Stereoselective quenching of cedryl carbocation in epicedrol biosynthesis

Epicedrol synthase catalyzes the cyclization of achiral diphosphate substrate, ( E , E )-farnesyldiphosphate (FPP) into epicedrol. GC–MS analysis of assay extracts obtained by incubating FPP with epicedrol synthase in 21.6 at % H 2 18 O buffer showed the molecular ion of 224 for epicedrol. The labeled oxygen study presented here unambiguously demonstrates that the hydroxyl group of the epicedrol synthase enzymatic product, epicedrol, is derived from a water molecule, not from the phosphate moiety of the FPP.