8-Hydroxypegolettiolide,a sesquiterpene lactone with a new carbon skeleton and further constituents from Pegolettia senegalensis

The investigation of Pegolettia senegalensis afforded several new sesquiterpene lactones, eight cis-6,12-germacra-trans,trans-1(10),4,11-trienolides, five cis-6,12-eudesmanolides, two elemanolides, 8,14-cyclogermacra-1(10),4,7(11)-trien-6,12-olide with a new carbon skeleton, three germacra-1(10),4,11(13)-trien-12-oic acids with ester residues at C-8, 18-hydroxygeranyl nerol, 1,3-dihydroxyoctadecane and a mixture of esters of 3,4-dihydroxy-dihydrocinnamyl alcohol. The structures were elucidated by high field ¹HNMR spectroscopy and some chemical transformations. The C-10 configuration of 6,12-cis-eudesmanolides from Calostephane divaricata and Inula crithmoides most likely has to be corrected. The chemotaxonomic situation of the genus Pegolettia and biogenetic considerations are discussed briefly.     

The incorporation of [5,6-13C2]Nicotinic acid into the tobacco alkaloids examined by the use of 13C nuclear magnetic resonance

[5,6-¹⁴C,¹³C₂]Nicotinic acid was prepared from [¹⁴C,¹³C]methyl iodide via nitromethane, 2-nitroacetaldehyde oxime, 3-nitroquinoline, 3-aminoquinoline, and quinoline in 20% overall yield. Administration of this material to Nicotiana tabacum and N. glauca afforded labeled anabasine, anatabine, nicotine, and nornicotine. Qualitative and quantitative incorporation (0.07–4.5% specific incorporation) was determined by radioactive assay and by examination of the ¹³C NMR spectra of these alkaloids. Satellites due to spin-spin coupling of the incorporated contiguous ¹³C atoms were observed at the resonances due to C-5 and C-6 in anabasine, nicotine, and nornicotine. In anatabine, satellites were found at C-5, C-6, C-5′, and C-6′.     

The crystal structure of 6-epi-desacetyllaurenobiolide,a germacra-1(10),4-diene-12,8α-olide from Montanoa grandiflora

A chloroform extract of Montanoa grandiflora afforded a novel 6β-hydroxy-germacradien-8,12-olide. Its structure was shown to be 6-epi-desacetyllaurenobiolide by spectral studies, chemical transformations and single crystal X-ray diffraction. The X-ray data demonstrate that the ten-membered ring exists in the crystal in the highly unusual [₁₅D⁵,₁D¹⁴] conformation, in which the methyl group at C-4 is α-oriented and the methyl group at C-10 is β-oriented. The two double bonds are approximately parallel rather than crossed.     

Germacranolides from anvillea garcini

The aerial parts of Anvillea garcini afforded three germacranolides, two of which had not being isolated previously. The structures were elucidated by ¹H NMR spectroscopy. The configuration of 9-acetoxy parthenolide at C-9 has been revised.     

The syntheses of 3-substituted perfluoroalkyl steroids

The syntheses of three classes of C-3 perfluoroalkyl substituted steroids are described. They are the 3β-hydroxy-3α-perfluoroalkylandrost-4-en-17-ones (5a-c), 3-perfluoroalkylandrosta-3,5-dien-3-ones (8a-c) and 3β-hydroxy-3α-perfluoroalkylandrost-5-en-17-ones (12a-c). Addition of a series of perfluroalkylorganometallic reagents (R_FLi; R_F = C₂F₅, C₃F₇, or C₄F₉) to the 3 position of silylated testosterone 2b afforded Δ⁴ perfluoroalkyl carbinols 3. In Scheme 1, deprotection with HF and oxidation at the C-17 carbon with PCC produced Δ⁴ ketones 5. In Scheme 2 dehydration of 3 with 1,2-phenylenephosphorochloridite and iodine afforded Δ^3,5 dienes 6 which were deprotected and oxidized as above to the C-17 ketones 8. In Scheme 3 isomerization of the double bond of 3 from the C-4 to the C-5 position using the allylic halogenation followed by treatment with lithium aluminum hydride led to the synthesis of the double bond isomer series 12. A new method for dehydration was developed. On average and within experimental error, 3β-hydroxy-3α-perfluoroalkylandrost-5-en-17 ones (12a-c) were better than the 3-perfluoroalkylandrosta-3,5-dien-17-ones (8a-c) and 3β-hydroxy-3α-perfluoroalkylandrost-4-en-17-ones (5a-c) at inhibiting glucose-6-phosphate dehydrogenase.     

