Microbial Pyran-2-ones 2.1 Simple Pyran-ZonesThe simplest pyran-2-ones, from both a structural and a biosynthetic viewpoint, are the 4-hydroxypyrones, triacetic lactone, methyl triacetic lactone, tetraacetic lactone, and de hydroace tic acid.Methyl triacetic lactone (5) was the first of these to be isolated from a natural source, Penicillium stipitatum,' and was later isolated from another strain of P. stipitatum, along with triacetic lactone (4) and tetraacetic lactone (6).6 Triacetic lactone (4) had also been isolated from two unstipulated Penicillium species. ' Dehydroacetic acid had been known as a synthetic compound long before its isolation from Ramaria apiculata.8. It has also been isolated from Hypocrea sulphurea. lo

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An efficient, room temperature procedure for the cross-coupling of a range of terminal alkynes, using standard Sonogashira cross-coupling conditions (Pd/Cu) is presented. At higher reaction temperatures, head-to-tail or head-to-head dimerisation affords 1,3- and 1,4-disubstituted enynes, respectively as minor products.

An antifungal metabolite of Trichoderma harzianum has been shown to be ( E ) -4hydroxy-5,6dimethoxy-3-(2-methyl-l -oxohex-4-enyl)pyridin-2-one. The incorporation of [I -I3C]and [I ,2-'"G,] -acetic acid and [ Me-''C] methionine into harzianopyridone and the sites of labelling were established by n.m.r. methods. A low incorporation of [U-14C]aspartic acid was also observed.

The phyto-estrogens formononetin (7-hydroxy-4'methoxyisoflavone) and biochanin A (5-7-dihydroxy-4'-methoxyisoflavone) were independently incubated in vitro at 39 degrees C in bovine rumen fluid from a fistulated steer receiving an alfalfa hay diet. Formononetin was incubated in studies 1 and 2, whereas biochanin A was incubated in study 3. The isoflavones were separated and quantified by high performance liquid chromatography. In study 1, formononetin concentration, 14.80 micrograms/ml at time 0, declined to 1.16 micrograms/ml by 12 h and to .76 micrograms/ml by 24 h. Daidzein (7,4-dihydroxyisoflavone), .18 micrograms/ml at time 0, peaked at 12.92 micrograms/ml at 6 h and decreased to 1.30 micrograms/ml by 24 h. Equol (7,4'-dihydroxyisoflavan), detected at 6 h, peaked at 16.94 micrograms/ml at 18 h and dropped to 12.64 micrograms/ml at 24 h. In incubation study 2, formononetin declined from 17.57 micrograms/ml at time 0 to 7.08 micrograms/ml by 6 h. Daidzein concentration was 1.75 micrograms/ml at time 0 and increased to 12.03 micrograms/ml by 6 h. Equol was detected at 3 h and increased to 2.32 micrograms/ml at 6 h. The half-lives were 4.3 for formononetin and 9.8 h for daidzein in this in vitro system. In study 3, biochanin A, 8.54 micrograms/ml at time 0, decreased to 0 micrograms/ml by 12 h in incubation 3, whereas genistein (5,7,4'-trihydroxyisoflavone), 3.17 micrograms/ml at 1 h, peaked at 7.35 micrograms/ml at 4 h and decreased to .32 micrograms/ml at 24 h. Equol was not detected in incubation study 3. The half-lives of biochanin A and genistein were 3.9 and 5.5 h, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

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This paper describes the identification of carbon-arbon bond cleavage within a defined range of epoxides as being a reaction type which is specifically diagnostic of free radicals adjacent to the epoxide. The speed of the epoxide cleavage is greater than that of hex-5-enyl radical cyclisation, and hence the reaction is kinetically competent to act as a new and discriminating type of probe for free radicals in solution.