A COMPOUND OF FORMULA (I) WHEREIN N IS 0 TO 4； M IS 0 OR 1 WITH THE PROVISO THAT THE SULPHUR ATOM AND R₃ ARE IN VICINAL POSITION (IF M = 0 THEN R₃ IS IN POSITION 2’, AND IF M = 1 THEN R₃ IS ON POSITION 1’)； R IS ETHYL OR VINYL； R₁ IS HYDROGEN OR (C₁-₆)ALKYL, R₂ IS HYDROGEN OR -(C₃-₆)CYCLOALKYL, OR -UNSUBSTITUTED (C₁-₆)ALKYL, OR -(C₁-₆)ALKYL SUBSTITUTED BY ONE OR MORE OF -HYDROXY； PREFERABLY ONE OR TWO, -METHOXY, -HALOGEN, (C₃-₆)CYCLOALKYL, OR R₁ AND R₂ TOGETHER WITH THE NITROGEN ATOM TO WHICH THEY ARE ATTACHED FORM A 5 TO 7 MEMBERED HETEROCYCLIC RING CONTAINING AT LEAST 1 NITROGEN ATOM OR 1 NITROGEN AND 1 ADDITIONAL HETEROATOME E. G. SELECTED FROM N OR 0, OR R₁ IS HYDROXY AND R₂IS FORMYL； R₃ IS OH, OR₄, A HALOGEN ATOM, OR -WITH THE PROVISO THAT R₃ IS BOUND TO 2' R₃ REPRESENTS -0-(CH₂)p-0- WITH P IS 2 OR 3； R₄ IS UNSUBSTITUTED (C₁-₆)ALKYL OR (C₃-₆)CYCLOALKYL.
