Crystal structure of naltrexone chloride solvates with ethanol, propan-2-ol, and 2-methyl­propan-2-ol

Naltrexone [systematic name: 17-(cyclo­propyl­meth­yl)-3,14-di­hydroxy-4,5α-epoxymorphinan-6-one] is an opioid receptor competitive antagonist that has been widely used to prevent relapse in opioid- and alcohol-dependent subjects. Its chloride salt forms non-isomorphic solvates with ethanol (C(20)H(24)NO(4) (+)·Cl(−)·C(2)H(5)OH) (I), propan-2-ol (C(20)H(24)NO(4) (+)·Cl(−)·C(3)H(7)OH) (II), and 2-methyl­propan-2-ol (C(20)H(24)NO(4) (+)·Cl(−)·C(4)H(9)OH) (III). The naltrexone cation can be described as a T-shape made out of two ring systems, a tetra­hydro-2H-naphtho­[1,8-bc]furan system and a deca­hydro­isoquinolinium subunit, that are nearly perpendicular to one another. The flexible cyclo­propyl­methyl group can adopt various different conformations in response to its surroundings: an increase of available space around cyclo­propyl­methyl group may allow it to adopt a more favorable conformation. In all these structures, the alcohol mol­ecules occupy infinite solvent-filled channels. All three compounds described are attractive crystalline forms for unambiguous identification of naltrexone chloride after isolation from a pharmaceutical form. Compound (III) was refined as a two-component twin.