4-cyclohexene-1,3-dicarboxylic acid, 4-methyl-2-(2-methyl-1-propenyl)-6-oxo-, dimethyl ester, (1R,2S)- InChI=1/C15H20O5/c1-8(2)6-10-12(14(17)19-4)9(3)7-11(16)13(10)15(18)20-5/h6-7,10,12-13H,1-5H3/t10-,12?,13+/m0/s dimethyl rel-(1R,2S)-4-methyl-2-(2-methylprop-1-en-1-yl)-6-oxocyclohex-4-ene-1,3-dicarboxylate