Matías López-Rodríguez

Epoxide-Opening Cascades Triggered by a Nicholas Reaction: Total Synthesis of Teurilene†

The way in which nature approaches the synthesis of complex molecules is a great source of inspiration to organic chemists for planning a synthetic route to a natural product. In this context, cascade cyclizations are considered a valuable tool for obtaining molecular complexity in a straightforward manner. Focusing on polycyclic ethers, it is well accepted by the scientific community that these types of compounds originate from a cascade cyclization of a polyepoxide backbone, thus leading to structures such as the ones depicted in Figure 1. Therefore, epoxide-opening cascades have been

Crystal structures of self-assembled nanotubes from flexible macrocycles by weak interactions

Herein we report the crystal structures of tubular self-assemblies of flexible macrooligolides. The assembly is driven by the propensity of the macrocycles to create nearly flat structures displaying a void space within them and the cooperativity of weak directional interactions such as dipole–dipole interactions and CH⋯O hydrogen bonds and non-directional interactions such as van der Waals contacts. The significance of the stereochemistry and the size of the cavity in the formation of the nanotubes are also studied.

New anionic cobalt complexes using highly hindered bis-amides with varying donor abilities as ligands

Four potential tetradentate ligands of formulae 1,2-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)ethane (H(4)L(1), 1), 1,2-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)propane (H(4)L(2), 2), 1,2-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)benzene (H(4)L(3), 3) and 1,8-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)naphthalene (H(4)L(4), 4) have been prepared and the crystal structures of three of them (1, 3 and 4) determined by single crystal X-ray diffraction. The investigation of their complexing ability toward Co(II) afforded the compounds of formulae [Co(III)(L(3))Na(I)(H(2)O)(2)] (5), [Co(III)(L(n))Li(I)(H(2)O)2] with n = 1 (6), 2 (7) and 3 (8) and [Co(II)(L(4))Li(I)(2)] (9). Complexes 5-8 are square planar Co(III) species, as corroborated by the crystal structure of 5. In this compound, two amide-nitrogen and two phenolate-oxygen atoms of a fully deprotonated (L(3))(4-) anion build a slightly distorted square planar surrounding around the cobalt atom, the Co-N distances [1.858(3) and 1.861(3) A] being somewhat longer than the Co-O ones [1.798(3) and 1.801(3) A]. Magnetic and 1H NMR data at room temperature for 6-8 support the occurrence of an intermediate S = 1 low-lying state for the Co(III) center which is stabilized by the strong donating ability of the fully deprotonated bis-amidate ligands. In the case of the compound with the naphthalene derivative (9), the analytical and spectroscopic data suggest the occurrence of a low spin Co(II) complex. The weakening of the ligand field strength of the tetradentate bis-amidate ligand in the naphthalene derivative (5-6-5 ring-membered fused chelate) when compared to the situation in complexes 5-8 (5-5-5 ring-membered fused chelate) would account for this feature.

Sesquiterpenes, flavonoids, shikimic acid derivatives and pyrrolizidine alkaloids from Senecio kingii Hook

Twenty-four compounds including eleven eremophilanolides (1-11), one eremophilane (13), five shikimic acid derivatives (14-18), six flavonoids (19-24), and the macrocyclic unsaturated pyrrolizidine alkaloid integerrimine (25) were isolated from Senecio kingii, an endemic species from the Magallanes Region (Chile). Compounds 3, 5, 6, 8-11 and 13-18 have not been previously reported as natural products. Their molecular structures were determined by NMR spectroscopic analysis and comparison with published NMR data. An X-ray-analysis of compound 3 has been performed. Their insecticidal and antifungal activities were tested, being compound 3 the strongest insect antifeedant. Compounds 6, 9 and 18 were moderate antifungals.

Propane-1,3-diyl bis­(pyridine-4-carboxyl­ate)

The title compound. C15H14N2O4, (I), has a gauche–gauche (O/C/C/C—O/C/C/C or GG) conformation and is a positional isomer of propane-1,3-diyl bis(pyridine-3-carboxylate), (II). The molecule of (I) lies on a twofold rotation axis, which passes through the central C atom of the aliphatic chain, giving one half-molecule per asymmetric unit. There is excellent agreement of the geometric parameters of (I) and (II). The most obvious differences between them are the O/C/C/C—O/C/C/C torsion angles [56.6 (2)° in (I) and 174.0 (3)/70.2 (3)° in (II) for GG and TG conformations, respectively] and the dihedral angle between the planes of the aromatic rings [80.3 (10)° in (I) and 76.5 (3)° in (II)]. The crystal structure is stabilized by weak C—H⋯ N and C—H⋯ O hydrogen bonding.

