Nitroindolenines en serie vincadifformine : intermediaires d'acces a la vincamone et a un squelette azahomoaspidospermane

Vincadifformine and its 10-substituted analogs give in good yields 16-nitro indolenines of which the reactivity has been studied. By a two step process (demethoxycarbonylation and chloration on C16) nitro-indolenine $\text{2b}$ leads to gem-chloro-nitro $\text{6}$. By an other two step sequence (NaBH₃CN, NaH) nitro-indo-lenine $\text{2c}$ yields compound $\text{10}$ via a 16 → 1 COOCH₃ migration. By heating compounds $\text{6}$ and $\text{10}$ in CF₃COOH, rearranged products are obtained : vincamione $\text{5}$ from $\text{6}$ and azahomoaspidospermane $\text{13}$ from $\text{18}$. Mechanisms of formation of $\text{5}$, $\text{10}$ and $\text{13}$ are discussed.     

Condensation of a p-diazooxide with dimethyl acetylenedicarboxylate: formation of a spiro [4.5] Decatetraenone and a nonenolizable naphthalenone in a single reaction

The condensation of p-diazooxide $\text{1}$ with dimethyl acetylenedicarboxylate at 90°–100°C yields two C₂₆H₃₂O₉ products, corresponding to addition of two molecules of ester to one of the carbene $\text{2}$. The major product is the novel spirodecatetraenone $\text{4}$, and the minor product is the remarkable, nonenolizable naphthalenone $\text{5}$. Spirodecatetraenone $\text{4}$ is not a precursor of $\text{5}$, since the former is stable to acids and rearranges only above 200° to give the blocked azulenone $\text{8}$. A mechanism for the concomitant formation of product $\text{4}$ and $\text{5}$ is proposed.     

Kalashine,a novel type aporphine-benzylisoquinoline alkaloid

$\text{Berberis orthobotrys}$ produces the new dimer kalashine ($\text{1}$), together with the previously reported pakistanamine ($\text{2}$) and pakistanine ($\text{3}$). Kalashine is the first aporphine-benzylisoquinoline known to be substituted at C-11. Acid catalyzed rearrangement of pakistanamine ($\text{2}$) in 3N HCl leads to 1-0-methylpakistanine ($\text{6}$) together with small amounts of 1-0-methylkalashine ($\text{7}$) and (+)-armepavine ($\text{8}$). Rearrangement of $\text{2}$ using methanol containing a little 3N HCl gives about equal amounts of $\text{6}$ and 1,10-di-O-methylpakistanine ($\text{9}$).     

The quettamines: a new class of isoquinoline alkaloids

Three quettamine type alkaloids, which incorporate either a benzofuran or a dihydrobenzofuran moiety within the molecular framework, have been obtained from $\text{Berberis}$$\text{baluchistanica}$. These are dihydrosecoquettamine ($\text{1}$), secoquettamine ($\text{2}$), and quettamine chloride ($\text{3}$). Alkaloids $\text{1}$ and $\text{3}$ are racemates. Hofmann degradation of quettamine ($\text{3}$) provides secoquettamine ($\text{2}$) and the styrene $\text{4}$ which has a trans relationship between the hydrogens at C-1 and C-α, thus indicating the identical stereochemistry in quettamine. Emde reduction of quettamine leads to dihydrosecoquettamine ($\text{1}$) and the stilbene $\text{5}$. Two other polar alkaloids in the plant are (+)-armepavine methochloride ($\text{6}$) and oblongine chloride ($\text{7}$). An oblongine type alkaloid must be the biogenetic precursor for the quettamines. Arguments are presented favoring direct oxidative coupling in the biogenesis of the cularine alkaloids.     

Cycloadditions des arsoles a haute temperature

At room temperature 1-phenyl-2,5-dimethylarsole $\text{1}$ gives [4+2] cycloadditions with dienophiles whereas at 160 °C it yields arsenic atoms which react with tolane to give the 1,4-diarsabicyclo[2.2.2]octatriene $\text{8}$; 1,2,5-triphenylarsole $\text{2}$ is less reactive at room temperature but isomerizes at 160°C to give the 2$\text{H}$-arsole $\text{5}$ which reacts as a diene with tolane to yield the 1-arsanorbornadiene $\text{6}$, and as a dienophile through its AsC double bond with dimethylbutadiene to give the 1-arsabicyclo[4.3.0]nonadiene $\text{7}$.     

The formation and subsequent cyclisation of novel hydroperoxides from a 1,4− and a 1,5-diene

The preparation of the unsaturated hydroperoxides ($\text{3}$,$\text{4}$,$\text{5}$,$\text{6}$ and $\text{7}$) by the sensitized photooxidation of the 1,4-diene($\text{1}$) and the 1,5-diene($\text{2}$) is described, together with the attempted free-radical cyclisation of these.     