Biosynthesis of dioscorine : Incorporation of nicotinic acid into the isoquinuclidine moiety

The administration of nicotinic-[2-¹⁴C] acid to Dioscorea hispida plants afforded radioactive dioscorine (1.9% absolute incorporation) and a systematic degradation of the alkaloid indicated that essentially all the activity was located at C-3. Dioscorine derived from nicotinic-[5,6-¹⁴C, ¹³C₂] acid was also labelled. Its proton noise decoupled ¹³C NMR spectrum contained satellites at C-1 and C-7 due to spin-spin coupling of contiguous ¹³C atoms arising from direct incorporation of the labelled nicotinic acid. A biosynthetic scheme representing a novel utilization of nicotinic acid is proposed.     

Peucelinendiol,a new acyclic diterpenoid from Peucedanum oreoselinum

A new diterpenoid has been isolated from roots of Peucedanum oreoselinum. Mainly by spectroscopic methods, its structure is shown to be (+)-(E)-7-hydroxymethyl-2,6,10,14-tetramethyl-2,9,13-pentadecatrien-6-ol, yet without specification of stereochemistry at C-6 and C-7. Furthermore the roots afforded a high yield of falcarindiol, (+)-(Z)-heptadeca-1,9-dien-4,6-diyn-3,8-diol.     

Isoswinholide B and swinholide K,potently cytotoxic dimeric macrolides from Theonella swinhoei

Chemical investigation of an Indonesian specimen of Theonella swinhoei afforded the new dimeric macrolides isoswinholide B (5) and swinholide K (6), along with the known swinholides A (1), B (2) and D (3) and isoswinholide A (4). Isoswinholide B showed an unprecedented 21/19′ lactonization pattern, while swinholide K included an sp² methylene attached at C-4 and an additional oxymethine group at C-5, whose configuration has been determined through application of J-based configuration analysis. The isolated swinholides (1–6), with the exception of isoswinholide B, showed a cytotoxic activity on HepG2 (hepatocarcinoma cell line) in the nanomolar range.     

Enzymatic regioselective deprotection of peracetylated mono- and disaccharides

Selective enzymatic hydrolysis of the peracetylated disaccharides, namely cellobiose, lactose, maltose and melibiose, with lipase from Asperilligus niger in aqueous buffer and organic solvent for 30 min afforded exclusively the corresponding heptaacetates with a free hydroxyl group at C-1 in high yield. Prolonged reaction of the β-1,4 linked cellobiose and lactose peracetates afforded selectively their hexaacetates with free hydroxyl groups at C-1,2, whereas the α-1,4 linked disaccharides maltose and melibiose peracetate gave a complex mixture of products. The reaction of 2-acetamido-2-deoxy-1,3,4,6-tetra-O-acetylglucopyranose (11) for 22 h afforded as the major product the diacetate 12 with free hydroxyl groups at C-1,4.     

Tetrahydrofuran-type terpenoids from Tanacetum vulgare

Investigation of a rare genotype of Tanacetum vulgare afforded a series of tetrahydrofuran-type terpenoids, whose pattern was different in flowers and leaves. The major constituent of the flowers was the trans Δ^3,4-hydroperoxide of davanone, whereas the leaves gave mostly a peroxyhemiketalic compound resulting from the intramolecular cyclization of the cis Δ^3,4-hydroperoxide of davanone. Structures were elucidated by spectral data and chemical reactions, including correlation with natural (+)-davanone. The peroxyhemiketalic compound upon acylation of its hydroxyl group gave an instantaneous complex reaction, resulting in the formation of a β-acyloxyenone and loss of one molecule of acetone. Among the minor constituents of the leaves, a C-10 carboxylic acid biogenetically related with davanone was isolated.     

Hirsutinolides and other sesquiterpene lactones from Vernonia species

The investigation of Vernonia compactiflora afforded in addition to known compounds a hirsutinolide and a glaucolide; the latter is most probably the direct precursor of the former. The aerial parts of V. monocephala contain the same hirsutinolide as well as the corresponding acetate, while those of V. chalybaea afforded glaucolide B. A reinvestigation of the aerial parts of V. cotoneaster gave in addition to the allenic lactone isolated before two further known ones as well as a new glaucolide. The structures of the lactones were elucidated by spectroscopic methods and some chemical transformations. The erroneously assigned stereochemistry at C-10 in the hirsutinolides has been revised. The biogenetic relationship of the Vernonia lactones is discussed briefly.     

