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PubMedDate not supplied

Characterization of the cis-syn and cis-anti diastereoisomers of 5-methoxypsoralen pyrone-side monocycloadducts to thymidine.

The photoreaction of 5-methoxypsoralen (5-MOP) with thymidine as a DNA model compound was investigated under dry-state conditions. In this respect, a thin film of thymidine and 5-MOP in a ratio 10:1 was exposed to 350-nm UV light. Four [2 + 2] photocycloadducts were isolated in a 0.5-2.2% yield with respect to 5-MOP by HPLC and characterized as two pairs of cis-syn and cis-anti diastereoisomers, respectively, on the basis of extensive spectroscopic measurements, including UV, fast atom bombardment mass spectrometry, 1H and 13C NMR, and CD. Information concerning the absolute configuration of the four photocycloadducts was inferred from detailed nuclear Overhauser enhancement experiments. This is indicative of a 3R,4S,5R,6S and a 3S,4R,5S,6R configuration for the cis-anti cycloadducts and a 3S,4R,5R,6S) and a 3R,4S,5S,6R configuration for the cis-syn cycloadducts. In addition, conformational features of the four photocycloadducts were obtained from consideration of various 1H NMR measurements including NOE data.

5-Methoxypsoralen↗
PubMed1989

Biosynthesis of chaetochromin A, a bis(naphtho-gamma-pyrone), in Chaetomium spp.

The biosynthesis of chaetochromin A, a metabolite of Chaetomium gracile, has been studied using [13CH3]methionine, sodium [1-13C]acetate, sodium [1,2-13C2]acetate, sodium [1-13C,2,2,2-2H3]acetate, and sodium [1-13C,1,1-18O2]acetate as precursors. The folding pattern of the polyketide chain in chaetochromin A, biosynthesized from sodium [1,2-13C2]acetate as the precursor, was determined to be the same as that of rubrofusarin by carbon-13 nuclear magnetic resonance (13C-NMR) analysis. By using [13CH3]methionine as a precursor, the source of 2-CH3 was determined. When sodium [1-13C,2,2,2-2H3]acetate was fed, a beta-isotope-shifted peak was observed only for carbon 2. In the 13C-NMR spectra of chaetochromin A and of its hexamethyl ether derived from sodium [1-13C,1,1-18O2]acetate, isotope-shifted peaks were observed for carbons 4, 5, 6, 8 and 10a, but not for carbon 2. These results showed that oxygen 1 originated from the same unit of acetate as carbon 10a.

Ascomycota↗