Patent ID: 7166744

Claim:
A compound of the formula I: wherein X is O, NH or S; R 1 and R 2 , which may be identical or different, are each independently —OH, —SH, —NH 2 , —COOH, —R(CH 2 ) m CH 3 , —RCOCO(CH 2 ) m CH 3 , —RCO(CH 2 ) m CHCH 3 CH 3 , —RCO(CH 2 ) m NR 4 CH 3 , —RCOCHOH(CH 2 ) m CH 3 , —RCOCH 2 (CH 2 ) m CH 3 , —RCOCH 2 CHOH(CH 2 ) m CH 3 , —RCOCH 2 (CH 2 ) m COOH, —RSO 2 CH 2 (CH 2 ) m CH 3 , —RPO 2 (OH)CH 2 (CH 2 ) m CH 3 or RCOCH(NHCOCH 3 )CH 2 CH 2 CONH 2 , in which each R is CH 2 , O, NH or S, R 4 is H or C 1 –C 6 alkyl, and each m is an integer of 0 to 5; and R 3 is H, with the proviso that if X is O, R 1 and R 2 , which may be identical or different, are not each independently —OH, —NH 2 , —COOH, —R(CH 2 ) m CH 3 , wherein R is CH 2 , NH or O, m is 0 to 5, —RCO(CH 2 ) m CHCH 3 CH 3 , wherein R is NH, m is 0 to 5, —RCOCH 2 (CH 2 ) m CH 3 , wherein R is NH, m is 0 to 5, —RCO(CH 2 ) m NR 4 CH 3 , wherein R is NH, m is 0, R 4 is H or C 1-6 alkyl, —RSO 2 CH 2 (CH 2 ) m CH 3 , wherein R is NH, m is 0 to 5, or pharmaceutically acceptable salts thereof.