Tetraludins D to N,eleven new melampolides from Tetragonotheca ludoviciana

Eleven new melampolides, tetraludins D-N, were isolated from aerial parts of Tetragonotheca ludoviciana. Tetraludins D and E, F and G, J and K, and L and M represented epimeric pairs which differed only at one chiral centre of the five-carbon ester side chain at C-8. In benzene-d₆, the ¹H NMR spectra of the diastereomeric pairs of melampolides exhibited well-separated signals in particular for the absorptions due to the ester side chains that differed in chirality.     

Flavonoids from Artemisia ludoviciana var. ludoviciana

Nineteen flavonoids were isolated from Artemisia ludoviciana var. ludoviciana, including a new 2′- hydroxy- 6-methoxyflavone, 5,7,2′,4′-tetrahydroxy-6,5′-dimethoxyflavone. The known compounds include quercetagetin 3,6,3′,4′-tetramethyl ether, eupatilin, 5,7-dihydroxy-3,6,8,4′-tetramethoxyflavone, luteolin 3′,4′-dimethyl ether, jaceosidin, 5,7,4′-trihydroxy-3,6-dimethoxyflavone, tricin, hispidulin, chrysoeriol, kaempferol 3-methyl ether, apigenin, axillarin, eupafolin, selagin and luteolin together with three flavones which were previously isolated for the first time from Artemisia frigida: 5,7,4′-trihydroxy-6, 3′,5′-trimethoxyflavone, 5,7,3′-trihydroxy-6,4′,5′-trimethoxyflavone and 5,7,3′,4′-tetrahydroxy-6,5′- dimethoxyflavone.     

Ludalbin,a new lactone from Artemisia ludoviciana

Artemisia ludoviciana Nutt. ssp. albula (Woot.) Keck, a member of the vulgaris complex, contains a sesquiterpene lactone, ludalbin, which is 8-α-acetoxydouglanine.     

Iridoid glucosides in Griselinia, Aralidium and Toricellia

From three of five investigated species of Griselinia a new iridoid glucoside, griselinoside, was isolated. It was found to be present also in foliage of Aralidium pinnatifidum and Toricellia angulata, accompanied in the former by aralidioside another novel iridoid glucoside. The structures and absolute configurations of the two iridoids were elucidated by NMR spectroscopy and chemical conversions. From G. littoralis and T. angulata the glucosides magnolioside and syringoside respectively were isolated. ¹³C NMR spectra are given for thirteen iridoid derivatives.     

The flavonoids of tetragonotheca (compositae)

Fifteen flavonols, five aglycones and ten glucosides were isolated from the four species of Tetragonotheca, T. repanda, T. helianthoides, T. texana and T. ludoviciana. Included among the isolated flavonols are four previously unreported 7-O-glucosides, 6-hydroxykaempferol 7-O-glucoside, 6-hydroxykaempferol 6-methyl ether 7-O-glucoside, quercetagetin 6,3′-dimethyl ether 7-O-glucoside and quercetagetin 3,6-dimethyl ether 7-O-glucoside.     

Three sesquiterpene lactones from Helianthus niveus subsp. canescens and H. argophyllus

Further investigation of the minor terpenoids in Helianthus niveus subsp. canescens and H. argophyllus afforded two known 12,8-fused sesquiterpene lactones, 3-acetylchamissonin and simsiolide as well as one new germacranolide, argophyllin C. Identification and structure elucidation of these lactones by ¹H NMR and chemical transformations are described.     

Germacranolides in Helianthus mollis

Desacetyleupaserrin, eupaserrin and two new germacranolides, mollisorin-A and mollisorin-B, were isolated from H. mollis. ¹H NMR and ¹³C NMR data and chemical interconversions of the four germacranolides are described.     

(25R)-Isonuatigenin,an unusual steroidal sapogenin from Vestia lycioides

(25R)-Isonuatigenin, a ⁵-spirosten-3β,25-diol, was isolated from aerial parts of Vestia lycioides. Its structure was elucidated mainly by ¹H NMR and ¹³C NMR spectroscopy. A mixture of (25R)-nuatigenin and (25S)-isonuatigenin was also characterized. This is the first report on the natural occurrence of the two (25R)-isomers.     

Isoflavidinin and iso-oxoflavidinin,two 9,10-dihydrophenanthrenes from the orchids Pholidota articulata, Otochilus porecta and Otochilus fusca

The structures of isoflavidinin and iso-oxoflavidinin, two new modified 9, 10-dihydrophenanthrenes of the orchids Pholidota articulata, Otochilus porecta and O. fusca have been established. ¹³C NMR spectral analysis of isoflavidinin acetate was made to confirm its structure.     

Ent-labdane derivatives from gutierrezia grandis

Two new diterpenes, 3α-angeloyloxy-18-hydroxy-13-furyl-ent-labda-8(17)-ene and 3α-hydroxy-18-angeloyloxy- 13-furyl-ent-labda-8(17)-ene and an only recently reported third diterpene, 3α, 18-dihydroxy-13-furyl-ent-labda-8(17)-ene, were isolated from the leaves of Gutierrezia grandis. Their structures were determined by mass spectral, IR, ¹H NMR and ¹³C NMR data was well as chemical evidence.     

In vivo and in vitro preparation of divinyl-132,173-cyclopheophorbide-a enol

Divinyl-13²,17³-cyclopheophorbide-a enol was in vivo produced as a metabolite of divinyl-chlorophyll-a by protists and in vitro prepared by the intramolecular cyclization of methyl divinyl-pyropheophorbide-a, one of the divinyl-chlorophyll-a derivatives. The ¹H NMR spectra in CDCl₃ showed that the obtained product took exclusively its enol form in the solution. The intramolecular cyclization of chlorin π-system at the C13² and C17³ positions affected the optical properties of such chlorophyll derivatives including the non-fluorescent emission of the enol.     

