The invention relates to derivative compounds of partially-reduced isoquinoline with substitution of a sec-butyl group at position 3 with calpain inhibitor activity. The inventive compound comprises an ester or amide derived from (3-sec-butyl-1-oxo-2,3-dihydro-1H-isoquinolin-4-yliden)-acetic acid and (3-sec-butyl-1-thioxo-2, 3-dihydro-1H-isoquinolin-4-yliden)-acetic acid. Compounds having formula I or II can be used in the preventive or therapeutic treatment of a degenerative disease.