Gareth L. Nealon

Most Proteaceae and some Fabaceae species produce specialised cluster roots (CRs), and are abundant in severely phosphorus (P)‐impoverished soils in southwest Australia. Two types of CRs, compound and simple, have been identified. However, the difference in their P‐mining strategies remains unclear. Therefore, we conducted glasshouse and field experiments to compare the P‐acquisition strategies among 18 CR‐producing species in Proteaceae and Fabaceae. Proteaceae produced a significantly larger mass of CRs than Fabaceae. Particularly, Banksia species produced the largest mass of compound CRs and exhibited the greatest net plant‐absorbed P in pots and consistently higher mature leaf manganese concentration in the field. In contrast, Hakea and Grevillea species produced less mass of simple CRs but three times as much soil adhered to their CRs per CR dry weight, resulting in greater absorbed P per CR weight. All plants depleted similar P compounds from soil and accessed c . 52% of P that was not extracted by a NaOH‐EDTA solution, suggesting that both CRs shared a common physiological function for mining scarcely available P. This study highlights two divergent P‐acquisition strategies: greater biomass investment in compound CRs versus greater P‐acquisition efficiency in simple CRs.

Two novel free porphyrins, isabellins A and B, as well as the known compounds corallistin D and deuteroporphyrin IX were isolated from a marine sponge Isabela sp. LC-MS analysis of the crude extract revealed that the natural products were present both as free porphyrins and iron(III) coordinated hemins, designated isabellihemin A, isabellihemin B, corallistihemin D and deuterohemin IX, respectively. Structures were determined via high-resolution mass spectrometry, UV-Vis spectroscopy and extensive NOESY NMR spectroscopic experiments. The type-I alkyl substitution pattern of isabellin A and isabellihemin A was assigned unambiguously by single crystal X-ray diffraction. Biological evaluation of the metabolites revealed potent cytotoxicity for isabellin A against the NS-1 murine myeloma cell line.

Docetaxel (DTX) is a widely used chemotherapy drug that is associated with numerous side effects and limited bioavailability. Macromolecular conjugates of DTX may improve drug targeting, solubility, reduce off-target toxicity, and overcome mechanisms of multidrug resistance. However, most polymer conjugates of DTX investigated to date make use of biopolymers, which are of fixed structure and are not well suited to optimisation and subsequent reaction to introduce further functionality. Here, we show the preparation of synthetic copolymer conjugates of DTX with drug loading of up to 20% w/w that also has potential for tuning backbone hydrophilicity and the number of reactive sites for conjugation. The intermediates produced are comprehensively characterised, as are the macromolecular conjugates, which are tested in the MCF-7 human breast adenocarcinoma cell line to assess toxicity and anticancer efficacy. The conjugates produced have IC₅₀ values within one order of magnitude of DTX, as expected for slow release of DTX by ester hydrolysis. The results suggest that the system is promising for delivery of DTX and future work may examine conjugates of a wider molecular weight range, optimisation of DTX and PEG conjugation efficiency, and in vivo biodistribution.

Two previously reported bis-indole alkaloids, echinosulfone A and echinosulfonic acid B, have been isolated for the first time from a Western Australian marine sponge, Crella sp. (order: Poecilosclerida, family: Crellidae). Single-crystal X-ray diffraction of a decomposition product of echinosulfone A prompted our investigation and subsequent structure reassignment of the echinosulfonic acid natural product family, which we report here. The reassignments are supported by analysis of 1D and 2D NMR data, MS fragmentation, and DFT calculations of ¹³C NMR shifts.

The synthesis of the Rh(I)-aryl complex, Rh(I)(nbd)(BiPh)(P(4-FC₆H₄)₃) is reported and its efficacy as an initiator for the (co)polymerization of phenylacetylenes established. The X-ray crystal structure indicates that the complex adopts a slightly distorted square planar geometry whose purity and structure was also confirmed by elemental analysis and ¹H, ¹³C, ³¹P, ¹⁹F, ¹⁰³Rh, and ³¹P-¹⁰³Rh{¹H} HMQC NMR spectroscopy. We demonstrate that Rh(I)(nbd)(BiPh)(P(4-FC₆H₄)₃) mediates the (co)polymerization of phenylacetylenes in a controlled fashion with initiation efficiencies as high as 0.98, as evidenced by the pseudo-first-order kinetic and number-average molecular weight versus conversion profiles. The ability to form well-defined AB diblock copolymers, in a stereoregular manner, by sequential monomer addition is verified in the block copolymerization of phenylacetylene with 4-fluorophenylacetylene with quantitative crossover efficiency, as determined by size exclusion chromatography.

Polymers are an attractive anchoring platform for the synthesis of radioimmunoconjugates. They enable independent control over the amount of radioisotope loading and antibody attachment, which is pivotal in developing tailorable formulations for personalised medicine. Herein, we report the synthesis of p(HEMA-ran-GMA) for the conjugation of lutetium ions and rituximab as a functional platform for radioimmunotherapy. We demonstrate the suitability of this platform using non-Hodgkin's lymphoma cells.

