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Photocycloadditlon of (+)-isoplperltenone and cyclobutene-1-carboxylic acid gives an adduct which upon reduction with NaCNBH3 followed by thermolysis yields an isomer of isoaristolactone in an overall yield of 26%.

The eremantholides 1A, 1B, 1E, 1G, 1H, 1J and the germacranolides 2A, B were found in the molluscidal extract from EREMANTHUS GLOMERULATUS L.

The structure of the cytotoxic sesquiterpene lactone, stizolicin, reisolated from Stizolophus balsamitus (Centaurea b.) was revised to a trans, trans germacranolide (1) on the basis of simultaneous application of lanthanide shift reagent and NOE in the NMR.

The roots of Eupatoriadelphus purpureus contain tridecapentaynene, β-pinene and five p -hydroxyaecetophenone derivatives. By contrast, the aerial parts have germacrene D, lupeol and its isomers, coumarin, a new sesquiterpene tiglate and a new germacranolide.

A new chemotype of Artemisia herba alba has been analysed and been shown to contain two known sesquiterpene lactones, herbolides E and F, and three new ones, herbolides G, H and I.

A new germacranolide isolated from M. sieboldii was shown to be 15-acetoxycostunolide by spectroscopic and chemical methods. 1 H NMR spin decoupling and NOE experiments in the presence of a lanthanide shift reagent were used for structure elucidation.

Chemical and spectral evidence is presented for the structure and stereochemistry of two new sesquiterpene lactone acetates, lipiferolide and γ-liriodenolide, isolated from the leaves and root bark, respectively, of Liriodendron tulipifera L.

The structure revision of the germacranolide salonitenolide and the preferential C-8 relactonization of germacranolides containing C-6 and C-8 lactonizable α-oxygen groups are described.

An allyl hydroperoxy sesquiterpene lactone, peroxyferolide (2), from the leaves of L. tulipifera was characterized by spectral and chemical methods and prepared from lipiferolide (1) by photosensitized oxygenation.

In addition to cordifene (1) and cordifene 4β, 15-oxide (5), four new companion compounds cordifolia-54, -55, -P2, and -31 have been isolated from the insect-antifeedant plant Erlangea cordifolia. Cordifolia-54(2) is related to cordifene as the 2,3-dihydrodeoxy derivative, and cordifolia-55(3) is the acetate of a C-2,O-2-seco-cordifene resulting from a formal epoxide reduction. Cordifolia-31 is the methacrylate ester of the same sesquiterpene core as is present in cordifene 4β,15-oxide.Cordifolia-P2 has 1H and 13C n.m.r. data consistent with structure (4) but certain chemical shifts, multiplicities, and coupling constants suggest a conformation markedly different from the five other Erlangea structures. This has been confirmed by a single crystal X-ray analysis. Cordifolia-P2, in contrast to cordifene and its 4β, 15-oxide, has a negative Cotton effect near the n→π* maximum in the c.d. spectrum. This is explained by McPhail's generalisation if all three compounds have the same absolute configuration, since the C(5)–C(6)–C(7)–C(8) torsion angle is significantly 120°(157°, 159°) for cordifene and its oxide. On the other hand the idealised McPhail relationship between this torsion angle and the CC–CO torsion angle of the lactone is incompletely obeyed since the latter is measured as +0.7° in cordifolia-P2.

Two biomodified esters (1) and (2) of a new germacranolide sesquiterpene lactone, melnerin, have been isolated from the leaves of Melapodium cinereum. Their structures have been characterized by 1H and 13C n.m.r. spectroscopy, and gas chromatography–mass spectrometry of trimethylsilyl-derivatives, and single-crystal X-ray diffraction. Melnerin A, (1), C20H28O7, with an isobutyrate side-chain, and melnerin B, (2), C21H30O7 with a 2-methylbutyrate side-chain, co-crystallize in ca. 4 : 1 ratio, in the orthorhombic space group P212121, with a= 9.322(2), b= 11.655(2), c= 19.032(4)A, Z= 4. The crystal structure, which is disordered in the ester side-chain, was solved by direct phasing procedures and refined by weighted full-matrix least-squares to R 8.2% 1 711 reflections. The Δ1(10)-cis-germacrene ring has the same conformation as cis-cyclodecene. Substituents at C(4)(hydroxymethylene) and C(10)(methoxycarbonyl) are syn and α-oriented, while the ester group attached to C(8) is β-oriented. The α-methylene-γ-lactone, trans-fused at C(6) and C(7), is non-planar with right-handed chirality. The absolute configuration is assigned from biogenetic considerations and correlation with known structures.