Structure and anomeric configuration of the 3,6-anhydro-osazone derivatives obtained from d-altro-2-heptulose phenylosazone

Dehydration of d-altro-2-heptulose phenylosazone with methanolic sulfuric acid afforded two 3,6-anhydro-osazone derivatives (2 and 3). Compound 3 was obtained as the preponderant isomer, with inversion at C-1 (C-3 of the starting osazone), and 2 was obtained without inversion. Refluxing of 3 with copper sulfate afforded the C-nucleoside analog, namely, 2-phenyl-4-β-d-ribofuranosyl-1,2,3-osotriazole (4). Acetylation of 4 afforded the tri-O-acetyl derivative 5. The anomeric configuration was determined by c.d. and n.m.r. spectroscopy. The mass spectra of compounds 2–5 are discussed.     

Helenanolides from Gaillardia powellii

The chloroform extract of the aerial parts of Gaillardia powellii afforded four known and four new helenanolides, the latter all oxygenated on C-15, as well as the flavones hispidulin and eupafolin.     

Neue diterpene aus Schkuhria-arten

The investigation of two further Schkuhria species afforded, in addition to several known compounds, three new diterpenes from the labdane series of the manoyl oxide type. The structures were elucidated by spectroscopic methods and by some chemical transformations, although the absolute configuration and that at C-13 could not be established with certainty. Furthermore a new thymol derivative was obtained. The chemotaxomonic situation is discussed briefly.     

Caryophyllene derivatives from Pulicaria arabica

The aerial parts of Pulicaria arabica afforded in addition to known caryophyllene derivatives seven new ones. The configuration at C-11 of previously reported derivatives has to be corrected as followed from the observed NOEs.     

Pseudojujubogenin,a new sapogenin from Bacopa monniera

Acid hydrolysis of bacoside A, a saponin of Bacopa monniera, afforded ebelin lactone and bacogenin-A₁, while Smith-de Mayo degradation of bacoside A yielded jujubogenin and pseudojujubogenin as sapogenins. The structure of pseudojujubogenin except the absolute configurations at C-20 and C-22 was established by chemical and spectroscopic investigations. Bacoside A was separated by droplet counter-current chromatography into two fractions, A₁ and A₂, which, however, are mixtures, since they both afforded two sapogenins, in different ratios by Smith-de Mayo degradation.     

The first acetylenic monoterpene and other constituents from Senecio clevelandii

The aerial parts of Senecio clevelandii afforded three new monoterpene lactones, one of them being the first acetylenic monoterpene to be isolated, a C-14 acetylenic angelate, a tetrahydroquinol ester and several known compounds, among them the tricyclic precursor of the polycyclopentanoide sesquiterpenes.     

Sulfation of agarose from subantarctic Ahnfeltia plicata (Ahnfeltiales,Rhodophyta): studies of its antioxidant and anticoagulant properties in vitro and its copolymerization with acrylamide

Aqueous extraction of Ahnfeltia plicata collected in the Magellan ecoregion afforded agarose devoid of sulfate groups. This neutral agarose was subjected to sulfation with SO₃-pyridine complex, giving an aqueous soluble derivative with 35.5 % sulfate groups. Analysis by Fourier transform infrared spectroscopy (FT-IR) and by ¹H and ¹³C NMR spectroscopy indicated that this derivative was sulfated at positions C-6 of the β-galactopyranosyl residue and C-2 of the α-3,6-anhydrogalactopyranosyl residue and partially sulfated at position C-2 of the β residue. The antioxidant capacity of sulfated agarose was evaluated by the oxygen radical absorbance capacity (ORAC) method, ABTS radical cation, hydroxyl radicals, and chelating assays. This capacity of sulfated agarose toward peroxyl radicals was higher than that of commercial λ-carrageenan, while native agarose presented good activity, with an ORAC value similar to that of commercial κ-carrageenan. Sulfated agarose presented good antioxidant capacity toward other radicals. Copolymerization of sulfated agarose with acrylamide was achieved using ceric ammonium nitrate as initiator. NMR spectroscopy indicated grafting of polyacrylamide at position C-4 of β-galactopyranosyl residues.     

Further sesquiterpene lactones from costa rican eupatorieae

The aerial parts of Ayapana elata afforded two new germacranolides. The configuration at C-3 in one of them was the same as that of some bejaranolides, the structures of which therefore have to be revised. Critonia quadrangularis gave in addition to known compounds three elemanolides, a germacranolide, an isodaucane derivative and tremetone derivative. Critonia hebebotrya contained large quantities of known diterpene acids. Koanophyllon pittieri gave two epimeric ent-labdanes. The structures were elucidated by highfield NMR spectroscopy.     

5-deoxystansioside,an iridoid glucoside from Tecoma stans

In addition to plantarenaloside and stansioside, a new iridoid glucoside with a formyl group at C-4 has been isolated from Tecoma stans. The new glucoside was shown to be 5-deoxystansioside by ¹³C NMR and ¹H NMR spectroscopy.