Synthesis of detoxininolactone derivatives and the revised absolute stereochemistry of detoxinine

A stereospecific synthesis of acetyl-$\text{L}$-valyl-detoxininolactone has been performed and the absolute stereochemistry of detoxinine has been revised to (2$\text{S}$, 3$\text{R}$, 1′$\text{S}$)-2-(2′-carboxy-1′-hydroxyethyl)-3-hydroxypyrrolidine.     

Calozeylanic acid,a new bark acid from three calophyllum species (guttiferae)

Calozeylanic acid has been isolated from the bark of three $\text{calophyllum}$ species: $\text{C.lankaensis}$ (= $\text{C.zeylanicum}$), $\text{C.thwaitesii}$ and $\text{C.walkeri}$. Its structure has been established as 2(R),3(R)-2,3-Dimetyl- 5-hydroxy-6-(3-methylbutanyl)-6-(3,7-dimethylocta-3,6-dienyl)-7-oxo-8- (2-carboxy-1-phenylethyl)-2,3,6,7-tetrahydrobenzo-4-pyrone.     

Isolation,identification and synthesis of the sex pheromone of the citrus mealybug,Planococcus citri (risso)

The sex attractant pheromone of the citrus mealybug, $\text{Planococcus citri}$ (Risso), has been Identified as (1$\text{R}$-$\text{cis}$)-(+)-2,2-dimethyl-3-(1-methylethenyl)cyclobutanemethanol acetate (VI).     

Successive methyl migrations occurring in the acid treatment of 1-epoxyethyl-1,2,2-trimethyl-cyclopentane derivative

Acid treatment of (IR, 3S,1′S)-1-(1′,2′-Epoxyethyl)-1,2,2-trimethyl-3-acetoxymethyl-cyclopentane $\text{6}$) has been shown to yield three products ($\text{8}$, $\text{9}$, $\text{10}$), among which $\text{8}$ and $\text{9}$ are 1-oxa-bicyclo[3.3.0]octane derivatives formed $\text{via}$ successive methyl migrations followed by an oxorane ring closure.     

Application of 2d-nmr spectroscopy in the structural determination of a new tobacco cembranoid

Proton-proton shift correlated 2D-NMR spectroscopy has been used to determine the structure of a new tobacco cembranoid as (1$\text{S}$,2$\text{E}$,4$\text{S}$,6$\text{R}$,7$\text{E}$)-4,6-dihy-droxy-2,7,12(20)-cembratrien-11-one (1). This assignment has been verified by chemical means.     

Conversion of adenosine to a pentacyclic structure by a 4-nitroquinoline-1-oxide metabolite model.

A new pentacyclic compound $\text{2A}$ has been obtained from the reaction of adenosine $\text{1}$ with 1-acetoxy-4-(acetoxyimino)-1,4-dihydroquinoline $\text{3}$, a model for the ultimate metabolite of the carcinogen 4-nitroquinoline-1-oxide. 9-propyladenine $\text{5}$ gives an analogous pentacyclic product $\text{6A}$ whose crystal structure has been determined.     

Synthesis of 3-methylisoguanosine,a positional isomer of pharmacologically active nucleosides from marine animals

3-Methylisoguanosine ($\text{4c}$) has been synthesized from 5-(cyanomethylamino)-1(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)imidazole-4-carboxamide ($\text{1b}$) through the carbonitrile ($\text{2b}$).     

Chiral synthesis of statine

Statine ($\text{8a}$) has been obtained in high enantiomeric purity as its N-Boc-ethyl ester ($\text{8b}$) in a chiral synthesis. The sequence involves the enantio- and erythro-selective aldol condensation of N-Boc-L-leucinal ($\text{5}$) with (S)-4-(1-methylethyl)-3-[(methylthio)acetyl]-2-oxazolidinone ($\text{1}$) via the boron enolate, followed by desulfurization and saponification in ethanol, according to the methodology of Evans.     

Synthesis of trans-(3S,4S)-dibenzyloxycyclopentanone

The 1-cyano-1-thiophenylcyclopentone derivative $\text{1}$, obtained from (R,R)-(+)-tartaric acid, has been converted into a number of derivatives including the important $\text{trans}$-(3S,4S)-dibenzyloxycyclopentanone $\text{2}$ in 45% overall yield.     

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 $\text{2a-d}$.     

Alicyclische verbindungen-v. darstellung diverser 1,3-butadienylcyclobutane

$\text{cis}$-($\text{3}$) and $\text{trans}$-1,3-Butadienylcyclobutane ($\text{4}$), all-$\text{trans}$-1-(1 ,3-butadieny1 )-2- vinylcyclobutane ($\text{10}$), and all-$\text{trans}$-1,2-bis(1,3-butadienyl)cyclobutane ($\text{15}$) have been prepared from readily available starting materials, and pyrolyzed to various cyclohexenes.     

Conformational analysis of trans-2,3-diaryloxy-1,4-dioxanes. A tool for discriminating between steric and electronic effects in the position of

The conformation of several $\text{trans}$-2,3-diaryloxy-1,4-dioxanes has been studied using ¹H NMR techniques. $\text{Trans}$-2,3-bis(4-nitrophenoxy)-1,4-dioxane and $\text{trans}$-2,3-bis(4-methoxyphenoxy)-1,4-dioxane have been found to be predominantly ( ≈98%) in diaxial conformation in CDCl₃). On the other hand, $\text{trans}$-2,3-bis(2,6-dimethylphenoxy)-1,4-dioxane exists in the same conditions as a 66:33 mixture of diaxial and diequatorial conformers. An explanation based on the fulfilment of the exo-anomeric effect is provided.     

