Pierluigi Gariboldi

Taxanes from Taxus baccata

Abstract A winter collection of yew needles gave two pairs of taxicin-I and taxicin-II diesters, the structures of which were established by spectral data and chemical reactions. The mixture of these diesters might correspond to the so-called ‘desdimethylaminotaxine’ of the old literature on yew. A detailed NMR analysis of the diesters allowed an unambiguous assignment of all 1 H and 13 C NMR resonances of these and related taxane derivatives.

Taxanes from the needles of Taxus wallichiana

Abstract Besides known compounds, the needles of T. wallichiana gave five new taxanes, whose constitution, stereochemistry and conformation were established

Cycloartane triterpene glycosides from Astragalus trigonus

Three new cycloartane glycosides, trigonoside I, II and III, and the known astragalosides I and II were isolated from the roots of Astragalus trigonus. The structures of the new glycosides were totally elucidated by high field (600 MHz) NMR analyses as cycloastragenol-6-O-beta-xylopyranoside, cycloastragenol-3-O-[alpha-L-arabinopyranosyl(1-->2)-beta-D- xylopyranosyl]- 6-O-beta-D-xylopyranoside and cycloastragenol-3-O-[alpha-L-arabinopyranosyl (1-->2)-beta-D-(3-O-acetyl)-xylopyranosyl]-6-O-beta-D-xylopyranoside.

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.

Rearranged taxanes from Taxus baccata

Abstract The needles of Taxus baccata gave two rearranged taxanes of the 11 (15 → 1)- and 2 (3 → 20) abeo -type. A taxicin I triester was also isolated.

14β-Hydroxy-10-deacetylbaccatin III, a new taxane from Himalayan yew (Taxus wallichiana Zucc.)

The needles of T. wallichiana Zucc. gave a new taxane, whose structure was established as 14β-hydroxy-10-deacetylbaccatin III on the basis of chemical reactions, spectroscopic data and X-ray analysis.

Pseudoalkaloid taxanes from Taxus baccata

Abstract The needles of Taxus baccata gave three pseudoalkaloid taxanes, whose structures were established by spectroscopical data.

SAPONINS FROM CROSSOPTERYX-FEBRIFUGA

Abstract Two bisdesmosidic saponins from the roots of Crossopteryx febrifuga were isolated by means of reversed phase HPLC. They were characterized on the basis of chemical and spectral data as 3-O-β- d -glucopyranosyl-2β,3β,6β,16α,23-pentahydroxyolean-12-en-28-oic acid 28-O-[α- l -rhamnopyranosyl(1→3)] [β- d -xylopyranosyl-(1→4)] [α- l -rhamnopyranosyl(1→2)]α- l -arabinopyranoside and 3-O-[β- d -apiofuranosyl(1→3)]β- d -glucopyrano-syl-2β,3β,6β,16α,23-pentahydroxyolean-12-en-28-oic acid 28-O-[α- l -rhamnopyranosyl(1→3)] [β- d -xylopyranosyl-(1→4] [α- l -rhamnopyranosyl(1→2)]α- l -arabinopyranoside. 2D NMR experiments were useful in providing complete information on the structure and geometry of the new sapogenin present.

Crispolide, an unusual hydroperoxysesquiterpene lactone from Tanacetum vulgare

Abstract Crispolide, a hydroperoxysesquiterpene lactone with a modified germacrane skeleton, was isolated from the aerial parts of Tanacetum vulgare var. crispum and from two T. vulgare chemotypes. Its structure, 1β-hydroperoxy-5β-hydroxy-4,14-cyclogermacra-9,11-dien-6,12-olide, was elucidated by spectroscopic data and chemical reactions.