Crystal structure of ethyl (-)-(1S,2R,5S,7S,8R,4'S,5'S)-2-methoxy-8-(2' ,2'- dimethyl-5'-phenyl-1',3'-dioxolane-4'-yl)-6-oxo-tricyclo[3.2.1.02.7]octane-1-carboxylate, C23H28O6