Structural Variations of 2D and 3D Lanthanide Oxalate Frameworks Hydrothermally Synthesized in the Presence of Hydrazinium Ions.

Depending on the nature of the 4f element, six different lanthanide oxalate families were hydrothermally synthesized in the presence of hydrazinium ions. Four of them correspond to the general formula NH[(CO)]·HO but have different structural formulas according to the number of coordinated water molecules or hydrazinium ions and the structural arrangement, NH[La(CO)] (); NH[{(NH)}(CO)]·4HO, = Ce, Pr, Nd, and Sm (); NH[{(HO)}(CO)], = Sm, Eu, Gd, Tb, Dy, and Ho (); NH[(CO)]·HO, = Yb, = 3, and Lu, = 2 (). The two others do not contain hydrazinium ions.

Multifaceted Study on a Cytochalasin Scaffold: Lessons on Reactivity, Multidentate Catalysis, and Anticancer Properties.

An intramolecular Diels-Alder (IMDA) reaction efficiently accelerated by Schreiner's thiourea is reported, to build a functionalized cytochalasin scaffold (periconiasin series) for biological purposes. DFT calculation highlighted a unique multidentate cooperative hydrogen bonding in this catalysis. The deprotection end game afforded a collection of diverse structures and showed the peculiar reactivity of the Diels-Alder cycloadducts upon functionalization.

Structurally Diverse Diterpenoids from Sandwithia guyanensis.

Bioassay-guided fractionation of an EtOAc extract of the trunk bark of Sandwithia guyanensis, using a chikungunya virus (CHIKV)-cell-based assay, afforded 17 new diterpenoids 1-17 and the known jatrointelones A and C (18 and 19). The new compounds included two tetranorditerpenoids 1 and 2, a trinorditerpenoid 3, euphoractines P-W (4-11), and euphactine G (13) possessing the rare 5/6/7/3 (4-7), 5/6/6/4 (8-11), and 5/6/8 (13) fused ring skeletons, sikkimenoid E (12), and jatrointelones J-M (14-17) possessing jatropholane and lathyrane carbon skeletons, respectively. Jatrointelones J (14) and M (17) represent the first naturally occurring examples of C-15 nonoxidized lathyrane-type diterpenoids.

New selective cyclooxygenase-2 inhibitors from cyclocoumarol: Synthesis, characterization, biological evaluation and molecular modeling.

In this work, a serie of cyclocoumarol derivatives was designed, synthesized, characterized and studied for their potentialities as selective inhibitors of COX-2. All target compounds have been screened for their anti-inflammatory activity by the assay of PGE production. Among them, compound 5d exhibited the most potent inhibitory activity with a PGE inhibition compared to NS-398 (79% and 88% respectively) and showed non-inhibitory activity towards the COX-1 enzyme.

All-metal aromatic cationic palladium triangles can mimic aromatic donor ligands with Lewis acidic cations.

We present that cationic rings can act as donor ligands thanks to suitably delocalized metal-metal bonds. This could grant parent complexes with the peculiar properties of aromatic rings that are crafted with main group elements. We assembled Pd nuclei into equilateral mono-cationic triangles with unhindered faces.

Cytotoxic Prenylated Stilbenes Isolated from Macaranga tanarius.

With the aim of discovering new cytotoxic prenylated stilbenes of the schweinfurthin series, Macaranga tanarius was selected for detailed phytochemical investigation among 21 Macaranga species examined by using a molecular networking approach. From an ethanol extract of the fruits, seven new prenylated stilbenes, schweinfurthins K-Q (7-13), were isolated, along with vedelianin (1), schwenfurthins E-G (2-4), mappain (5), and methyl-mappain (6). The structures of the new compounds were established by spectroscopic data analysis.

Enantioselective Organocatalytic Intramolecular Aza-Diels-Alder Reaction.

A highly efficient catalytic enantioselective intramolecular Povarov reaction was developed with primary anilines as 2-azadiene precursors. A wide variety of angularly fused azacycles were obtained without column chromatography in high to excellent yields and with excellent diastereo- and enantioselectivity (d.r.

First Total Synthesis, Structure Revision, and Natural History of the Smallest Cytochalasin: (+)-Periconiasin G.

The total synthesis of the smallest cytochalasin isolated so far, periconiasin G, which bears a seven-membered ring in lieu of the usual macrocycle, has been performed from both enantiomers of citronellal, relying on an intramolecular Diels-Alder reaction in favor of the natural endo stereochemistry. We show that, among the four synthesized stereoisomers, including the exo isomers, the one matching the NMR data of the natural product was not that assigned in the original report, imposing structure revision. The natural product, previously isolated from a plant-mutualistic fungus, was biologically investigated taking into account its natural history, showing significant effects against the phytopathogenic fungus Botrytis cinerea and thus opening new opportunities in combating this pest.

