- Palladium-catalysed Conversion of Alkenols into Five- and Six-membered Ring Lactones at Room Temperature and Atmospheric Pressure
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Unsaturated alcohols react with carbon monoxide, oxygen, palladium chloride, copper(II) chloride, and hydrochloric acid in tetrahydrofuran to give lactones in 42-80percent yield.
- Alper, Howard,Leonard, Danielle
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- Nanoflow microreactor for dramatic increase not only in reactivity but also in selectivity: Baeyer-Villiger oxidation by aqueous hydrogen peroxide using lowest concentration of a fluorous lanthanide catalyst
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Not only the reaction rate but also the regioselectivity in the scandium bis(perfluorooctanesulfonyl)amide-catalyzed Baeyer-Villiger reaction is remarkably increased by the development of the fluorous nanoflow microreactor system continuously controlled by the nanofeeder DiNaS (Direct Nanoflow System) even in the lowest concentration of the catalyst (?0.1 mol%). The Baeyer-Villiger reaction completes within few seconds as a contact time in the nanoflow microreactor to give the lactone products with high regioselectivity without hydrolysis.
- Mikami, Koichi,Yamanaka, Masahiro,Islam, Md. Nazrul,Tonoi, Takayuki,Itoh, Yoshimitsu,Shinoda, Masaki,Kudo, Kenichi
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- Nanoflow system for perfect regiocontrol in the Baeyer-Villiger oxidation by aqueous hydrogen peroxide using lowest concentration of a fluorous lanthanide catalyst
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The scandium bis(perfluorooctanesulfonyl)amide-catalyzed Baeyer-Villiger reaction significantly increased the regioselectivity as well as the reaction rate by nanoflow system continuously controlled by a nanofeeder even in the lowest concentration of the catalyst (0.1mol%). The Baeyer-Villiger reaction completed within few seconds as a contact time in the microcell to afford the lactone products high regioselectively without hydrolysis.
- Mikami, Koichi,Islam, Md. Nazrul,Yamanaka, Masahiro,Itoh, Yoshimitsu,Shinoda, Masaki,Kudo, Kenichi
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- A New Synthesis of Alkylated 2H-Pyran-2-ones and Its Application to the Determination of the Relative and Absolute Configuration of Supellapyrone, Sex Pheromone of the Brownbanded Cockroach, Supella longipalpa
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The sex pheromone of the brownbanded cockroach, Supella longipalpa, can be synthesized by direct coupling of a brominated pyrone with an alkylzinc reagent.The stereochemistry of the natural pheromone has been assigned as (2'R,4'R)-5-(2',4'-dimethylheptanyl)-3-methyl-2H-pyran-2-one by a combination of synthesis, chiral gas chromatrography, and electrophysiological measurement.
- Shi, Xiongwei,Leal, Walter Soares,Liu, Zhi,Schrader, Eric,Meinwald, Jerrold
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- Reductive Opening of α-Methylspiroketals
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Syntheses of 5-methyl-1,7-dioxaspiroundecane 4 and its three congeners 5, 6, and 7 (α-methylspiroketals), and their reductive ring opening using aluminum hydride or silane - Lewis acid system have been investigated.Each spiroketal was synthesized through stereocontrolled acetalization with 42 - 96percent diastereomeric excess (de).The diisobutylaluminum hydride reduction of α-methylspiroketals proceeded via the tight oxocarbenium ion pair complex wherein the C-O bond which located at the opposite site against the C(α) - methyl bond was cleaved, affording a configuration-retentive product with 50 - 100percent de.The regioselectivity in the silane - Lewis acid reduction of the simplest monomethylspiroketal 4 was controlled by the equilibration of the two possible oxocarbenium ionic intermediates.On the other hand, dimethylspiroketal 5 and siloxyspiroketal 6 showed moderate to high regio- and stereoselectivity (10-100percent de), that originated from regioselective formation of the oxocarbenium ionic species and the subsequent stereoselective hydride attack.In these cases, the coordination site of the Lewis acid was controlled by the steric interaction of the methyl group on C(α) with the Lewis acid.To the resultant oxocarbenium ion, stereoelectronically-favored axial hydride attack occured with high stereoselection.The reduction of benzyloxyspiroketal 7 also exhibited good selectivity (62 - 100percent de) while the outcome was opposite to those of 5 and 6.Such a dramatic change could be attributed to the bidentate chelation of the Lewis acid to both the benzyl ether and the neighboring acetal oxygens.The whole procedure, the thermodynamic spiroketalization and the subsequent reductive ring opening, could be regarded as a remote stereochemical control using the spiroketal templates.