Intramolecular azide cycloaddition to a photochemically generated zwitterion

Photochemical rearrangements of 2,5-cyclohexadienones $\text{7a}$ and $\text{7b}$ to bridged triazenes $\text{11a}$ and $\text{11b}$$\text{via}$ zwitterions $\text{10a}$ and $\text{10b}$ are described.     

Phosphazene spirannique a partir de derives du phophore dicoordine

The reaction of azidoalcohol $\text{2}$ on triazaphosphole $\text{1}$ takes place according to pathway $\text{a}$ and not $\text{b}$, as shown by the isolation of spirannic phosphazene $\text{3}$. The diazadiphosphetidines $\text{4}$, dimers of $\text{3}$ are also caracterized.     

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.     

Synthesis of erythrinin A,a naturally occurring pyranoisoflavone

Erythrinin A ($\text{10}$) has been synthesised by the oxidative rearrangement of dihydropyranochalcone $\text{1}$ with thallium(III) nitrate (TTN) in trimethyl orthoformate (TMOF) to the dimethyl acetal $\text{2}$, followed by cyclisation to $\text{3}$, demethylation to $\text{6}$ and dehydrogenation. Compound $\text{10}$ could also be obtained from chalcone $\text{4}$ on similar rearrangement followed by cyclisation, demethoxymethylation and dehydrogenation. In another route, chalcone $\text{7}$ was oxidatively rearranged with TTN in TMOF, to $\text{8}$ which on treatment with HCl yielded $\text{10}$.     

Parviflorine,a glycosidic spirobenzylisoquinoline alkaloid

(+)-Parviflorine ($\text{1}$), found in $\text{Fumaria parviflora}$ Lam. (Fumariaceae), is the first known glycosidic spirobenzylisoquinoline alkaloid. Its acid hydrolysis yields (+)-parfumine ($\text{4}$) and D-glucose. Klyne's rule indicates that $\text{1}$ is a β-D-glucoside. The absolute configuration shown in expressions $\text{1-11}$ is predominant among spirobenzylisoquinolines. A generalization has been drawn between plant source and the oxygenation pattern of ring C for the spirobenzylisoquinoline alkaloids.     

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.     

Photolysis of a 2-tetbazeio from an enehydrazine

Photolysis of the 2-tetrazene $\text{1}$ gives the triazole $\text{2}$ by homolysis of one single N,N-bond. The formation of the other products $\text{4}$ – $\text{13}$ can be rationalized by regarding the aza-allyl radical $\text{3}$ as a common precursor.     

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.     

Synthesis of oxazolidin-2-ones using carbonate ion on a polymeric support

Through the insertion of a carbon dioxide molecule, the oxazolidin-2-ones ($\text{5a}$) and ($\text{5b}$) were prepared by treataent of the salts ($\text{4a}$) and ($\text{4b}$) with carbonate anion on polymeric support. The hydrolysis under basic conditions of ($\text{5a}$) and ($\text{5b}$) afforded the erythro-3-amino-1,2-diols ($\text{6a}$) and ($\text{6b}$) which were fully acetylated: the 2-amino-2-deoxyerythritol derivative ($\text{7b}$) was obtained in 91% yield.     

Carbocyclic analogs of C-nucleosides: a key intermediate via a novel and efficient CC ring scission

Treatment of hydroxymethylene ketone $\text{6}$ with trimethylene dithiotosylate according to literature conditions,^3b led to the novel CC ring scission product $\text{7}$ in high yield; also, the hydroxide-initiated cleavage⁴ of $\text{1}$ gave the β-elimination product $\text{13}$ which underwent a highly stereospecific addition of diazomethane to provide $\text{15}$.     

An efficient conversion of berberine into a rhoeadine via an indenobenzazepine

Treatment of ketoaziridine $\text{4}$ with aqueous formaldehyde gives the unusual bridged indenobenzazepine derivative $\text{6}$ whose reduction uith sodium cyanoborohydride produces trans ketol $\text{8}$. In the presence of hydrochloric acid, $\text{8}$ undergoes irreversible conversion to the more stable cis ketol $\text{10}$. Periodate oxidation of $\text{8}$ supplies γ-laotone $\text{11}$. NaBH₄ reduction of $\text{11}$ followed by acid treatment affords δ-lactone $\text{12}$ which upon reduction and O-methylation furnishes cis rhoeadine analog $\text{14}$.     

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.     

Dedoublement et configuration absolue de la methyl-3 δ3(3a)-hydrindenone-4.etude de l'isomerisation en methyl-3 δsu3a(7a)-hydrindenone-4.

During the hydrogenation of the Δ^3(3a)-4-hydrindenones $\text{1}$ or $\text{3}$ on Pd or Ni, we observe a shift of the double bond to Δ^3a(7a)-4-hydrindenones $\text{2}$ and $\text{4}$. The absolute configuration established for ketones $\text{1}$ and $\text{2}$ shows that the reaction is a suprafacial process. By deuteriation experiments, we observe that the reaction is irreversible and occurs with a molecular hydrogen exchange.