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We have developed and rationalized a biomimetic transformation mimicking halimane synthases based on a Lewis acid-catalyzed cascade of cyclizations and rearrangements of epoxypolyprenes. Two rings, three stereogenic centers, and a new double bond were generated in a single chemical operation. Based on this cascade transformation, we achieved a unified strategy toward the stereoselective total syntheses of halimene-type terpenoids and analogues as a proof-of-concept study. This method has been applied to the rapid synthesis of diterpene isotuberculosinol, a virulence factor of Mycobacterium tuberculosis as a representative example.

A series of diclofenac N-derivatives (2, 4, 6, 8c, 9c, 10a-c) were synthesized in order to test their anti-cancer and anti-inflammatory effects. The anticarcinogen activity has been assayed against three cancer cell lines: HT29, human colon cancer cells; Hep-G2, human hepatic cells; and B16-F10, murine melanoma cells. First, we determined the cytotoxicity of the different compounds, finding that the most effective compound was compound 8c against all cell lines and both compounds 4 and 6 in human Hep-G2 and HT29 cell lines. Compounds 4 and 8c were selected for the percentage of apoptosis determination, cell cycle distribution, and mitochondrial membrane potential measure because these products presented the lowest IC50 values in two of the three cancer cell lines assayed (B16-F10 and HepG2), and were two of the three products with lowest IC50 in HT29 cell line. Moreover, the percentages of apoptosis induction were determined for compounds 4 and 8c, showing that the highest values were between 30 to 60%. Next, the effects of these two compounds were observed on the cellular cycle, resulting in an increase in the cell population in G2/M cell cycle phase after treatment with product 8c, whereas compound 4 increased the cells in phase G0/G1, by possible differentiation process induction. Finally, to determine the possible apoptosis mechanism triggered by these compounds, mitochondrial potential was evaluated, indicating the possible activation of extrinsic apoptotic mechanism. On the other hand, we studied the anti-inflammatory effects of these diclofenac (DCF) derivatives on lipopolysaccharide (LPS) activated RAW 264.7 macrophagesmonocytes murine cells by inhibition of nitric oxide (NO) production. As a first step, we determined the cytotoxicity of the synthesized compounds, as well as DCF, against these cells. Then, sub-cytotoxic concentrations were used to determine NO release at different incubation times. The greatest antiinflammatory effect was observed for products 2, 4, 8c, 10a, 10b, and 9c at 20 µg·mL−1 concentration after 48 h of treatment, with inhibition of produced NO between 60 to 75%, and a concentration that reduces to the 50% the production of NO (IC50 NO) between 2.5 to 25 times lower than that of DCF. In this work, we synthesized and determined for the first time the anti-cancer and anti-inflammatory potential of eight diclofenac N-derivatives. In agreement with the recent evidences suggesting that inflammation may contribute to all states of tumorigenesis, the development of these new derivatives capable of inducing apoptosis and anti-inflammatory effects at very low concentrations represent new effective therapeutic strategies against these diseases., MINISTERIO DE ECONOMÍA Y COMPETITIVIDAD, PID2019-106222RB-C32/SRA (State Research Agency, 10.13039/501100011033), “Consejería de Economía, Conocimiento, Empresas y Universidad. Junta de Andalucía”, grant number B1-BIO-281-UGR18

The system I2/dimethyl sulfoxide mediates the one-step transformation of α-isopropylidene ketones into furan rings following a biomimetic approach. This methodology has been used for the synthesis ...

A new dysprosium based Metal-Organic Framework with {[Dy(dhbdc)(DMF)]·DMF} formula has been obtained from solvothermal reaction with 2,5-dihydroxyterephthalic acid ligand and dysprosium chloride. This coordination polymer has been characterized and its crystal structure has been solved by X-ray diffraction methods elucidating a three-dimensional network. Magnetic studies of this compound reveal the existence of weak antiferromagnetic interactions among the metal ions with θ value of −0.26 K. Dynamic ac magnetic susceptibility measurements were carried out under an external dc field of 1 kOe, highlighting that at high frequencies two relaxation processes can be observed. However, when studying the diamagnetically diluted analogue 1, a single relaxation process was detected highlighting the effect of the weak but not negligible exchange interactions. Finally, photoluminescence measurements were performed at different temperatures with the aim of getting a more representative characterization of the emissive performance of the material for potential applications in lighting and thermometry., Financial support was given by Junta de Andalucía (Spain) (project number FQM-394 and FQM-1484), University of the Basque Country (GIU 17/13), Gobierno Vasco/Eusko Jaurlaritza (IT1005-16) and the Spanish Ministry of Economy and Competitiveness (MCIU/AEI/FEDER, UE) (PGC2018-102052-A-C22, PGC2018-102052-B-C21 and CTQ-2015-64049-C3-3R). The authors thank for technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF). A.Z.-L. is grateful to the Government of the Basque Country for the predoctoral fellowship

