Beta-triketone inhibitors of plant p-hydroxyphenylpyruvate dioxygenase: modeling and comparative molecular field analysis of their interactions.

p-Hydroxyphenylpyruvate dioxygenase (HPPD) is the target site of beta-triketone herbicides in current use. Nineteen beta-triketones and analogues, including the naturally occurring leptospermone and grandiflorone, were synthesized and tested as inhibitors of purified Arabidopsis thaliana HPPD. The most active compound was a beta-triketone with a C(9) alkyl side chain, not reported as natural, which inhibited HPPD with an I(50) of 19 +/- 1 nM.

Bullatenone, 1,3-dione and sesquiterpene chemotypes of Lophomyrtus species.

The only known natural source of the volatile bioactive compounds bullatenone 1 and 4-methyl-1-phenylpentane-1,3-dione 2 is the New Zealand endemic shrub Lophomyrtus bullata (Myrtaceae). GC and NMR analyses of essential oils and solvent extracts of L. bullata, L.

Novel chemotaxonomic markers of the Alternaria infectoria species-group.

Two new structurally related metabolites, novae-zelandin A (1) and novae-zelandin B (2), as well as the novel metabolite 4Z-infectopyrone (3) were purified from extracts of filamentous fungi belonging to the Alternaria infectoria species-group. The structures were elucidated by a combination of 1D and 2D NMR spectroscopic data and MS data. 1-3 are important chemotaxonomic markers of the A.

Triketones active against antibiotic-resistant bacteria: synthesis, structure-activity relationships, and mode of action.

A series of acylated phloroglucinols and triketones was synthesized and tested for activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecalis (VRE) and multi-drug-resistant Mycobacterium tuberculosis (MDR-TB). A tetra-methylated triketone with a C12 side chain was the most active compound (MIC of around 1.0 microg/ml against MRSA) and was shown to stimulate oxygen consumption by resting cell suspensions, suggesting that the primary target was the cytoplasmic membrane.

Sesquiterpenes from the New Zealand Liverwort Lepidolaena hodgsoniae.

NMR studies have shown that seven new sesquiterpenoids, 3, 4, 5a, and 7-10, isolated from dried samples of the New Zealand liverwort Lepidolaena hodgsoniae have the same substituted cyclopentapyran ring system as the previously described insecticidal sesquiterpene diene hodgsonox (1), which has been reported only from this plant. In all but one compound, 10, the 1,1-disubstituted double bond of hodgsonox has migrated into an endocyclic position, but only two, 5a and 9, have the double bonds in conjugation. These seven new compounds represent a variety of different oxidation levels.

Synthesis of the 3-methylene-2-vinyltetrahydropyran unit; the hallmark of the sesquiterpene, hodgsonox.

[structure: see text] The synthesis of some simple compounds containing the previously unreported 3-methylene-2-vinyltetrahydropyran system, a unique feature of the liverwort metabolite, hodgsonox is reported. Key features are the creation of an acrolein substituted in the alpha-position with a three-carbon chain bearing a terminal electrophilic site, addition of a vinyl group, and cyclization.

Determination of the absolute configuration of Anisotome irregular diterpenes: application of CD and NMR methods.

Several Anisotome diterpene derivatives were synthesized in an attempt to obtain a crystalline compound for X-ray analysis. Although we were unable to obtain a suitable crystal, the absolute configuration of the irregular diterpene skeleton was determined using two other techniques: a circular dichroism (CD) protocol based on a tetraarylporphyrin molecular tweezer that allowed prediction of the absolute stereochemistry on a microscale level, and a method employing differences in NMR shifts from derivatization of the naturally occurring acid 1 with enantiomers of a phenylglycine methyl ester (PGME) chiral anisotropic reagent. The excellent agreement between the CD and NMR methods led to the assignment of a 2S-absolute configuration for anisotomenoic acid 1.

Ether-linked biflavonoids from Quintinia acutifolia.

The New Zealand tree Quintinia acutifolia has yielded four biflavonoids, the new 2,3,2'',3''-tetrahydroochnaflavone (3), and its 7,7''-di-O-methyl derivative (1). The rare 7-O-methyl-2,3,2'',3''-tetrahydroochnaflavone (2) and 2'',3''-dihydroochnaflavone (4), both previously identified only from members of the Ochnaceae, were also isolated. Structures were determined by spectroscopic methods.

2-Hydroxyflavanones from Leptospermum polygalifolium subsp. polygalifolium Equilibrating sets of hemiacetal isomers.

2,5-Dihydroxy-6-methyl-7-methoxyflavanone and its isomer 2,5-dihydroxy-8-methyl-7-methoxyflavanone have been identified as the principal components in the ethanol extract of L. polygalifolium subsp. polygalifolium.

Biosynthesis of the sesquiterpene hodgsonox from the New Zealand liverwort Lepidolaena hodgsoniae.

The incorporation of [1-13C] labelled glucose into hodgsonox, a sesquiterpene epoxide with a unique, doubly allylic ether functionality has been studied in axenic cultures of the liverwort Lepidolaena hodgsoniae. Quantitative 13C NMR spectroscopic analysis showed that the isoprene units are derived exclusively from the methylerythritol phosphate pathway.

A New Tetracycle from Dimerization of the N-Methylpyridazinium Ion in Aqueous Solution.

In a one-pot synthesis at room temperature the N-methylpyridazinium ion (1) dimerizes stereospecifically and with 100 % conversion in a series of OH -catalyzed processes to give a new tetraazafluorene (2). Four of the individual steps can be identified directly and monitored by H NMR spectroscopy.