Sur la synthèse du pollinastanol à partir du cycloartanol

The partial synthesis of pollinastanol (14) from cycloartanol (3) is reported. The transformation proceeds through the methylenic intermediate 12; the ring enlargement with cyanogen azide affords pollinastanone (13) further reduced to 14, The 4-keto isomer of pollinastanone (17) as well as a series of 5-β isomeric compounds are also described.     

Oligomérisation anionique de l'ethylène. III. Application à la synthèse d'alcools à longue chaine

Living oligomers of ethylene obtained by n-BuLi complexed with TMEDA have been deactivated by ethylene oxide. The nuclear magnetic resonance study of the product obtained allowed us to follow the influence of TMEDA toward the functionalization. Three products have been characterized: By increasing the ratio [TMEDA]/[n-BuLi] one obtains a decrease of the functionalization reaction.     

Recherches en vue de la synthèse de barbiturates organostanniques

Triphenyl and tributyltin hydrides have been found to add to the terminal double bond of unsaturated ethyl malonates to give organotin substituted ethyl malonates. Attempted cyclisation of the latter into barbituric compounds failed.     

Les anions-radicaux de l'isoprène et du butadiène intermédiaires de synthèse en chimie organique

We have synthesized a series of alkadiene and dialcohol homologs of terpenoid natural products by using anion-radicals of isoprene and butadiene. The reactions of the two monomers were initiated anionically by use of alkali metal–aromatic hydrocarbon complexes. The polymerization was stopped at the dimer stage. This method constitutes a route of synthesis for numerous organic compounds, such as alcohols and hydrocarbons.     

Application de la réaction de Wittig à la synthèse de dérivés de bromoénosuloses et d'esters bromoénuroniques. Note de laboratoire

Use of the Wittig reaction for the synthesis of derivatives of bromoenosuloses and bromoenuronic esters Treatment of 3-O-benzyl (or 3-O-methyl)-1, 2-O-isopropylidene-α-D -xylo-pentodialdo-1, 4-furanoses ( 2 or 1 ) with acetylbromomethylidenetriphenylphosphorane ( 3 ), benzoylbromomethylidenetriphenylphosphorane ( 4 ) or bromoethoxycarbonylmethylidenetriphenylphosphorane ( 5 ) gave in good to excellent yields the expected enose ( 6--11 ). In all cases but one ( 8 where some 10% of the E-isomer was formed) the reaction led to the exclusive formation of the Z-isomer whose configuration was established by NMR.     

Sur la synthèse de quelques furochromènes,analogues pharmacochimiques de la xanthylétine et de la séseline

Some furochromenes substituted at the 2-position by an electron-attracting group were obtained starting from ortho-hydroxyformyl derivatives of 2,2-dimethyl-2H-chromene following various processes which are indicated. These new furochromenes are pharmacochemical analogues of some natural pyranocoumarins, and as such they are potential photosensitizers.     

Utilisation d'ylides du phosphore en chimie des sucres. XV. Synthèse de sucres à insaturation terminale

Treatment of 3-O-benzyl-1, 2-O-isopropylidene-3-O-methyl-α-D -xylo-pentodialdlo-1,4-furanose and 2,5-anhydro-3,4-O-isopropylidene-aldehydo-D -ribose with moderately stable and stable phosphonium ylides led to the corresponding terminal-unsaturated sugars obtained as a mixture of cis and trans isomers. The cis:trans ratios were determined by ¹H-NMR. and (or) GLC. They showed that steric factors play an important role in the control of the stereochemistry of these reactions.     

Sur la synthèse d'acides thiazolotriazolylacétiques

During the synthesis of thiazolotriazolylacetic acids, the condensation of ethyl 4-chloro-3-oxobutyrate with triazolinethiones was studied. The use of an alkaline reagent (triethylamine) leads only to S-alkylation and not to the expected cyclized product. The cyclization of the intermediate β-ketoester is observed only by use of acidic reagents (phosphorous oxychloride, hydrogen chloride).     

Nouvelle méthode de synthèse de thiazolopyridines

It has been established that the direct condensation between aromatic and aliphatic thioesters and the variously generated anion of amino-chloropyridines represents the best method for the synthesis of thiazolo-pyridines. The transient thioamides, sometimes isolated, can be easily converted chemically or photochemically into the desired fused heterocycles.     

Nouvelle voie de synthèse des dérivés de l'ellipticine et analogues alcaloïdes à activité antitumorale

A new snythesis of 6H-pyrido[4,3-b]carbazoles is described starting from substituted cyclohexanones involving the combination of Borsche's carbazole preparation and Cranwell and Saxton's ellipticine synthesis where the starting materials are easily available. The dehydrogenation step is accomplished at an early stage. In some cases (11-desmethyl ellipticines derivatives), 7H-pyrido[3,4-c]carbazoles were also obtained.     