Efficient procedures based on the use of iodine for the aromatization of a series of terpenoids possessing diene and homoallylic or allylic alcohol functionalities are described. Different examples are reported as a proof-of-concept study. Furthermore, iodine also proved to mediate the dehydrogenation of testosterone.

We decided to follow the so-called “collective total synthesis” approach to synthesize several structurally different molecules from a common intermediate possessing appropriate stereochemistry and functionalities. As the common precursor for the efficient preparation of these bioactive molecules, we chose (+)-3,4-dihydro-γ-ionone (1), a natural compound present in minor quantities in ambergris and in the plant Bellardia trixago. Thus, we report herein the enantioselective synthesis of siccanochromene F (2), metachromins U (3) and V (4), and bicyclic squalene derivative 5 as well as the formal syntheses of ambrein (6), phenazinomycin (7), and (–)-siccanin (8).

The titanocene-mediated cyclization of suitably functionalized acyclic C10 epoxy-polyprenes leads, with moderate stereoselectivity, to high yields of functionalized terpenic cyclopentanes with three contiguous stereogenic centers. These highly functionalized cyclopentanes are useful intermediates for the synthesis of several natural compounds that include this interesting subunit in their structure. Both the regioselectivity of the process leading to cyclopentanes and the stereoselectivity of the cyclization could be controlled by using malonyl derivatives or α,β-unsaturated nitriles as radical acceptors.

Covering: 1998 to 2008 The biosynthetic origin of most of triterpenes lies in cascade cyclizations and rearrangements of the acyclic precursors squalene (S) and 2,3-oxidosqualene (OS), processes leading to tetra- and pentacyclic triterpene skeleta. Apart from these, a number of triterpenoid structures derived from cyclization processes, that are different from those leading to tetra- and pentacyclic triterpenes, are also found in Nature. We have defined these processes as unusual cyclizations, and grouped them in three blocks, namely, incomplete cyclizations of the corresponding S-derived precursors, cyclizations of S or OS towards polycyclic triterpenes and subsequent cleavage of the preformed ring systems, and two independent cyclizations of the S- or OS-derived precursor. Apart from the molecules obtained from intact organisms, we will also consider the compounds obtained from in vitro cyclizations promoted by enzyme systems. After establishing which compounds could unambiguously be grouped under the term ‘unusually cyclized triterpenes’, this review moves on to the advances achieved in this kind of structure during the last ten years. These advances are presented in three parts. The first one presents the structure and biological properties of the unusual triterpenes reported in the last decade. The second part considers the main biosynthetic pathways which justify the formation of these triterpenes from their corresponding acyclic precursors. Finally, we look at the achievements made in different synthetic strategies directed at some of these molecules. One hundred and twenty-three references are cited.

Sulfanyl radicals trigger a tandem addition–cyclization protocol in linalool or citronelene derivatives for the efficient construction of the iridane monoterpene skeleton. Best results in yields and diastereoselectivity were obtained when phenylethylsulfanyl was used as radical initiator. We have proved the utility of this protocol with the enantiospecific synthesis of natural iridane dehydroiridomyrmecin starting from a (−)-linalyl acetate ester derivative in five steps with a 28% overall yield.

Following the principles of collective total synthesis, a number of natural products sharing an optically pure, multifunctional, cyclopentanic core were synthesized from a common precursor: plinol A (1). This intermediate was efficiently obtained in only four steps from (-)-linalool (2) using as the key step a Ti(III)-mediated diastereoselective radical cyclization. The feasibility of this approach was confirmed with the expedient enantiospecific synthesis of cyclonerodiol (3), and the formal synthesis of chocol G (4) and piperitone (5).

A route to simpler analogues to bioactive puupehedione derivatives involving a hetero Diels–Alder cycloaddition of a o -quinone methide is described. These intermediate species are generated via fluoride-induced desilylation of silyl derivatives of o -hydroxybenzyl iodides. Remarkable short reaction times and very mild experimental conditions are the main features of this method.

