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Stereochemistry of Monoterpene Cyclization

  • Rodney Croteau

Abstract

The vast majority of the several hundred naturally occurring monoterpenes are cyclic and represent a relatively small number of skeletal themes multiplied by a very large range of simple derivatives, positional isomers and stereochemical variants.1 A unified conceptual framework for the origin of the various terpenoid types was put forward three decades ago by Ruzicka in formulating the “biogenetic isoprene rule.”2 As applied to the monoterpenes, this scheme (Fig. 1) posits intramolecular electrophilic attack of C1 of the neryl cation on the distal double bond to yield a monocyclic (α-terpinyl) intermediate, which by a series of subsequent internal additions, hydride shifts, and Wagner-Meerwein rearrangements give rise to the cationic equivalents of most known skeletal types. The latter species, by deprotonation to the corresponding olefin or capture by a nucleophile, could yield many of the common monoterpenes, and by subsequent, often oxidative, modification of these cyclic progenitors most other monoterpenes could be generated. This seminal contribution by Ruzicka set the foundation for nearly all subsequent biogenetic investigations, which have supported the broad outlines of this basic proposal. More recent investigations at the enzyme-level, however, have necessitated revision of some elements of the scheme, and, moreover, have allowed reformulation of the general model for monoterpene cyclization in explicit mechanistic and stereochemical terms. Detailed descriptions of the biosynthesis of cyclic monoterpenes are available;3, 4 the focus of this chapter is the stereochemical aspects of the cyclization process.

Keywords

Diphenyl Phosphate Enzymatic Cyclization Geranyl Pyrophosphate Hydride Shift Isomerization Step 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1987

Authors and Affiliations

  • Rodney Croteau
    • 1
  1. 1.Institute of Biological ChemistryWashington State UniversityPullmanUSA

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