Patent ID: 7649012

Claim:
A compound of formula I: wherein: R 1 =H R 2 =—OH, —OR 5 , —OCH 2 C(O)R 5 , —OCH 2 C(O)NHR 5 , —OC(O)R 5 , —OC(O)OR 5 , —OC(O)NHNH—R 5 , or —OC(O)NR 5 R 6 , where R 5 and R 6 are each independently H, C 1 -C 20 alkyl, cycloalkyl, alkenyl, alkynyl, aryl, arylalkyl, or alkylaryl, and where R 5 and R 6 can each optionally contain halogen atoms; R 3 =H, C 1 -C 20 alkyl, cycloalkyl, alkenyl, aryl, arylalkyl, or alkylaryl; R 4 =C 1 -C 20 alkyl, cycloalkyl, alkenyl, aryl, arylalkyl, or alkylaryl; with the proviso that when R 2 is —OH, —OCH 3 , or —OC(O)CF 3 and R 3 is —CH 3 , then R 4 is not —CH 2 (C 6 H 5 ), or —CH═CH—CH 3 , and the further proviso that when R 3 is —CH 2 —(C 6 H 5 ), then R 4 is not —CH 3 or —CH 2 CH 3 .