Compound 1 - benzyl - (4 - (5,6 - dimetoxi - 1 - indanona) - 2 - YL metilpiperidin, inhibitor of acetylcholinesterase.Agent for preventing and treating various kinds of senile dementia and process to produce 1 - benzyl - (4 - (5,6 - dimetoxi - 1 - indanona) - 2 - YL metilpiperidin the