Self-condensation of 1,3,4,6-tetraketones. The electrocyclic reaction of a dienone system derived from the dienolic form.

A synthesis of dihydropyrones $\text{4}$ is described involving the dimerisation of tetraketones $\text{1}$ and thermal reaction of intermediate dienone $\text{2}$ derived from a dienolic system.     

A revised structure for hermonionic acid

Hermonionic acid and its decarboxylated product have been isolated from $\text{Garcinia}$$\text{quaesita}$. ¹³C NMR spectral and chemical evidence indicate that hermonionic acid is 2-0-[2-(3-methylbut-2-enyl)-3-methoxy- 4-hydroxy-5-(3,7-dimethylocta-2,6-dienyl]-4-methoxy-5-(3-methylbut-2-enyl-6-hydroxybenzoic acid. The previously assigned dienone structure for this acid is incorrect.     

A total synthesis of (+)-anhydrocannabisativine.

Racemic anhydrocannabisativine has been efficiently synthesized by employing a β -lactam-imino ether coupling reaction. The key to the formation of the tetrahydropyridine moiety of the natural alkaloid is a stereoselective intramolecular conjugate addition of a secondary amino group to a $\text{Z}$,$\text{E}$ dienone.     

Migration reversible du methyle 19 en serie cholestane

Hydroxyketone $\text{4}$ is partially dehydrated and rearranged when heated at reflux temperature in DMF/BBr. Upon further heating, dienone $\text{5}$ suffered a reversible migration of the 19-methyl group C-5/C-10.     

Photocyclization of benzofurancarboxanilides. Photorearrangement of the benzodihydrofuran system to 3-o-hydroxyphenylquinolones

$\text{cis}$-Dihydrobenzofuro[2,3-c]quinolone ($\text{4a}$) and $\text{cis}$-dihydrobenzofuro-[3,2-c]quinolone ($\text{5}$) undergo photorearrangement, characteristic to the benzodihydrofuran system, leading to 3-$\text{o}$-hydroxyphenylquinolone ($\text{6}$). A plausible mechanism involving a cyclopropyl dienone ($\text{12}$) was discussed.     

3-Bromo-2-(tert-butylsulfonyl)-1-propene. A multi-coupling reagent. Part 2. <1

3-bromo-2-(tert-butylsulfonyl)-1-propene 1 reacts in good yields with various electrophiles (aldehydes, ketones, nitriles and alkynes) in the presence of zinc metal to give unsaturated sulfones of type 4. These compounds can further react with soft or hard nucleophiles (alkyl-, vinyl-, aryllithium compounds, a nitroparaffin or dimethylmalonate) to yield highly functionnalized sulfones of type 5 which can be readily transformed into enones or into a dienone. Thus sulfone 1 is a versatile multi-coupling reagent which is synthetically equivalent to the $\text{a}{}^2\text{a}{}^{\mathrm{2\prime }}$ synthon 8 and to the $\text{d}{}^2\text{d}{}^{\mathrm{2\prime }}$ synthons 9 and 10.     

Optical resolution of tricarbonyl(1-carboxycyclohexa-1,3-diene) iron and the absolute configuration of the products

Resolution of the acid ($\text{1}$) (shown as the (+)-isomer) into its optically pure (+) and (?) isomers and reduction of the CO₂H yields the 2-Me derivative ($\text{2}$) (shown as the (?)-isomer). The absolute configuration of ($\text{2}$) is defined by conversion of the salt ($\text{3}$) of known configuration into ($\text{2}$) and ($\text{4}$). This is the first resolution leading to preparation of pure complexes of known absolute configuration.     

Stereochemical studies — 79 synthesis and kinetic study on the retrodiene decomposition of norbornene-condensed 1,3-oxazin-4-ones

The $\text{cis}$-$\text{cxo}$- amino acid $\text{c}$ with norbornene skeleton was converted into 2-aryvl-$\text{cis}$-$\text{cxo}$-1,3-oxazin-4-ones $\text{5a}$-$\text{d}$. These compounds, similarly to the $\text{diendo}$ isomers $\text{1a}$-$\text{d}$ studied by us earlier, undergo retrodiene decomposition under mild conditions to give 2-aryl-6$\text{2}$-l,3-oxazin-6-ones ($\text{2}$$\text{a}$-$\text{d}$) in 50-60% yield. The ratio of the decomposition rate constants of the tricyclic $\text{diendo}$ and $\text{diexo}$-1,3-oxazin-4-ones, measured in toluene solution, is about 2.     

The ready conversion of anguidine into verrucarol and trichodermol

Anguidine, $\text{1}$, is readily converted into verrucarol diacetate, $\text{2d}$, in 85 percent yield by application of the Barton-McCombie deoxygenation procedure. To enable conversion into trichodermol, $\text{3a}$, the primary hydroxyl group of verrucarol, $\text{2a}$, is selectively acetylated or is selectively acetylated or preferably silylated, thereby paving the way for its deoxygenation in three simple, high-yield reactions.     