Transformation par adsorption sur terre bentonitique du 4α,5α-epoxyinunolide en inuviscolide, 4α,5α-epoxy-10α-14H-inuviscolide et 8-epiconfertine

Five new sesquiterpene lactones, callitrin (1) (an elemanolide), callitrisin (2) and dihydrocallitrisin (6) (eudesmanolides), and columellarin (4) and dihydrocolumellarin (5) (guaianolides) have been isolated from Callitris columellaris heartwood along with the germacranolide (3) which is a new natural product previously only known synthetically. These compounds are the first sesquiterpene lactones isolated from the Cupressaceae. Lactones (1), (2) and (6) all share a novel cis-fused lactone ring in which the C7-C11 bond is axial to a cyclohexane ring.

The molecular structure of a fluoro-derivative (IV) of a guaianolide has been established by single-crystal X-ray diffraction techniques. The compound is a product of the BF3-catalyzed opening of an epoxide group in a 1,10-epoxyguaianolide (III) derived from the germacranolide sesquiterpene lactone dihydroparthenolide (I). Crystals of (IV) are orthorhombic, space group P212121, with Z= 4 in a unit cell of dimensions a= 8.975(2), b= 11.174(2), c= 14.583(6)A. The structure was refined to R 0.027 for 1 648 reflections. The molecule features a fullysaturated cis-fused guaianolide-type skeleton with idealized symmetry Cs, having the seven-membered ring in the chair and the five-membered ring in the envelope conformation. Substituents on this fused ring system are α-F at C(1), α-OH and β-Me at C(4), an α-methyl-γ-lactone trans-fused at C(6) and C(7), and α-Me and β-OH substituents at C(10). The stereochemistry of the precursor 1,10-epoxide is thus inferred to be β.

A new germacranolide from Vernonia scorpioides has been isolated and its stereostructure elucidated on the basis of spectroscopic data and an X-ray analysis; it has a unique conformation for a cyclodecadiene.

Single-crystal X-ray analysis has established the structure and relative stereochemistry of the title compound (I). The absolute configuration follows from the sign of the Cotton effect of then n→π* transition of the α-methylene γ-lactone CC–CO chromophore. Crystals are orthorhombic, space group P212121, a= 14.28(2), b= 11.52(2), c= 9.68(2)A, Z= 4. The structure was solved by direct phase-determining methods and atomic parameters refined by full-matrix least-squares calculations to R 0.093 over 1 437 reflections from photographic data. The Δ1(10)trans, Δ4cis-cyclodecadiene ring is in a chair, boat conformation with the C(4) and C(10) methyl groups oriented anti. The anomalous relationship between the sign of the measured Cotton effect of the CC–CO chromophore n→π* transition for Δ1(10)trans, Δ4cis germacranolide C(6), C(7)-trans-fused α-methylene γ-lactones and the position and stereochemistry of the lactone ring fusion is discussed with respect to the preferred cyclodecadiene ring conformation.

Cnicin was isolated as the major sesquiterpene lactone from Aegialophila pumila Jus. Boiss. The germacranolide salonitenolide was isolated as a minor constituent. Cnicin demonstrated pronounced cytotoxic activity when tested in vitro against TLX-5 mice lymphoma cells.

The crystal structure of crispolide diacetate (1b), a 4,14-cyclogermacranolide bearing a secondary peroxy ester group, was determined by direct methods from 1 612 reflections, and refined to R= 0.041. The crystals are orthorhombic, space group P212121. The methyl group at C(4) and the hydroxy group at C(5) are cis-oriented on the β-face of the eight-membered ring, in accordance with the proposed biogenetic derivation for the unique terpenoid skeleton. The secondary peroxy ester group adopts a conformation different from that found in solution and in the solid state for tertiary peroxy esters.

