| 摘要 |
Compounds of the formulae <IMAGE> and <IMAGE> in which R<1> is lower alkyl, esterified carboxy, a group <IMAGE> where R<2> and R<3> together are oxo or protected oxo and X is hydrogen, hydroxy or acyloxy, or a group -(CH2)n-OY, where n is 1 or 2 and Y is hydrogen, alkyl or acyl; Ar is aryl; and R<4> is acyl, are useful as intermediates for the manufacture of tetracyclic compounds having antibiotic or antitumour activity. |
