A compound of formula I ##STR5## wherein: R represents phenyl optionally substituted by a substituent selected from the group consisting of hydroxy, chlorine, bromine, fluorine, methoxy, ethoxy, {TAIL ~ ethyl}, methyl, isopropyl, isobutyl, isopropoxy, isobutoxy, amino, nitro, phenyl, mercapto, {HEAD ~ methylthio}, methylsulfinyl and methylsulfonyl 
A compound of formula I # # STR5 # # wherein : R represents phenyl optionally substituted by a substituent selected from the group consisting of hydroxy , chlorine , bromine , fluorine , methoxy , ethoxy , { TAIL ~ ethyl } , methyl , isopropyl , isobutyl , isopropoxy , isobutoxy , amino , nitro , phenyl , mercapto , { HEAD ~ methylthio } , methylsulfinyl and methylsulfonyl
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