Enantioselective Aziridination of Unactivated Terminal Alkenes Using a Planar Chiral Rh(III) Indenyl Catalyst.

Chiral aziridines are important structural motifs found in natural products and various target molecules. They serve as versatile building blocks for the synthesis of chiral amines. While advances in catalyst design have enabled robust methods for enantioselective aziridination of activated olefins, simple and abundant alkyl-substituted olefins pose a significant challenge. In this work, we introduce a novel approach utilizing a planar chiral rhodium indenyl catalyst to facilitate the enantioselective aziridination of unactivated alkenes. This transformation exhibits a remarkable degree of functional group tolerance and displays excellent chemoselectivity favoring unactivated alkenes over their activated counterparts, delivering a wide range of enantioenriched high-value chiral aziridines. Computational studies unveil a stepwise aziridination mechanism in which alkene migratory insertion plays a central role. This process results in the formation of a strained four-membered metallacycle and serves as both the enantio- and rate-determining steps in the overall reaction.

Accelerating PROTAC drug discovery: Establishing a relationship between ubiquitination and target protein degradation.

PROTACs have emerged as a new class of drugs that can target the "undruggable" proteome by hijacking the ubiquitin proteasome system. Despite PROTACs' success, most current PROTACs interface with a limited number of E3 ligases, hindering their expansion to many challenging therapeutic uses. Currently, PROTAC drug discovery relies heavily on traditional Western blotting and reporter gene assays which are insensitive and prone to artifacts, respectively. New reliable methods to monitor true PROTAC function (i.e., ubiquitination and subsequent degradation of targets at physiological expression levels) without external tags are essential to accelerate the PROTAC discovery process and to address many unmet therapeutic areas. In this study, we developed a new high-throughput screening technology using "TUBEs" as ubiquitin-binding entities to monitor PROTAC-mediated poly-ubiquitination of native target proteins with exceptional sensitivity. As a proof of concept, targets including BRD3, Aurora A Kinase, and KRAS were used to demonstrate that ubiquitination kinetics can reliably establish the rank order potencies of PROTAC with variable ligands and linkers. PROTAC-treated cell lysates with the highest levels of endogenous target protein ubiquitination - termed "UbMax" - display excellent correlations with DC50 values obtained from traditional Western blots with the added benefits of being high throughput, providing improved sensitivity, and reducing technical errors.

Tandem Ubiquitin Binding Entities (TUBEs) as Tools to Explore Ubiquitin-Proteasome System and PROTAC Drug Discovery.

The ubiquitin proteasome system (UPS) is a complex pathway that involves multiple enzymes and culminates in the formation of a polyubiquitin chain on a target protein. As its importance is becoming more evident in drug discovery, there is a renewed interest in understanding the role that polyubiquitin chains play. This has been a challenge, mostly due to the lack of experimental tools for detecting the polyubiquitinated forms of a protein of interest (POI). Tandem Ubiquitin Binding Entities (TUBEs) are engineered protein domains that bind specifically to polyubiquitin chains. These polyubiquitin affinity matrices are highly sensitive as they bind to polyubiquitin chains in the nanomolar range. They exist in two forms: pan-selective TUBEs and chain-selective TUBEs. The ability of TUBEs to be conjugated to different entities is truly what makes them unique. TUBEs are used in a wide variety of experiments such as in protein pulldowns to enrich for polyubiquitinated proteins. They are an alternative to ubiquitin antibodies in Western blots. Further, TUBEs are used as capture reagents for immobilizing polyubiquitinated proteins on a microtiter plate. The use of TUBEs as components of in vitro and cell-based assays presents the unique feature of confirming and assessing the polyubiquitination of a POI in response to inhibitors, activators, or PROTAC® molecules. Therefore, TUBEs not only play a big role in studying the UPS but also have a huge potential for speeding up the drug discovery process.

Sodium Bicyclo[1.1.1]pentanesulfinate: A Bench-Stable Precursor for Bicyclo[1.1.1]pentylsulfones and Bicyclo- [1.1.1]pentanesulfonamides.

