| 摘要 |
The compounds of formula I in which 1) R5 is a hydroxyl group or a hydrogen atom, R7 is a hydrogen atom and R6 and R8, which are identical, are both ethyl groups or both t-butyl groups, or 2) one from R5, R6, R7 and R8 has the formula V in which X is a hydrocarbon chain optionally substituted by an -OH group and containing from 2 to 10 carbon atoms, and the symbols remaining from R5, R6 and R8 are all hydrogen atoms, or one of its pharmaceutically acceptable salts or esters, are prepared by dehydration of a corresponding 2-hydroxy-3-hydro or 2-hydro-3-hydroxy compound. The compounds of formula I are known antiallergic medicaments. The new process makes it possible to obtain them in a purer state and under more certain and more economic conditions than by the prior processes. <IMAGE> <IMAGE>
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