Methods are disclosed for forming heptan-4-one, and, optionally, heptan-4-ol, from fermentable sugars. The sugars are fermented using a bacteria or yeast that predominantly forms butyric acid. The butyric acid is subjected to catalytic ketonization conditions to form heptan-4-one, with concomitant loss of water and carbon dioxide. The heptan-4-one can be subjected to catalytic hydrogenation to form heptan-4-ol, an either of these can be included in gasoline compositions. In one aspect, the fermentable sugars are derived from lignocellulosic materials such as wood products, switchgrass, or agricultural wastes, which are delignified to form lignin, cellulose and hemicellulose. The cellulose and hemicellulose can be depolymerized to form glycose and xylose, either or both of which can be fermented by the bacteria. Thus, the methods described herein can convert biomass to a fuel composition or fuel additive, which can be used in a conventional gasoline engine, unlike traditional fuels such as ethanol or biodiesel.