Herein, we present the synthesis of the bench-stable sodium bicyclo[1.1.1]pentanesulfinate (BCP-SO2 Na) and its application in the synthesis of bicyclo[1.1.1]pentyl (BCP) sulfones and sulfonamides. The salt can be obtained in a four-step procedure from commercially available precursors in multigram scale without the need for column chromatography or crystallization. Sulfinates are known to be useful precursors in radical and nucleophilic reactions and are widely used in medicinal chemistry. This building block enables access to BCP sulfones and sulfonamides avoiding the volatile [1.1.1]propellane which is favorable for the extension of SAR studies. Further, BCP-SO2 Na enables the synthesis of products that were not available with previous methods. A chlorination of BCP-SO2 Na and subsequent reaction with a Grignard reagent provides a new route to BCP sulfoxides. Several products were analyzed by single-crystal X-ray diffraction.

Characterization of genes required for both Rpg1 and rpg4-mediated wheat stem rust resistance in barley.

BACKGROUND: Puccinia graminis f. sp. tritici (Pgt) race TTKSK and its lineage pose a threat to barley production world-wide justifying the extensive efforts to identify, clone, and characterize the rpg4-mediated resistance locus (RMRL), the only effective resistance to virulent Pgt races in the TTKSK lineage. The RMRL contains two nucleotide-binding domain and leucine-rich repeat (NLR) resistance genes, Rpg5 and HvRga1, which are required for resistance. The two NLRs have head-to-head genome architecture with one NLR, Rpg5, containing an integrated C-terminal protein kinase domain, characteristic of an "integrated sensory domain" resistance mechanism. Fast neutron mutagenesis of line Q21861 was utilized in a forward genetics approach to identify genetic components that function in the RMRL or Rpg1 resistance mechanisms, as Q21861 contains both genes. A mutant was identified that compromises both RMRL and Rpg1-mediated resistances and had stunted seedling roots, designated required for P. graminis resistance 9 (rpr9). RESULTS: The rpr9 mutant generated in the Q21861 background was crossed with the Swiss landrace Hv584, which carries RMRL but contains polymorphism across the genome compared to Q21861. To map Rpr9, a Hv584 x rpr9 F6:7 recombinant inbred line (RIL) population was developed. The RIL population was phenotyped with Pgt race QCCJB. The Hv584 x rpr9 RIL population was genotyped with the 9 k Illumina Infinium iSelect marker panel, producing 2701 polymorphic markers. A robust genetic map consisting of 563 noncosegregating markers was generated and used to map Rpr9 to an ~ 3.4 cM region on barley chromosome 3H. The NimbleGen barley exome capture array was utilized to capture rpr9 and wild type Q21861 exons, followed by Illumina sequencing. Comparative analysis, resulting in the identification of a 1.05 Mbp deletion at the chromosome 3H rpr9 locus. The identified deletion contains ten high confidence annotated genes with the best rpr9 candidates encoding a SKP1-like 9 protein and a F-box family protein. CONCLUSION: Genetic mapping and exome capture rapidly identified candidate gene/s that function in RMRL and Rpg1 mediated resistance pathway/s. One or more of the identified candidate rpr9 genes are essential in the only two known effective stem rust resistance mechanisms, present in domesticated barley.

Pyramiding rpg4- and Rpg1-Mediated Stem Rust Resistance in Barley Requires the Rrr1 Gene for Both to Function.

