4-(5-ethyl-2-thienyl)-4-oxobutyric acid3-(5-ethyl-2-thenoyl)propanoic acid3-(5-ethyl-2-thenoyl)propionic acid4-(5-ethylthiophen-2-yl)-4-oxobutanoic acid4-(5-ethylthiophen-2-yl)-4-oxobutyric acid4-oxo-4-(5-ethylthien-2-yl)butanoic acid4-oxo-4-(5-ethylthien-2-yl)butyric acid