Regioselective hydrogen elimination from the 10-methyl group of geranyl diphosphate in the biological formation of the 8(9)-double bond of limonene

The biological formation of the 8(9)-double bond of both (4S)-(–)- and (4R)-(+)-limonenes in Mentha spicata and Citrus unshiu is found to be stereospecifically controlled by the regioselective elimination of a hydrogen atom from the 10-methyl group, i.e. the Z-methyl group, of geranyl diphosphate.