| abstract |
A compound represented by formula (V): ##STR1## in which R 1 is selected from the group consisting of hydrogen, unbranched and branched C 1-7 alkyl, unbranched and branched C 3-9 alkenyl, and (C 3-7 )cycloalkyl(C 1-6 )alkyl groups, and R 2 is selected from the group consisting of hydrogen, unbranched and branched C 1-7 alkyl,(C 3-7 )cycloalkyl(C 1-3 )alkyl, aryl(C 1-3 )alkyl, aryloxy(C 1-3 )alkyl, arylthio(C 1-3 ) alkyl, arylsulphonyl(C 1-3 )alkyl and heteroaryl (C 1-3 ) alkyl groups. |