Stem rust, caused by Puccinia graminis f. sp. tritici (Pgt) is an economically important disease of wheat and barley. Rpg1 is the only resistance gene deployed in Midwestern US barley varieties and provides remarkable resistance to most North American races, except Pgt race QCCJB. Rpg1 is also ineffective against Pgt race TTKSK and its lineage that originated in Africa. The barley rpg4-mediated resistance locus (RMRL) conferring resistance to Pgt races QCCJB and TTKSK was isolated from line Q21861, which is resistant to all known Pgt races due to Rpg1 and RMRL. To develop elite barley varieties RMRL was pyramided into the varieties, Pinnacle and Conlon (both contain Rpg1), producing the near isogenic lines (NILs), Pinnacle RMRL-NIL (PRN) and Conlon RMRL-NIL (CRN). The CRN was resistant to Pgt races QCCJB (RMRL specific) and HKHJC (Rpg1 specific) at the seedling stage and Pgt race TTKSK (RMRL specific) at the adult stage. In contrast, PRN was susceptible to QCCJB and HKHJC at the seedling stage and TTKSK at the adult stage. Interestingly, PRN's susceptibility to QCCJB and HKHJC showed that RMRL was non-functional in the Pinnacle background but its presence also suppressed Rpg1-mediated resistance. Thus, in the absence of a gene/s found in the Q21861 background, Rpg1 becomes non-functional if RMRL is present, suggesting that another polymorphic gene, that we designated Rrr1 (required for rpg4-mediated resistance 1), is required for RMRL resistance and Rpg1-mediated resistance in the presence of RMRL. Utilizing a PRN/Q21861 derived recombinant inbred line (RIL) population, Rrr1 was delimited to a ∼0.5 MB physical region, slightly proximal (∼1.8 MB) of RMRL on barley chromosome 5H. A second gene, designated required for Rpg1-mediated resistance 2 (Rrr2), with duplicate gene action to Rrr1 in Rpg1-mediated resistance function, was genetically delimited to a physical region of ∼0.7 MB, slightly distal (∼3.1 MB) to Rpg1 on the short arm of barley chromosome 7H. Thus, Rrr1 is required for RMRL resistance and Rrr1 or Rrr2 is required for functional Rpg1-mediated resistance in the presence of the RMRL introgression. Candidate Rrr1 and Rrr2 genes were identified that need to be considered when pyramiding Rpg1 and RMRL in barley.

Fast growth involves high dependence on stored resources in seedlings of Mediterranean evergreen trees.

BACKGROUND AND AIMS: The carbon (C) and nitrogen (N) needed for plant growth can come either from soil N and current photosynthesis or through remobilization of stored resources. The contribution of remobilization to new organ growth on a whole-plant basis is quite well known in deciduous woody plants and evergreen conifers, but this information is very limited in broadleaf evergreen trees. This study compares the contribution of remobilized C and N to the construction of new organs in spring, and assesses the importance of different organs as C and N sources in 1-year-old potted seedlings of four ecologically distinct evergreen Mediterranean trees, namely Quercus ilex, Q. coccifera, Olea europaea and Pinus hapelensis. METHODS: Dual (13)C and (15)N isotope labelling was used to unravel the contribution of currently taken up and stored C and N to new growth. Stored C was labelled under simulated winter conditions. Soil N was labelled with the fertilization during the spring growth. KEY RESULTS: Oaks allocated most C assimilated under simulated winter conditions to coarse roots, while O. europaea and P. halepensis allocated it to the leaves. Remobilization was the main N source (>74 %) for new fine-root growth in early spring, but by mid-spring soil supplied most of the N required for new growth (>64 %). Current photosynthesis supplied >60 % of the C in new fine roots by mid-spring in most species. Across species, the proportion of remobilized C and N in new shoots increased with the relative growth rate. Quercus species, the slowest growing trees, primarily used currently acquired resources, while P. halepensis, the fastest growing species, mainly used reserves. Increases in the amount of stored N increased N remobilization, which fostered absolute growth both within and across species. Old leaves were major sources of remobilized C and N, but stems and roots also supplied considerable amounts of both in all species except in P. halepensis, which mainly relied on foliage formed in the previous growing season to supply stored resources. CONCLUSIONS: Seedlings of Mediterranean evergreen trees have distinct C and N storage physiologies, with relative growth rate driving the contribution of remobilized resources to new growth. These differences may reduce competition and facilitate species coexistence.

A nonparametric temperature controller with nonlinear negative reaction for multi-point rapid MR-guided HIFU ablation.

