| 摘要 |
There is described a process for the production of a compound of formula I, I in which (i) R5 is hydroxy or hydrogen, R7 is hydrogen, and R6 and R8, which are the same, are both ethyl or are both t-butyl, or (ii) one of R5, R6, R7 and R8 is of formula V, V in which X represents a hydrocarbon chain optionally substituted by an -OH group and containing from 2 to 10 carbon atoms, and the remainder of R5, R6, R7 and R8 are all hydrogen, or a pharmaceutically acceptable derivative thereof, which comprises dehydrating a compound of formula II, II or an ester thereof, in which R5a, R6a, R7a and R8a have the same significances as R5, R6, R7 and R8 above, save that one of R5a, R6a, R7a and R8a may be a group of formula VI, or an ester thereof, X is as defined above, and one of each pair of A and B is hydrogen and the other is hydroxy. |
