The isolation and structures of euphoscopins a and b

Two new toxic substances, euphoscopins A and B, have been isolated from the plant $\text{Euphorbia}$$\text{helioscopia}$ L., and their absolute stereostructures also been elucidated on the basis of their spectral data coupled with an X-ray crystallographic analysis of the $\text{p}$-bromobenzoate readily obtained on treatment of euphoscopin A with $\text{p}$-bromobenzoyl chloride - pyridine. These antitumor substances belong to a group of jatrophone-type diterpenes.     

Structural and conformational studies on euphornin and related diterpenes

In addition to euphornin, three new toxic substances (euphornins A, B and C) have been isolated from the plant $\text{Euphorbia}$$\text{helioscopia}$ L., and their absolute stereostructures also been elucidated on the basis of their spectral data and some chemical evidence together with an X-ray crystallographic analysis of the p-bromobenzoate derived from euphornin. Furthermore, their conformations have also been discussed.     

Isolation and stereostructures of citreoviral,citreodiol, and epicitreodiol

Three new metabolites (citreoviral, citreodiol, and epicitreodiol) have been isolated from the mycelium of $\text{Penicillium}$$\text{citreo-viride}$ B.(IFO 6050) and their stereostructures have been elucidated on the basis of their spectral data coupled with some chemical evidence. Furthermore, the absolute configurations of citreodiol and epicitreodiol have been determined by syntheses of the corresponding antipodes starting from L-rhamnose.     

Synthesis and 13C nmr characterization of some π-excessive heteropolyaromatic compounds

Several π-excessive heteropolyaromatic compounds, which contain furan and thiophen ring and are possible antifungal agents, have been synthesized in good yields according to two general methods. The first method has been used to prepare compounds possessing thiophens linked by their 2- and 5-positions, such as the ter-aryls $\text{2b}$, $\text{2d}$ and $\text{2a}$. Two precursors of these compounds have been obtained either by the Glaser reaction, or using a novel Pd-mediated reaction. The second method,which consists of the Ni-or Pd-catalyzed heteroarylation of heteroarene halides via cross-coupling with heteroaryl Grignard reagents or zinc halides,has been used to prepare the bi-aryls $\text{1a-e}$, which contain two heteroaromatic units, and the ter-aryl $\text{2c}$. Compound $\text{1e}$ has been also prepared starting from 2-(2-thienyl) furan ($\text{1c}$) by selective lithiation, followed by bromination.The ¹³C NMR signals of $\text{1a-e}$ and $\text{2a-d}$ have been assigned on the basis of the literature data and by relaxation measurements. Relaxation data have been also used to obtain qualitative informations on the conformational equilibria of the bi-aryls $\text{1a}$, $\text{1c}$ and the ter-aryls $\text{2a-d}$.     

Labdane diterpene glycosides with 6-deoxy-L-idose from Aster spathulifolius Maxim.

Three labdane type diterpene glycosides ($\text{1}$, $\text{2}$ and $\text{3}$) with 6-deoxy-L-idose have been isolated from Aster spathulifolius Maxim. and their structures have been determined on the basis of chemical and spectral data.     

Structures of kokzeylanol and kokzeylanonol two new natural tri- and tetra- oxygenated D:A-friedo-oleananes

Kokzeylanol and kokzeylanonol obtained from $\text{Kokoona}$$\text{zeylanica}$ have been shown to be 6β,27-dihydroxy-D:A-friedo-olean-3-one ($\text{1}$) and 6β,27-dihydroxy-D:A-friedo-oleana-3,21-dione ($\text{2}$), respectively by the deoxygenatlon of their 27-acetoxy derivatives using Lithium-ethylene diamine reduction coupled with spectroscopic and irradiation methods. Kokzeylanonol represents the first tetraoxygenated D:A-friedo-oleanane isolated from a natural source.     

Ichthyotoxic sesterterpenoids from the neo guinean sponge carteriospongia foliascens

Six 20,24-dimethylscalarane derivatives ($\text{5}$, $\text{12}$, $\text{15}$, $\text{17}$, $\text{19}$, and $\text{21}$) have been isolated from the Neo Guinean sponge Carteriospongia foliascens. Compound $\text{12}$ is identical with a C₂₇ tetracyclic terpene previously isolated from an Australian specimen of the same sponge. The five other derivatives are new and their structures have been established on the basis of their spectral data. The structure of $\text{5}$ was confirmed by single-crystal X-ray diffraction and that of $\text{15}$ by chemical correlation with $\text{12}$. The configuration at C-4 for all these compounds has been determined through ¹³C NMR data. Evidence leading to reverse the configuration at this centre in previously reported C₂₇ tetracyclic terpenes is discussed. An ecological function is suggested for these molecules.     

Fomajorin S and D from fomes annosus (FR) cooke

Fomajorin S and D, two new isocoumarins have been isolated from the sporophores and ageing cultures of Fomes annosus, and have been assigned structures $\text{2}$ and $\text{:3}$ respectively on the basis of spectroscopic evidence of the natural products and their derivatives.     

New polyoxygenated steroidal glucosides from chrysolina hyperici (coleoptera : chrysomelidae)

Two new polyoxygenated steroidal glucosides ($\text{1}$ and $\text{2}$) have been isolated from the defensive secretion of C. hyperici and their structures have been determined by spectroscopic and chemical methods.     

18-oxygenated polyfunctional steroids from the gorgonian isishippuris

Two new 18-oxygenated, polyfunctional steroids ($\text{2}$, $\text{3}$) related to hippurin-1 have been isolated from the gorgonian $\text{Isis}$$\text{hippuris}$ collected off Okinawa and their structures were determined.     