Magnetic resonance-guided high intensity focused ultrasound (MRgHIFU) is a noninvasive method for thermal ablation, which exploits the capabilities of magnetic resonance imaging (MRI) for excellent visualization of the target and for near real-time thermometry. Oncological quality of ablation may be obtained by volumetric sonication under automatic feedback control of the temperature. For this purpose, a new nonparametric (i.e., model independent) temperature controller, using nonlinear negative reaction, was designed and evaluated for the iterated sonication of a prescribed pattern of foci. The main objective was to achieve the same thermal history at each sonication point during volumetric MRgHIFU. Differently sized linear and circular trajectories were investigated ex vivo and in vivo using a phased-array HIFU transducer. A clinical 3T MRI scanner was used and the temperature elevation was measured in five slices simultaneously with a voxel size of 1 ×1 ×5 mm(3) and temporal resolution of 4 s. In vivo results indicated a similar thermal history of each sonicated focus along the prescribed pattern, that was 17.3 ± 0.5 °C as compared to 16 °C prescribed temperature elevation. The spatio-temporal control of the temperature also enabled meaningful comparison of various sonication patterns in terms of dosimetry and near-field safety. The thermal build-up tended to drift downwards in the HIFU transducer with a circular scan.

An experimental model to investigate the targeting accuracy of MR-guided focused ultrasound ablation in liver.

BACKGROUND: Magnetic Resonance-guided High Intensity Focused Ultrasound (MRgHIFU) is a hybrid technology that aims to offer non-invasive thermal ablation of targeted tumors or other pathological tissues. Acoustic aberrations and non-linear wave propagating effects may shift the focal point significantly away from the prescribed (or, theoretical) position. It is therefore mandatory to evaluate the spatial accuracy of ablation for a given HIFU protocol and/or device. We describe here a method for producing a user-defined ballistic target as an absolute reference marker for MRgHIFU ablations. METHODS: The investigated method is based on trapping a mixture of MR contrast agent and histology stain using radiofrequency (RF) ablation causing cell death and coagulation. A dedicated RF-electrode was used for the marker fixation as follows: a RF coagulation (4 W, 15 seconds) and injection of the mixture followed by a second RF coagulation. As a result, the contrast agent/stain is encapsulated in the intercellular space. Ultrasonography imaging was performed during the procedure, while high resolution T1w 3D VIBE MR acquisition was used right after to identify the position of the ballistic marker and hence the target tissue. For some cases, after the marker fixation procedure, HIFU volumetric ablations were produced by a phased-array HIFU platform. First ex vivo experiments were followed by in vivo investigation on four rabbits in thigh muscle and six pigs in liver, with follow-up at Day 7. RESULTS: At the end of the procedure, no ultrasound indication of the marker's presence could be observed, while it was clearly visible under MR and could be conveniently used to prescribe the HIFU ablation, centered on the so-created target. The marker was identified at Day 7 after treatment, immediately after animal sacrifice, after 3 weeks of post-mortem formalin fixation and during histology analysis. Its size ranged between 2.5 and 4 mm. CONCLUSIONS: Experimental validation of this new ballistic marker method was performed for liver MRgHIFU ablation, free of any side effects (e.g. no edema around the marker, no infection, no bleeding). The study suggests that the absolute reference marker had ultrasound conspicuity below the detection threshold, was irreversible, MR-compatible and MR-detectable, while also being a well-established histology staining technique.

Elevated CO2 and/or ozone modify lignification in the wood of poplars (Populus tremula x alba).

Trees will have to cope with increasing levels of CO(2) and ozone in the atmosphere. The purpose of this work was to assess whether the lignification process could be altered in the wood of poplars under elevated CO(2) and/or ozone. Young poplars were exposed either to charcoal-filtered air (control), to elevated CO(2) (800 µl l(-1)), to ozone (200 nl l(-1)) or to a combination of elevated CO(2) and ozone in controlled chambers. Lignification was analysed at different levels: biosynthesis pathway activities (enzyme and transcript), lignin content, and capacity to incorporate new assimilates by using (13)C labelling. Elevated CO(2) and ozone had opposite effects on many parameters (growth, biomass, cambial activity, wood cell wall thickness) except on lignin content which was increased by elevated CO(2) and/or ozone. However, this increased lignification was due to different response mechanisms. Under elevated CO(2), carbon supply to the stem and effective lignin synthesis were enhanced, leading to increased lignin content, although there was a reduction in the level of some enzyme and transcript involved in the lignin pathway. Ozone treatment induced a reduction in carbon supply and effective lignin synthesis as well as transcripts from all steps of the lignin pathway and some corresponding enzyme activities. However, lignin content was increased under ozone probably due to variations in other major components of the cell wall. Both mechanisms seemed to coexist under combined treatment and resulted in a high increase in lignin content.

