Investigations of Bicyclo(3.1.1)heptane Terpenes in Higher Plants: Stereochemistry of Pinene Biosynthesis and Isolation of Bergamoten-12-Oic Acids

Cell-free enzyme preparations of (+)-pinene cyclase I and ($-$)-pinene cyclase II isolated from leaves of common sage (Salvia officinalis) are known to convert geranyl pyrophosphate (GPP) to the bicyclic monoterpenes (+)-α-pinene (cyclase I) and ($-$)-α-pinene and ($-$)-β-pinene (cyclase II). The stereochemical course of these cyclizations at the gem dimethyl position of the pinene products was investigated. (6E)- (8-$\sp3$H) GPP was synthesized in ten steps from geraniol and incubated with each cyclase to afford (+)- ($\sp3$H) -α-pinene, ($-$)- ($\sp3$H) -α-pinene, and ($-$)- ($\sp3$H) β-pinene. A 10-step reaction sequence, which involved oxidative conversion of the endo methyl group of each pinene to the carbonyl carbon of 2-hydroxy-2,6-dimethylbicyclo (3.1.1) heptane-6-carboxylic acid lactone, was used to determine the stereochemical fate of the distal methyl groups of GPP. Complete retention of tritium in all three pinene products established that the E methyl group of GPP became the exo methyl group at the gem dimethyl position of each pinene. It is concluded that the pinenes are formed via enantiomeric, least motion cyclizations of boat-like α-terpinyl carbocation intermediates.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Denissen, Jon Francis

• Chemistry, Organic

Identifier

(UMI)AAI8803015

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70384