The distribution of acetate-derived oxygens in the tetronic acids of Penicillium multicolor

Abstract

Incorporation of sodium [I -l3C, '802]acetate by Penicillium multicolor into multicoianic, multicolic, and multicolosic acids, (I), ( 2 ) , and (3), respectively, has given samples which when derivatised and examined by spin echo Fourier transform (S.E. F.T.) 3C n.m.r. spectroscopy show 80-induced l3C-satellites, confirming the previously proposed biosynthetic pathway involving oxidative fission of the P-ketide derived intermediate 6-pentylresorcylate ( 8 ) and establishing that lactonisation of the tetronic acid ring occurs by displacement from the C -I carboxy-group by the C-4 enolic oxygen, rather than by lactol formation. lsO-Induced changes in the l3C-chernical shifts of directly attached carbon atoms have recently been shown to provide an extremely valuable addition to the armoury of n.m.r. techniques available for the investigation of biosynthetic path-

Quorum sensing as a method for improving sclerotiorin production in Penicillium sclerotiorum

“…(Kasettrathat et al, 2008), vulpinic acid and pinastric acid by Tuckermannopsis pinastri (Golojuch and Lawrey, 1988), penicillic acid by Penicillium cyclopium and viridicatic acid by Penicillium viridicatum (Gedge and Pattenden, 1979). Labelling studies suggested that multicolosic acid is a polyketide synthesised by oxidative cleavage of an aromatic precursor 6-pentylresorcylate (Holker et al, 1983(Holker et al, , 1987. Multicolanic acid and related derivatives have also been classified as hexaketides because of their polyketide origin (Turner and Aldridge, 1983).…”

“…5). Labelling studies have suggested that multicolosic acid and related derivatives are synthesised by oxidative cleavage of an aromatic precursor 6-pentylresorcylate (Holker et al, 1983(Holker et al, , 1987. Therefore, it is unlikely that 4-hydroxybutyric acid lactone will act as a precursor for the synthesis of methyl-O-methylmulticolate acetate.…”

Highly Selective Synthesis of Polyfunctionalized Carbo- and Heterocycles Based on Ring Expansion of Squaric Acid Derivatives

“…Such a stereocontrol, in a sense, mimics the biogenetic route of naturally occurring 5-ylidene-2(5H)-furanones, in which the covalent bond fixes the E-geometry. 15 Scheme 5 4. Radical-and cation-mediated ring expansion of 4-hydroxy-2cyclobutenones to 2-(5H)-furanone/4-cyclopentene-1,3-dione Four-to five-membered ring expansion occurs not only via thermal/ photochemical (above) and catalyzed (with transition-metal) rearrangements, but also by those via reactive intermediates, which should expand the synthetic utility of 1 as a C 4 -synthon.…”

“…In the reactions of 2-4 with allylsilanes and silyl enol ethers, a more congested reaction site caused deviation from the 1,2 to the 1,4 mode (entries 2, 4,11,13,18). The reaction with silyl ketene acetals gave a 1,2-adduct with TiCl 4 and a 1,4-adduct with ZnCl 2 , regardless of the substitution pattern of the organosilanes (entries 6-9, 14, 15,19); competitive formation of a titanate intermediate, prior to addition, may change the course of the reaction. The reaction of diester 5 occurred only with a silyl enol ether and a silyl ketene acetal according to a 1,4-addition (entries 20, 21).…”

Biosynthesis of the meroterpenoid, austin, by Aspergillus ustus: incorporation of 18O2, sodium [1-13C, 18O2]acetate, and [Me-13C, 2H3]methionine

“…However for the C-3 resonance, three isotopically shifted signals appeared due to species having 1 8 0 in (a) the singly-bonded oxygen, (b) the doubly-bonded oxygen, and mainly (c) both the singly and doubly-bonded oxygens. 5 Since the resonances corresponding to (a) and (b) probably result from residual 1 6 0 2 in the fermentation, both oxygen atoms of the spiro-lactone are added by oxidative processes, in agreement with observations for andibenin B.6 In the aliphatic region the resonances due to C-4, C-11, C-3', and C-5' all show isotope shifts which complement those observed in the carbonyl region, thereby accounting for all five ' 8 0 atoms incorporated into austin. Interestingly, C-6' also has a shifted signal (Table 1).…”