The synthesis of a novel Rh(I)-aryl complex is detailed and its ability to serve as an initiator in the stereospecific polymerisation of phenylacetylene evaluated. Targeting the Rh(I) species, (2-phenylnaphthalen-1-yl)rhodium(I)(2,5-norbornadiene)tris(para-fluorophenylphosphine), Rh(nbd)(P(4-FC₆H₄)₃)(2-PhNapth), following recrystallization we obtained the isomeric (2-(naphthalen-2-yl)phenyl)rhodium(I) complex, Rh(nbd)(P(4-FC₆H₄)₃)(2-NapthPh), as determined by X-ray single-crystal structure analysis, and confirmed by X-ray powder diffraction. The isolation of the latter species was proposed to occur from the target (2-PhNapth) derivative via an intramolecular 1,4-Rh atom migration. This supposition was supported by density functional theory (DFT) calculations that indicated the isolated (2-NapthPh) derivative has lower energy (−19 kJ mol⁻¹) than the targeted complex. The structure of the isolated (2-NapthPh) species was confirmed by multinuclear NMR spectroscopy including 2D ³¹P–¹⁰³Rh{¹H, ¹⁰³Rh}, heteronuclear multiple-quantum correlation (HMQC) experiments; however, NMR analysis indicated the presence of a second, minor species in solution in an approximate 1 : 4 ratio with the 2-NapthPh complex. The minor species was identified as a second structural isomer, the 3-phenylnaphthyl derivative, proposed to be formed under a dynamic equilibrium with the 2-NapthPh derivative via a second 1,4-Rh atom migration. DFT calculations indicate that this 1,4-migration proceeds through a low-energy pathway involved in the oxidative addition of a C–H bond to Rh followed by a reductive elimination with the distribution of the products being thermodynamically controlled. The recrystallized Rh(nbd)(P(4-FC₆H₄)₃)(2-NapthPh) complex was subsequently evaluated as an initiator in the polymerisation of phenylacetylene (PA); gratifyingly, the Rh(I) species was an active initiating species with the pseudo-first-order kinetic and molecular weight evolution vs time plots both linear implying a controlled polymerisation while yielding (co)polymers with low dispersities (Đ = M_w/M_n typically ≤1.25) and high cis-transoidal stereoregularity (>95%). Typical initiation efficiencies, while not quantitative (as judged by size exclusion chromatography), were nonetheless high at ca. 0.8. The presence of the minor 3-phenylnaphthyl species when in solution is proposed to be the cause of the observed non-quantitative initiation.

Several trinuclear ferrocenes are obtained by Friedel–Crafts reaction of octamethylferrocene with ferrocenoyl chloride and subsequent modifications. 1,1′-Diferrocenoyloctamethylferrocene (3) is transformed to the divinyl derivative (4a) by reaction with MeLi and AlCl₃. The reactive 4a cyclizes spontaneously to a [4]ferrocenophane with buta-1,3-diene handle (5) or in the presence of AlCl₃ to a [3]ferrocenophane with propene handle (6). Structure assignments are supported by X-ray crystallography and NMR spectroscopy, and mechanisms are proposed. Electrochemical behavior of the compounds was investigated with cyclic voltammetry, and assignments of the redox processes were carried out with the aid of density functional theory calculations. The synthesized compounds and demonstrated transformations represent useful tools for preparation of materials for charge-transport studies in metal−molecule−metal junctions.

The synthesis, characterization and use, as initiators for phenylacetylene polymerizations, of three new rhodium(I)‐vinyl complexes containing fluorenyl functionality with fluorine‐functionalized phosphine ligands is described. Rh(nbd)(CPh=CFlu)P(4‐FC₆H₄)₃, Rh(nbd)(CPh=CFlu)P(4‐CF₃C₆H₄)₃, and Rh(nbd)(CPh=CFlu)P[3,5‐(CF₃)₂C₆H₃]₃ (nbd: 2,5‐norbornadiene; Flu: fluorenyl) were prepared and isolated as discrete, orange compounds and were readily recrystallized yielding X‐ray quality crystals. All complexes were characterized by a combination of ¹H, ³¹P, ¹⁹F, ¹⁰³Rh NMR spectroscopy and 2D ³¹P‐¹⁰³Rh/³¹P‐¹⁰³Rh{¹⁰³Rh} heteronuclear multiple‐quantum correlation (HMQC) experiments, elemental analysis, and single‐crystal X‐ray analysis. The complexes were active as initiators in the co‐ordination insertion polymerization of phenylacetylene, with initiation efficiencies spanning the range 13–56 %, and yielded polyphenylacetylenes of low dispersity (Ð = M_w/M_n) with high cis‐transoidal stereoregularity.

Synthetic auxin herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D) are widely used for selective control of broadleaf weeds in cereals and transgenic crops. Although the troublesome weed wild radish (Raphanus raphanistrum) has developed resistance to 2,4-D, no populations have yet displayed an enhanced capacity for metabolic detoxification of the herbicide, with both susceptible and resistant wild radish plants readily metabolizing 2,4-D. Using mass spectrometry and NMR, the major 2,4-D metabolite was identified as the glucose ester, and its structure confirmed by synthesis. As expected, both the endogenous and synthetic compounds retained auxin activity in a bioassay. The lack of detectable 2,4-D hydroxylation in wild radish, and the lability of the glucose ester, suggest that metabolic 2,4-D resistance is unlikely to develop in this species.