(3S,4R,4aS,7aR,12bS)-3-Cyclo-propyl-meth-yl-4a,9-dihy-droxy-3-methyl-7-oxo-2,3,4,4a,5,6,7,7a-octa-hydro-1H-4,12-methano-1-benzofuro[3,2-e]isoquinolin-3-ium 2,2,2-trifluoro-acetate methanol solvate.

In the title compound, C(21)H(26)F(3)NO(6) (+)·CF(3)COO(-)·CH(3)OH or S-MNTX·CF(3)COO(-)·CH(3)OH (MNTX = methyl-naltrexone), the conformation of the polycyclic backbone of the noroxy-morphone skeleton can be simplified in terms of the angles between the least-squares planes of these rings. The dihedral angle between the cyclohexene and piperidine rings is 84.5 (6)°, while the dihedral angles between the planes of cyclohexane ring and the benzene, cyclohexene and piperidine rings, respectively, are 85.8 (6),80.0  (7) and 10.3 (7)°. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds. The trifluoro-acetate F atoms are disordered in a 0.710 (14):0.710 (14) ratio. The absolute stereochemistry was inferred from the use of (4R,4aS,7aR,12bS)-3-(cyclo-propyl-meth-yl)-4a,9-dihy-droxy-2,3,4,4a,5,6-hexa-hydro-1H-4,12-meth-ano-benzofuro[3,2-e]isoquinolin-7(7aH)-one as one of the starting materials.