Patent ID: 7160335

Claim:
A compound of formula I wherein R 1 and R 3 are each independently of the other —NHR 5 , —NHSO 2 R 5 , —NHCOR 5 , —OR 6 or —SR 7 , R 2 and R 4 are each independently of the other —OR 6 or —SR 7 , with the proviso that not all of the substituents R 1 to R 4 are —SR 7 , R 5 is hydrogen, alkyl, aryl, aralkyl or a group of formula —(C n H 2n X) m —H wherein X is —O—, —S—, —SO 2 —, —NH—, —NR 8 —, —CONH— or —CONR 8 — and R 8 is alkyl or aryl, n is a number from 2 to 6 and the m is a number from 1 to 10, R 6 is an unsubstituted aryl or unsubstituted heteroaryl and R 7 is alkyl, unsubstituted aryl, unsubstituted heteroaryl or a group of formula —(C n H 2n X) m —H wherein X is —O—, —S—, —SO 2 , —NH—, —NR 8 , —CONH— or —CONR 8 and R 8 is alkyl or aryl, n is a number from 2 to 6 and m is a number from 1 to 10.