[Haskell] deriving with newtypes

[Wolfgang Jeltsch]

Hello,

I'm trying to use GHC's deriving mechanism for newtypes in the following way:
    class C a b
    instance C [a] Char
    newtype T = T Char deriving C [a]
Unfortunately, this isn't possible. Is there a reason for this? Can I 
circumvent this restriction?

Wolfgang