Patent ID: 7547699

Claim:
A compound of formula wherein R 1 and R 2 form together with the carbon atoms C a and C b to which they are attached R 3 is hydrogen, alkyl or cycloalkyl; R 4 is hydrogen, alkyl, cycloalkyl, alkylcarbonyl or cycloalkylcarbonyl; R 5 is alkyl or cycloalkyl; R 6 and R 7 are independently selected from hydrogen, alkyl, cycloalkyl, hydroxyalkyl and alkoxyalkyl; R 8 and R 9 are independently selected from hydrogen, alkyl, cycloalkyl, hydroxyalkyl and alkoxyalkyl; R 10 and R 11 are independently selected from hydrogen and alkyl; and R 12 and R 13 are independently selected from hydrogen and alkyl; or pharmaceutically acceptable salts and esters thereof.