2-Diazoacetoacetic acid, an efficient and convenient reagent for the synthesis of alpha-diazo-beta-ketoesters

The formation of various alpha-diazo acetoacetic esters can be obtained in a single transformation with good to excellent yields using readily available 2-diazoacetoacetic acid

Efficiency of the Wang-Landau algorithm: a simple test case

We analyze the efficiency of the Wang-Landau algorithm to sample a multimodal distribution on a prototypical simple test case. We show that the exit time from a metastable state is much smaller for the Wang Landau dynamics than for the original standard Metropolis-Hastings algorithm, in some asymptotic regime. Our results are confirmed by numerical experiments on a more realistic test case

Permutation-invariant distance between atomic configurations

We present a permutation-invariant distance between atomic configurations, defined through a functional representation of atomic positions. This distance enables to directly compare different atomic environments with an arbitrary number of particles, without going through a space of reduced dimensionality (i.e. fingerprints) as an intermediate step. Moreover, this distance is naturally invariant through permutations of atoms, avoiding the time consuming associated minimization required by other common criteria (like the Root Mean Square Distance). Finally, the invariance through global rotations is accounted for by a minimization procedure in the space of rotations solved by Monte Carlo simulated annealing. A formal framework is also introduced, showing that the distance we propose verifies the property of a metric on the space of atomic configurations. Two examples of applications are proposed. The first one consists in evaluating faithfulness of some fingerprints (or descriptors), i.e. their capacity to represent the structural information of a configuration. The second application concerns structural analysis, where our distance proves to be efficient in discriminating different local structures and even classifying their degree of similarity

A Second-Generation Synthesis of the Cyanthiwigin Natural Product Core

An improved synthesis of the cyanthiwigin natural product core enabled by new catalytic technology is reported. The key double catalytic enantioselective alkylation has been reoptimized using a recently developed protocol employing low loadings of palladium catalyst, thereby facilitating large-scale production of the tricyclic cyanthiwigin framework. Additionally, preparation of the penultimate aldehyde intermediate is expedited through the application of anti-Markovnikov Tsuji–Wacker oxidation

The targeting of zero-rated basic foodstuffs under value-added tax (VAT) in South Africa

Since the inception of VAT in South Africa, various studies have been conducted to investigate the distributional impact of the tax as well as the effectiveness of zero-rating as tool to alleviate the burden on poor households. This paper argues that the targeting of the zero-rated basket can be improved to enhance the intended equity gain. Using the food category of vegetables as a case study, and distinguishing between sub-groups of vegetables, this paper conducts tax incidence analyses to compare the relative burden of VAT on different categories of vegetables for various income groups. The findings suggest that canned vegetables should be included in the zero-rated basket, frozen vegetables should remain zero-rated, but some (not ‘basic’) fresh vegetables should be taxed at the standard rate. It also strongly suggests that the specific items in the zero-rated basket should be reviewed on a regular basis.Department of HE and Training approved lis

Influence of seed treatment with mineral nutrient products on emergence and growth in spring oilseed rape (Brassica napus L.)

Seed treatment with mineral nutrients in spring oilseed rape (SOR) under cold climatic conditions has the potential to improve the outcome of production. The objectives of this study were to investigate the effects of mineral nutrients applied as seed treatment on germination and growth of roots and biomass in SOR. In addition, seed yield and oil content were also measured. Seed vigour tests and in-field experiments were performed in Central Sweden in 2016 and 2017. Seven products with different composition of mineral nutrients were applied to the seed in a combination with binder, filler and fungicide (BFF), or applied directly onto the seed. The results showed that a treatment with mineral nutrients increased the plant size at stage BBCH 60 (early flowering stage) when the products were applied in combination with BFF in the field experiments. However, the increased plant size did not influence seed yield. Furthermore, when seeds were treated only with a nutrient product the addition of BFF decreased plant size by 10% on average and seed and crude fat yields by 4% on average. The use of BFF may thereby be questioned and is subject to further investigation

The Total Synthesis of (–)-Scabrolide A

The first total synthesis of the norcembranoid diterpenoid scabrolide A is disclosed. The route begins with the synthesis of two chiral pool-derived fragments, which undergo a convergent coupling to expediently introduce all 19 carbon atoms of the natural product. An intramolecular Diels–Alder reaction and an enone–olefin cycloaddition/fragmentation sequence are then employed to construct the fused [5–6–7] linear carbocyclic core of the molecule and complete the total synthesis

Enantioselective Iridium-Catalyzed Allylic Alkylation Reactions of Masked Acyl Cyanide Equivalents

The first enantioselective iridium-catalyzed allylic alkylation reaction of a masked acyl cyanide (MAC) reagent has been developed. The transformation allows for the use of an umpoled synthon, which serves as a carbon monoxide equivalent. The reaction proceeds with good yield and excellent selectivity up to gram scale for a wide range of substituted allylic electrophiles, delivering products amenable to the synthesis of highly desirable, enantioenriched vinylated α-aryl carbonyl derivatives