1-Piperidinecarboxylic acid, 2-[2-[8-chloro-2,4-dihydro-3-methyl-4-oxo-2-(tetrahydro-2H-pyran-2-yl)- 5H-pyrazolo[4,3-c]quinolin-5-yl]ethyl]-, 1,1-dimethylethyl ester