Anna Barlow - Academia.edu (original) (raw)

Papers by Anna Barlow

ChemInform, 2010

Chemistry of New Zealand Apiaceae: New Irregular Diterpenes from Anisotome flexuosa and A. haasti... more Chemistry of New Zealand Apiaceae: New Irregular Diterpenes from Anisotome flexuosa and A. haastii Showing Conformational Exchange.-The isolation and structure elucidation of two novel anisotomene derivatives (I) from the title plants are described.-(VAN KLINK,

FEBS Journal, 2008

A set of thirty-two natural and ten semisynthetic ecdysteroids was assayed in murine 3T3 cells ac... more A set of thirty-two natural and ten semisynthetic ecdysteroids was assayed in murine 3T3 cells across ten different ecdysteroid receptor (EcR) ligandbinding domains derived from nine arthropod species in an engineered gene switch format. Among the ecdysteroids tested, the most biologically widespread ecdysteroid, 20-hydroxyecdysone (20E), was moderately and consistently potent across the tested EcRs. The most potent ligand-receptor combination (EC 50 = 0.3 nm) was ponasterone A (PoA) actuating the Nephotettix cincticeps EcR switch. The most robust ligand-receptor combination, as measured by potency and efficacy, was PoA actuating either the Bombyx mori EcR or a 'VY' (E274V ⁄ V390I ⁄ Y410E) mutant of Choristoneura fumiferana EcR. Parallel ecdysteroid structure-activity relationships were observed across species; addition of hydroxyl groups at positions 2, 3, 14, 20 and 22 incrementally enhanced potency, whereas hydroxylation at position 25 retarded potency. Nevertheless, several outlier ligand-EcR combinations, such as cyasterone actuating the VY C. fumiferana EcR mutant and canescensterone activating Bemisia argentifolii EcR, exhibited an inversion of relative potency, and therefore lend themselves to construction of orthogonal duplex gene switches. The potency inversion between these two ligand-receptor pairs can be accounted for by steroid-tail contact residues Tyr411 and Met502 in VY C. fumiferana EcR corresponding to two threonines in B. argentifolii EcR. Another potency inversion was also observed with cyasterone operating on the VY mutant of C. fumiferana EcR and polypodine B activating Aedes aegypti EcR. The ecdysteroid-EcR dataset, generated in a non-natural system, nevertheless invites conjecture regarding relative ecdysteroid potencies, plant species distribution of certain phytoecdysteroids, and the role of phytoecdysteroids as chemodefense against relevant insect herbivores.

Tetrahedron Letters, 1999

A novel class of irregular diterpene has been discovered in the New Zealand subalpine plant Aniso... more A novel class of irregular diterpene has been discovered in the New Zealand subalpine plant Anisotome flexuosa Dawson (Apiaceae/Umbelliferae). The structure and relative stereochemistry ofanisotomenoic acid 4 (3,3a,4,4tetramethy•-3-(4-methy•-3-penteny•)-2•3•3a•4•5•6-hexahydr•-•H-2-indenecarb•xy•ic acid) was determined by NMR correlation experiments conducted on 4 and a primary alcohol derivative 5 (3,3a,4,4-tetramethyl-3-(4-methyl-3-pentenyl)-2,3,3a,4,5,6-hexahydro-1H-2-indenyl) methanol). Alcohol 5 was subsequently confirmed as a natural product.

Phytochemistry, 2001

The incorporation of 13C labelled glucose into trichocolein, deoxytomentellin, trans-phytol and s... more The incorporation of 13C labelled glucose into trichocolein, deoxytomentellin, trans-phytol and stigmasterol has been studied in axenic cultures of the liverwort Trichocolea tomentella. Quantitative 13C NMR spectroscopic analysis of the resulting labelling patterns showed that the isoprene units of the hemi- and monoterpenoid moieties and the diterpene phytol are derived from the methylerythritol phosphate pathway, whereas the isoprene units of stigmasterol are built up via the mevalonic acid pathway. These results indicate the involvement of both IPP biosynthetic pathways in different cellular compartments. A new, hydroperoxy geranyl phenyl ether derivative is also described.

Phytochemistry, 2003

The incorporation of [1-13 C] labelled glucose into hodgsonox, a sesquiterpene epoxide with a uni... more The incorporation of [1-13 C] 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 13 C NMR spectroscopic analysis showed that the isoprene units are derived exclusively from the methylerythritol phosphate pathway.

The Journal of Organic Chemistry, 2005

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

Journal of natural products, 2005

NMR studies have shown that seven new sesquiterpenoids, 3, 4, 5a, and 7-10, isolated from dried s... more 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. Two of the new derivatives, 9 and 10, were isolated only from an aged sample and are presumably artifacts. The only other terpenoid isolated in significant quantity was (7R,10R)-calamenene (2).

Chirality, 2004

Several Anisotome diterpene derivatives were synthesized in an attempt to obtain a crystalline co... more 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.