Chiral Phosphoric Acid Catalyzed [3 + 2] Cycloaddition and Tandem Oxidative [3 + 2] Cycloaddition: Asymmetric Synthesis of Substituted 3-Aminodihydrobenzofurans.

Asymmetric [3 + 2] cycloaddition of quinones with ene- and thioene-carbamates was achieved by chiral phosphoric acid catalysis, providing the corresponding 3-amino-2,3-dihydrobenzofurans in excellent yields with moderate to good diastereoselectivities and excellent enantioselectivities. An asymmetric tandem oxidative cycloaddition protocol starting from hydroquinones was also accomplished with phenyliodine(III) diacetate and a chiral phosphoric acid in the same reaction vessel.

Halocyclization of Unsaturated Guanidines Mediated by Koser's Reagent and Lithium Halides.

The synthesis of halogenated cyclic guanidines through iodine(III)-mediated umpolung of halide salts is described. Cyclic guanidines of various sizes can be obtained with generally excellent regioselectivities through either a chloro- or a bromocyclization, using Koser's reagent and the corresponding lithium salt.

Regio-, Diastereo-, and Enantioselective Nitroso-Diels-Alder Reaction of 1,3-Diene-1-carbamates Catalyzed by Chiral Phosphoric Acids.

Chiral phosphoric acid-catalyzed asymmetric nitroso-Diels-Alder reaction of nitrosoarenes with carbamate-dienes afforded cis-3,6-disubstituted dihydro-1,2-oxazines in high yields with excellent regio-, diastereo-, and enantioselectivities. Interestingly, we observed that the catalyst is able not only to control the enantioselectivity but also to reverse the regioselectivity of the noncatalyzed nitroso-Diels-Alder reaction. The regiochemistry reversal and asynchronous concerted mechanism were confirmed by DFT calculations.

A Simple Synthesis of Triangular All-Metal Aromatics Allowing Access to Isolobal All-Metal Heteroaromatics.

A simple synthetic method allows the one-pot assembly of C3 -symmetric, 44-core-valence-electron, triangular Pd or Pt clusters and their heterobimetallic mixed Pd/Pt analogues. These mixed metal complexes are the first examples of stable triangular all-metal heteroaromatics. In contrast to traditional heteroaromatic molecules formed combining main-group elements, they actually retain structural and electronic features of their homonuclear analogues.

Antibacterial Labdane Diterpenoids from Vitex vestita.

A large-scale in vitro screening of tropical plants using an antibacterial assay permitted the selection of several species with significant antibacterial activities. Bioassay-guided purification of the dichloromethane extract of the leaves of the Malaysian species Vitex vestita, led to the isolation of six new labdane-type diterpenoids, namely, 12-epivitexolide A (2), vitexolides B and C (3 and 4), vitexolide E (8), and vitexolins A and B (5 and 6), along with six known compounds, vitexolides A (1) and D (7), acuminolide (9), 3β-hydroxyanticopalic acid (10), 8α-hydroxyanticopalic acid (11), and 6α-hydroxyanticopalic acid (12). Their structures were elucidated on the basis of 1D and 2D NMR analyses and HRMS experiments.

Formal Asymmetric Organocatalytic [3+2] Cyclization between Enecarbamates and 3-Indolylmethanols: Rapid Access to 3-Aminocyclopenta[b]indoles.

A highly enantio- and diastereoselective synthesis of 3-aminocyclopenta[b]indoles has been developed through formal [3+2] cycloaddition reaction of enecarbamates and 3-indolylmethanols. This transformation is catalyzed by a chiral phosphoric acid that achieves simultaneous activation of both partners of the cycloaddition. Mechanistic data are also presented that suggest that the reaction occurs through a stepwise pathway.

Direct biosynthetic cyclization of a distorted paracyclophane highlighted by double isotopic labelling of L-tyrosine.

The biosynthesis of pyrrocidines, fungal PK-NRP compounds featuring a strained [9]paracyclophane, was investigated in Acremonium zeae. We used a synthetic L-tyrosine probe, labelled with oxygen 18 as a reporter of phenol reactivity and carbon 13 as a tracer of incorporation of this exogenous precursor. The ((18)O)phenolic oxygen was incorporated, suggesting that phenol behaves as a nucleophile during the formation of the bent aryl ether.