Total syntheses of (±)-isoagatholactone and (±)-12α-hydroxyspongia-13(16),14-dien

(±)-Isoagatholactone $\text{1}$ and (±)-12α-hydroxyspongia-13(16),14-dien $\text{2b}$, a fundamental skeleton of spongiadiol $\text{2a}$ and its congeners, have been synthesized from (±)-labda-8(20),13-dien-15-oic acid $\text{3}$.     

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.     

Synthesis of binzindene prostaglandins: a novel potent class of stable prostacyclin analogs

The phenols $\text{13}$, $\text{16}$, and $\text{21}$, produced with remarkable regioselectivity by the cyclization of compounds $\text{10}$ and $\text{12}$, have been converted to the benzindene prostaglandin analogs $\text{25}$, $\text{20}$, and $\text{24}$, respectively. Compounds $\text{24}$ and $\text{25}$ are potent prostacyclin mimics.     

Etude des reactions des diazoderives avec les cycloimmonium ylures-I : Action des sels de diazonium sur quelques pyridinium - ylures

The synthesis of cycloimmonium salts of the type $\text{7}$, $\text{8}$ and the corresponding cycloimmonium ylides $\text{9}$, $\text{10}$ are reported. In the reaction with diazonium salts $\text{11}$, $\text{12}$ the pyridinium monosubstituted carbanion ylides $\text{9}$, $\text{10}$ give the pyridinium disubstituted carbanion ylides $\text{17}$ – $\text{20}$. These are new types of isolable stable ylides. The synthesis involves the formation “in situ” of ylides $\text{9}$, $\text{10}$ which are bonded by their nucleophile ylide carbon atom to the nitrogen atom in diazonium salts. The intermediat formation of cycloimmonium salts $\text{13}$ – $\text{16}$ must be accepted. The structures of all compounds presented in this paper have been established by using elementary analysis, IR and ¹H-RMN spectra.     

The structure of ailanthol,a new triterpenoid from Ailanthus Malabarica DC

The structure of ailanthot (1), having the triterpene skeleton (20$\text{S}$)-4 4,8 β - trimethyl-14, 18-cyclo 5a, 13a, 14a, 17a-cholestane, has been assigned by spectral analysis and X-ray crystal structure determination.     

13C-NMR of some ajmalane alkaloids

The ¹³C-NMR spectra of the alkaloid ajmaline ($\text{1}$) and its stereoisomers isoajmaline ($\text{2}$), sandwichine ($\text{3}$) and isosandwichine ($\text{4}$) are reported. The different stereochemistry at C (17), C(20) and C(21) of the four isomers can be directly ascertained by chemical shifts data.     

Molecular rearrangements of 5-azido substituted 1,2,3-triazoles

5-Azido-4-methoxycarbonyl-1-phenyl-1,2,3-triazole ($\text{8a}$) and its phenyl substituted derivatives $\text{8b}$,$\text{c}$ rearrange at 60–80°C to give tetrazolyldiazoacetates $\text{9}$, which have been isolated. When the reactions are allowed to go to completion, products derived from the diazo compounds are obtained; i.e. norcaradienes ($\text{10}$) from benzene solutions and imidazotetrazoles ($\text{12}$) from nitrite solutions. The latter decompose photochemically into diazacyclopentadienonimines ($\text{13}$). A kinetic study of the rearrangement $\text{8}$ → $\text{9}$ has been carried out and the mechanism (Scheme VI) is discussed in comparison with the Dimroth rearrangement.     

An intramolecular diels-alder approach to quassinoids—a stereoselective construction of a-aromatic klaineanone

Thermolysis of a benzocyclobutene derivative ($\text{20}$) prepared from norcamphor produced stereoselectively a tetracyclic compound ($\text{2}$), which was converted to a lactone ($\text{21}$) having correct stereochemistry at C₇, C₈, C₉, C₁₁, C₁₃, and C₁₄ positions of (±)-klaineanone.     

Pyridazines XXIV: Application of radicalic ethoxycarbonylation to the synthesis of pyridazine mono- and polycarboxylic acid esters

Reactivity of pyridazines $\text{1}$, $\text{2}$, $\text{3}$, $\text{16}$ towards ethoxycarbonylradical (generated by redox decomposition of oxyhydroperoxide of ethylpyruvate) was studied. Application of this type of homolytic substitution for synthesis of hitherto not accessible pyridazine carboxylic acid esters $\text{6}$, $\text{8}$, $\text{9}$, $\text{12}$, $\text{13}$, $\text{14}$, $\text{15}$, $\text{17}$ is demonstrated. In addition improved synthesis of diethyl 4,5-pyridazinedicarboxylate ($\text{5}$) is proposed.     

Hydrodynamic properties and conformation of molecules of para- and meta-isomers of polyoxyphenylbenzoxazoleterephthalamide

Translational diffusion and intrinsic viscosity in 96% H₂SO₄ have been investigated for 20 samples of the para-isomer of polyoxyphenylbenzoxazoleterephthalamide (PpOPhBT) and 17 samples of its meta-isomer (PmOPhBT). The Mark-Kuhn equations have been obtained. The equilibrium rigidity of macromolecules in solution, calculated by using the wormlike chain theory, was characterized for PpOPhBT by the length of the Kuhn segment $\text{A = 320}\text{A}\text{?}$, the number of monomer units in a segment s = 17 and the coefficient of hindrance to intramolecular rotation in the chain σ = 1.5. For PmOPhBT the corresponding values are: $\text{A = 96}\text{A}\text{?}$, s = 5.9 and σ = 1.6. Analysis of flexibility mechanisms was carried out for PpOPhBT and PmOPhBT chains in solution.     

