Zacarías D. Jorge

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.

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.

Eudesmane Derivatives from Verbesina turbacensis

Four eudesmane sesquiterpene were isolated from the aerial parts of Verbesina turbacensis and were characterised by spectroscopic methods, including 2D NMR experiments.

Two derivatives of costic acid from Centaurea arguta

Abstract The aerial parts of Centaurea arguta afforded, in addition to four known flavonoids and two known guaianolides, two new derivatives of costic acid.

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.

Phenylpropanoids from Bupleurum fruticosum

The aerial parts of Bupleurum fruticosum yielded, in addition to spinasterol and erythrodiol, nine phenylpropanoids, of which eight are new natural products. Their structures were established by spectroscopic means.

Eudesmanolides from Melanoselinum decipiens

The aerial part of Melanoselinum decipiens yielded, in addition to the previous known decipienin A, two sesquiterpene lactones whose structures were elucidated by spectroscopic methods. Both substances belong to a stereostructural type of eudesmanolides which is described for the first time from Umbelliferae. The stereochemistry of one of the lactones was confirmed by X-ray diffraction analysis. The biogenetic relevance is discussed.

Sesquiterpenolides from Melanoselinum decipiens

Abstract Seventeen new eudesmanolides have been isolated from Melanoselinum decipiens , together with the previously known lasolide and the decipienins A, B, D and F. Relative configurations of decipienin B have been assigned by spectroscopic means.