Détermination de la Conformation et de la Configuration de Sulfoxydes à Sept Chainons,Intermédiaires de Synthèse d'un Analogue de la Biotine

The conformation of the two isomeric 8,10-diaza-8,10-dibenzyl-4-thiabicyclo[5.3.0]decan-9-one 4-oxides has been studied by NMR. The vicinal coupling constants show that these two sulfoxides exist in a highly preferred chair conformation where the S→O bond is axial.     

Synthèse de nouveaux types de dérivés C-glycosyliques à partir de sucres acétyléniques ou de leurs équivalents synthétiques partiels

Synthesis of Novel Types of C-Glycosyl-derivatives from Acetylenic Sugars or Partial Synthetic Equivalents thereof The concept of synthetic equivalent is not unequivocal and, for example, α-fluoroenamines may behave in some cases as synthetic equivalents of ynamines and, in other situations, quite differently. Some uses of these α-fluoroenamines, ‘partial synthetic equivalents’ of ynamines, for the synthesis of C-glycosyl derivatives of coumarins, chromones, quinolines, quinolones, thietenes and isoxazoles are described. We also report the preparation of a series of mono- and diglycosylthiophenes by reacting HS^? with mono- and diglycosylbutadiynes. Acetylenic sugar derivatives have also been used for the synthesis of a diglycosylazaphosphorine and a spirooxolenone.     

Synthèse de composés cyclopentaniques chiraux,di, tri et tétrasubstitués. Application à la synthèse de dérivés Oxa-13-prostanoïques

The cyclopentenecarbaldehyde 1a , acetals 2a , 2b and the cyclopentenone 2c have been transformed through regio and stereocontrolled reactions into a variety of enantiomerically pure substituted cyclopentanes. Using appropriately selected Wittig reagents, aldehyde 1a furnished the condensation products 3 , 4 , 5 . Michael addition of diethyl malonate on the α,β-unsaturated aldehyde 1a under phasetransfer conditions led efficiently to 7 . Reduction of the cyclopentenone 2c gave 21 in high yield. The cyclopentenes 2a , 2b and 23 , submitted to hydroboration-oxidation furnished the cyclopentanols 10 , 13 and 24 , respectively, in 30, 70 and 50% yields, reflecting the substitution pattern of the starting alkenes. The salient feature of these reactions is the stereospecificity due to the chiral centre of the molecules 1a , 2a , 2b and 2c , leading to compounds with two, three and four asymmetric centres. The straightforward synthesis of 11α-hydroxy-13-oxaprostanoic acid 20 is described and an approach towards the preparation of 9α, 11α-dihydroxy-13-oxaprostanoic acid 34 is also presented. The structure of these products has been determined by ¹H- and ¹³C-NMR spectroscopy.     

Addition de la proline à quelques alcènes et alcynes électrophiles

Addition of proline in acetic anhydride to propiolic and pbenylpropiolic ester gave rise to two isomeric pyrroles 5 and 6 . Addition under the same conditions, to electrophilic alkenes pY-PhCH = C(X) (CN) led to a pyrroline-2 8 which eliminated HCN and produced pyrrole 9 . Addition of proline to fumarodinitrile is unusual, the reaction led to a new α-amino acid 10 and compound 11 . The structure of this product 11 was confirmed by X-ray measurements.     

Nouveaux polyéthers et polyesters à base d'isosorbide: synthèse et caractérisation

A new family of multifunctional polyethers was synthesized with acceptable yields by condensation of isosorbide with aliphatic and aromatic dihalides in solid-liquid heterogeneous medium (solid KOH in DMSO). Molecular weights evaluated by GPC are rather low (polydispersed oligomers with n = 2–9). On the other hand, polycondensation with aliphatic or aromatic acid dichlorides in mass or in solution allowed the elaboration of polyethers with appreciable weights (4000–8000) in good yields.     

Voies d'accès à un analogue pyrannique de la puromycine

In a continuation of our studies with methyl 3-amino-3,4-dideoxypetopyranosides, two pyranic analogues of puromycin 3A and 3b have been synthesized by two routes starting from methyl 2,3-anhydro-4-deoxy-or D, L -erythro-pentopyranosides. In the first one, both amino group and erythro stereochemistry have been introduced before the introduction of the purine moiety; in the second one the introduction of the erythro stereochemistry and of the 3-butrigeb atom has, more advantageously, been performed in the same step using an intermediate (22) with a suitable conformation. The two diastereoisomerws 3A and 3B have been separated and, after assignment of absolute configuration and the heterocyclic studies, will permit and evaluation of the role plays played by the heterocyclic oxygen atom by comparison with previous studies on cyclohexyl puromycin analogues (Vince et al.).