The reaction of the Cp2TiCl complex with oxiranes leads to homolytic opening of the heterocycle with high regioselectivity. Although the resulting β-titanoxyl radical can evolve in different ways, when the epoxide reacting with Cp2TiCl possesses suitable unsaturated moieties such as olefins, triple bonds, carbonyls or nitriles in its structure, intramolecular addition of this β-titanoxyl radical to these unsaturated groups can take place, leading to a cyclization process. Structures containing from three- to seven-membered rings have been synthesized using either stoichiometric or catalytic quantities of titanocene. Although a number of applications for these titanium-mediated cyclization reactions have been reported in the synthesis of natural products and bioactive compounds such as antibiotic γ-lactones, lignans and β-lactams, we consider that the strategy involving the opening and ensuing cyclization of the monoepoxides of polyprenes, which resulted in the preparation of C10, C15, C20 and C30 terpenoids, including mono-, bi- and tricyclic natural products, deserves special mention. Attractive aspects of this reaction are good stereochemical control and the oxidative termination of the process, which leads regioselectively to exocyclic olefins. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

[reaction: see text] Titanocene chloride catalyzes the regioselective alpha,alpha'-homocoupling of terpenic allylic halides. This process has been employed in the short and effective synthesis of terpenoids such as beta-onoceradiene (1), beta-onocerin (2), and squalene (3). Evidence is presented for eta1-allyltitanium species being involved in the coupling.

The enantioselective synthesis of preoleanatetraene (1) has been accomplished via a convergent approach of two C-15 synthons. The key step of this synthesis has been an interesting enantioselective variant of the Robinsonannulation using the Nazarov reagent and a chiral enamine to obtain the bicyclic moiety A. This asymmetric methodology opens the access to other irregular triterpene skeletons whose biogenetic implication should not be underestimated.

Five new abietanes, three of them isolated as the corresponding acetate derivatives, i.e., 9α,13α-epidioxiabiet-8(14)-en-18-ol, 7α,18-diacetoxy, 9β,13β-epidioxiabiet-8(14)-ene, 7α,18-diacetoxyabiet-8(14)-en-13β-ol, 7α,18-diacetoxy-13β-methoxyabiet-8(14)-ene, and 13β-hydroxyabiet-8(14)-en-7-one, were isolated from the neutral part of the hexane extract of the cones of Cedrus atlantica collected in Middle Atlas, Morocco. The structures of these compounds were established by spectroscopic techniques, including 2D NMR spectra, and in the case of 1 , by chemical correlation. The cytotoxicity of these abietane diterpenoids was tested against five cell lines.

A new route to podolactones functionalized in the A ring has been achieved. Two key steps were employed in this synthesis, the construction of the bicyclic skeleton via a Mn(III)-mediated radical cyclization and the transformation of this bicyclic intermediate into the tetracyclic podolactone skeleton through a Pd (II)-mediated bislactonization of the corresponding conjugate diene. The reported synthesis of 3beta-hydroxy-13,14,15,16-tetranorlabda-7,9(11)-dien-(19,6beta),(12,17)-diolide (1) let us reassign the structure of wentilactone B, for which structure 1 was wrongly reported. [reaction: see text]

Two catalytic cascade cyclization methods (radical and cationic) to obtain aromatic polycyclic diterpenes hydroxylated at C3 starting from aromatic epoxypolyprenes were developed. The catalytic use of the Lewis superacid bismuth triflate produces a good yield of cyclized 2 from epoxypolyprene 3. This research may well direct future efforts to the synthesis of bioactive natural products.

The analysis of the essential oil from the wood of Juniperus thurifera has provided the isolation of seven new natural products, including the first described examples of 2-epi-cedranes and 2-epi-duprezianane. The co-occurrence in the oil of the three cedrane-type arrangements (cedrane, 1,7-diepi-cedrane and 2-epi-cedrane) has permitted, after a thorough 2D NMR analysis the unequivocal spectro- scopical assignment of each of the three cedrane skeletons, and subsequently the development of an unambiguous method for establishing their stereochemistries. A useful pattern for distinguishing between the two duprezianane stereochemistries is also given. q 2000 Elsevier Science Ltd. All rights reserved.

The neutral fraction of the hexane extract of the aerial parts of Santolina viscosa afforded eight new longipinene derivatives (1-8), oblongifolidiol (9), and several other known compounds. The structures of 1-8 were established by spectroscopic methods and chemical transformations. The vulgarone A-type structure previously reported for oblongifolidiol has been reassigned as the longipinene derivative 9 using 2D NMR, chemical correlations, and X-ray diffraction.

