| 摘要 |
This invention provides new compounds of formula I, <IMAGE> I <IMAGE> wherein X is H-Ala, D-Ala, beta -Ala, propionyl or Ac-Ala (wherein Ac is pharmaceutically acceptable acyl), Y is hydrogen or a direct bond between the sulphur atoms in positions 3 and 14, and Z is the radical -COOH, -COOR1 (wherein R1 is lower alkyl), <IMAGE> (wherein R2 and R3 independently are hydrogen or lower alkyl) or -CH2OH, with the proviso that X is other than H-Ala, when Z is COOH.
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