abstract |
A polypeptide compound of the following general formula (I): ** (Formula) ** in which R1 is hydrogen or an acyl group, R2 is hydrogen or an acyl group, R3 is (C1-C6) alkyl having one or plus hydroxy or protected hydroxy, R4 is hydrogen or hydroxy, R5 is hydroxy, (C1-C6) alkoxy or hydroxysulfonyloxy R6 is hydroxy or acyloxy, or a salt thereof. |