Combating arthropods with stereoisomers of 2,2-dimethyl-3-(2,2-dichlorovinyl)-cyclopropane-1-carboxylic acid .alpha.- c

A substantially pure stereoisomer of 2,2-dimethyl-3-(2,2-dichlorovinyl)-cyclopropane-1-carboxylic acid .alpha.-cyano-3-phenoxy-4-fluorobenzyl ester of the formula ##STR16## selected from the group consisting of esters in which the asymmetric C atoms 1 , 3 , and .alpha. have the following configuration:

• ______________________________________ Absolute configuration at the center Isomer 1 3 .alpha. ______________________________________ a R R R b R R S c R S R d R S S e S S S f S S R g S R S h S R R, ______________________________________
• the diastereomeric mixture of (1R)-cis-2,2-dimethyl-3-(2,2-dichlorovinyl)-cyclopropane-1-carboxylic acid (R,S)-.alpha.-cyano-3-phenoxy-4-fluoro-benzyl esters of the formula ##STR17## and the diastereomeric mixture of (1R)-trans-2,2-dimethyl-3-(2,2-dichlorovinyl)-cyclopropane-1-carboxylic acid (R,S)-.alpha.-cyano-3-phenoxy-4-fluoro-benzylesters of the formula ##STR18##