| abstract |
A pharmaceutically acceptable salt of a compound of formula C: **(See formula)** in which R2 is hydrogen or hydroxyl; R4 is unsubstituted alkyl; and R16 is hydroxyl, alkoxy, or halogen, where alkyl includes saturated aliphatic groups, including straight chain alkyl groups, branched chain alkyl groups, cycloalkyl groups, alkyl-substituted cycloalkyl groups, and cycloalkyl-substituted alkyl groups. |