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, ethyl, methyl, isopropyl, isobutyl, isopropoxy, isobutoxy, amino, nitro, phenyl, mercapto, {HEAD ~ methylthio}, methylsulfinyl and {TAIL ~ 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 , ethyl , methyl , isopropyl , isobutyl , isopropoxy , isobutoxy , amino , nitro , phenyl , mercapto , { HEAD ~ methylthio } , methylsulfinyl and { TAIL ~ methylsulfonyl }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL