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PubMed1999

Total Synthesis of Natural Bicyclic Lactones (+)-Dihydrocanadensolide, (+/-)-Avenociolide, and (+/-)-Isoavenociolide via Tungsten-pi-Allyl Complexes.

A synthetic method using tungsten-pi-allyl compounds is developed for total syntheses of natural bislactones including (+)-dihydrocanadensaolide (2), (+/-)-avenociolide (3), and (+/-)-isoavenociolide (4). Syntheses of these natural compounds are based on a common intermediate, trans-alpha-methylene butyrolactones bearing an anti-homoallylic alcohol. The kep steps in the syntheses involve an intramolecular alkoxycarbonylation of propargyltungsten complexes to yield tungsten-pi,gamma-lactonyl species, followed by condensation of their CpW(NO)I(pi-allyl) derivatives with suitable aldehydes. This new method is very efficient for the synthesis of (+/-)-avenociolide (3) and (+/-)-isoavenociolide (4). Total syntheses of compounds 3 and 4 require only six and three steps, respectively, on the basis of chloropropargyl derivatives.

Journal Article↗
PubMed2002

P(RNCH(2)CH(2))(3)N-catalyzed 1,2-addition reactions of activated allylic synthons.

Activated allylic compounds of the type RCH:CHCH(2)Z (Z = CN, CO(2)Me) react efficiently with aromatic aldehydes in the presence of 20-40 mol % of P(R'NCH(2)CH(2))(3)N at -94 to -63 degrees C. Both R = H and R = Me lead exclusively to alpha-addition products. When R = H and Z = CN, an allylic transposition occurs to afford a Baylis-Hillman product as the only product.

Aldehydes↗
PubMed2001

Synthesis and biological evaluation of O-alkylated tropolones and related alpha-ketohydroxy derivatives as ribonucleotide reductase inhibitors.

A series of O-alkylated tropolones and related alpha-ketohydroxy compounds were evaluated for their biological activities and were shown to present an expected ribonucleotide reductase inhibition and cytotoxicity against some cancer cell lines but no antitubulin activity. Pharmacomodulation studies were realised to understand and enhance the observed activities. These original benzylic, heterocyclic and allylic compounds have been synthesised by a phase-transfer catalysed O-alkylation developed in our laboratories.

Animals↗
PubMed2003

Synthesis, molecular structure, and C-C coupling reactions of carbeneruthenium(II) complexes with C5H5Ru(=CRR') and C5Me5Ru(=CRR') as molecular units.

The ethene derivatives [(eta(5)-C(5)R(5))RuX(C(2)H(4))(PPh(3))] with R=H and Me, which have been prepared from the eta(3)-allylic compounds [(eta(5)-C(5)R(5))Ru(eta(3)-2-MeC(3)H(4))(PPh(3))] (1, 2) and acids HX under an ethene atmosphere, are excellent starting materials for the synthesis of a series of new halfsandwich-type ruthenium(II) complexes. The olefinic ligand is replaced not only by CO and pyridine, but also by internal and terminal alkynes to give (for X=Cl) alkyne, vinylidene, and allene compounds of the general composition [(eta(5)-C(5)R(5))RuCl(L)(PPh(3))] with L=C(2)(CO(2)Me)(2), Me(3)SiC(2)CO(2)Et, C=CHCO(2)R, and C(3)H(4). The allenylidene complex [(eta(5)-C(5)H(5))RuCl(=C=C=CPh(2))(PPh(3))] is directly accessible from 1 (R=H) in two steps with the propargylic alcohol HC triple bond CC(OH)Ph(2) as the precursor. The reactions of the ethene derivatives [(eta(5)-C(5)H(5))RuX(C(2)H(4))(PPh(3))] (X=Cl, CF(3)CO(2)) with diazo compounds RR'CN(2) yield the corresponding carbene complexes [(eta(5)-C(5)R(5))RuX(=CRR')(PPh(3))], while with ethyl diazoacetate (for X=Cl) the diethyl maleate compound [(eta(5)-C(5)H(5))RuCl[eta(2)-Z-C(2)H(2)(CO(2)Et)(2)](PPh(3))] is obtained. Halfsandwich-type ruthenium(II) complexes [(eta(5)-C(5)R(5))RuCl(=CHR')(PPh(3))] with secondary carbenes as ligands, as well as cationic species [(eta(5)-C(5)H(5))Ru(=CPh(2))(L)(PPh(3))]X with L=CO and CNtBu and X=AlCl(4) and PF(6), have also been prepared. The neutral compounds [(eta(5)-C(5)H(5))RuCl(=CRR')(PPh(3))] react with phenyllithium, methyllithium, and the vinyl Grignard reagent CH(2)=CHMgBr by displacement of the chloride and subsequent C-C coupling to generate halfsandwich-type ruthenium(II) complexes with eta(3)-benzyl, eta(3)-allyl, and substituted olefins as ligands. Protolytic cleavage of the metal-allylic bond in [(eta(5)-C(5)H(5))Ru(eta(3)-CH(2)CHCR(2))(PPh(3))] with acetic acid affords the corresponding olefins R(2)C=CHCH(3). The by-product of this process is the acetato derivative [(eta(5)-C(5)H(5))Ru(kappa(2)-O(2)CCH(3))(PPh(3))], which can be reconverted to the carbene complexes [(eta(5)-C(5)H(5))RuCl(=CR(2))(PPh(3))] in a one-pot reaction with R(2)CN(2) and Et(3)NHCl.

Journal Article↗
PubMed2002

Unusual pathways for metal-assisted C[bond]C and C[bond]P coupling reactions using allenylidenerhodium complexes as precursors.

The rhodium allenylidenes trans-[RhCl[[double bond]C[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] [R = Ph (1), p-Tol (2)] react with NaC(5)H(5) to give the half-sandwich type complexes [(eta(5)-C(5)H(5))Rh[[double bond]C[double bond]C[double bond]C(Ph)R](PiPr(3))] (3, 4). The reaction of 1 with the Grignard reagent CH(2)[double bond]CHMgBr affords the eta(3)-pentatrienyl compound [Rh(eta(3)-CH(2)CHC[double bond]C[double bond]CPh(2))(PiPr(3))(2)] (6), which in the presence of CO rearranges to the eta(1)-pentatrienyl derivative trans-[Rh[eta(1)-C(CH[double bond]CH(2))[double bond]C[double bond]CPh(2)](CO)(PiPr(3))(2)] (7). Treatment of 7 with acetic acid generates the vinylallene CH(2)[double bond]CH[bond]CH[double bond]=C=CPh(2) (8). Compounds 1 and 2 react with HCl to give the five-coordinate allenylrhodium(III) complexes [RhCl(2)[CH[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] (10, 11). An unusual [C(3) + C(2) + P] coupling process takes place upon treatment of 1 with terminal alkynes HC[triple bond]CR', leading to the formation of the eta(3)-allylic compounds [RhCl[eta(3)-anti-CH(PiPr(3))C(R')C[double bond]C[double bond]CPh(2)](PiPr(3))] [R' = Ph (12), p-Tol (13), SiMe(3) (14)]. From 12 and RMgBr the corresponding phenyl and vinyl rhodium(I) derivatives 15 and 16 have been obtained. The previously unknown unsaturated ylide iPr(3)PCHC(Ph)[double bond]C[double bond]C[double bond]CPh(2) (17) was generated from 12 and CO. A [C(3) + P] coupling process occurs on treatment of the rhodium allenylidenes 1, 2, and trans-[RhCl[[double bond]C[double bond]C[double bond]C(p-Anis)(2)](PiPr(3))(2)] (20) with either Cl(2) or PhICl(2), affording the ylide-rhodium(III) complexes [RhCl(3)[C(PiPr(3))C[double bond]C(R)R'](PiPr(3))] (21-23). The butatrienerhodium(I) compounds trans-[RhCl[eta(2)-H(2)C[double bond]C[double bond]C[double bond]C(R)R'](PiPr(3))(2)] (28-31) were prepared from 1, 20, and trans-[RhCl[[double bond]C[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] [R = CF(3) (26), tBu (27)] and diazomethane; with the exception of 30 (R = CF(3), R' = Ph), they thermally rearrange to the isomers trans-[RhCl[eta(2)-H(2)C[double bond]C[double bond]C[double bond]C(R)R'](PiPr(3))(2)] (32, 33, and syn/anti-34). The new 1,1-disubstituted butatriene H(2)C[double bond]C[double bond]C[double bond]C(tBu)Ph (35) was generated either from 31 or 34 and CO. The iodo derivatives trans-[RhI(eta(2)-H(2)C[double bond]C[double bond]C[double bond]CR(2))(PiPr(3))(2)] [R = Ph (38), p-Anis (39)] were obtained by an unusual route from 1 or 20 and CH(3)I in the presence of KI. While the hydrogenation of 1 and 26 leads to the allenerhodium(I) complexes trans-[RhCl[eta(2)-H(2)C[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] (40, 41), the thermolysis of 1 and 20 produces the rhodium(I) hexapentaenes trans-[RhCl(eta(2)-R(2)C[double bond]C[double bond]C[double bond]C[double bond]C[double bond]CR(2))(PiPr(3))(2)] (44, 45) via C-C coupling. The molecular structures of 3, 7, 12, 21, and 28 have been determined by X-ray crystallography.

