 Ethyl methacrylate

$\mathrm{C}{\mathrm{H}}_2=\mathrm{C}(\mathrm{Me})\mathrm{C}{\mathrm{O}}_2\mathrm{Et}$, an alpha-methyl-substituted acrylate. Conjugate addition installs a chain whose carbon next to the ester retains the methyl substituent.