abstract |
Connection with the formula wherein R 1 is Boc, Z, Ac or H, L Leu is, X is Leu or Asp (OR 4 ), R 2 is CH 2 -CH (CH 3 ) 2 , R 3 is CH 2 -OH, CH = O, CH (OH) -C≡C-phenyl, R 4 is t-butyl, benzyl or H, except a compound in which, when X is Leu, R 3 is CH = O, and pharmaceutically acceptable salts thereof. |