| 摘要 |
A tetrapeptide derivative represented by the following formula or a salt thereof has a higher cyto-static activity than dolastatin 10, and is useful as an antitumor agent: (see above formula I) wherein, R1, R2, R3 and R4 are the same or different and each represent a hydrogen atom, a lower alkyl group or an aralkyl group; Q represents (see formula II) or a group of -A2-R7, wherein, A1 represents a direct bond or (see formula III) Y represents a hydrogen atom or -COR6, R5 represents a hydrogen atom, a lower alkyl group or an aralkyl group, R6 represents a hydroxyl group, a lower alkoxy group, an aralkyloxy group or (see formula IV) wherein, R8 and R9 are the same or different and each represent a hydrogen atom, a lower -80- alkyl group, a phenyl group or a 4- to 7-membered heterocyclic group containing one or two hetero atoms selected from S, O and N, or alternatively R8 and R9 may combine together with the nitrogen atom to which they are bonded to form a 4- to 7-membered heterocyclic ring optionally further containing one hetero atom selected from S, O and N, A2 represents a direct bond or a lower alkylene group, and R7 represents a cycloalkyl group, an aryl group or an indolyl group, provided that the case is excluded where both R1 and R2 represent isopropyl groups, R3 repre-sents a sec-butyl group, R4 represents a methyl group, and Q represents an .alpha.-(2-thiazolyl) phene-thyl group.
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