Treatment of germacrone (1) with different electrophiles, and of its epoxy derivatives germacrone-4,5-epoxide (2), germacrone-1,10-epoxide (3) and isogermacrone-4,5-epoxide (4) with Bronsted/Lewis acids and Ti(III), gives rise to a great structural diversity. Thus, by using a maximum of two steps, the production of more than 40 compounds corresponding to 14 skeletons is described. Computational calculations rationalizing the structural divergence produced are also described. Finally, since some of the compounds generated are bioactive natural sesquiterpenes, the mechanisms of formation of these substances will provide new insights in their biosynthesis.

The first synthesis of (+)-myrrhanol C (1), an antitumor polypodane-type bicyclic triterpene with inhibitory activity against androgen insensitive prostate cancers, is reported herein (IC(50) 10 μmolar). A key step in our convergent synthesis of (+)-myrrhanol C and related analogues is the employment of a microbial stereo- and regioselective late stage C-H oxidation. A low-waste and sustainable process has been developed to prepare (+)-myrrhanol C for further biological studies.

An asymmetric concise total synthesis of the (+)-seco-C-oleanane 1 was accomplished. The successful route to this natural product involves as the key step a stepwise regio- and stereocontrolled catalytic radical polyene cascade cyclization from preoleanatetraene oxide (16), a process mediated by Cp(2)TiCl. The use of this single-electron-transfer complex permits mild cyclization conditions without using unnecessary prefunctionalizations and stops the process at the bicyclic level. Theoretical data revealed high activation energy for the third ring closure, which would account for the control of the cyclization. This process also led to natural (-)-achilleol B, camelliol A, and (+)-seco-β-amyrin as minor compounds.

As a result of a combined theoretical and experimental study, we describe a two-step protocol for the preparation of an optically pure, multifunctional, cyclopentanic core shared by a number of natural products. This process is based on a hitherto unreported Ti(III)-mediated diastereoselective cyclization in which the hydroxy-directed template effect played by the Ti(III) species was found to be crucial for the stereoselective outcome of the reaction. The viability of this concept was confirmed with the first protecting-group free synthesis of three enantiopure chokols, namely, chokols K, E, and B.

Highly efficient preparations of anticancer β-elemene and other bioactive elemanes were carried out using the natural product germacrone as a renewable starting material. The syntheses were achieved in only 3-5 steps with excellent overall yields (43-54%). An enantioselective approach to these molecules is also described.

Investigations detailed herein, including density functional theory (DFT) calculations, demonstrate that the formation of either alkoxy− or hydroxy−Ti(III) complexes considerably decreases the energy of activation for C−O bond homolysis. As a consequence of this observation, we described two new synthetic applications of Nugent’s reagent in organic chemistry. The first of these applications is an one-step methodology for deoxygenation−reduction of alcohols, including benzylic and allylic alcohols and 1,2-dihydroxy compounds. Additionally, we have also proved that Ti(III) is capable of mediating carbonyl coupling−olefination. In this sense, and despite the fact that for over 35 years it has been widely accepted that either Ti(II) or Ti(0) was the active species in the reductive process of the McMurry reaction, the mechanistic evidence presented proves the involvement of Ti(III) pinacolates in the deoxygenation step of the herein described Nugent’s reagent-mediated McMurry olefination. This observation shed...

The synthesis of the fungicide oidiolactone C starting from diterpenic trans-communic acid was carried out with an overall yield of 11.7%. The key step in the process consists of a new bislactonization reaction catalyzed by Pd(II), which gives rise to the podolactone-type tetracyclic skeleton from a norlabdadienedioic acid. We also carried out a study of the structure−biological activity of different natural podolactones and their synthetic precursors. Thus, the highest cytotoxic activity was found in dienic dilactones with ether-type substitutions on C-17, whereas the closure of the γ-lactone ring is not critical for presenting a maximal antimicrobial activity.

Investigations detailed herein, including density functional theory (DFT) calculations, demonstrate that the formation of either alkoxy- or hydroxy-Ti(III) complexes considerably decreases the energy of activation for C-O bond homolysis. As a consequence of this observation, we described two new synthetic applications of Nugent's reagent in organic chemistry. The first of these applications is an one-step methodology for deoxygenation-reduction of alcohols, including benzylic and allylic alcohols and 1,2-dihydroxy compounds. Additionally, we have also proved that Ti(III) is capable of mediating carbonyl coupling-olefination. In this sense, and despite the fact that for over 35 years it has been widely accepted that either Ti(II) or Ti(0) was the active species in the reductive process of the McMurry reaction, the mechanistic evidence presented proves the involvement of Ti(III) pinacolates in the deoxygenation step of the herein described Nugent's reagent-mediated McMurry olefination. This observation sheds some light on probably one of the mechanistically more complex transformations in organic chemistry. Finally, we have also proved that both of these processes can be performed catalytically in Cp(2)TiCl(2) by using trimethylsilyl chloride (TMSCl) as the final oxygen trap.

