Gian Mario Nano

An asymmetric approach to coumarin anticoagulants via hetero-Diels–Alder cycloaddition

Abstract We have developed a general, two-step protocol for the synthesis of chiral non-racemic coumarin anticoagulants (e.g. warfarin, coumachlor and acenocoumarol). This approach features a one-pot three-component tandem Knoevenagel–hetero-Diels–Alder reaction between in situ generated 3-arylidene-2,4-chromanediones and iso -propenyl ether derived from (−)-menthol.

Prenylated coumarins and sesquiterpenoids from Ferula communis

Abstract From the latex of Ferula communis , two 4-hydroxycoumarin derivatives were isolated bearing a farnesylic and a 12-hydroxyfarnesylic residue, respectively, at C-3. Prenylated coumarins, which represent toxic principles of the plant, were absent in other samples, which gave, besides known compounds, a germacrane alcohol (hallohedycariol) and a daucane ester (siol p -hydroxybenzoate).

Ferprenin, a prenylated coumarin from Ferula communis

Abstract The structure of ferprenin, a prenylated coumarin from Ferula communis, has been established from spectral data, and by synthesis from E,E-farnesal and 4-hydroxycoumarin. Ferprenin could also be obtained from ferulenol, the major constituent of the plant investigated, by a Cr6+-mediated oxidative cyclization, for which a possible mechanism is proposed.

ω-Oxygenated prenylated coumarins from Ferula communis

Abstract From the toxic variety of Ferula communis, derivatives of the prenylated coumarins ferulenol and ferprenin bearing an oxygen function (hydroxyl, acetoxyl, aldehydic carbonyl) at the ω-composition have been isolated. The structures of the coumarins were established by spectral methods and by chemical reactions. Photooxygenation of ferulenol and (E) ω-hydroxyferulenol gave o-hydroxyphenylglyoxylic esters, resulting from the oxidative decarbonylation of the 4-hydroxycoumarinic nucleus and loss of the prenyl side chain. Ethyl o-hydroxyphenylglyoxylate was also isolated from the plant extract, suggesting that a reaction of this type might be responsible for the degradation of the prenylated coumarins in plant samples and extracts of Ferula communis.

Tetrahydrofuran-type terpenoids from Tanacetum vulgare

Abstract Investigation of a rare genotype of Tanacetum vulgare afforded a series of tetrahydrofuran-type terpenoids, whose pattern was different in flowers and leaves. The major constituent of the flowers was the trans Δ3,4-hydroperoxide of davanone, whereas the leaves gave mostly a peroxyhemiketalic compound resulting from the intramolecular cyclization of the cis Δ3,4-hydroperoxide of davanone. Structures were elucidated by spectral data and chemical reactions, including correlation with natural (+)-davanone. The peroxyhemiketalic compound upon acylation of its hydroxyl group gave an instantaneous complex reaction, resulting in the formation of a β-acyloxyenone and loss of one molecule of acetone. Among the minor constituents of the leaves, a C-10 carboxylic acid biogenetically related with davanone was isolated.

Sesquiterpene coumarin ethers from asafetida

Abstract A commercial sample of Asafetida gave three new sesquiterpene coumarin ethers based on an acyclic terpenoid moiety. The structure of asacoumarin B was revised.

Isomeric hydroperoxyeudesmanolides from Artemisia umbelliformis

Abstract Investigation of the aerial parts of Artemisia umbelliformis afforded the new eudesmanolides 5-desoxy-5-hydroperoxytelekin and 5-desoxy-5-hydroperoxy-5-epitelekin. A conformational study of the latter and some transformation products showed that these cis -decalin-type eudesmanolides exist in solution at room temperature as single preferred rotamers whose conformation depends on the substituent at C-5.

Sesquiterpenoid esters from the fruits of Ferula communis

Abstract The fruits of the toxic variety of Ferula communis gave a series of 1-oxojaeskeanadiol esters, whose structure was established by spectroscopic data and chemical reactions, including correlation with jaeskeanadiol. Treatment of these esters with potassium hydroxide gave two polienonic products, resulting from the stepwise elimination of the ester group and one water molecule. Both compounds were unstable; the dienone underwent rapid deconjugation via a 1,5-sigmatropic hydrogen shift, whereas the trienone was oxidized in air at the terminal bond of the conjugated system. The toxic prenylated coumarins were not found in the fruits.

A sesquiterpene alcohol from the fruits of Laurus nobilis

Abstract Besides known sesquiterpene lactones, the fruits of Laurus nobilis gave a germacrane derivative with a rare oxygenation pattern of the isopropyl side-chain.

Tanacetols A and B, non-volatile sesquiterpene alcohols, from Tanacetum vulgare

Abstract Chemical investigation of a rare chemotype of Tanacetum vulgare attorded a series of non-volatile sesquiterpene alcohols which have been called tanacetols. The structures of tanacetols A and B, the two most abundant, have been established on the basis of spectroscopic data, chemical reactions and X-ray diffraction analysis of tanacetol A and tanacetol B acetate.