Patent ID: 7825086

Claim:
A compound of formula (1): wherein R 1 is H, (C 1 -C 4 )alkyl, (C 3 -C 6 )cycloalkyl, hydroxy(C 1 -C 4 )alkyl, benzoyl(C 1 -C 4 )alkyl or phenyl; R 2 is H, OH, hydroxy(C 1 -C 4 )alkyl, (C 1 -C 4 )alkyl or —CH 2 R a ; R 3 is H, (C 1 -C 4 )alkyl or hydroxy(C 1 -C 4 )alkyl; R 4 is OH or R a ; wherein each R a is independently -Q-X—Y-Z (n) -R; each Q is independently S or O; each X, Y and Z is independently Met, Val, Thr, Tyr, Trp, Ser, Ala or Gly; each R is independently H or an amino-protecting group; and each n is independently 0 or 1; wherein at least one of R 2 is —CH 2 R a or R 4 is R a ; or a pharmaceutically acceptable salt thereof.