2-keto-4-methylthiobutyrate 2-keto-4-methylthiobutyric acid 2-ketomethiobutyrate 2-oxo-4-methylthiobutanoic acid 4-methylthio-2-ketobutanoate 4-methylthio-2-ketobutyrate 4-methylthio-2-oxobutanoate 4-methylthio-2-oxobutyrate CPD-479 KMTB alpha-keto-4-methylthiobutyrate alpha-keto-gamma-methylthiobutyrate alpha-keto-gamma-methylthiobutyric acid alpha-ketomethiobutyrate alpha-ketomethiobutyric acid