Synthesis with benzenesulfenyl chloride. A new way to cyclosativene

The total synthesis of the tetracyclic methylketone $\text{2}$, a synthetic precursor of cyclosativene $\text{1}$, is reported. The tricyclene ring system of $\text{2}$ is obtained by the electrophilic addition of benzenesulfenyl chloride to a suitably substituted methylenenorbornene $\text{7}$. Closure of the fourth ring is achieved by intramolecular acylation of an α-alkylated sulfone.     

Synthesis of “9-deazaadenosine”; A new cytotoxic C-nucleoside isostere of adenosine

The synthesis of 7-(β-$\text{D}$-ribofuranosyl)-4-amino-5H-pyrrolo[3,2-$\text{d}$]pyrimidine (9-deazaadenosine) $\text{9}$ is described. It involves base-catalyzed cyclization of N-carboethoxyenamine $\text{4}$ to give β- and α-ribosylated 3-amino-2-cyanopyrroles $\text{6}$ and $\text{7}$, respectively, followed by a one-step conversion to the desired pyrrolo[3,2-$\text{d}$]pyrimidine system.     

Synthesis of the n-benzoyl derivatives of L-arabino,L-xylo and L-lyxo (L-vancosamine) isomers of 2,3,6-trideoxy-3-C-methyl-3-aminohexose from a non-carbohydrate precursor

The synthesis of the N-benzoyl derivatives of $\text{L}$-$\text{arabino}$ (10),$\text{L}$-$\text{xylo}$ (13) and $\text{L}$-$\text{lyxo}$ ($\text{L}$-vancosamine) (12) 2,3,6-trideoxy-3-$\text{C}$-methyl-3-aminohexose from the (2$\text{S}$,3$\text{R}$) diol (1) prepared in fermenting bakers' yeast from α-methylcinnamaldehyde and acetaldehyde is reported     

Synthesis of enantiomerically enriched atrolactic acid and other α-hydroxy acids

The α-anions of 2-substituted 1,3-dioxolan-4-ones derived from chiral mandelic and lactic acid ($\text{2a}$, $\text{2b}$; $\text{3a}$; $\text{10a}$, $\text{10b}$) were alkylated with high stereoselectivity. The products formed were hydrolysed to α-hydroxy acids with 65–85% e.e. ((S)(+)-$\text{5}$,$\text{7}$,$\text{9}$, (R)(–)-$\text{13}$).     

O-silylated ketene acetal chemistry; β-(alkoxycarbonyl)methyl O-silyl enolates,useful synthons for α-substituted-β-(alkoxycarbonyl)methylalkanones

Conjugate addition of O-silylated ketene acetals $\text{2}$ to α,β-unsaturated carbonyl compounds $\text{1}$ in acetonitrile gave quantitative yields of the corresponding β-(alkoxycarbonyl)methyl O-silyl enolates $\text{4}$. Site specific electrophilic substitutions of $\text{4}$ yielded the corresponding α-substituted β-(alkoxycarbonyl)-methylalkanones $\text{5}$, $\text{7}$, and $\text{8}$.     

Dienophilie des cyano-1 enamines,nouveaux equivalents de cetenes pour les cycloadditions de diels-alder1

The Diels-Alder reactivity of two captodative olefins, 2-morpho-lino-acrylonitrile $\text{15}$ and 2-(N-methlanilino) -acrylonitrile $\text{16}$, towards four conjugated dienes is evaluated.In every cases, isomeric {4+2} cyclo-adducts are obtained.With olefin $\text{15}$ yields are better than with olefin $\text{16}$. The adducts are easily transformed in to the corresponding ketones by a mild hydrolysis of the α-aminonitrile group. Thus, the 1-cyanoenamines can be considered as good ketene equivalents very useful for the synthesis of unsaturated cyclohexanones.     

Regiochemistry of reactions of α-alkoxyallylphosphine oxide ylides with electrophiles.

Anions $\text{4}$, derived from α-methoxyallylphosphine oxides $\text{3}$, react with electrophiles in a highly regioselective fashion to give products of α-attack or γ-attack depending upon the substitution pattern of the ylid $\text{4}$ and the nature of the electrophile.     

Influence of the localisation of the excitation energy on the photochemistry of α,β-epoxyketones

Irradiation at 366 nm of α-epoxyketones $\text{8}$, $\text{11}$, $\text{12}$ in solution gave fragmentation to aldehydes and rearrangement either to β or α-diketones depending on the nature and localisation of the reactive triplet state in the starting molecule.     

C-C - connective synthesis of α-dialkylamino - ketones from aldehydes and sec.-amines

A simple and efficient 3 - step synthesis of α-dialkylamino - ketones $\text{3}$ starting from aldehydes and sec.-amines is described. The unsymmetrically aminoketones are obtained as pure regioisomers via reaction of metalated α-aminonitriles $\text{1}$ with aldehydes, followed by thermal HCN-elimination/tautomerization.     

