The crystal structure of 7α-[（R）-1-hydroxyl-1-methyl-3-（thien-2-yl）propyl]-6,14-endoethanotetrahydrothebaine （C29H37NO4S, Mr=495.66） has been determined by single-crystal X-ray diffraction analysis. The crystal belongs orthorhombic, space group P212121 with α=10.063（4）, b=12.571（5）, c=19.626（8）A°, V=2482.9（17）A°^3, Z=4, Dc=1.326 g/cm^3,μ=0.167 mm^-1, F（000）=1064, the final R=0.0537 and wR=0.0888. The C（7） substituent is l-hy-droxyl-1-methyl-3-（thienyl-2-）propyl group adopting R-configuration. The N-methyl group is located at the equatorial position as expected. The crystal structure shows the presence of intra- molecular hydrogen bonds, O（1）-H（1）…O（2）.
The reaction of 7α-acetyl-6,14-endoethano-6,7,8,14-tetrahydrothebaine with 2-（thien-2-yl）ethylmagnesium bromide was investigated. The tertiary alcohol derivative 7α-[R-l-hydroxyl-l-methyl-3-（thien-2-yl）propyl]）-6,14- endoethano-6,7,8,14-tetrahydrothebaine （3） and a by-product 4 were isolated. The structure of 4 was elucidated by X-ray analysis. The Grignard reaction shows high degree of stereoselectivity according with Cram rule. The crystal structure of 4 indicates that dihydrofuran ring was opened to form a phenolic hydroxyl group and a three-membered ring structure. It maintains the main rigid structure of morphine and contains a C（6）-C（14） enthano bridge. The 1-hydroxyl-1-methyl-3-（thien-2-yl）propyl group at C（7） position adopted S-configuration.