Synthetic studies in the β-carboline area new entry into4-substituted and 3,4-disubstituied β-carbolines

The [3,3] sigmatropic rearrangement of the allyl ether $\text{2}$ to provide $\text{3}$ represents a new synthetic entry into 3,4-disubstituted β-carbolines. In keeping with the interest in such substituted β-carbolines, the hydrazine mediated conversion of 4-oxo-tetrahydro β-carboline $\text{1b}$ into 4-amino β-carboline $\text{2b}$ is also described, as well as the analogous reaction in the isoquinoline series.     

A route to Prelog-Djerassi lactone from methyl α,D-glucopyranoside

The enone $\text{1}$ obtained from methyl α,D-glucopyranoside is converted into the corresponding diene $\text{5}$ which is hydrogenated to give predominantly the diequatorial dimethyl hexopyranoside $\text{3}$. C6 of the latter is converted stepwise to the methyl ketone from which Prelog-Djerassi Lactone $\text{8}$ and its 2-epimer $\text{9}$ are prepared in 3:2 ration.     

From penicillin to penem and carbapenem. III C1-unit introduction at C-4 position of azetidinone

Monocyclic β-lactams ($\text{1}$) were converted into 4-cyano derivative $\text{2}$ (C₁-unit introduction) under two phase reaction conditions. The cyano group in $\text{2}$ was successively transformed into $\text{3}$ and $\text{4}$, which are thought to be important precursors for the carbapenem synthesis.     

A general entry to guaianolides. An illustrative synthesis of (±)-compressanolide

A short and efficient synthesis of a key intermediate $\text{2}$ for the formation of guaianolides is described. The potentiality of $\text{2}$ is illustrated by its transformation into the natural occurring guaianolide, (±)-compressanolide $\text{1}$.     

Ag(I)-assisted hydrolysis of mestranol methanesulfonate into epimestranol

Epimestranol ($\text{1b}$) is obtained in 80% yield from mestranol ($\text{1a}$) by converting $\text{1a}$ into its methanesulfonate $\text{2}$ and treating $\text{2}$ with silver(I) nitrate in a mixture of tetrahydrofuran and water.     

Homologation of selenoesters to (phenylseleno)- or (methylseleno)methyl ketones with diazomethane

The copper or cuprous iodide-catalyzed insertion of diazomethane into the acylselenium linkage of selenoesters $\text{1a}$– $\text{1f}$ and selenocarbonate $\text{1g}$ afforded the corrresponding ketones $\text{2a}$– $\text{2f}$ and the ester $\text{2g}$, respectively, as the chief products.     

A novel synthesis of linear polyenes via conjugate addition of cuprates to α,β-γ,δ-diunsaturated sulfones followed by SO2 extrusion

The two 1,3-butadienyl 2-propenyl sulfones $\text{5}$ and $\text{6}$, 1,3,5-heptatriene synthons, have been transformed into the tri- and tetraenes $\text{1}$ - $\text{4}$ by alkylcuprate addition and Ramberg-Bäcklund SO₂ extrusion. The reaction stereochemistry is discussed.     

Cis - oxyamination routes to amimo sugars: A simple synthesis of holacosamine

The known D-$\text{threo}$ hex-2-enopyranoside $\text{1a}$ is converted into an N-methyl allyl amine, the methyl urethane of which undergoes electrophile-induced cyclisation to give the iodocyclic urethane $\text{9}$. The $\text{cis}$ relationship of H3 and H4 in the latter is confirmed by NMR spectroscopy. Reduction at C2 and C6 is done simultaneously and the cyclic urethane is hydrolysed. The amino group is then acetylated and the hydroxy group methylated.     

A new route to 1-phenylnaphthalenes by cycloaddition: a simple and selective synthesis of some naphthalene lignan lactones

2-(2-Dithianyl)benzhydrols ($\text{2}$ a-c) undergo facile cycloaddition reaction with maleic anhydride under thermal conditions to give 1-phenyl-naphthalenes ($\text{7}$ a-c) in one step. The naphthalenes ($\text{7}$ a-c) have been converted into the naphthalene lignan lactones, ($\text{9}$ a-c) and ($\text{10}$ a-c).     

Stereoselective synthesis of (1R,3S)-cis-chrysanthemic acid through microbiological reduction of 2,2,5,5-tetramethyl 1,4-cyclohexanedione.

An efficient, highly stereoselective synthesis of (1$\text{R}$,3$\text{S}$)-$\text{cis}$-chrysanthemic acid 6 is described. The crucial step of this synthesis was the microbiological reduction of dione 1 into ($\text{S}$)-ketol 2.