Use of ¹³C in biosynthetic studies. Incorporation of ¹³C-labeled acetate into chartreusin by Streptomyceschartreusis

Abstract

Examination by 13C nuclear magnetic resonance spectroscopy of chartreusin produced in cultures of Streptomyces chartreusis supplemented with [I-13C] and [2-13C]acetate showed that the 19-carbon aglycone component was derived entirely from acetate. In the spectrum of chartreusin enriched from [1,2-13C]acetate the signals for 16 of the carbon atoms were accompanied by satellites due to spin-spin coupling of intact 13C-13C units. The coupled pairs were matched with the aid of homonuclear single 3C-frequency decoupling. Of the uncoupled carbon atoms, two were derived from methyl groups of acetate and the third came from an acetate carboxyl group. The arrangement of paired and unpaired 13C atoms in chartreusin suggests that the aglycone is derived from a single 22-carbon polyketide chain. Cyclization to a benzpyrene-like intermediate followed by ring cleavage and loss of three carbon atoms provides a plausible route from the polyketide to the substituted isocoumarin structure of the aglycone.

Alternariol: evidence for biosynthesis via norlichexanthone

“…This notion is strongly supported by the recent isolation from Penicillium notatum of lichenxanthone (4) as a congener of AME (9). The same general mechanism, oxidative cleavage of an aromatic ring followed by rotation of the fragmented aryl structure, has also been reported in the formation of the a-pyrone structure of chartreusin in the Streptomycetae (10). These and other considerations led us to consider norlichexanthone, NLX (S), as a possible precursor.…”

Understanding the Biosynthesis of Paxisterol in Lichen-Derived Penicillium aurantiacobrunneum for Production of Fluorinated Derivatives

“…The interpretation of the results concluded that two directly connected C-13 carbons of glucose were utilized during the biosynthesis. This finding was also confirmed by the feeding experiment using 13 C-labelled sodium acetate, showing that acetyl coenzyme A was involved in paxisterol biosynthesis [ 8 , 9 ]. We thus hypothesized that fluorinated paxisterol can be produced if the biosynthetic enzyme that can use sodium monofluoroacetate is present in P. aurantiacobrunneum .…”

Pyrones. VIII. Biosynthetic investigations of the fungal metabolite phacidin

“…(B) Sodium acetate-l-13C labelling experiment Labelled sodium acetate was fed to growing cultures of P. balsamicola and the distribution of the I3C label in the resulting phacidin determined according to the method of McInnes et al (15), by comparing the 13Cmr spectra of natural abundance and enriched compounds recorded under identical instrument parameters. In order to make the comparisons more valid, the carbons to be compared should have similar substituents.…”