Covering: 1998 to 2008 The biosynthetic origin of most of triterpenes lies in cascade cyclizations and rearrangements of the acyclic precursors squalene (S) and 2,3-oxidosqualene (OS), processes leading to tetra- and pentacyclic triterpene skeleta. Apart from these, a number of triterpenoid structures derived from cyclization processes, that are different from those leading to tetra- and pentacyclic triterpenes, are also found in Nature. We have defined these processes as unusual cyclizations, and grouped them in three blocks, namely, incomplete cyclizations of the corresponding S-derived precursors, cyclizations of S or OS towards polycyclic triterpenes and subsequent cleavage of the preformed ring systems, and two independent cyclizations of the S- or OS-derived precursor. Apart from the molecules obtained from intact organisms, we will also consider the compounds obtained from in vitro cyclizations promoted by enzyme systems. After establishing which compounds could unambiguously be grouped under the term ‘unusually cyclized triterpenes’, this review moves on to the advances achieved in this kind of structure during the last ten years. These advances are presented in three parts. The first one presents the structure and biological properties of the unusual triterpenes reported in the last decade. The second part considers the main biosynthetic pathways which justify the formation of these triterpenes from their corresponding acyclic precursors. Finally, we look at the achievements made in different synthetic strategies directed at some of these molecules. One hundred and twenty-three references are cited.

Sulfanyl radicals trigger a tandem addition–cyclization protocol in linalool or citronelene derivatives for the efficient construction of the iridane monoterpene skeleton. Best results in yields and diastereoselectivity were obtained when phenylethylsulfanyl was used as radical initiator. We have proved the utility of this protocol with the enantiospecific synthesis of natural iridane dehydroiridomyrmecin starting from a (−)-linalyl acetate ester derivative in five steps with a 28% overall yield.

The first total synthesis of (-)-achilleol B was achieved using a convergent approach with a longest linear sequence of 14 steps. Three key steps were employed, including an enantioselective Robinson annelation for the construction of the bicyclic moiety. The monocyclic synthon was prepared through a Ti(III)-mediated cylization of a chiral monoepoxide obtained via asymmetric dihydroxylation of geranylacetone. The asymmetric preparation of these subunits also permitted us to achieve the enantioselective synthesis of elegansidiol, achilleol A, and farnesiferol B.

The first total synthesis of (-)-achilleol B was achieved using a convergent approach with a longest linear sequence of 14 steps. Three key steps were employed, including an enantioselective Robinson annelation for the construction of the bicyclic moiety. The monocyclic synthon was prepared through a Ti(III)-mediated cylization of a chiral monoepoxide obtained via asymmetric dihydroxylation of geranylacetone. The asymmetric preparation of these subunits also permitted us to achieve the enantioselective synthesis of elegansidiol, achilleol A, and farnesiferol B.

Two new efficient methods for the regioselective homocoupling of allylic halides using either catalytic TiIII or the combination Mn/ZrIV catalyst have been developed. The regio- and stereoselectivity of the process proved to increase significantly when the Mn/ZrIV catalyst is used as the coupling reagent and when cyclic substituted allylic halides are used as substrates. The use of Lewis acids such as collidine hydrochloride allowed the quantity of catalyst to be lowered up to 0.05 equiv. We have proved the utility of these protocols with the synthesis of different terpenoids such as (+)-β-onoceradiene (1), (+)-β-onocerine (2), squalene (5), and advanced key-intermediates in the syntheses of (+)-cymbodiacetal (3) and dimeric ent-kauranoids as xindongnin M (4a).

Titanocene monochloride catalyzes the homocoupling of benzylic halides and benzylic gem-dibromides to give the corresponding bibenzyl and stilbenyl systems. Exposure of benzylic bromides to Ti(III) in the presence of aldehydes gave rise to the Barbier-type products. Examples of the utility of the herein described processes are included.