Journal Article↗
PubMed2005

Quantitative urinalysis of the mercapturic acid conjugates of allyl formate using high-resolution NMR spectroscopy.

As end products of xenobiotic metabolism via glutathione conjugation, mercapturic acids (MCAs) can be used as markers to indicate exposure to allylic compounds as well as the rate and efficiency of their excretion. In addition, the formation of certain MCAs indicates metabolism via the known toxin acrolein, a strong electrophile. High-resolution 1H NMR spectroscopy has been employed to quantitatively measure the presence of MCAs in the urine of Sprague-Dawley rats, collected in the 8 h following 25 and 50 mgkg(-1) i.p. doses of allyl formate (AF), a model toxin. 3-Hydroxypropylmercapturic acid (HPMA) was found to be the only 1H NMR-observable MCA excreted in the urine, exhibiting a percentage recovery of approximately 20% at the 25 mgkg(-1) dose level, and approximately 30% at the 50 mgkg(-1) dose level.

Acetylcysteine↗
PubMed1986

Central effects of N-allyl,N'-methyl-barbital and N-allylmethyprylon in mice.

Pharmacological activities (hypnotic, anticonvulsant and convulsant activities, acute toxicity and pentobarbital (PB) synergism) of N-allyl,N'-methyl derivatives of barbiturates and related N-allyl substituted compounds were studied in mice. N-Allylhexobarbital (AHB), N-allylglutethimide (AGI) and N-allylmethyprylon (AMP) showed hypnotic activity. N-Allyl,N'-methyl derivatives of barbital (B), phenobarbital (PheB) and PB (AMB, AMPheB and AMPB), AHB and AMP exhibited anticonvulsant activity against pentylenetetrazol (PTZ)-induced seizures. AMP was the most potent agent among the allyl compounds tested in the protective effect against PTZ-induced seizures. N-Allyl, N'-methylallobarbital (AMAlloB) showed a weak convulsant activity at a dose of 640 mg/kg, i.p. All allyl compounds tested showed potentiation of the PB-induced sleep. AMB prolonged the PB-induced sleep 30-fold as compared with the control. These results indicate that AMB, AMP and the other N-allyl compounds possess some depressant effects on the central nervous system.

Allyl Compounds↗
PubMed2000

Hydrophilic sponges based on 2-hydroxyethyl methacrylate: part VII: modulation of sponge characteristics by changes in reactivity and hydrophilicity of crosslinking agents.

Despite previous unsuccessful attempts to use hydrated poly(2-hydroxyethyl methacrylate) sponges as implantable biomaterials, recently these materials became important as peripheral components in an artificial cornea of the core-and-skirt design. The low mechanical strength of sponges prompted this study on possible improvement of tensile properties by the use of a variety of crosslinking agents. Three vinylic (dimethacrylates) and two allylic compounds were used at different concentrations (0.1 to 2% (mol)) as crosslinking agents in the production of sponges. Their influence on the mechanical properties, porous morphology and swelling behavior of resulting sponges was evaluated. The onset of phase separation during polymerization was also measured by visible spectrophotometry. The results suggested an inherent heterogeneity of sponges, i.e. pores of non-uniform size and structural inhomogeneities. While the effects of changes in the nature and concentration of crosslinking agents on the equilibrium water content of sponges were ambiguous, some of the mechanical properties, such as toughness and elasticity, were improved by crosslinking with allylic agents. Scanning electron microscopic examination suggested that the mechanical effect is related to the variation of size of the polymer particles constituting the sponge structure, which was proved to be dependent upon the onset of phase separation during polymerization.

Journal Article↗
PubMed1988

Purification of geranylgeranyl diphosphate synthase from Phycomyces blakesleanus.

Geranylgeranyl diphosphate synthase has been purified to homogeneity from the carotene-overproducing strain M1 of Phycomyces blakesleanus. Usually two activity peaks with molecular weights of 60,000 and 30,000 eluted on gel exclusion chromatography, suggesting that the enzyme consists of two subunits, with a tendency to dissociate. With homogeneous protein, a single-staining band with molecular weight of 30,000 appeared on sodium dodecyl sulfate gel electrophoresis, confirming a subunit molecular weight of 30,000. Only isopentenyl diphosphate and farnesyl diphosphate were accepted by this enzyme for geranylgeranyl diphosphate formation. The smaller allylic compounds, dimethylallyl and geranyl diphosphate, were utilized at less than 1/20th the rate of farnesyl diphosphate. Michaelis constants of 9 microM for isopentenyl diphosphate and 60 microM for farnesyl diphosphate were found. The isoelectric point is 4.8.

Dimethylallyltranstransferase↗
PubMed1994

Synthesis of new 16-spirosteroids.

