Francisco M. Guerra

Allylic Oxidation of Alkenes Catalyzed by a Copper–Aluminum Mixed Oxide

A strategy for the allylic oxidation of cyclic alkenes with a copper-aluminum mixed oxide as catalyst is presented. The reaction involves the treatment of an alkene with a carboxylic acid employing tert-butyl hydroperoxide as the oxidant. In all cases, the corresponding allylic esters are obtained. When L-proline is employed, the allylic alcohol or ketone is obtained. The oxidation of cyclohexene and valencene has been optimized by design of experiments (DoE) statistical methodology.

Enantioselective synthesis of α-hydroxyacids through oxidation of terminal alkenes with AD-mix/TEMPO

Abstract α-Hydroxyacids can be enantioselectively prepared by means of a two-step oxidation process, involving first the asymmetric dihydroxylation of a terminal alkene and subsequent oxidation with TEMPO/NaOCl/NaClO 2 in good to excellent yields. No fragmentation of the glycol intermediate was detected.

Enantioselective synthesis of arylmethoxyacetic acid derivatives

Abstract The preparation of several arylmethoxyacetic acids by a sequence of asymmetric dihydroxylation and further oxidation of the resulting glycol with TEMPO/NaClO/NaClO2 is described. The scope and limitations of the reaction are discussed.

CeCl3/NaClO: a safe and efficient reagent for the allylic chlorination of terminal olefins

The preparation of allylic chlorides by reaction of terminal olefins with sodium hypochlorite in the presence of cerium trichloride heptahydrate is described. The scope, limitations and synthetic perspectives of the reaction are discussed.

Enantioselective synthesis of (+)-decipienin A

Abstract The enantioselective synthesis of (+)-decipienin A has been carried out. The oxidation of 7-epi-cyperone 2 with molecular oxygen in the presence of methanolic KOH provides de C-6-hydroxylated derivative in quantitative yield. The oxidation of glycols 5a through a Swern oxidation and 14a with TEMPO radical opens up a route to the synthesis of 11-hydroxy sesquiterpenolides. All attempts of oxidation of 5a or 14a with other different oxidation reagents led invariably to fragmentation products.

An easy route to 11-hydroxy-eudesmanolides. Synthesis of (±) decipienin A

Abstract The preparation of 11-hydroxy-eudesmanolides with the stereochemistry found in the Umbelliferae family of plants is described. The decalin system of the eudesmane skeleton is produced by the addition of 5-methyl-2-furyllithium to 3-ethoxycyclohex-2-enone and acidic treatment of the resulting adduct. The stereochemistry of the decalones obtained by this method has been corrected. The α-hydroxy-γ-lactone moiety is obtained by condensation of the appropriate decalone with methyl pyruvate and subsequent reduction under Luche conditions. The usefulness of this procedure has been proven in the synthesis of decipienin A.

Regioselective cyclization of α,ω-alkynoic acids catalysed by TpRu complexes: synthesis of endocyclic enol lactones [Tp = hydrotris(pyrazolyl)borate]

The σ-enynyl complex [TpRu{C(Ph)C(Ph)CCPh}(PMeiPr2 )] efficiently catalyses the regioselective cyclization of α,ω-alkynoic acids to yield endocyclic enol lactones having ring size up to 12 atoms.

Guaianolides and an ethylcyclohexane lactone from Andriala integrifolia

Abstract The reinvestigation of the aerial parts of Andriala integrifolia afforded three new lactones, a guaianolide, a guaianolide glucopyranoside and an ethylcyclohexane lactonic derivative with a quinol structure, together with five known compounds. Their structures were established by high field 1H NMR spectroscopy and chemical correlation.

Acyloxylation of 1,4-Dioxanes and 1,4-Dithianes Catalyzed by a Copper−Iron Mixed Oxide

The use of a copper-iron mixed oxide as a heterogeneous catalyst for the efficient synthesis of α-acyloxy-1,4-dioxanes and 1,4-dithianes employing t-butyl peroxyesters is reported. The preparation and characterization of the catalyst are described. The effect of the heteroatoms and a plausible mechanism are discussed. The method is operationally simple and involves low-cost starting materials affording products in good to excellent yields.

A Phenylpropanoid, a Slovenolide, Two Sulphur-Containing Germacranes and Ca2+-ATPase Inhibitors from Thapsia villosa

A phenylpropanoid 1, a slovenolide 2, and two germacranes bearing a methylthiopropenoate moiety, 3 and 4, along with twenty known metabolites have been isolated from the roots of Thapsia villosa var. villosa L. The structures of two known phenylpropanoids 5 and 6 have been corrected. Compounds 7 and 8 showed activity as potential inhibitors of the sarco- and endoplasmic Ca(2+)-dependent ATPases (SERCA) pump. Compounds 9, 10 and 11 increased significantly the cytoplasmic free calcium concentration ([Ca(2+)](c)) in human platelets in a concentration-dependent manner.