Latrunculins: NMR study,two new toxins and a synthetic approach

A complete ¹H and ¹³C NMR assignment of one of the latrunculins (B) was accomplished with the aid of 2D NMR COSY and CH shift-correlation experiments. The various H-H Coupling constants have been datermined and a conformation of the macrolide and the tetrahydropyran (THP) ring suggested on basis of the J-values and measured NOE's. The absolute configuration of latrunculin-A($\text{1}$) was determined on the grounds of its earlier X-Ray analysis, and a chemical degradation to a known compound. Two novel latrunculins, -C($\text{3}$) and -D($\text{4}$), were isolated from the Red Sea sponge $\text{L. magnifica}$ and their structures elucidated. Starting with L-cysteine a synthon for the latrunculins has been synthesized.     

Drei neue furanogermacrene aus myrrhe

From the essential oil of myrrh (Commiphora molmol ENGLER) three new furanogermacrens have been isolated and their structures elucidated to $\text{1}$,$\text{2}$ and $\text{3}$.     

Bioactive marine metabolites IX. Mycalisines A and B,novel nucleosides which inhibit cell division of fertilized starfish eggs,from the marine sponge mycale sp.

Two novel nucleosides, mycalisines A and B, have been isolated from a marine sponge and their structures elucidated as 4-amino-5-cyano-7-(3-$\text{O}$-methyl-5-deoxy-β-D-$\text{erythro}$-pent-4-enofuranosyl)-pyrrolo[2,3-$\text{d}$]pyrimidine and 5-cyano-7-(3-$\text{O}$-methyl-5-deoxy-β-D-$\text{erythro}$-pent-4-enofuranosyl)-pyrrolo[2,3-$\text{d}$]pyrimidine-4-one, respectively. Both compounds inhibit cell division of fertilized starfish eggs.     

3,4-Epoxyprecocenes: thermal and acid promoted dimerisation

Thermal dimerisation of 3,4-epoxyprecocene II ($\text{2b}$) in absence of solvents afforded high yields (65%) of tetrahydrofuran dimer $\text{4}$ and minor amounts of benzopyran-3-one $\text{3}$. On the other hand, two new dimers, γ-hydroxyketone $\text{5}$ and dioxane $\text{7a}$ have also been isolated from treatment of $\text{2b}$ with different acids. Structural elucidations for all these dimers have been carried out by spectroscopic and analytical methods, combined with the use of selected deuteriated precursors in the corresponding dimerisation procedures.     

Synthesis of erythro- and threo-α-bromo-α′-fluorosuccinic acids

$\text{erythro}$- and $\text{threo}$-α-Bromo-α′-fluorosuccinic acids have been prepared from their corresponding dimethyl esters. Because of the extreme readiness of elimination of hydrogen fluoride in basic medium, a special method of acid hydrolysis had to be applied. Hydrogen and fluorine NMR spectra are reported.     

Palisadins A,B and related monocyclofarnesol-derived sesquiterpenoids from the red marine alga Laurencia cf. palisada

Five new monocyclofarnesol-derived sesquiterpenoids, along with the previously reported lactone aplysistatin, have been isolated from the tropical red alga $\text{Laurencia}$ cf. $\text{palisada}$. The structures of these new compounds were defined by spectral and chemical analyses, including their partial interconversion with aplysistatin.     

Total synthesis and the absolute configuration of citreoviral and citreoviridin

Both citreoviral and citreoviridin, metabolites of $\text{Penicillium citreo-viride}$ B., have been synthesized starting from D-glucose, in connection with which their absolute configuration has also been established.     

Enzymic control of stereochemistry among the Thalictrum bisbenzylisoquinoline alkaloids

The new bisbenzylisoquinolines (+)-tha1igrisine $\text{1}$ and (+)-tha1iphylline ($\text{6}$) have been isolated from $\text{Thalictrum minus}$ var. $\text{microphyllum}$. Four rules are described which correlate the structures of Thalictrum bisbenzylisoquinolines with their stereochemistry at C-1 and C-1'. As a result, (+)-tha1rugosamine is shown to be identical with (+)-homoaromo1ine ($\text{14}$). (+)-Thalisamine and (+)-N'-norhernandezine are also identical and are represented by expression $\text{18}$. The sole exception to the rules is (-)-isothalidezine ($\text{15}$).     

A new class of macrocyclic diterpenes from Bertyadimerostigma (euphorbiaceae)

Three diterpene acids, representing a new class of bicyclic diterpenes, have been isolated from $\text{Bertya dimerostigma}$ F. Muell. (Euphorbiaceae). Spectroscopic and X-ray cryatallographic evidence for their structure is presented. A rationale for their origin $\text{via}$ modification of the casbane skeleton is given.     

Synthesis,structure, and reactions of thiocarbonic acid derivatives new pentathiodipercarbonates, (RSS)2 CS, α,α,α-tris(disulfides), and the first α,α,α-tris(trisulfide)

Novel bis(perhaloalkyl) pentathiodipercarbonates $\text{5b-d}$ have been synthesized by reaction of sulfenyl chlorides with metal trithiocarbonates, and the heptathio analog $\text{21a}$ was prepared similarly. Lenthionine $\text{19}$ is the main product when diiodomethane is treated with sodium tetrathiopercarbonate. A rearrangement of bis(alkyldithio)chloromethanesulfenyl chlorides $\text{22}$ to alkyldithio) (alkyltrithio)dichloromethanes $\text{24}$ has been observed. Additions of sulfenyl chlorides and of thiosulfenyl chlorides to the thiocarbonyl compounds $\text{5}$ and $\text{21a}$ were achieved in acetonitrile. The structures of the first crystalline pentathiodipercarbonate $\text{5a}$ and α,α,α-tris(disulfide) $\text{29a}$, and of the first reported α,α,α-tris(trisulfide)$\text{31a}$ have been determined by X-ray crystallography.