Rosalina F. Moro

Pyrrolizidine alkaloids from Senecio gallicus and S. Adonidifolius

Abstract Four alkaloids, ligularizine, senkirkine and senecionine N-oxide, were isolated from S. gallicus. Apart from florosenine, a new alkaloid was isolated from S. adonidifolius and identified as 12,13,19-trihydroxy-15,20-epoxy-15,20-dihydro(12S,15R,20R senecionan-11,16-dione. Two dimensional spectroscopic correlation experiments (1H1H and 13C1H) were performed, permitting the unequivocal assignation of the 1H and 13C NMR spectra of the alkaloids and enabling us to correct some of the data appearing in the literature.

Meroterpenes from Cystoseira usneoides II

Abstract Two new meroterpenes, usneoidols Z and E, have been isolated from the brown seaweed Cystoseira usneoides . Their structures were established by means of 2D NMR experiments: 1 H/ 1 H (COSY) and 1 H/ 13 C one bond and long range (HCCORR) correlations. Both compounds exhibit antitumoural and antiviral activities.

Meroterpenes fromCystoseira usneoides

Abstract Two new meroterpenes have been isolated from the brown seaweed Cystoseira usneoides usneoidone E and usneoidone Z. Their structures were established mainly by means of 2D NMR experiments: 1 H/ 1 H (COSY) and 1 H/ 13 C one bond and long range (HCCORR) correlations. Both compounds exhibit antitumoural and antiviral activities.

Acetophenones and terpenoids from Senecio Gallicus

Abstract Six new compounds isolated from the aerial part of Senecio gallicus were: 7,11,15-trimethyl-3-methylene hexadecan-1,2-diol diacetate; 7,11,15-trimethyl-3-methylenehexadecan-1,2-diol; 3,5-bis(3-methyl-2-butenyl)-4-acetoxyacetophenone; 3-(2-hydroxy-3-methyl-3-butenyl)-5-(3-methyl-2-butenyl)4-hydroxacetophenone; 3-(2,3-dihydroxy-3-methyl-butyl)-5-(3-methyl-2-butenyl)-4-hydroxyacetophenone and 1,10-epoxy-8α-hydroxy eremophilenolide.

Synthesis and absolute configuration of (−)-chrysolic acid and (+)-isofregenedol

Abstract An efficient synthesis of (−)-chrysolic acid and (+)-isofregenedol has been achieved from zamoranic acid and sclareol. The characteristic tetrahydronaphtalenic system was obtained by use of a cationic rearrangement of bicyclic systems adequately functionalized. The absolute configuration of the natural products was established using Sharpless asymmetric epoxidation.

Chemistry of 7-labden-3β,15-diol (I): homochiral synthesis of fregenedadiol

Abstract 7-labden-3β,15-diol was transformed into its diacetyl or dimethoxy derivatives. By double bond isomerization, allylic oxidation and dehydrogenation the diacetyl derivative was transformed into a dienone that was aromatized with good yield by methyl loss to afford 3β,15-diacetoxy-20-nor-5,7,9-labdatrien-7-ol. An analog procedure was used to transform the dimethoxy derivative into 3β,15-dimethoxy-20-nor-5,7,9-labdatrien-7-ol. The triflate of the latter was transformed by a cross-coupling reaction into fregenedadiol dimethyl ether that was demethylated to afford fregenedadiol.

Side-chain migration reactions and ring B aromatization in labdanes: scope and limitations. Synthesis of isofregenedane type tetrahydronaphthalenic diterpenes

Abstract The reaction of bicyclic diterpenes with an allylic oxygenated function or an equivalent functionality on ring B in the presence of I2/benzene afforded a simple and rapid synthesis of tetrahydronaphthalenic diterpenes of the isofregenedane class.

Fregenedadiol: A rearranged labdane from Halimium viscosum

Abstract A diterpene diol with a new carbon skeleton was isolated from the neutral part of Halimium viscosum (La Fregeneda). Its structure, corresponding to a rearranged labdane with the B-ring aromatized, was determined by spectroscopic methods including two-dimensional heteronuclear correlation experiments, 1 H/ 13 C (normal and long range) and differential NOE.

Hydroxylated diterpenoids from Halimium viscosum

Several hydroxylated bi- and tri-cyclic terpenoids have been isolated from the aerial parts of Halimium viscosum (Celorico da Beira, Portugal). Together with valparolone, with the same skeleton, two additional compounds have been identified: (4S)-2β-acetoxyvalparol-15-en-3-one and (4S)-2β-acetoxyvalparol-8(14)-en-3-one. Together with the well-known valpara-3(19),15-dien-2β-ol, valpara-1,13-dien-2α-ol and 2β-acetoxyvalpara-4,15-dien-3α-ol, two new compounds have been isolated, belonging to the valparane class, and identified as valpara-3,15-dien-2β-ol and 3α-hydroxyvalpara-4,15-dien-2-one. There are several bicyclic diterpenoids that should be noted: with labdane skeleton; a diformate and the monoformylderivatives of labd-7-en-3β,15-diol and with halimane skeleton the 15-hydroxy-ent-halim-1(10)-en-18,2β-olide. The total composition of the aerial parts of this plant allows the identification of Celorico da Beira Halimium viscosum as a new chemotype.

Approach to the Synthesis of Diterpenes with the Bicyclo[5.3.0]decane System: (±) 10-epi-tormesol

Abstract The synthesis of (±) 10-epi-tormesol, 27, has been achieved from (±) 1-acetyl-3a,6 dimethylhexahydroazulene 1, by coupling of 5, a dehydroderivative of 1, with 23. The same synthetic procedure afforded a series of diterpenes 24–26 and 28 with the same biannular system. Direct reduction of 1 with different methods does not give the desired spatial relationship (trans/cis) between Me-C7/H-6/H-10 on the substrate, affording instead trans/trans (compounds 5 and 18) and cis/cis (compound 9). Indirect reduction: epoxydation followed by catalytic hydrogenation afforded the desired stereochemistry on the intermediate but deoxygenation caused epimerization at C-10. This synthetic achievement confirmed the original structure assigned to tormesol some years ago.