Large scale synthesis and absolute configuration of (-)-3-ppp,a selective dopamine autoreceptor agonist

A large scale synthesis for (-)-3-PPP has been developed. The racemic methoxy compound $\text{1}$ was prepared in a three step procedure in 63% yield. This was resolved as a diastereomeric salt by crystallization of the (-)-di-p-toluoyltartrate. Two crystallizations gave the pure (-)-enantiomer $\text{2}$ in 50% of the theoretical yield and with an enantiomeric excess of >95%. Demethylation using aqueous HBr gave (-)-3-PPP, ($\text{3}$). Compound $\text{2}$ was also prepared in a stereoselective synthesis from $\text{S}$-(-)- N-propyl-2- chloromethylpyrrolidine $\text{4}$. By X-ray crystallography it was shown that (-)-3-PPP has the $\text{S}$-configuration at the chiral carbon.     

Studies on the syntheses of heterocyclic and natural compounds. Part 939: An efficient and stereoselective synthesis of des-a-ring steroids—potential intermediates to estradiol,cortisone and progesterone

A stereoselective synthesis of des-A-ring steroids $\text{9}$ and $\text{17}$ has been achieved by an intramolecular cycloaddition of 3-isopropenyl-5-(4-methoxybenzocyclobutenyl) pentan-2-one-2-ethylene ketal $\text{7}$ and 1-(4-methoxy-benzocyclobutenyl)-4-methylpent-4-en-3-ol $\text{16}$, respectively.     

The ring closure and rearrangement of 1-(2-amino)-benzoyl-1-methylhydrazones of β-dicarbonyl compounds: on the formation and crystal structure of 3a,9a-dihydro- -1,3,3a,9a-tetramethyl-4H-pyrazolo[3,4-b]quinolin-4-one

The conversion of 1-(2-amino)-benzoyl-1-methylhydrazones of β-dicarbonyl compounds into heterocyclic derivatives yielded in addition to the already known type of product $\text{2}$ further three novel pyrazole derivatives $\text{3}$, $\text{4}$ and $\text{5}$. The structures of these products have been established by chemical and spectroscopic (MS) methods. The crystal structure of $\text{5}$ has been determined by X-ray diffraction.     

Acid catalyzed isomerization of bicyclic alkenes: a facile betweenanene synthesis

Isomerization of $\text{cis}$-bicyclo[10.8.0]eicos-1(12)-ene ($\text{1a}$) and $\text{cis}$-bicyclo[10.10.0]docos-1(12)-ene ($\text{1b}$) to [10.8]- and [10.10]betweenanene ($\text{2a}$ and $\text{2b}$) has been effected by sulfuric acid. In both cases, the betweenanene isomers were found to predominate at equilibrium (70/30 $\text{2a}$/$\text{1a}$ and 95/5> $\text{2b}$/$\text{1b}$).     

New tetrahydropyrans from a marine sponge

Two new tetrahydropyrans have been isolated from the sponge Haliclona sp. From chemical and spectroscopic evidence they are shown to be (1′$\text{R}$, 2$\text{S}$, 2″$\text{E}$, 5$\text{R}$, 6$\text{R}$)-2-(1′-bromethyl)-2,5-dimethyl-6-(penta-2″,4″-dienyl)-tetrahydropyran and (1′$\text{R}$, 2$\text{S}$, 5$\text{R}$, 6$\text{R}$)-2-(1′-bromoethyl)-2,5-dimethyl-6-(pent-4″-enyl)-tetrahydropyran.     

The catabolism of phthalideisoquinoline alkaloids

Fumariflorine ($\text{1a}$, the only known alkaloidal $\text{o}$-(β-dimethylaminoethyl)benzoic acid, has been isolated as its ethyl ester $\text{1}$ from $\text{Fumaria}$$\text{parviflora}$ Lam. (Fumariaceae). Since alkaloids $\text{2}$–$\text{6}$ are also present in the plant, it is probable that the biogenetic sequence for the catabolism of the lactonic phthalideisoquinolines involves initial quatermination to an N-metho salt, Hofmann elimination, and oxidative cleavage of the resulting olefin to supply a substituted $\text{o}$-(β-dimethylaminoethyl)benzoic acid.     

A novel product from the reaction of p-methylbenzyl chloride with guanosine in neutral aqueous solution

An unanticipated product from reaction of guanosine with $\text{p}$-methylbenzyl chloride in neutral aqueous solution has been identified as 4-($\text{p}$-methylbenzyl)-5-guanidino-1-β-D-ribofuranosylimidazole.     

Condensed cyclic and bridged-ring systems : part 12: A novel synthetic route to 4-p-methoxyphenyl-bicyclo[ 2.2.2 ]octan-2-ones and some bicyclo [ 3.2.1 ] octane derivatives by acid-catalyzed intramolecula

The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{5}$) and 4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{6}$) from easily accessible starting materials. The carbinol $\text{20}$, derived from $\text{5}$, undergoes facile rearrangement leading to 1-$\text{p}$-methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene ($\text{22}$), which has been transformed to $\text{endo}$-1-$\text{p}$-methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one ($\text{25}$).