Ring size on Ti(III)-mediated radical cyclization of monoepoxypolyprenoids can be controlled by varying the substitution pattern and/or the electronic distribution of the double bond involved in the ring closure. The feasibility of applying this idea to tandem cyclizations has also been proven. Besides, when a silyloxy function is located in α position to the oxirane ring of the acyclic polyprene, the cyclization leads to carbocyclic terpenoids doubly functionalized in the A ring with acceptable yields. These results widen significantly the scope of this methodology.

Regioselective halogenation of the terminal isopropylidene unit of different acyclic polyolefinic polyprenoids (farnesyl acetate, geranylgeranyl acetate, squalene, etc.) using NCS/catalytic polymer-supported selenenyl bromide is described; good to excellent yields are obtained (68−96%). The first applications of this protocol include the concise synthesis of bioactive terpenoids 1−3.

Sulfanyl radicals promote radical cyclization both in linalyl acetate (2) and its derivative 3, leading highly selectively to monoterpenoids with an iridane skeleton. We have investigated the addition of different sulfanyl radicals such as PhS . , 4-NO 2 C 6 H 4 S . and PhCH 2 CH 2 S . and found that the latter radical produces the best results (87-93%). Natural iridoid dehydroiridomyrmecin (1) at an overall yield of 28% was synthesized in four steps using this method.

Five new abietanes, three of them isolated as the corresponding acetate derivatives, i.e., 9alpha,13alpha-epidioxiabiet-8(14)-en-18-ol, 7alpha,18-diacetoxy, 9beta,13beta-epidioxiabiet-8(14)-ene, 7alpha,18-diacetoxyabiet-8(14)-en-13beta-ol, 7alpha,18-diacetoxy-13beta-methoxyabiet-8(14)-ene, and 13beta-hydroxyabiet-8(14)-en-7-one, were isolated from the neutral part of the hexane extract of the cones of Cedrus atlantica collected in Middle Atlas, Morocco. The structures of these compounds were established by spectroscopic techniques, including 2D NMR spectra, and in the case of 1, by chemical correlation. The cytotoxicity of these abietane diterpenoids was tested against five cell lines.

Six new diterpenic acids isolated as their methyl ester derivatives, i.e., methyl 12-oxo-8alpha,15-dihydroxyabiet-13-en-19-oate, methyl 12-oxo-8alpha-hydroxyabiet-13-en-19-oate, methyl 15-hydroperoxy-8alpha,12alpha-epidioxiabiet-13-en-19-oate, methyl 15-hydroxy-8alpha,12alpha-epidioxiabiet-13-en-19-oate, methyl 15-hydroperoxy-8alpha,14alpha,12alpha,13alpha-diepoxiabietan-13-en-19-oate, and methyl 7alpha,12beta-dihydroxysandaracopimarate, together with two new isovalerate derivatives of p-methoxycinnamyl alcohol and linalool, were isolated from the leaves of Juniperus thurifera var. africana and Juniperus phoenicea, grown in Morocco. The structures of these compounds were established by using spectroscopic techniques, including 2D NMR spectra. The cytotoxicity of the abietane diterpenoids was tested against five cell lines.

More than seventy podolactones have been isolated mainly from Podocarpus species. Some of these structures have also been found in filamentous fungi. The different biosynthetic origin of these molecules considering their vegetal or fungic source is discussed in this review. These molecules present a wide range of biological activities: anti-tumor activity, anti-inflammatory activity, fungicide activity, insecticidal activity and plant growth regulatory activity. These biological properties are analyzed in detail, and in the light of their results, structure/activity relationships are discussed. Finally, chemical reactivity, including interconversion reactions, and synthetic approaches to these compounds are summarized.

The analysis of the essential oil from the wood of Juniperus thurifera has provided the isolation of seven new natural products, including the first described examples of 2-epi-cedranes and 2-epi-duprezianane. The co-occurrence in the oil of the three cedrane-type arrangements (cedrane, 1,7-diepi-cedrane and 2-epi-cedrane) has permitted, after a thorough 2D NMR analysis the unequivocal spectro- scopical assignment of each of the three cedrane skeletons, and subsequently the development of an unambiguous method for establishing their stereochemistries. A useful pattern for distinguishing between the two duprezianane stereochemistries is also given. q 2000 Elsevier Science Ltd. All rights reserved.

The terpenic compositions of two populations of Parentucellia viscosa growing in the west-central and southern parts of the Iberian Peninsula have been studied. Seven labdadienes were identified from the former population, whereas the main terpenic constituents of the latter were ent-clerodadienes. The biosynthetic significance of this dramatic change in the diterpenic distribution of both populations is discussed.