Benzoxazinones from Coix lachryma-jobi var. ma-yuen

The absolute configurations of 2-O-β-D-glucopyranosyl-7-methoxy-1,4(2H)-benzoxazin-3-one and three congeners isolated from Coix lachryma-jobi var. ma-yuen were determined by X-ray analysis and chemical correlation as the 2R type. ¹³C NMR spectra of all congeners and coixol were fully assigned.     

Sesquiterpenes and acetylenes from Argyranthemum adauctum ssp. jacobaeifolium

The roots of Argyranthemum adauctum ssp. jacobaeifolium, a rare endemic from Gran Canaria, afforded two new derivatives of the aromatic acetylene frutescin and 8-isovaleryloxymyrcene, while the aerial parts gave a new bisabolol derivative. Furthermore several known compounds were isolated. The structures were elucidated by high field ¹H NMR spectroscopy and a few chemical reactions.     

13C NMR spectroscopy of Pyrrolizidine alkaloids

The ¹³C NMR spectra of nine pyrrolizidine alkaloids of the macrocyclic diester type, seven of the corresponding N-oxides and of the parent base retronecine have been recorded and the signals assigned. The 13C NMR signals were found to be sensitive to structural variation in both the diester moiety and the heterocyclic ring system, providing useful information for structural elucidation, particularly when the ¹H NMR spectra may be difficult to interpret.     

Iridoid aglycones from Deutzia scabra

Scabrogenin and deutziogenin, the stable aglycones of known iridoid glucosides scabroside and deutzioside, have been isolated from Deutzia scabra. Their structures and mutarotational equilibria were investigated by detailed analysis of ¹H NMR and ¹³C NMR data.     

Sulphides and furanones from steam volatile oils of Allium fistulosum and Allium chinense

The constituents of the steam volatile oils from two kinds of Allium fistulosum, A. fistulosum var. caespitosum and A. chinense, have been investigated by GC and spectral techniques (IR, UV, GC/MS, ¹H NMR and ¹³C NMR). The compounds identified from the neutral fraction of each volatile oil included sulphides, thiolanes, alcohols, aldehydes, ketones, furanones and others. Among the sulphur compounds, dipropyl disulphide comprised ca 28% of A. fistulosum oil, ca 23% of A. fistulosum var. caespitosum oil and ca 30% of A. chinense oil. A. fistulosum oil was characterized by a large quantity of tridecan-2-one (ca 52%) and 2,3-dihydro-2-octyl-5-methylfuran-3-one (ca 16%). Also, a large amount of 2,3-dihydro-2-hexyl-5-methylfuran-3-one (ca 20%) was isolated from A. chinense oil.     

Tetraludin A,B and C,three new melampolides from Tetragonotheca ludoviciana

The investigation of the roots of the four Tetragonotheca species, T. ludoviciana, T. repanda, T. texana and T. helianthoides, resulted in the isolation of the known heptadeca-2-(Z)-8,10-(E)-16-tetraene-4,6-diin-1-ol and its aldehyde derivative from all four species. Aerial parts of T. ludoviciana also contained the acetate of the latter compound as a minor constituent and provided three new melampolide-type sesquiterpene lactones, tetraludin A, B and C.     

Coumarin-hemiterpene ethers from Artemisia species

In addition to a known derivative, five new coumarin-hemiterpene ethers were isolated from the leaves of Artemisia laciniata, A. armeniaca and A. tanacetifolia and identified by ¹H NMR and, in part, by ¹³C NMR spectroscopy. The coumarin patterns are characterized particularly by compounds with a hydroxylated and saturated isoprenoid unit attached to oxygen at the C-8 position and by 5,7,8-trioxygenated derivatives. The chemotaxonomic significance of the coumarin-terpenoid ethers within Artemisia is discussed.     

Flavonoid constituents of Ephedra alata

Two new flavonol glucosides have been identified in Ephedra alata, namely, herbacetin 8-methyl ether 3-O- glucoside-7-O-rutinoside and herbacetin 7-O-(6″-quinylglucoside). The known flavonoids vicenin II, lucenin III, kaempferol 3-rhamnoside, quercetin 3-rhamnoside and herbacetin 7-glucoside were also found. The structure of the isolated compounds was determined mostly by FABMS and ¹H NMR spectroscopy. The final structure of the new compounds and of herbacetin 7-glucoside was confirmed by ¹³C NMR spectroscopy.     

[Benzilato(2−)-O,O]bis[1,3-diphenylpropane-1,3-dionato(1−)-O,O]silicon(IV): a neutral heteroleptic hexacoordinate silicon(IV) complex with an SiO6 skeleton

Reaction of tetramethoxysilane with 1,3-diphenylpropane-1,3-dione and benzilic acid (molar ratio 1:2:1) in tetrahydrofuran/n-pentane yielded the neutral heteroleptic hexacoordinate silicon(IV) complex [benzilato(2−)-O¹,O²]bis[1,3-diphenylpropane-1,3-dionato(1−)-O,O]silicon(IV) (5). Compound 5 was structurally characterized by single-crystal X-ray diffraction, solid-state VACP/MAS NMR spectroscopy (²⁹Si), and solution NMR spectroscopy (¹H, ¹³C, ²⁹Si). The chiral silicon(IV) complex, with its octahedral SiO₆ coordination polyhedron, is configurationally stable in solution on the NMR time scale (solvent: CDCl₃; maximum temperature studied: 58 °C).