X-RAY CRYSTALLOGRAPHIC STRUCTURAL STUDY ON A CINNAMOLIDE-CLASS SESQUITERPENE LACTONE FROM DRIMYS WINTERIFORST. VAR. CHILENSIS

In order to ascertain the structure and secure the assignment of the stereochemistry of the title compound an X-ray analysis was performed, the absolute configuration was not determined by this analysis. 1 . Chemical studies has shown the presence of a variety of sesquiterpenes with drimano skeleton 2 and flavonoids. Some of these structures have shown significant antibacterial, antifungi, antitumor and insecticide properties 3, 4 . The extract of Drimys winteri leaves afforded Cinnamolide and Drimenin two lactones with drimano skeleton. Cinnamolide have not been previuosly reported for these specie. Recently it has been reported that the title compound was also isolated of Cinnamosma macrocarpa 5 . In order to ascertain the structure and secure the assignment of the stereochemistry of the title compound an X-ray analysis was performed, the absolute configuration was not determined by this analysis. The X-ray crystallographic analysis confirms the previously proposed molecular structure, including the molecular conformation. The molecular structure is shown in Fig.1 and selected geometric parameters are given in Table I. The structure consists of a drimane skeleton. The methyl group at C9a is seen to be β-oriented. The cyclohexene ring A and cyclohexane ring B exist in a half-chair and a chair conformation, respectively (Q T = 0.538(3) A, ϕ 2 = 227.4(4) °, q 2 = 0.428 (3) A for ring A; Q T = 0.556(4) A , ϕ 2 = 21 (4)o, q 2 = 0.060 (4) A for ring B) , and the lactone ring an envelope on C3a conformation 6 . The A and B rings are trans-fused. Bond lengths are within expected ranges 7

Additional Insights into the Obtusallene Family: Components of Laurencia marilzae

The obtusallenes are a significant subset of C15-halogenated acetogenins that incorporate 12-membered cyclic ethers. We have recently reported the isolation from Laurencia marilzae of 12-epoxyobtusallene IV (1) and its related α,β-unsaturated carboxylate ester (2), both of special biogenetic relevance. Here we describe the final step of our study, the isolation of three new analogues (3-5), among these, the first bromopropargylic derivative (3) of this class of macrocyclic C15-acetogenins. The structures were elucidated by analysis of NMR and X-ray data. 12-Epoxyobtusallene IV (1), its new isomer 4, and known obtusallene IV (6) were evaluated for their apoptosis-inducing activities in a human hepatocarcinoma cell line.

Bioactive constituents from transformed root cultures of Nepeta teydea

A phytochemical study of an extract from transformed root cultures of Nepeta teydea, induced by Agrobacterium rhizogenes, led to the isolation of the following new compounds: the sesquiterpene (-)-cinalbicol, the diterpene teydeadione (6,11,14-trihydroxy-12-methoxy-abieta-5,8,11,13,15-penten-7-one), a degraded C23-triterpene (teydealdehyde) and three fatty acid esters of lanosta-7,24-dien-3β-ol. The propyl ester of rosmarinic acid was also isolated for the first time from a natural source. In addition, two dehydroabietane diterpenes, eight triterpenes and eighteen known phenolic compounds were obtained. The antifeedant, cytotoxic and phytotoxic activities of the isolated compounds have also been investigated.

A monoclinic modification of propane-1,3-diyl bis-(pyridine-3-carboxyl-ate).

In the title compound, C15H14N2O4, (I), the molecule lies on a twofold rotation axis which passes through the central C atom of the aliphatic chain, giving one half-molecule per asymmetric unit. The structure is a monoclinic polymorph of the triclinic structure previously reported [Brito, Vallejos, Bolte & López-Rodríguez (2010). Acta Cryst. E66, o792], (II). The most obvious difference between them is the O/C/C/C—O/C/C/C torsion angle [58.2 (7)° in (I) and 173.4 (3)/70.2 (3)° in (II) for GG and TG conformations, respectively]. Another important difference is observed in the dihedral angle between the planes of the aromatic rings [86.49 (7)° for (I) and 76.4 (3)° for (II)]. The crystal structure features a weak π–π interaction [centroid–centroid distance = 4.1397 (10)Å]; this latter kind of interaction is not evident in the triclinic polymorph.

Supramolecular Structure, Thermal and Spectroscopic Properties of a New Coordination Polymer: Catena-Bis(μ2-4,4′-dipyridyldisulfide-κ2N,N′)-Bis(AQUO)-Copper(II)di-trifluoromethanesulfonate

A new supramolecular network of copper (II), [{Cu(bpds)2(H2O)2}] • 2CF3SO3]n, (I), (bpds = 4,4′-bipyridildisulfide) has been synthesized and characterized by elemental analysis and Fourier transform infrared (FT-IR) and its structure determined using X-ray crystallography. The thermal decomposition mechanism of the complex was studied by using thermogravimetry-derivative thermogravimetry (TG-DTG) techniques. X-ray structural analysis revealed that the coordination polymer displays 1D chains. The octahedral O2N4 chromophore surrounding the metal ion forms via two trans located water oxygen and four nitrogen from four bpds ligand. The structure consists of Cu(H2O)2 fragments linked by pairs of bpds ligand to form a double-stranded chain. The thermogravimetric analysis indicates sequential loss of adsorbed and coordinated water and triflate counter ion, prior to more comprehensive ligand fragmentation at elevated temperatures.