Both of the components of prallethrin SF [(4S)-l-oxo-2propargyl-3-methylcyclopent-2-en-4-yl (IRI-cis,trans-chrysanthemate], a novel potent insecticidal pyrethroid, were labelled with carbon-14 at the cyclopentenyl-2 position for use in metabolic studies. Carbonation of 2-lithio-5-methylfuran (4) with carbon-14 dioxide (2) gave 5-methyl-2-[~arboxyl-~~~]furoic acid
(2). 14 oxidation with manganese dioxide afforded 5-methyl[carbonylfurfural (L). Modified Grignard reaction of 1 with propargyl bromide and magnesium in the presence of mercuric chloride 14 yielded 1-(5-methy1-2-furyl)[l-C]but-3-yn-l-ol (i). Molecular rearrangement of 8 followed by isomerization afforded Z-propargyl-3-methy1[2-C]cyclopent-2-en-4-ol-l-one (2) in 30% yield from barium [ Clcarbonate (2). Direct optical resolution of? by preparative HPLC with a chiral-phase column gave ( + ) -( 4 S ) and ( -) -( N U isomers (10 and 11) quantitatively. Condensation of with (IRI-cisor (IRI-trans-chrysanthemoyl chloride (e or 12b) yielded (4S), (lR)-nis-or (4s). (1R)-trans-[cyclopentenyl-2 -Clprallethrin (la or e). Both overall radiochemical yields of and were about 9% from 2.
Reduction of 5 with lithium aluminium hydride followed by