Stereochemistry of cyclization in carotenoid biosynthesis; use of 13C-labelling to elucidate the stereochemical behaviour of the C-1 methyl substituents during zeaxanthin biosynthesis in a Flavobacterium
Abstract
[2-13C]Mevalonate has been incorporated into the carotenoid zeaxanthin and its acyclic precursor, lycopene, in a Flavobacterium species; n.m.r. analysis showed 13C enrichment in both compounds at C-4, C-8, C-12, C-16, C-4′, C-8′, C-12′, and C-16′ so that in lycopene the C-1 methyl substituent trans to the main carbon chain was enriched and in zeaxanthin the 1α(axial) methyl substituent was labelled, enabling us to define the stereochemistry of the behaviour of the C-1 methyl groups during cyclization.
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