(5 S ,11a S )-5-Hydroperoxy-1,5,11,11a-tetrahydro[1]benzothieno[3,2- f ]indolizin-3(2 H )-one

The absolute configuration of the title compound, C14H13NO3S, was assigned from the synthesis and confirmed by the structure determination. The central six-membered ring of the indolizine moiety adopts an envelope conformation, with the greatest deviation from the mean plane of the ring being 0.661 (2) Å for the bridgehead C atom. The benzothiene ring attached to the indolizine ring system is planar to within 0.008 (2) Å. In the crystal, molecules form chains parallel to the b axis via O—H...O hydrogen bonds.