Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

The magic effect of endocyclic but non-sterically hindering biisoquinoline chelates: From fast-moving molecular shuttles to [3]rotaxanes

The use of 8,8′-diaryl-substituted 3,3′-biisoquinolines allows the construction of new multi-component assemblies that are inaccessible with the 2,9-diaryl-substituted 1,10-phenanthroline ligands previously developed by the Sauvage group. This is due to the sterically non-hindering nature of the new chelates, which makes three-component entanglements around octahedral metal centres such as iron(II), cobalt(II) and ruthenium(II) readily possible. Among the newly synthesized molecular assemblies are [3]rotaxanes and [3]pseudorotaxanes in which two molecular strings pass through a single macrocycle, as well as molecular shuttles that exhibit greatly improved shuttling kinetics when compared to previously investigated molecular machines that are based on copper(I)/copper(II) redox chemistry.     

A unique single carboxylate-bridged spin-frustrated chiral Mn(II) metallatriangle

The reaction between Hmbpymca ligand (prepared in situ from the hydrolysis of 5-methyl-4-cyano-bispyrimidine with NaOH and further neutralization with 2 M HCl) and Mn(ClO(4))(2)·4H(2)O in 1:1 molar ratio afforded the triangulo-trimanganese(II) complex [Mn(3)(bpymca)(3)(H(2)O)(6)]Cl(3)·6H(2)O 1. The chloride anions in this complex come from the HCl used in the neutralization process. The molecular structure of 1 consists of cationic molecular triangles [Mn(3)(μ-mbpymca)(3)(H(2)O)(6)](3+) with C(3) symmetry, chloride anions and crystallization water molecules, all of them involved in an extensive network of hydrogen bonds, leading to a chiral network. Within the [Mn(3)(μ-mbpymca)(3)(H(2)O)(6)](3+) cations, seven-coordinated Mn(II) ions are bridged by both oxygen atoms of the carboxylate groups and exhibit a MnO(5)N(2) compressed pentagonal bipyramidal coordination environment. The temperature dependence of the magnetic susceptibility shows the presence of weak antiferromagnetic interactions between Mn(II) ions mediated by the carboxylate group of the mbpymca ligand and the existence of a 3D antiferromagnetic ordering below 4 K, which has its origin in the AF inter-trimer exchange interactions mediated by the strong hydrogen bonds present in the crystal of 1. The experimental magnetic susceptibility data above 7 K could be satisfactorily fitted to the theoretical analytical expression derived from the spin Hamiltonian H = -J(S(1)S(2) + S(1)S(3) + S(2)S(3)) with J = -0.782(3) cm(-1) and g = 2.092(3). The model predicts a degenerate ground state with an S = 1/2, which is typical of triangular trimetallic spin frustrated systems containing metal with non-integer spins. DFT calculations were performed on the molecular structure as found in the solid state to support the experimental J value and the Mn-O(carb)-Mn as the primarily exchange pathway.     

CuLn complexes with a single μ-oximato bridge

Two original dinuclear (LnYb, 3 and LnEr, 4) and one trinuclear Cu^IILn^IIICu^II (LnGd, 5) complexes derived from a polydentate non symmetrical Schiff base ligand H₂L have been prepared. The ligand possesses two functions (phenol and oxime) able to coordinate the Ln ions, but structural studies (X-ray diffraction and powder X-ray diffraction) show that the Cu^II and Ln^III ions are only bridged by the oximato (NO) pair. The missing phenoxo bridge is replaced by a surprising pseudo-bridge involving one oxygen atom of the nitrato anion linked to the Cu and Ln ions according to a η²: η¹: μ mode. Although this latter contact has no role from the magnetic point of view, it introduces a large deformation of the unique bridging network. The CuYb complex 3 and the trinuclear CuGdCu complex 5 present antiferromagnetic interactions, with a J_CuGd interaction equal to ?1.25 cm^?1 in 5. The genuine single bridge can be considered as responsible for the antiferromagnetic character of the interaction.     

