Essential oil of Plectranthus tenuicaulis for flavour and fragrance: Synthesis of derivatives from natural and synthetic 6,7-epoxyocimenes

ABSTRACT (R)‐(E)‐6,7‐Epoxyocimene, the major constituent of the essential oil from Plectranthus tenuicaulis, as well as the racemic (Z)‐isomer previously synthesized from commercial (Z)‐β‐ocimene were used as starting material for the synthesis of fragrant derivatives. Among the 14 compounds obtained from these precursors (alcohols, diols, diepoxy, sulfur and carbonyl derivatives), four were described for the first time and three were enantiomerically pure. All compounds were fully characterized by one‐ and two‐dimensional nuclear magnetic resonance analysis as well as by gas chromatography and mass spectroscopy (electron ionization). Additionally, their odour properties were evaluated. Copyright © 2012 John Wiley & Sons, Ltd. (R)‐(E)‐6,7‐epoxyocimene (1), the major component of the essential oil from Plectranthus tenuicaulis collected in Gabon, and the racemic (Z)‐isomer (2), previously synthesized from commercial (Z)‐β‐ocimene, were used as starting material for the synthesis of fourteen fragrant derivatives (i.e. alcohols, diols, diepoxydes, sulfur and carbonyl compounds). The spectroscopic data (mass, 1H and 13C NMR) as well as the GC retention indices are given for all derivatives.