Isidro S. Marcos

Triterpenes from Euphorbia broteri

The triterpenes have been investigated in the aerial part and the latex of Euphorbia broteri. The aerial part contains two new triterpenes, 25,26,27-trisnor-3β-hydroxy-24-dimethoxycycloartane and 3,4-seco-4(23),14-taraxeradien-3-oic acid, and eleven other triterpenes identified as cycloartenol, butyrospermol, 24-methylenecycloartanol, cycloart-25-ene-3β,24-diol, euphan-8,25-diene-3β,24-diol, 3β-hydroxycycloart-25-ene-24-one, obtusifoliol, 3,4-seco-4(23),20(30)-lupadien-3-oic acid (canaric acid), betulin, cycloart-23-ene-3β,25-diol and the C-24 diastereomers of cycloartane-3β,24,25-triol. The latex contains a new triterpene, 24,25-epoxycycloartanol (C-24 diastereomers), and nine other compounds identified as euphol acetate, cycloartenyl acetate, butyrospermyl acetate, 24-methylenecycloartanyl acetate, euphol, cycloartenol, butyrospermol, 24-methylenecycloartanol and obtusifoliol.

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.

Ambergis compounds from labdanolic acid

Abstract Labdanolic acid (Cistus ladaniferus) is transformed into derivatives with amber odor. The strategy used allowed a process in which the oxidative decarboxylation reaction was carried out with the hydroxyl group protected.

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.

A diterpene alcohol from Halimium viscosum

Abstract A hexane extract of Halimium viscosum collected at La Fregeneda (Salamanca, Spain) yielded a new diterpene alcohol, tormesol. Its structure was determined by chemical transformations and NMR spectroscopy with 1 H 1 H (COSY), 13 C 13 C (2D-inadequate) and 1 H 13 C (one bond and long range correlations) two-dimensional experiments.

Prenylflavonoids and prenyl/alkyl-phloroacetophenones: Synthesis and antitumour biological evaluation

Several prenylflavonoids have been synthesised and tested against human tumour cell lines. The prenyl unit has been geranyl or a labdane diterpene. These labdane-flavonoids have been synthesised for the first time. The antitumour activity increase with the prenylation at C-8 position. Twenty-three C and O-prenylated acylphloroglucinols have been synthesised as well. In this case the C-alkylation products have resulted, in general, more active.

Chemistry of zamoranic acid. Part V Homochiral semisyntheses of active drimanes: Pereniporin B, polygodial and warburganal

Abstract Methyl 14,15-dinor-13-oxo-7-labden-15-oate was obtained from acid zamoranic acid methyl ester. The former by photochemical cleavage yielded methyl 7,9(11)-drimadien-12-oate, whose chemoselective epoxidation afforded methyl 9α,11-epoxy-7-drimen-12-oate, which is the key synthetic precursor for pereniporin B, polygodial and warbuganal.

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.

Chemistry of zamoranic acid. Part IX homochiral synthesis of polygodial and warburganal from 17-acetoxy-7-labden-15-ol

Abstract 14,15-di nor -17-acetoxy-7-labden-13-one, 4 was prepared from zamoranic acid methyl ester 5 . Photochemical cleavage of 4 gave 12-acetoxy-7,9(11)-drimadiene, 3 , in 75% overall yield. The chemo- and diastereoselective epoxidation of 3 afforded 12-acetoxy-9α and 9β(11)-epoxy-7-drimene, 17 and 18 in 4:1 ratio. Ring-opening of 17 (or the mixture 17 18 ) using BF 3 ·Et 2 O or ring-opening of the mixture 17 18 lead to the synthetic precursor of polygodial: (9 R )-12-acetoxy-drimen-11-al, 20 , with a 90% diastereoisomeric excess. The chemo- and diastereoselective cis -hydroxylation of diene 3 led to the synthetic precursor of warburganal 9α,11,12-trihydroxy-7-drimene, 29 with 47% yield. Polygodial and warburganal were prepared from zamoranic acid methyl ester in 55 and 27% overall yield, respectively.

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.