Patent ID: 7291734

Claim:
A compound of formula wherein R 1 is unsubstituted (C 6-18 )aryl, or (C 6-18 )aryl substituted by aminocarbonyl, halogen or halo(C 1-6 )alkyl, R 2 ′ is (C 1-12 )alkoxycarbonyl (C 1-6 )alkylcarbonyl, (C 3-6 )cycloalkyl(C 1-6 )alkylcarbonyl or unsubstituted (C 6-18 )aryl, or (C 6-18 )aryl substituted by aminocarbonyl, halogen or halo(C 1-6 )alkyl, R 3 and R 5 together are (C 1-4 )alkylene, and R 4 is hydrogen.