Mario Rubiralta

ALKALOIDS FROM NARCISSUS BICOLOR

Abstract Investigation of the bulbs of Narcissus bicolor growing in Spain afforded three new alkaloids, bicolorine, 5,6-dihydrobicolorine and oxoassoanine- N -oxide, whose structures were determined by mass and spectral analyses. Three known alkaloids, pretazettine, 9- O -demethylhomolycorine and 3-epimacronine were also isolated. The 13 C NMR data of 3-epimacronine are reported for the first time.

Alkaloids from Narcissus confusus

Abstract We report the isolation of haemanthamine, galanthamine, pretazettine and the new alkaloid N-formylgalanthamine from Narcissus confusus plants. Structural determination was carried out by spectroscopic analyses and application of two-dimensional NMR spectroscopy.

Phenanthridine alkaloids from Narcissus assoanus

Abstract The rare phenanthridine alkaloid assoanine and its new 7-oxo derivative, oxoassoanine, have been isolated from Narcissus assoanus collected at flowering. HPLC analysis of crude extracts of the plant has been carried out to ascertain that oxoassoanine is not an artefact.

Synthetic applications of 2-(1,3-dithian-2-yl)indoles VI.1 Synthesis of 20-epidasycarpidone

Abstract 20-Epidasycarpidone ( 10 ) and its N -benzyl analogue 9 have been synthesized via a conjugate addition of 2-(1,3-dithian-2-yl)indole ( 6 ) and 3-ethyl- Δ 3 -piperidein-2-ones 7 and 8 , respectively. The transformation of 20-epidasycarpidone to 20-epiuleine ( 11 ) has been carried out as described in the literature in order to corroborate the structural assignments.

Alkaloids from Crinum kirkii

The new alkaloids, kirkine and 8-O-demethylvasconine, have been isolated from bulbs of Crinum kirkii. Their structures were established by physical and spectroscopic methods.

Synthetic applications of 2-(1,3-Dithian-2-yl)indoles V.1 asymmetric synthesis of dasycarpidone-type indole alkaloids

Chiral tetracyclic dasycarpidone-type compounds (αR, 1S, 5R)-4 and (αR, 1R, 5S)-16 have been synthesized from 2-(1,3-dithian-2-yl)indole 6 and (αR)-N-(β-hydroxy-α-phenylethyl)-Δ3-piperidein-2-one8 in three steps, following the methodology that we described recently.

Synthetic applications of 2-(1,3-dithian-2-yl)indoles. IV: New synthesis of the tetracyclic ABED ring system of Strychnos alkaloids

Abstract A new and versatile synthesis of tetracyclic compounds 10, 22 and 24 presenting the ABED ring system of Strychnos alkaloids is described by closure of the C1C11b bond in the key step. The intermediate tetrahydropyridinium salts 2 have been obtained from 2-(1,3-dithian-2-yl)indole (3) and either 2-cyano-3-ethyl-1-methyl-1,2,3,6-tetrahydropyridine (4a) or N-substituted Δ3-piperidein-2-ones (5).

Alkaloids from Narcissus muñozii-garmendiæ

Abstract Whole plants of Narcissus munozii-garmendiae were found to contain homolycorine, lycorenine and O -methyllycorenine. The structure of O -methyllycorenine has been completely assigned by means of 2D NMR studies. The isolation of these alkaloids is hitherto unreported from this plant source.

Use of dioxiranes for the chemoselective oxidation of tertiary amines bearing alkene moieties

A neat and high yield chemoselective epoxidation of alkene moieties present in tertiary amines is accomplished by treatment of the corresponding amine–boron trifluoride adduct with dimethyldioxirane or methyl(trifluoromethyl)dioxirane.

Two alkaloids from Narcissus requienii

The aerial part of Narcissus requienii (Amaryllidaceae) was found to contain pseudolycorine as the major alkaloid, and two new phenolic bases: 2-O-acetylpseudolycorine and 1-O-acetylpseudolycorine. The present communication reports the complete assignments of the NMR spectra of pseudolycorine, and the structure elucidation of the other comnounds by means of 2D 1H-1H and 1H-13C NMR chemical shift correlation experiments.