrance phase of H5N1
virus infected cells; and the compounds are a new inhibitor resisting the entrance of
avian influenza virus, and can be used as a
medicine for preventing or treating H5N1 avian influenza.