Synthesis of (-)-albrassitriol and (-)-6-epi-albrassitriol from (+)-larixol.

A novel synthesis of natural drimanic compounds, (-)-albrassitriol (2) and (-)-6-epi-albrassitriol (3), has been carried out starting from an easily available labdane diterpenoid, (+)-larixol (1). In a two-step procedure, (+)-larixol (1) was converted into 14,15-bisnorlab-7-ene-6,13-dione (9), which was then submitted to a Norrish type II photochemical degradation yielding drim-7,9(11)-diene-6-one (10), whose treatment with OsO4 led selectively to the formation of drim-7-ene-9α,11-diol-6-one (12). The same compound was obtained by selective epoxidation of the C(9)-C(11) double bond in drim-7,9(11)-diene-6-one (10) with monoperphtalic acid.

Synthesis of 5,10-seco analogs of testosterone.

A number of 5,10-seco analogs of testosterone has been synthesized starting from products of the radical oxidation of 3beta,17beta-diacetoxy-5alpha-androstan-5alpha-ol. The obtained compounds possess a flexible 10-membered ring with substituents (O, -OH) at C-3 and C-5. Similar derivatives with an (E)- and (Z)-Delta(1(10))-double bond have been prepared also.

Saponins, classification and occurrence in the plant kingdom.

Saponins are a structurally diverse class of compounds occurring in many plant species, which are characterized by a skeleton derived of the 30-carbon precursor oxidosqualene to which glycosyl residues are attached. Traditionally, they are subdivided into triterpenoid and steroid glycosides, or into triterpenoid, spirostanol, and furostanol saponins. In this study, the structures of saponins are reviewed and classified based on their carbon skeletons, the formation of which follows the main pathways for the biosynthesis of triterpenes and steroids.

A new type of steroids with a cyclobutane fragment in the AB-ring moiety.

The synthesis of a 5,10-seco steroid containing two double bonds in a AB-macrocycle as well as the preparation of a steroidal skeleton with a cyclobutane fragment is described. The structures of these compounds are different from those of natural steroids, but they are very similar with respect to conformation of the carbon skeleton.

Isolation and structure elucidation of new radical oxidation products of 5-hydroxy steroids.

Three new products have been isolated from the lead-tetraacetate version of the hypoiodite oxidation of 3beta,17beta-diacetoxy-5-hydroxy-5 alpha-androstane. Along with the expected 1(10)-unsaturated 5,10-seco steroidal 5-ketones, the fragmentation reaction gave two epimeric C-4 iodides. Their structural assignment was based on X-ray data of one of them ((4R,10S)-4-iodo-3beta,17beta-diacetoxy-5,10-secoandrostan-5-one).

Reaction of (13S)-13-iodo-6beta-methoxy-3alpha,5-cyclo-13,14-seco-5alpha-androstane-14,17-dione with hydroxylamine and its application to the synthesis of new 13,14-seco steroids.

The synthesis of 13,14-seco steroids starting from easily available (13S)-13-iodo-6beta-methoxy-3alpha,5-cyclo-13,14-seco-5alpha-androsta-14,17-dione is described. The C-17 ketone was converted regioselectively into its oxime with simultaneous stereoselective deiodination at C-13. The remaining C-14 carbonyl group was then reduced stereoselectively with Ca(BH4)2.

Synthesis of 13,14-secotestosterone derivatives.

A number of testosterone analogs with a 13,14-secosteroidal fragment have been prepared from (13S)-13-iodo-6beta-methoxy-3alpha, 5-cyclo-13,14-seco-5alpha-androstan-14,17-dione. The key steps involved stereoselective deiodination of the starting compound with triphenylphosphine and selective protection of the 17-keto group with trimethylsilylcyanide. Removal of iodine at C-13 proceeded with inversion of the configuration at C-13, which has been established by X-ray crystallography.

The synthesis of functionalized 13,14-seco-steroids via Grob fragmentation.

A synthetic methodology for the synthesis of 13,14-seco-steroids with substituents at C-14 and C-17 is described. The approach involves Grob fragmentation of 14beta-hydroxy-17beta-tosylates, hydroboration-oxidation of the intermediate delta13(17)-olefin, and hydride reduction of the 14-ketone. An unambiguous structural assignment of (13R,14S,17S)-14,17-diacetoxy-3-methoxy-7alpha-methyl-13,14-secoestra-1,3,5(10)-triene was determined by X-ray analysis.

Qualitative and quantitative variation among volatile profiles induced by Tetranychus urticae feeding on plants from various families.

Many plant species are known to emit herbivore-induced volatiles in response to herbivory. The spider mite Tetranychus urticae Koch is a generalist that can feed on several hundreds of host plant species. Volatiles emitted by T.

Chemical and enzymatic hydrolysis of anthraquinone glycosides from madder roots.

For the production of a commercially useful dye extract from madder, the glycoside ruberythric acid has to be hydrolysed to the aglycone alizarin which is the main dye component. An intrinsic problem is the simultaneous hydrolysis of the glycoside lucidin primeveroside to the unwanted mutagenic aglycone lucidin. Madder root was treated with strong acid, strong base or enzymes to convert ruberythric acid into alizarin and the anthraquinone compositions of the suspensions were analysed by HPLC.

Insect antifeedant activity of clerodane diterpenes and related model compounds.

A comprehensive compilation of all test results on the insect antifeedant activity of clerodane diterpenes and related model compounds is reported. To increase the compatibility of data from different sources, some of the results reported in the literature have been converted into a standardized form. The compounds were sorted into groups according to the different types of sidechain attached to C-9.

Isolation and structure elucidation of radical scavengers from Thymus vulgaris leaves.