The crystal and molecular structure of melampodin B, C17H18O7, has been determined by single crystal X-ray diffraction. Crystals are monoclinic, P21, a= 9.714(4), b= 6.922(1), c= 12.503(1)A, β= 106.76(1)°, Z= 2. The structure was refined to an R value of 3.0% over 1 871 total reflections. The cyclodeca-4,5-cis-9,10-trans-diene ring is in a conformation theoretically derivable from a cyclodeca-4,5-cis-1,10-cis-diene precursor, as determined by empirical force field calculations. Lactone rings are fused to the cyclodecadiene at C(6)–C(7) and at C(8)–C(10). Intermolecular hydrogen bonds between the hydroxy group and a lactone carbonyl oxygen atom link molecules in the solid.

Alatolide (1), a germacrane sesquiterpenoid lactone has been studied by X-ray diffraction and the conformation shown to be similar to that of costunolide. The torsion angles about the double bonds in the cyclodeca-1,5-diene ring are C(3)–C(4)–C(5)–C(6) 154° and C(2)–C(1)–C(10)–C(9) 167°. The negative n→π* Cotton effect of the α-methylene γ-lactone is consistent with the trans-fusion of the lactone at C(6)–C(7) but the CC–CO chromophore is planar and, hence, non-chiral in the crystal. The hydroxy-groups at C(14) and C(15) are associated in an intramolecular hydrogen bond. The compound crystallized as a hydrate, with a= 13.175(2), b= 12.495(2), c= 11.663(4)A, space group P212121, and Z= 4. The crystal structure was determined by direct-phasing methods and the atomic parameters were refined by least-squares calculations to R 6.4% over 1 560 diffractometer reflections.

The structure and stereochemistry of neoliacine, a novel germacranolide sesquiterpene isolated from Neolitsea acciculata Koidz., have been elucidated on the basis of chemistry transformation, spectral, and single-crystal X-ray analysis.

The stereochemistry of glaucolide A (1), a germacrane sesquiterpenoid lactone, has been defined by X-ray crystalstructure analysis. The ten-membered ring, which carries an epoxide function at C(4)–C(5), has a conformation related to those of several other germacrane sesquiterpenoids and to one of the less-stable conformations of cyclodecane. The αβ-unsaturated γ-lactone ring is essentially planar. Crystals are orthorhombic, a= 9·075(6), b= 18·901(6), c= 13·654(6)A, Z= 4, space group P212121. The structure was solved by direct methods and atomic parameters adjusted by least-squares calculations, which converged to R 6·2% over 1701 reflections measured by diffractometer.

An attempt is made by proposing new conventions to avoid the ambiguity and confusion implicit in the present method of representing germacranolides in two dimensions.

Two crystalline compounds urospermal A and B, isolated from Urospermum dalechampii, are interconvertible in solution, and evidence is presented which indicates that they are conformers of the germacranolide aldehyde (II) or its mirror image.

The structure and absolute configuration of molephantin, a novel cytotoxic germacranolide isolated from Elephantopus mollis H.S.K., have been determined on the basis of physicochemical data and X-ray crystallographic analysis.

A new germacranolide, laurenobiolide, has been isolated from Laurus nobilis L. and its stereostructure was elucidated on the basis of the spectroscopic data for the lactone and for some reaction products.

The structure of melampodin B, a new sesquiterpene dilactone isolated from Melampodium leucanthum, has been elucidated on the basis of physical properties, predominantly 13C and 1H n.m.r. data.

The structure of melampodin, a new sesquiterpene lactone isolated from Melampodium leucanthum Torr. and Gray. var. leucanthum, has been elucidated on the basis of physical properties.

The enol acetate (VI), derived from α-santonin, was irradiated and hydrolysed to give the cyclodecadienone (VIII), which yielded dihydronovanin (XI) upon reduction followed by acetylation.

The conformations of the two conformational isomers of isabelin (1), a germacranolide dilactone isolated from Ambrosia psilostachya DC. (Compositae), have been determined in chloroform solution by use of the intramolecular nuclear Overhauser effect; and further, the configuration of the endocyclic double-bond in its ten-membered ring has been confirmed. It has been concluded that the major and minor isomers of isabelin mainly adopt the conformations (A) and (B), respectively, which have a trans-orientation of the endocyclic double-bond. Since isabelin has been correlated with artemisiifolin (3), salonitenolide (4), and cnicin (5), the results obtained here have also established a trans configuration for these three germacranolide monolactones. In addition, isoisabelin (2), a geometrical isomer of isabelin, has been examined to determine the configuration of its C(9)–C(10) double-bond and its conformation.