A pilot study for clinical feasibility of the near-harmonic 2D referenceless PRFS thermometry in liver under free breathing using MR-guided LITT ablation data.

OBJECTIVES: The conventional implementations of proton resonance frequency shift (PRFS) magnetic resonance thermometry (MRT) require the subtraction of single or multiple temporal references, a motion sensitive critical feature. A pilot study was conducted here to investigate the clinical feasibility of near-harmonic two-dimensional (2D) referenceless PRFS MRT, using patient data from MR-guided laser ablation of liver malignancies. METHODS: PRFS MRT with respiratory-triggered multi-slice gradient-recalled (GRE) acquisition was performed under free breathing in six patients. The precision of the novel referenceless MRT was compared with the reference phase subtraction. Coupling the referenceless MRT with a model-based, real-time compatible regularisation algorithm was also investigated. RESULTS: The precision of MRT was improved by a factor of 3.3 when using the referenceless method as compared to the reference phase subtraction. The approach combining referenceless PRFS MRT and model-based regularisation yielded an estimated precision of 0.7° to 2.1°C, resulting in millimetre-range agreement between the calculated thermal dose and the 24 h post-treatment unperfused regions in liver. CONCLUSIONS: The application of the near-harmonic 2D referenceless MRT method was feasible in a clinical scenario of MR-guided laser-induced thermal therapy (LITT) ablation in liver and permitted accurate prediction of the thermal lesion under free breathing in conscious patients, obviating the need for a controlled breathing under general anaesthesia.

ARFI-prepared MRgHIFU in liver: simultaneous mapping of ARFI-displacement and temperature elevation, using a fast GRE-EPI sequence.

MR acoustic radiation force imaging (ARFI) is an elegant adjunct to MR-guided high intensity focused ultrasound for treatment planning and optimization, permitting in situ assessment of the focusing and targeting quality. The thermal effect of high intensity focused ultrasound pulses associated with ARFI measurements is recommended to be monitored on line, in particular when the beam crosses highly absorbent structures or interfaces (e.g., bones or air-filled cavities). A dedicated MR sequence is proposed here, derived from a segmented gradient echo-echo planar imaging kernel by adding a bipolar motion encoding gradient with interleaved alternating polarities. Temporal resolution was reduced to 2.1 s, with in-plane spatial resolution of 1 mm. MR-ARFI measurements were executed during controlled animal breathing, with trans-costal successively steered foci, to investigate the spatial modulation of the focus intensity and the targeting offset. ARFI-induced tissue displacement measurements enabled the accurate localization, in vivo, of the high intensity focused ultrasound focal point in sheep liver, with simultaneous monitoring of the temperature elevation. ARFI-based precalibration of the focal point position was immediately followed by trans-costal MR-guided high intensity focused ultrasound ablation, monitored with a conventional proton resonance frequency shift MR thermometry sequence. The latter MR thermometry sequence had spatial resolution and geometrical distortion identical with the ARFI maps, hence no coregistration was required.

Reference-free PRFS MR-thermometry using near-harmonic 2-D reconstruction of the background phase.

