Antonio Galindo

Two sesquiterpene lactones from Centaurea canariensis

Abstract From the aerial part of Centaurea canariensis three sesquiterpene lactones were isolated: cynaropicrin, deacylcynaropicrin and aguerin A . The same species, grown from seed, yielded cynaropicrin, deacylcynaropicrin and aguerin B . The guaianolides aguerin A and B are reported for the first time. Aguerin B was subsequently found to be present in Centaureana linifolia, C. canariensis (var subspinnata ) and C. sventenii .

A Very Simple Oxidation of Olefins and Ketones with UHP-Maleic Anhydride

The oxidation of olefins and ketones to oxiranes and esters, respectively, is carried out with the UHP (urea-hydrogen peroxide complex) - maleic anhydride system in a mild and very simple procedure

The structure and stereochemistry of artemin

Abstract Artemin was isolated from the aerial part of Artemisia maritima . Its structure and stereochemistry were determined on the basis of chemical transformations and spectral evidence

Biomimetic cyclization of gallicin to form guaianolides

Abstract A biomimetic-type cyclization of gallicineas carried out to form guaianolides. The possible mechanism is discussed and the stereoselectivity of the reaction explained by a preferred reacting conformation.

The biomimetic cyclization of melampomagnolide B

Abstract Melampomagnolide B (9) was prepared and converted to the epimeric trans-(1αH,5βOH)-guaianolides (19) and 1,5-epoxygermacranolide (15).The 11,13-dihydroderivative (10) afforded (20) and (16). The biogenetic implications of this process are discussed.

The biomimetic synthesis of trans-(1β-h,5α-h)-guaianolides

Abstract 1-epigallicin 11 underwent biomimetic cyclization to trans-(1β-H,5α-H)-guaianolide 22 ,the stereoespecificity of this cyclization being credited to the fact that it took place via the reacting TC conformation 27 . The epimeric nor-guaianolides 15 and 17 were prepared and their rearrangements studied. The biogenetic implications of these processes are discussed.

Biomimetic synthesis of 5α-hydroxy-guaianolides

Abstract A 5α-hydroxy-guaianolide was synthesized biomimetically from a 5-oxo-E-1(10)-germacrenolide, the stereoselectivity of the cyclization being attributed to preferred conformation.

HETERO DIELS-ALDER VS MUKAIYAMA ALDOL PATHWAYS IN THE REACTION OF MONOACTIVATED DIENES AND ALDEHYDES. A LEWIS ACID STUDY

Abstract The effect of Lewis acid on the reaction of 2-monoactivated dienes and aldehydes was studied searching for more general reaction conditions than those previously published. It was found that BF 3 ·OEt 2 in diethyl ether gave the best yields of Dieis-Alder adducts with good endo/exo selectivities. The Mukaiyama aldol-Michael cyclization pathway which has been reported to occur with this Lewis acid in the reaction of diactivated dienes, does not seem to operate with the monoactivated ones. Other Lewis acids gave good yields of silylated aldol products, and a crossover experiment showed that the recently proposed silatropic-ene pathway does not occur under the conditions used.

Absolute configuration and synthesis of gallicadiol

Abstract A new cis -eudesmanolide,gallicadiol (3) was isolated and its structure was determined by spectroscopy,X-ray analysis and synthesis from vulgarin 6.

Chemistry of the compositae. Part 38. Structure and absolute configuration of gallicin, a new germacranolide from Artemisia

Gallicin, a new germacranolide, was isolated from Artemisia maritima gallica Willd and assigned structure (3a) on chemical and spectroscopic evidence. Its absolute configuration was determined by the fact that it can be converted to the dihydrosantamarin (5) by a biogenetic cyclization process.