A compound of formula I ##STR5## wherein: {HEAD ~ R} represents {TAIL ~ 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, methylthio, methylsulfinyl and methylsulfonyl 
represents
A compound of formula I # # STR5 # # wherein : { HEAD ~ R } represents { TAIL ~ 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 , methylthio , methylsulfinyl and methylsulfonyl
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL 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