A rhodium-catalyzed enantioselective insertion into the C-C bond of tert-cyclobutanols and subsequent proto-demetalation provides access to methyl substituted quaternary stereogenic centers in excellent yields and enantioselectivities. The reaction was used for a synthesis of (S)-4-ethyl-4-methyl-octane, the simplest saturated hydrocarbon with a quaternary stereogenic center.