Patent ID: 8546147

Claim:
A compound of formula I: wherein: R 1 is a methyl, benzyl, 4-hydroxy-benzyl, 4-fluoro-benzyl, 4-iodio-benzyl or β-naphthylmethyl group; R 2 is a methyl, phenyl, cyclopentyl, 2-propynyl, 4-fluoro-phenyl, 4-chloro-phenyl, 3-chloro-phenyl, 4-iodio-phenyl, 4-methyl-phenyl, 4-methoxy-phenyl, 4-hydroxy-phenyl, 3,5-bis-trifluoromethyl-phenyl, adamantyl, mercaptobenzyl, an Electron Withdrawing Group (EWG) or an Electron Donating Group (EDG); R 3 is H or 0; R 4 is a H, phenyl, 4-hydroxy-phenyl, 4-amino-phenyl, 4-methoxy-phenyl, 3-pyridinyl, 3,4-(methylendioxy)-phenyl, 2-methoxypyrimidin-5-yl, 4-acetoxy-phenyl or 4-(2,6 diaminohexanoyloxy)-phenyl; R 5 is acetate, pivalate, pivaloyloxymethyl group or 0; X is oxygen, sulfur, sulfoxide, nitrogen, selenium, iron, copper, cadmium or europium.