Proton resonance frequency shift (PRFS) MR thermometry (MRT) is the generally preferred method for monitoring thermal ablation, typically implemented with gradient-echo (GRE) sequences. Standard PRFS MRT is based on the subtraction of a temporal reference phase map and is, therefore, intrinsically sensitive to tissue motion (including deformation) and to external perturbation of the magnetic field. Reference-free (or reference-less) PRFS MRT has been previously described by Rieke and was based on a 2-D polynomial fit performed on phase data from outside the heated region, to estimate the background phase inside the region of interest. While their approach was undeniably a fundamental progress in terms of robustness against tissue motion and magnetic perturbations, the underlying mathematical formalism requires a thick unheated border and may be subject to numerical instabilities with high order polynomials. A novel method of reference-free PRFS MRT is described here, using a physically consistent formalism, which exploits mathematical properties of the magnetic field in a homogeneous or near-homogeneous medium. The present implementation requires as input the MR GRE phase values along a thin, nearly-closed and unheated border. This is a 2-D restriction of a classic Dirichlet problem, working on a slice per slice basis. The method has been validated experimentally by comparison with the "ground truth" data, considered to be the standard PRFS method for static ex vivo tissue. "Zero measurement" of the gradient-echo phase baseline was performed in healthy volunteer liver with rapid acquisition (300 ms/image). In vivo data acquired in sheep liver during MR-guided high intensity focused ultrasound (MRgHIFU) sonication were post-processed as proof of applicability in a therapeutic scenario. Bland and Altman mean absolute difference between the novel method and the "ground truth" thermometry in ex vivo static tissue ranged between 0.069 °C and 0.968 °C, compared to the inherent "white" noise SD of 0.23 °C. The accuracy and precision of the novel method in volunteer liver were found to be on average 0.13 °C and respectively 0.65 °C while the inherent "white" noise SD was on average 0.51 °C. The method was successfully applied to large ROIs, up to 6.2 cm inner diameter, and the computing time per slice was systematically less than 100 ms using C++. The current limitations of reference-free PRFS thermometry originate mainly from the need to provide a nearly-closed border, where the MR phase is artifact-free and the tissue is unheated, plus the potential need to reposition that border during breathing to track the motion of the anatomic zone being monitored.A reference-free PRFS thermometry method based on the theoretical framework of harmonic functions is described and evaluated here. The computing time is compatible with online monitoring during local thermotherapy. The current reference-free MRT approach expands the workflow flexibility, eliminates the need for respiratory triggers, enables higher temporal resolution, and is insensitive to unique-event motion of tissue.

Correction of susceptibility-induced GRE phase shift for accurate PRFS thermometry proximal to cryoablation iceball.

INTRODUCTION: The susceptibility contrast between frozen and unfrozen tissue disturbs the local magnetic field in the proximity of the ice-ball during cryotherapy. This effect should be corrected for in real time to allow PRFS-based monitoring of near-zero temperatures during intervention. MATERIAL AND METHODS: Susceptibility artifacts were corrected post-processing, using a rapid numerical algorithm. The difference in bulk magnetic susceptibility between frozen and non-frozen tissue was approximated to be uniform over the ice-ball volume and was determined from the isothermal principle applied to the phase-transition frontier of compartments. Subsequently, the magnetic perturbation field was calculated rapidly in 3D using a Fourier-convolution. Experimental studies were performed for two scenarios: tissue defrosting in a water bath and induction of an ice-ball by a MR-compatible cryogenic probe. RESULTS: The susceptibility artifacts yielded PRFS temperature errors as high as 10-12°C proximal to the ice-ball, positive or negative depending on the relative orientation of the position vector from the B(o) direction. These effects were fully corrected for to within the noise range. The susceptibility-corrected PRFS temperature values were consistent with the phase-transition isothermal condition, irrespective of the local orientation of the position vector. CONCLUSION: By implementing on-line the post processing algorithm, PRFS MRT may be used as a safety tool for non-invasive and accurate monitoring of near-zero temperatures during MR-guided clinical cryotherapy.

Inflorescence of grapevine (Vitis vinifera L.): a high ability to distribute its own assimilates.

The distribution of carbon (C) into whole grapevine fruiting cuttings was investigated during flower development to determine the relative contribution of inflorescence and leaf photoassimilates in the total C balance and to investigate their partitioning towards other plant organs. A (13)C labelling procedure was used to label C photoassimilates by leaves and inflorescences in grapevine. Investigations were carried out at various stages of flower/berry development, from separated cluster to fruit set, using grapevine fruiting cuttings with four leaves (Vitis vinifera L. cv. Chardonnay). This is the first study reporting that, during its development, (i) the carbon needs of the inflorescence were met by both leaf and inflorescence photosynthesis, and (ii) the inflorescence amazingly participated significantly to the total C balance of grapevine cuttings by redistributing an important part of its own assimilates to other plant organs. With regard to flowering, 29% of C assimilated by the inflorescence remained in the inflorescence, while partitioning towards the stem reached 42% and, as a lower proportion, 15% in leaves, and 14% in roots.

