| 摘要 |
Compounds are provided of formula (1), wherein R<1> is (C1-C5)alkyl, C3-C6(cycloalkyl)alkyl, C5-C7(cycloalkenyl)alkyl, (C6-C12)aryl, (C6-C12)aralkyl, trans(C4-C5)alkenyl, allyl or furan-2-ylalkyl, R<2> is H, OH or O2C(C1-C5)alkyl; R<3> is H, (C6-C10)aralkyl, (C1-C5)alkyl or (C1-C5)alkylCO; X is O, S or NY, wherein Y is H, benzyl or (C1-C5)alkyl; R is CH(Z)CO2Y, wherein Z is H, CH2CO2Y or (CH2)nN(R<4>)(R<5>), wherein n is 1-5 and R<4> and R<5> are individually H, (C1-C4)alkyl, phenyl, (C=NH)NH2, benzyloxycarbonyl or (C=NHNO2); and the pharmaceutically acceptable salts thereof.
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