Patent ID: 7030267

Claim:
A compound of the formula I wherein R 1 and R 2 are selected, independently, from hydrogen, (C 1 –C 10 )straight or branched alkyl, (C 1 –C 10 )straight or branched alkoxyalkyl, phenyl-(C 1 –C 3 )straight or branched alkyl and phenyl-(C 1 –C 3 )straight or branched alkoxyalkyl, wherein said phenyl moieties can optionally be substituted with one or two substituents selected, independently, from halo or (C 1 –C 3 )alkyl; or R 1 and R 2, together with the carbon to which they are attached, form a cyclopentyl, cyclohexyl or cycloheptyl ring which can optionally be substituted with one or two substituents selected, independently, from the group of substituents named in the definition of R 1 and R 2 above; and R 3 and R 4 are selected, independently, from hydrogen and methyl; with the proviso that at least one of R 1 , R 2 , R 3 and R 4 is other than hydrogen; or a pharmaceutically acceptable salt thereof.