Monoterpenes interconversions

It has often been suggested that monoterpene interconversions may be carried out by relatively nonspecific enzymes. Few monoterpene intercon-... 

Battalle, A. J. Burbott, and W. D. Loomis, Monoterpene Interconversions Metabolism of pulegone by a cell-free system from Mentha piperita, Phytochemistry 7 1159 (1968). 

J. Burbott and W. D. Loomis, Monoterpene interconversions by cell-free enzymes from peppermint (Mentha piperita), Plant Physiol. Suppl. 65 96 (1980). 

Thus, it has been shown that the biogenesis of the thujane series of monoterpenes requires two 1,2-hydride shifts in the interconversions of the ions derived from a-terpinol and terpinen-4-... 

By contrast, biosynthetic studies on whole fruits have been limited and, probably because of the low levels of monoterpenes In grapes, the pathways In Vltls species remain unexplored. Since monoterpenes important to the flavor of grapes are mainly acyclic, Interconversions of neryl, geranyl and llnalyl derivatives may be of special significance. The oxidative steps leading to polyol production represent a shunt of flavor-active compounds to flavorless forms and require investigation. 

Many oxygenated monocarbocyclic monoterpenes are of use to the flavour and fragrance industry. Some are extracted from natural sources, and others are prepared from the major members of the family, usually by straightforward functional group interconversions. 

Fig. 6. Metabolic interconversions of monoterpenes in peppermint. Solid arrows indicate reactions demonstrated in ceU-free preparations (after Burbott and Loomis, 1980).

The facility and stereospecificity of the interconversions of the camphanyl, bornyl, and pinyl monoterpenes are renowned and provided the initial factual basis for the formulation of non-classical carbonium ion intermediates 39, 90). A tremendous number of investigations has been carried out upon the rearrangements of bicyclo[2.2.1]heptanes and the nature of the various carbonium ion intermediates 39). However, for the purposes at hand it will be sufficient to illustrate the characteristics of these rearrangements with the classical case of the camphene and pinene hydrochlorides (46-Cl and 47-Cl) rearrangements 91—93). 

---