2,2-Diphenyl-1-picrylhydrazyl radical (DPPH*) scavenging activity-guided fractionation of a leaf extract of Thymus vulgaris led to the isolation of the radical scavengers rosmarinic acid 1, eriodictyol, taxifolin, luteolin 7-glucuronide, p-cymene 2,3-diol, p-cymene 2,3-diol 6-6'-dimer, carvacrol, thymol, and a new compound, 2. The fractionation was considerably facilitated by using an on-line HPLC detector for radical scavenging activity. In this detector activity is monitored as the disappearance of the color of a postcolumn added stable radical after reacting with radical scavengers in a reaction coil.

Biosynthesis of costunolide, dihydrocostunolide, and leucodin. Demonstration of cytochrome p450-catalyzed formation of the lactone ring present in sesquiterpene lactones of chicory.

Chicory (Cichorium intybus) is known to contain guaianolides, eudesmanolides, and germacranolides. These sesquiterpene lactones are postulated to originate from a common germacranolide, namely (+)-costunolide. Whereas a pathway for the formation of germacra-1(10),4,11(13)-trien-12-oic acid from farnesyl diphosphate had previously been established, we now report the isolation of an enzyme activity from chicory roots that converts the germacrene acid into (+)-costunolide.

Identification of radical scavengers in sweet grass (Hierochloe odorata).

Extracts from aerial parts of sweet grass (Hierochloe odorata) were active DPPH free radical scavengers. The active compounds were detected in extract fractions using HPLC with on-line radical scavenging detection. After multistep fractionation of the extract, two new natural products possessing radical scavenging activity were isolated, and their structures were elucidated by NMR and MS.

Screening of plant extracts for antioxidant activity: a comparative study on three testing methods.

Three methods widely employed in the evaluation of antioxidant activity, namely 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method, static headspace gas chromatography (HS-GC) and beta-carotene bleaching test (BCBT), have been compared with regard to their application in the screening of plant extracts. The strengths and limitations of each method have been illustrated by testing a number of extracts, of differing polarity, from plants of the genus Sideritis, and two known antioxidants (butylated hydroxytoluene and rosmarinic acid). The sample polarity was important for the exhibited activity in the BCBT and HS-GC methods but not for the DPPH method.

Effect of acyl chain length and branching on the enantioselectivity of Candida rugosa lipase in the kinetic resolution of 4-(2-difluoromethoxyphenyl)-substituted 1,4-dihydropyridine 3,5-diesters.

Since 2,6-dimethyl-4-aryl-1,4-dihydropyridine 3,5-diesters themselves are not hydrolyzed by commercially available hydrolases, derivatives with spacers containing a hydrolyzable group were prepared. Seven acyloxymethyl esters of 5-methyl- and 5-(2-propoxyethyl) 4-[2-(difluoromethoxy)phenyl]-2,6-dimethyl-1,4-dihydro-3,5-pyridinedicarboxylate were synthesized and subjected to Candida rugosa lipase (CRL) catalyzed hydrolysis in wet diisopropyl ether. A methyl ester at the 5-position and a long or branched acyl chain at C3 gave the highest enantiomeric ratio (E values).

Base-Induced Rearrangement of Perhydronaphthalene-1,4-diol Monosulfonate Esters to 11-Oxatricyclo[5.3.1.0(2,6)]undecanes. Total Synthesis of Furanether B.

It is observed that mesylate 1 on exposure to Li(Ot-Bu)(3)AlH in refluxing toluene rearranges selectively to the 11-oxatricyclo[5.3.1.

About the Chiral Stability of Germacrene B and the Biomimetic Synthesis of Guaiane Sesquiterpenes.

The planar chirality of 15-hydroxygermacrene B (2) has been examined by means of the asymmetric Sharpless epoxidation, performed as a kinetic resolution. (1)H NMR experiments with Eu(hfc)(3) demonstrate that the recovered 2 is racemic. Consequently, 2 and most likely also germacrene B (1) are not enantiomerically stable at room temperature.

Synthesis of (E,E)-Germacrane Sesquiterpene Alcohols via Enolate-Assisted 1,4-Fragmentation.

An efficient method has been developed for the synthesis of (E,E)-germacrane sesquiterpene alcohols. The key step in these syntheses involves the enolate-assisted 1,4-fragmentation of properly functionalized perhydro-1-naphthalenecarboxaldehydes with 1 equiv of sodium tert-amylate as base, to give the corresponding (E,E)-germacrane aldehydes. These aldehydes are not very stable, and in situ reduction of the aldehyde function with Red-Al is required to obtain high yields of the desired germacrane alcohols.

Total Synthesis of Neohedycaryol. Its Possible Role in the Biosynthesis of Eudesmane Sesquiterpenes.

The total synthesis of neohedycaryol (4), the C(9)-C(10) double bond regioisomer of the germacrane sesquiterpene hedycaryol, was accomplished in 10 steps from the known dione 6. A Marshall fragmentation of the intermediate mesylate 14 was used to prepare the trans,trans-cyclodeca-1,6-diene ring present in neohedycaryol. During the synthesis of 14, a pronounced example of through-bond interactions (TBI) was observed.

Relative and Absolute Configuration of Allohedycaryol. Enantiospecific Total Synthesis of Its Enantiomer.

The enantiomer of (+)-allohedycaryol, a germacrane alcohol isolated from giant fennel (Ferula communis L.), has been synthesized, thereby elucidating the relative and absolute stereochemistry of the natural product. The synthesis of (-)-allohedycaryol started from (+)-alpha-cyperone (5) which was available in relatively large quantities via alkylation of imine 7 derived from (+)-dihydrocarvone and (R)-(+)-1-phenylethylamine.