Chrysomelidial by chromyl chloride oxidation: A revised structure for gastrolactone

Non-conjugated $\text{gem}$-dialkylated alkenes were oxidized to aldehydes in the presence of α,β-unsaturated carbonyl functional groups, providing a new synthesis of $\text{1}$ and a synthesis of $\text{2}$ that led to a revised structure for gastrolactone.     

Natural polyene α-pyrones. Total synthesis of citreomontanin from penicillium pedomontanum.

A total synthesis of all-$\text{E}$-citreomontanin (7), a novel polyene α-pyrone produced by $\text{Penicillium pedomontanum}$, is described.     

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.     

α-Phenylselenenylation d'aldehydes - synthese simple d'α-cetoaldehydes a fonction cetone protegee

Morpholinophenylselenenamide $\text{2}$ add to β-phenylselenoenamines $\text{1a}$ and yield β,β-bis(phenylseleno) enamines $\text{4}$. These compound undergo hydrolysis to form bis(phenylseleno) ethanal $\text{5a}$. Also, $\text{2}$ react with enolic aldehydes to give α-phenylselenoaldehydes $\text{3}$. This reaction allow a “one step” synthesis of cetoselenoacetals $\text{5}$ of α-cetoaldehydes with good yields.     

A new route to the 4H-1,2-oxazete ring system by the stereospecific oxidation of (Z)-3,3-dimethyl-1,1-bis(methylthio)-2-butanone oxime

A new synthesis of a functionalized 4$\text{H}$-1,2-oxazete by oxidation of α,α-$\text{bis}$-(alkylthio) oxime is described.     

Transposition des oximies de la 2H-naptho [1,8-bc] pyrannone-3 et de la 2H-benzo [b] furannone-3

Refluxing the oximes ($\text{2}$) of naphtho-[1,8-bc] pyran-3(2H)-one and ($\text{6}$) of 3 (2H)-benzofuranone with alcoholic hydrogen chloride give the corresponding α-alkoxy-ketones $\text{3}$, $\text{4}$, $\text{5}$ and α-chloroketone $\text{7}$ respectively. This transformation appears to be related to the acid conversion of N-aryhydroxylamines to o. and p. substituted anilines (BAMBERGER réarrangement.     

Synthesis of α-methylene-β-alanine and one of its naturally occurring α-ketomides

α-Methylene-β-alanine ($\text{1}$) has been synthesized from $\text{t}$-butyl bisbromomethyleneacetate by successively generating the α-methylene, then the β-amino function from a bromomethylene. Hydrolysis or methanolysis completes the synthesis of 1·HC1, and of its methyl ester ($\text{3}$)·HCl, from which the α-ketopalmitic acid amide of $\text{1}$ was prepared.     

β- and α-lithiaton of methyl β-methoxyacrylate: efficient synthesis of α,γ-substituted methyl tetronates - structure of aspertetronins and gregatins

Methyl β-methoxyacrylate ($\text{1}$) can be lithiated successively in β- and α-positions. Reaction with two electrophiles (at first a carbonyl compound) leads to α, γ-substituted methyl tetronates in a two step synthesis. Application of this method to the synthesis of methyl tetronate whose structure was assigned as that of gregatin B indicates that the gregatins and aspertetronins have the isomeric structures $\text{17}$.     

Ciral synthons for the multistriatins

The readily-obtained carbohydrate α-enones $\text{2}$, $\text{5}$ and $\text{8}$ are converted into the four diastereomeric 2,4-di-C-methyl glycopyranosides $\text{4}$$\text{7}$,$\text{10}$,$\text{11}$, which are chiral synthons for the four multistriatins $\text{1a}$-$\text{1d}$.     

Asymmetric synthesis of 2-substituted cycloalkanecarboxaldehydes

The 1,4-addition of Grignard reagents to chiral α,β-unsaturated cyclic aldimines ($\text{3}$), prepared from the corresponding cycloalkenecarboxaldehydes ($\text{1}$) and optically active α-amino acid tert-butyl esters ($\text{2}$, was found to give, after hydrolysis, trans-2-substituted cycloalkanecarboxaldehydes ($\text{5}$) in reasonably high enantiomeric purities.     

Biomimetic synthesis of bacterial c50 carotenoids decaprenoxanthin and c.p. 450

Alkylation of the distal double bond of pseudoionone $\text{4}$ has been carried out with isoprene epoxide (ZnCl₂ /MeNO₂ ) leading directly to α-$\text{cis 10 a}$, α-$\text{trans}$$\text{10b}$ and γ $\text{10c}$ hydroxyprenylionones. The α-$\text{cis}$ and γ-isomers have been converted in few steps into the C₅₀ carotenoids decaprenoxanthin $\text{1}$ and C.p. 450 $\text{3}$ respectively.