- Oikawa, Masato,Oikawa, Hideaki,Ichihara, Akitami
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- Isomerisation of ω-hydroxyalkenes under hydroxycarbonylation conditions in palladium catalysed aqueous phase systems
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The ω-hydroxyolefins 3-buten-1-ol, 3-buten-1-methyl-1-ol and 4-penten-1-ol were subjected to hydroxycarbonylation conditions in water in the presence of PdCl2(PhCN)2 and 4-8 equiv. of water soluble tris(3-sodiumsulfonatophenyl)phosphine (TPPTS), or N-bis(N′,N′-diethyl-2-aminoethyl)-4-aminomethylphenyl-diphenylphosphine (N3P). Under conditions of high conversion, the olefins primarily undergo isomerisation through a chain walking mechanism with selectivities for aldehyde ranging from 65% to 98%, with the lower values for longer chain alcohols. The lactones formed as the minor product are almost exclusively branched, indicating that in the first step 2,1-insertion is strongly favoured over 1,2-insertion. In the N3P system also linear lactone is produced at lower conversion. Running the reaction in D2O produces multiple deuterium incorporation in all positions of the carbon chain. A mechanism is discussed.
- Ionescu, Adriana,Ruppel, Markus,Wendt, Ola F.
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- Aldol Additions of Titanium and Boron Enolates of Achiral and Chiral δ-Lactones to Achiral Model Aldehydes: Simple and Induced Diastereoselectivities
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We studied the steric course of aldol additions of CpTiCl2 (novel) or Bu2B enolates of the unsubstituted δ-lactone and of the four monomethylated δ-lactones to isobutyraldehyde, crotonaldehyde, and para-bromobenzaldehyde. The titanium enolates reacted syn-selectively with >95:5 ds in most cases. The boron enolates reacted anti-selectively without exception (ds = 98:2 to 92:8). These selectivities paired with a preferred trans-orientation of the α-hydroxyalkyl substituents relative to the lactone's β- or γ-methyl group and with a preferred cis-orientation relative to the lactone's δ-methyl group. Our preparation of γ-methyl-δ-lactone (20) features a tandem glycol cleavage/lactol → lactone conversion with cat. TEMPO/stoichiom. PhI(OAc)2, which we believe is novel. Aldol additions of CpTiCl2 and Bu2B enolates of δ-lactone and its monomethyl derivatives to model aldehydes were studied. The CpTiCl2 enolates reacted syn-selectively (ds >95:5), the Bu2B enolates anti-selectively (ds up to 98:2). The α-hydroxyalkyl groups were oriented trans relative to the lactone's β- or γ-methyl group but cis relative to the lactone's δ-methyl group.
- Weber, Fabian,Becker, Fabian,Keller, Manfred,Hillebrecht, Harald,Brückner, Reinhard
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- Baeyer-Villiger oxidation of ketones to esters with sodium percarbonate/trifluoroacetic acid
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Sodium percarbonate in trifluoroacetic acid has been found to be an effective reagent for the Baeyer-Villiger oxidation of ketones to esters. The scope and limitations of the reaction were explored.
- Olah,Wang,Trivedi,Surya Prakash
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- Autocatalytic oxidation of ethers with sodium bromate
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Sodium and potassium bromate are stable and easily stored oxidants. They can oxidize both open and cyclic ethers in aqueous solution at room temperature yielding esters and lactones. Kinetic studies of the oxidation of tetrahydrofuran to γ-butyrolactone indicate that the major active oxidation species is bromine and not bromate. The bromate is only a supporting agent, responsible for the initiation step and supplying bromine molecules by oxidizing bromide ions during the propagation step. In the oxidation of tetrahydrofuran, high yields of γ-butyrolactone were obtained. (C) 2000 Elsevier Science Ltd.
- Metsger, Leonid,Bittner, Shmuel
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- Catalytic oxidation of cyclic ethers to lactones over various titanosilicates
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Various crystalline microporous metallosilicates have been used in the liquid phase catalytic oxidation of different cyclic ethers into their corresponding lactones in the presence of dilute aqueous H2O 2 as oxidant. Among the various metallosilicates studied for the oxidation of tetrahydrofuran to γ-butyrolactone, titanosilicates exhibited the best activity than the other metallosilicates such as chromium silicalite-1 (CrS-1), chromium silicalite-2 (CrS-2) and vanadium silicalite-1 (VS-1). The intrinsic activity of TS-1 was found to be marginally higher than the other titanosilicates. Cyclic ethers undergo αC-H oxidation to give the corresponding lactones; whereas open-chain ether produce carboxylic acids by initial αC-H bond oxidation to give ester as an intermediate product, which further undergoes cleavage of -O- linkage to give the final carboxylic acids. The conversion of substituted tetrahydrofuran is decreased with number of -CH3 groups at α- and/or β-position. The lactone formation is hindered when both the α-positions are substituted with methyl substituents. Mechanistically, titanium hydroperoxo complex formed in the titanosilicate/H2O2/H2O system is believed to oxidize the αC-H bond of ethers producing the respective α-hydroxylated product, which undergoes further oxidation to give the lactones (for cyclic ethers) or carboxylic acids (for open-chain ethers).
