The present invention is directed to a pure enantiomer of 1-(5-(4-chloro-3, 5-dimethoxyphenyl)furan-2-yl)-2-ethoxy-2-(4-(5-methyl-1,3,4-thiadiazol-2-yl)phenyl)ethanone, in particular, (S)-1-(5-(4-chloro-3,5-dimethoxyphenyl)furan-2-yl)-2-ethoxy-2-(4-(5-methyl-1,3,4-thiadiazol-2-yl)phenyl)ethanone. The present invention is also directed a crystal structure of (S)-1-(5-(4-chloro-3,5-dimethoxyphenyl)furan-2-yl)-2-ethoxy-2-(4-(5-methyl-1,3,4-thiadiazol-2-yl)phenyl)ethanone, a pharmaceutical composition of (S)-1-(5-(4-chloro-3,5-dimethoxyphenyl)furan-2-yl)-2-ethoxy-2-(4-(5-methyl-1,3,4-thiadiazol-2-yl)phenyl)ethanone, a method of inhibiting PDE10 with (S)-1-(5-(4-chloro-3,5-dimethoxyphenyl)furan-2-yl)-2-ethoxy-2-(4-(5-methyl-1,3,4-thiadiazol-2-yl)phenyl)ethanone, and a process and particular individual intermediates used in the production of (S)-1-(5-(4-chloro-3,5-dimethoxyphenyl)furan-2-yl)-2-ethoxy-2-(4-(5-methyl-1,3,4-thiadiazol-2-yl)phenyl)ethanone.