Structure elucidation, enantioselective analysis, and biogenesis of nerol oxide in Pelargonium species

A novel enantioselective synthesis of nerol oxide (3,6-dihydro-4-methyl-2-( 2-methyl-1-propenyl)-2H-pyran) was used for the determination of the absolu te configuration at C-2. The order of elution of the enantiomers on octakis -(2,3-di-O-butyryl-6-O-tert-butyldimethylsilyl)-gamma-cyclodextrin in OV 17 01-vi as the chiral stationary phase in enantioselective GC was determined as (2R) before (2S). Enantioselective multidimensional GC/MS (enantio-MDGC/ MS) was used for the determination of the enantiomeric ratios of nerol oxid e in different geranium oils. As a result, in all investigated oils nerol o xide occurs as a racemate. The biogenesis of nerol oxide in Pelargonium spe cies was investigated by feeding experiments using deuterium-labeled neryl glucoside as the precursor. The Pelargonium plants were able to convert the fed precursor into racemic nerol oxide, which has to be considered as a "n atural racemate"