Synthesis of an insecticidal tetrahydroisocoumarin, (3R,4S,4aR)-4,8-dihydroxy-3-methyl-3,4,4a,5-tetrahydro-1H-2-benzopyran-1-one

The insecticidal tetrahydroisocoumarin, (3R,4S,4aR)-4,8-dihydroxy-3-methyl-3,4,4a,5-tetrahydro-1H-2-benzopyran-1-one, was synthesized as a racemate and as an optically active form using one-pot esterification-Michael addition-aldol reaction of δ-hydroxy-α,β-unsaturated aldehyde and diketene as a key step.