Biosynthesis of the diterpene verrucosan-2beta-ol in the phototrophic eubacterium Chloroflexus aurantiacus. A retrobiosynthetic NMR study |
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Authors: | C Rieder G Strauss G Fuchs D Arigoni A Bacher W Eisenreich |
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Affiliation: | Department of Organic Chemistry and Biochemistry, Technische Universit?t München, Lichtenbergstrasse 4, D-85747 Garching, Germany. |
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Abstract: | The biosynthesis of verrucosan-2beta-ol in the green phototrophic eubacterium Chloroflexus aurantiacus was investigated by in vivo incorporation of singly or doubly 13C-labeled acetate. The 13C labeling of the isolated diterpene was analyzed by one- and two-dimensional NMR spectroscopy. The 13C-labeling patterns of verrucosan-2beta-ol were compared with the labeling patterns of intermediary metabolites (acetyl-CoA, pyruvate, and glyceraldehyde 3-phosphate) which were deduced from amino acids and nucleosides by retrobiosynthetic analysis. The results show that verrucosan-2beta-ol is synthesized via mevalonate and not via the deoxyxylulose pathway, which was discovered recently in some eubacteria, algae, and plants. A scheme for the formation of the unusual tetracyclic ring system is offered. The cyclization process is initiated by the solvolysis of pyrophosphate from geranyllinaloyl pyrophosphate and the mechanism involves a Wagner-Meerwein rearrangement, a 1,5-hydride shift, and a cyclopropylcarbinyl to cyclopropylcarbinyl rearrangement. |
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