Patent ID: 8399661

Claim:
A compound represented by the following general formula 1, wherein: R 1 is selected from the group consisting of H, R 5 and R 5 C(═O); R 2 is selected from the group consisting of S and (O═)S(═O); R 3 is selected from the group consisting of H, CH 3 and CH 2 CH 2 C(═O)OR 5 ; R 4 is selected from the group consisting of R 5 , OR 5 , N(R 5 ) 2 , NH 2 , NHR 5 and OH; and R 5 is selected from an alkyl group having one to six carbon atoms and a phenyl group; provided that when R 3 is CH 2 CH 2 C(═O)OR 5 , R 4 is OR 5 ; and when R 1 is H, R 2 is S and R 3 is H, R 4 is not CH 3 ; wherein the compound is selected from the group consisting of the compounds represented by the following formulae 3, 4, 5, 7, 9, 11, 12, 13, 16, 17, 18, 19, 21 and 22,