Asymmetric total synthesis of (+)-fumimycin via 1,2-addition to ketimines.

The first asymmetric total synthesis of fumimycin was accomplished. As a key step, a 1,2-addition of methyl Grignard reagents to ketimines with quinine as additive was employed. The absolute configuration of (+)-fumimycin was determined by CD-spectroscopy combined with time-dependent density functional calculations.

The total synthesis of (±)-fumimycin.

The antibiotic agent fumimycin has been synthesized for the first time. This natural product was found to inhibit the bacterial peptide deformylase and may represent a lead structure to a class of novel antibacterials. Our synthetic strategy towards fumimycin involved the following steps: Dakin oxidation of an aldehyde functionality, conversion of an oxime through radical fragmentation to form an N-diphenylphosphoryl group, construction of an α-trisubstituted amine by 1,2-addition to a ketimine, a Claisen rearrangement with subsequent transition-metal-catalyzed olefin isomerization to install a propenyl chain and final amidation.

Synthesis of methoxyfumimycin with 1,2-addition to ketimines.

The synthesis of (+/-)-methoxyfumimycin, a potential new bacterial peptide deformylase (PDF) inhibitor, is reported. To generate the stereogenic fully substituted carbon, the key step is a 1,2-addition of a methyl Grignard reagent to a ketimine. The overall synthetic strategy involves a Dakin oxidation of a vanillin derivative, Friedel-Crafts acylation, Claisen rearrangement, lactonization, and rhodium-catalyzed olefin isomerization.

Towards an asymmetric synthesis of the bacterial peptide deformylase (PDF) inhibitor fumimycin.

Studies towards the synthesis of the bacterial peptide deformylase (PDF) inhibitor fumimycin are reported. The synthetic approach features an organocatalytic access to the alpha,alpha-disubstituted amino acid unit and results in the synthesis of an advanced intermediate which already contains all functionalities of fumimycin.

Do elevation of CO(2) concentration and nitrogen fertilization alter storage and remobilization of carbon and nitrogen in pedunculate oak saplings?

Soil nitrogen can alter storage and remobilization of carbon and nitrogen in forest trees and affect growth responses to elevated carbon dioxide concentration ([CO(2)]). We investigated these effects in oak saplings (Quercus robur L.) exposed for two years to ambient or twice ambient [CO(2)] in combination with low- (LN, 0.6 mmol N l(-1)) or high-nitrogen (HN, 6.1 mmol N l(-1)) fertilization. Autumn N retranslocation efficiency from senescing leaves was less in HN saplings than in LN saplings, but about 15% of sapling N was lost to the litter. During the dormant season, nonstructural carbohydrates made up 20 to 30% of the dry mass of perennial organs. Starch was stored mainly in large roots where it represented 35-46% of dry mass. Accumulation of starch increased in large roots in response to LN but was unaffected by elevated [CO(2)]. The HN treatment resulted in high concentrations of N-soluble compounds, and this effect was reduced by elevated [CO(2)], which decreased soluble protein N (-17%) and amino acid N (-37%) concentrations in the HN saplings. Carbon and N reserves were labeled with (13)C and (15)N, respectively, at the end of the first year. In the second year, about 20% of labeled C and 50% of labeled N was remobilized for spring growth in all treatments. At the end of leaf expansion, 50-60% of C in HN saplings originated from assimilation versus only 10-20% in LN saplings. In HN saplings only, N uptake occurred, and some newly assimilated N was allocated to new shoots. Through effects on the C and N content of perennial organs, elevated [CO(2)] and HN increased remobilization capacity, thereby supporting multiple shoot flushes, which increased leaf area and subsequent C acquisition in a positive feedback loop.