| 摘要 |
Compounds of the structure <IMAGE> wherein R is hydrogen, lower alkyl containing 1 to 5 carbon atoms, cycloalkyl containing 3 to 7 carbon atoms, phenyl or phenyl substituted with halogen, trifluoromethyl, or lower alkyl or lower alkoxy having 1 to 4 carbon atoms and R1 is hydrogen, lower alkyl having 1 to 4 carbon atoms, phenyl or phenyl lower alkyl wherein the lower alkyl has 1 to 4 carbon atoms, are formed by cyclizing a compound of the structure <IMAGE> wherein R and R1 are as defined above, in the presence of an acid.
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