Amorphous structure and electronic properties of the Ge1Sb2Te4 phase change material

Ge1Sb2Te4 is one of the most commonly used phase change materials, due to the large optical and electrical contrast between a metastable crystalline phase and the amorphous phase. We use ab initio molecular dynamics to generate an amorphous Ge1Sb2Te4 structure. By analysing the distance distributions, we show that the structure can be analysed in terms of 21% of tetrahedrally coordinated Ge atoms and 79% of 3-fold Ge atoms. These are involved in distorted octahedral shells with bond length correlations that are similar to the a-GeTe structure as a consequence of a Peierls-distortion. The electronic properties are shown to be in reasonable agreement with the experiment with an electronic gap of 0.45 eV with. The optical conductivity curve is also in agreement with the experiment, with a maximal conductivity at an energy of ～3 eV.     

Two minor phytoecdysteroids of the plant Silene viridiflora

Chemical investigations of Silene viridiflora (L.) yielded a new ecdysteroid, 20-hydroxyecdysone 20,22-monoacetonide-25-acetate (1), and a known ecdysteroid, 2-deoxypolypodine B-3-beta-D-glucoside (2). The elucidation of the chemical structures was established by 1D and 2D NMR experiments.     

Trumpet with near-perfect harmonicity: design and acoustic results

This paper presents a mathematical design methodology for determining the shape of a trumpet air column that has near-perfect harmonicity, whose components are discontinuity-free, and whose input impedance peak heights are balanced over the playing range. The simulation model employed assumes linear wave propagation and uses cylindrical element discretization with a plane wave approximation. Acoustic measurements are made using a test set-up with an estimated relative measurement error of ±3 cents. Comparisons of measured results are given for the presented design (Macaluso trumpet) and the same trumpet air column with the bell replaced by a commercially used generic trumpet bell of unknown shape (Generic trumpet). For acoustic resonance modes 2-13 (233-1515 Hz), the measured root-mean-square (rms) harmonicity deviation is 5 cents for the Macaluso trumpet, whereas it is 18 cents for the Generic trumpet. However, considering the estimated measurement uncertainty, each of those deviations is somewhat over-stated. For that same range of resonances, the rms deviation between measured and calculated resonance frequencies for the Macaluso trumpet is 3 cents, thus validating the presented simulation model and equations.     

Spectral Measures Associated with the Factorization of the Lebesgue Measure on a Set via Convolution

Let \(Q\) be a fundamental domain of some full-rank lattice in \({\mathbb {R}}^d\) and let \(\mu \) and \(\nu \) be two positive Borel measures on \({\mathbb {R}}^d\) such that the convolution \(\mu *\nu \) is a multiple of \(\chi _Q\) . We consider the problem as to whether or not both measures must be spectral (i.e. each of their respective associated \(L^2\) space admits an orthogonal basis of exponentials) and we show that this is the case when \(Q = [0,1]^d\) . This theorem yields a large class of examples of spectral measures which are either absolutely continuous, singularly continuous or purely discrete spectral measures. In addition, we propose a generalized Fuglede’s Conjecture for spectral measures on \({\mathbb {R}}^1\) and we show that it implies the classical Fuglede’s Conjecture on \({\mathbb {R}}^1\) .     

A sharp lower bound for the log canonical threshold

In this note, we prove a sharp lower bound for the log canonical threshold of a plurisubharmonic function ${\varphi}$ with an isolated singularity at 0 in an open subset of ${\mathbb{C}^n}$ . This threshold is defined as the supremum of constants c > 0 such that ${e^{-2c\varphi}}$ is integrable on a neighborhood of 0. We relate ${c(\varphi)}$ to the intermediate multiplicity numbers ${e_j(\varphi)}$ , defined as the Lelong numbers of ${(dd^c\varphi)^j}$ at 0 (so that in particular ${e_0(\varphi)=1}$ ). Our main result is that ${c(\varphi)\geqslant\sum_{j=0}^{n-1} e_j(\varphi)/e_{j+1}(\varphi)}$ . This inequality is shown to be sharp; it simultaneously improves the classical result ${c(\varphi)\geqslant 1/e_1(\varphi)}$ due to Skoda, as well as the lower estimate ${c(\varphi)\geqslant n/e_n(\varphi)^{1/n}}$ which has received crucial applications to birational geometry in recent years. The proof consists in a reduction to the toric case, i.e. singularities arising from monomial ideals.