Pilar Basabe

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.

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.

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.

Labdane diterpenoids from Cistus ladaniferus

Abstract Three new diterpenic acids have been isolated from Cistus ladaniferus : 6,8(17) labdadien-15-oic, 7-oxo-8-labden-15-oic and 6β-acetoxy-7-oxo-8-labden-15-oic acids, beside labdanolic, 6-oxocativic,7α-hydroxy-8(17)-labden-15-oic, 8α-methoxy-labda-15-oic and 8α-hydroxy-13( E )-labden-15-oic acids.

Synthesis and absolute configuration of three natural ent-halimanolides with biological activity

The first three natural ent-halimanolides known until now have been synthesized from ent-halimic acid. Their structure have been confirmed as well as their absolute configurations established. Bestmann methodology has been used for the synthesis of butenolides and for the γ-hydroxybutenolides synthesis the Boukouvalas method has been employed. Biological testing has been carried out on these compounds.

Synthesis and absolute configuration of (-)-chettaphanin I and (-)-chettaphanin II

An efficient synthesis of chettaphanin I and II has been achieved from ent-halimic acid. The absolute configuration of the natural products was established by nOe experiment and by X-ray analysis of chettaphanin II.