Isolation and structural elucidation of heliangolidin,a new sesquiterpene lactone from artemisia canariensis

A new heliangolide has been isolated from aerial parts of $\text{Artemisia canariensis}$, and identified as (6$\text{E}$,10$\text{Z}$)(3$\text{S}$,3a$\text{R}$,4$\text{S}$,lla$\text{R}$)-3a,5,8,11a--tetrahydro-4-acetoxy-3,6, 1O-trimethyl-2,9 (3$\text{H}$, 4$\text{H}$) -cyclodeca[b] furandione. The structural elucidation of the new compound, named heliangolidin, was carried out by spectral means (MS, IR, ¹H and ¹³C NMR, and two dimensional ¹H-¹³C chemical shift correlations) and X-ray diffraction analysis.     

Athrotaxis alkaloids. Part I. Alkaloids of A. Cupressoides

Eleven homoerythrina-type alkaloids ($\text{tilda1}$-$\text{tilda9}$, $\text{tilda11}$, $\text{tilda12}$) have been isolated from A. cupressoides (Taxodiaceae), of which six ($\text{tilda6}$-$\text{tilda9}$, $\text{tilda11}$,$\text{tilda12}$) had not previously been reported.     

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 $\text{2a-d}$.     

Z,Z-dienes via acetylene carbocupration: synthesis of navel orangeworm pheromone

A range of conjugated $\text{Z}$,$\text{Z}$-dienes have been prepared in a stereo-specific manner $\text{via}$ acetylene carbocupration: the value of this procedure has been illustrated by an extremely short synthesis of hexadeca-11$\text{Z}$, 13$\text{Z}$-dienal a principle component of Navel Orangeworm Pheromone.     

Chirale synthese von (+)-lycoricidin

The synthesis of (+)-lycoricidine from D-glucose is described. Addition of the carbanion $\text{11}$ to the nitroolefine $\text{10}$ yields the adduct $\text{12}$ + $\text{13}$, from which crystalline lactone $\text{16}$ with $\text{muco}$-configuration in the cyclitol-ring can be isolated after hydrolysis and cyclization. Rearrangement to the lactam $\text{17}$ and elimination yields the (+)-lycoricidine.     

Structures of cytochalasin k,l and m,isolated from chalaramicrospora

The structures of cytochalasin K, L and M, isolated from the fungus $\text{Chalara}$$\text{microspora}$, have been determined by spectroscopic methods, primarily ¹H NMR and ¹³C NMR.     

Attempts to prepare a pyramidal carbocation with an apical fluorine substituent

Gem-difluorides $\text{7}$ and $\text{8}$, different only in the location of a methyl substituent and each a potential precursor of the same pyramidal carbocation $\text{9}$, ionize instead to give allylic carbocation $\text{13}$ and homotropylium ion $\text{20}$ respectively.     

Ylures sans sel,evolution en phosphoranes et equilibre ylure ⇌ phosphorane : I Synthese et structure

Synthesis of new salt-free ylids $\text{9}$,$\text{12}$ to $\text{16}$, $\text{19}$, $\text{20}$, $\text{22}$, $\text{27}$ and $\text{29}$ and phoiphoranes $\text{10}$, $\text{17}$, $\text{18}$, $\text{21}$, $\text{23}$, $\text{30}$ to $\text{33}$ by addition of a trivalent phosphorus compound (phosphites and amino-phosphines ) $\text{1}$ to $\text{7}$ with dimethyl acetylencedicartboxylate in presence of a protic trapping reagent are described. The results are consistent with trapping of carbanionic species. In relation with the. cyclic of acyclic structure of the triivalent phosphorus compound and the protic trapping reagent ie : methanol, phenol, carboxylic acid, etc.., several pathways are involved. Clearly), three phenomena are shown : one can obtain an ylid via a phosphorane or conversely a phosphorane via an ylid or an equilibrium Phoiphorane ? ylid. Results are dealing with thermodynamic or kinetically controlled reactions.     

Synthesis and NMR study of norbornane/norbornene-fused tetracyclic azetidinones

Tetracyclic azetidinones$\text{8}$,$\text{9}$ and $\text{12}$–$\text{17}$ were synthesized. In the cases of$\text{8}$ and$\text{9}$, the main component was isolated from the two-component product of the cycloaddition. The minor component was concentrated to give a mixture, from which a computer technique utilizing the known spectrum of the main component gave the proton resonance spectrum also of the minor component. Only one diastereomer could be isolated for the each of the analogues$\text{12}$–$\text{17}$. Reaction of the 1,3-oxazine $\text{3}$ with chloroacetyl chloride gave, besides the azetidinone $\text{12}$, the 1,3-oxazine [2,3-$\text{b}$]-1,3-oxazin-4-one derivative$\text{18}$. Configurations and conformations were determined by IR, ¹H and ¹³C NMR spectroscopy.     

Bicyclic aziridines as intermediates in the photolysis of polycyclic aromatic azides.

According to the subsequent treatment, azepines $\text{16}$, $\text{17}$, $\text{19}$ or 1,2-dihydro derivatives $\text{18}$ and $\text{20}$ are obtained in the photolysis in basic medium of β-anthracenic azides $\text{7b}$ and $\text{7c}$ and provide strong evidence for the intermediate formation of bicyclic aziridines.