Reaction of estrone methyl ether 1 with sodium hydride and 1,3-dibromopropane, 1,4-dibromobutane, and 1,5-dibromopentane, respectively, gives the 16-spirosteroid derivatives 2-4, which were reduced to the 17 beta-alcohols 7-9. Acetylation afforded the acetates 10-12. In the reaction of 1 and 1,3-dibromopropane a bis-allyl compound 5 and an annulated dihydropyran 6 were also formed. Cleavage of the ether moiety in 2 and 3 was accomplished with diisobutylaluminum hydride to give 3,17 beta-diols 13 and 14, respectively.

Acetylation↗
PubMed2003

Synthesis and characterization of Nb(OR)4[OC(O)OR] (R = Me, Et, Allyl) and their reaction with the parent alcohol to afford organic carbonates.

Nb(OR)(4)[OC(O)OR] (R = Me, Et, allyl) compounds have been synthesized by the reaction of dimeric alkoxo complexes [Nb(OR)(5)](2) with CO(2). The kinetics of the reaction has shown that the monomer in equilibrium with the dimer is the species that reacts with CO(2). The resulting compounds are monomeric with a eta(2)-O,O-bonded hemicarbonate group. The CO(2) uptake is reversible. The hemicarbonates react with the parent alcohol to afford the relevant organic carbonate (RO)(2)CO with a turnover number (TON) of >2.

Journal Article↗
PubMed2002

Highly efficient allyl cross-coupling reactions of allylindiums with organic electrophiles.

This paper describes highly efficient allyl cross-coupling reactions of allylindiums with organic electrophiles such as aryl and vinyl triflates, vinyl halides, dibromoolefin, and alkynyl iodide. The reactions were carried out using 4 mol % Pd(PPh3)4 in the presence of 3 equiv of LiCl in DMF at 100 degrees C under a nitrogen atmosphere. Allylindium, generated from the reaction of 1 equiv of indium with 1.5 equiv of allyl halide, gave the best result as a coupling partner. The present method is mild and simple to apply, and it produces a diverse range of allylic compounds in good to excellent yields.

Journal Article↗
PubMed2003

Cobalt-catalyzed direct electrochemical cross-coupling between aryl or heteroaryl halides and allylic acetates or carbonates.

The electroreduction of a mixture of functionalized aromatic or heteroaromatic bromides or chlorides and allylic compounds such as acetates or carbonates in an electrochemical cell fitted with a sacrificial iron anode affords, in the presence of cobalt halide associated with pyridine as ligand in acetonitrile or DMF, the corresponding coupling product in good yields.

Journal Article↗
PubMed1996

Nickel-Catalyzed Direct Electrochemical Cross-Coupling between Aryl Halides and Activated Alkyl Halides.

The electrochemical reduction of a mixture of aryl halides and activated alkyl halides in DMF in the presence of catalytic amount of NiBr(2)bipy leads to cross-coupling products in good to high yields. The method applies to the synthesis of alpha-aryl ketones, alpha-aryl esters, and allylated compounds from readily available organic halides. Optimization of the process has been obtained by slowly adding the most reactive organic halide (usually the activated alkyl halide) during the electrolysis which is best conducted at 70 degrees C when aryl bromides are involved.

Journal Article↗
PubMed2002

Synthesis of 7-substituted farnesyl diphosphate analogues.

[structure: see text] Six farnesyl diphosphate analogues modified in the central isoprene unit have been prepared via our stereoselective vinyl triflate-mediated route to isoprenoids. The 7-allyl compound 6 is a modest inhibitor of mammalian protein-farnesyl transferase, but surprisingly the other five analogues are effective alternative substrates for this enzyme.

Alkyl and Aryl Transferases↗
PubMed2005

Total synthesis of the proposed structure for pyragonicin.

[structure: see text] The total synthesis of acetogenin 1 reported for pyragonicin and its 10-epimer 32 is described. The common THP ring system was stereoselectively constructed through a SmI(2)-induced reductive cyclization of beta-alkoxy acrylate 5 followed by Mitsunobu inversion, and each chiral center at C-10 was created by Brown's asymmetric allylation. Compound 1 had spectroscopic data consistent with that of natural pyragonicin, but a different optical rotation.

Acetogenins↗
PubMed2000

Benzannulation from alkynes and allyl tosylates via a pi-allylpalladium intermediate

[reaction: see text] Allyl tosylate is a good allyl source for a novel palladium-catalyzed benzannulation that affords polysubstituted benzenes from 1 mol of an allyl compound and 2 mol of internal alkynes. Using triphenyl phosphite as a ligand, the reaction with terminal alkynes gave trisubstituted benzenes regioselectively.

Journal Article↗