1-tert-Butyl 4-methyl 5,6-dihydropyridine-1,4(2H)-dicarboxylate

for the following products 1,4(2H)-pyridinedicarboxylic acid, 3,6-dihydro-, 1-(1,1-dimethylethyl) 4-methyl ester and 1-tert-Butyl 4-methyl 5,6-dihydropyridine-1,4(2H)-dicarboxylate