Patent ID: 7449470

Claim:
A compound of formula: or a salt thereof, wherein X represents hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, —(CH 2 ) n -aryl, or substituted —(CH 2 ) n -aryl; Y′ represents hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, —(CH 2 ) n -aryl, substituted —(CH 2 ) n -aryl, alkoxy, thioalkyl, halo, NR 1 R 2 , NR 3 COR 4 , or NR 5 CONR 6 R 7 ; Y″ represents hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, —(CH 2 ) n -aryl, substituted —(CH 2 ) n -aryl, alkoxy, thioalkyl, halo, NR 1 R 2 , NR 3 COR 4 , or NR 5 CONR 6 R 7 ; wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, —(CH 2 ) n -aryl, or substituted —(CH 2 ) n -aryl; and whereby when R 1 and R 2 are in a NR 1 R 2 or when R 6 and R 7 are in a NR 6 R 7 R 1 and R 2 may be linked to form a heterocyclic group; Z represents oxygen, sulfur or selenium; and n is a number in the range of from 0 to 10.