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Published on: May 16, 2016
Absolute Configuration of Kelsoene and Prespatane
K Nabeta1, M Yamamoto, H Koshino
1a Department of Bioresource Science, Obihiro University of Agriculture and Veterinary Medicine.
The absolute configurations of rare sesquiterpenes, kelsoene and prespatane, were determined using advanced NMR techniques and a chiral reagent. This finding provides insights into the biosynthetic pathways of these complex natural products.
Area of Science:
- Natural Product Chemistry
- Organic Chemistry
- Biosynthesis
Background:
- Sesquiterpenes are a diverse class of natural products with complex structures.
- Kelsoene and prespatane are rare sesquiterpenes whose absolute configurations were previously undetermined.
- Understanding the stereochemistry of natural products is crucial for elucidating their biological activities and biosynthetic origins.
Purpose of the Study:
- To determine the absolute configurations of the rare sesquiterpenes, kelsoene and prespatane.
- To elucidate the stereochemical pathways involved in the biosynthesis of these sesquiterpenes.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy, including NOESY and NOEDS experiments.
- Derivatization with a chiral reagent, 2'-methoxy-1,1'-binaphthalene-2-carbohydroximoyl chloride (MBCC).
- Analysis of chemical shifts and Nuclear Overhauser Effects (NOEs) to establish stereochemistry.
Main Results:
- The absolute configurations of kelsoene and prespatane were successfully determined.
- Kelsoene was assigned the configuration (1S, 2R,5S, 6S, 7R, 8R)-2,8-dimethyl-6-(1-methylethenyl)tricyclo[5.3.0.0(2,5)]decane.
- Prespane was assigned the configuration (1R, 2S, 5R, 6R, 7R, 8S)-1,5-dimethyl-8-(1-methylethenyl)tricyclo-[5.3.0.0(2,6)]decane.
Conclusions:
- The determined absolute configurations suggest distinct cyclization pathways from farnesyl pyrophosphate (FPP).
- Cyclization from the si-face of FPP leads to kelsoene via a 10R-germacradienyl cation intermediate.
- Cyclization from the re-face of FPP leads to prespatane via a 10S-germacradienyl cation intermediate.
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