- Sasidharan, Manickam,Bhaumik, Asim
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- LYMPH DIRECTING PRODRUGS
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H:\dar\Interwoven\NRPortbl\DCC\DAR\8230712_1.doc-12/08/2015 Abstract The present invention relates to compounds and their uses, in particular, compounds in the form of prodrugs that promote transport of a pharmaceutical agent to the lymphatic system and subsequently enhance release of the parent drug.
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Page/Page column 75; 76
(2016/02/29)
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- Enantioselective Construction of Quaternary Carbon Stereocenter via Palladium-Catalyzed Asymmetric Allylic Alkylation of Lactones
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An efficient and practical method for the synthesis of α,α-disubstituted six-membered lactones was developed. Enantioselective construction of quaternary carbon centers by utilizing Pd-catalyzed asymmetric allylic alkylation proved its feasibility.
- Li, Xiao-Hui,Wan, Shi-Li,Chen, Di,Liu, Qing Rong,Ding, Chang-Hua,Fang, Ping,Hou, Xue-Long
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supporting information
p. 1568 - 1572
(2016/05/24)
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- Biocatalytic Characterization of Human FMO5: Unearthing Baeyer-Villiger Reactions in Humans
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Flavin-containing mono-oxygenases are known as potent drug-metabolizing enzymes, providing complementary functions to the well-investigated cytochrome P450 mono-oxygenases. While human FMO isoforms are typically involved in the oxidation of soft nucleophiles, the biocatalytic activity of human FMO5 (along its physiological role) has long remained unexplored. In this study, we demonstrate the atypical in vitro activity of human FMO5 as a Baeyer-Villiger mono-oxygenase on a broad range of substrates, revealing the first example to date of a human protein catalyzing such reactions. The isolated and purified protein was active on diverse carbonyl compounds, whereas soft nucleophiles were mostly non- or poorly reactive. The absence of the typical characteristic sequence motifs sets human FMO5 apart from all characterized Baeyer-Villiger mono-oxygenases so far. These findings open new perspectives in human oxidative metabolism.
- Fiorentini, Filippo,Geier, Martina,Binda, Claudia,Winkler, Margit,Faber, Kurt,Hall, Mélanie,Mattevi, Andrea
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p. 1039 - 1048
(2016/05/19)
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- Functional divergence between closely related Baeyer-Villiger monooxygenases from Aspergillus flavus
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Baeyer-Villiger monooxygenases (BVMOs) catalyse the chemo-, regio- and enantioselective oxidation of ketones to esters and lactones. To date, most of the cloned BVMOs available are derived from bacteria, although Baeyer-Villiger oxidations using fungi have frequently been demonstrated. Here we report the cloning and characterization of four BVMOs from the fungus Aspergillus flavus NRRL3357. Phylogenetic analysis shows these four BVMOs to cluster in a distinct group apart from other well-characterized BVMOs including cyclohexanone, phenylacetone and 4-hydroxyacetophenone monooxygenase. Building on the Grogan classification/clustering of BVMOs, we have designated this new group of BVMOs, Group VI. Group VI BVMOs show an early divergence from the cyclopentanone monooxygenase (CPMO) type BVMOs (Group I). Substrate profiling using cyclic, bicyclic, aliphatic and aryl ketones show a clear divergence in function and specificity not only between this new group of BVMOs and the CPMO-type BVMOs, but also between the four A. flavus BVMO paralogues despite their high sequence similarity. This study not only contributes to the growing number of available BVMOs, but also addresses the current classification of Type I BVMOs, and the usefulness of phylogenetic clustering and prediction of function and selectivity when genome-mining is used to search for new biocatalysts.
- Ferroni,Smit,Opperman
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- Exploration of the interrupted Fischer indolization reaction
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A convergent method to access the fused indoline ring system present in a multitude of bioactive molecules has been developed. The strategy involves the condensation of hydrazines with latent aldehydes to ultimately deliver indoline-containing products by way of an interrupted Fischer indolization sequence. The method is convergent, mild, operationally simple, broad in scope, and can be used to access enantioenriched products. In addition, our approach is amenable to the synthesis of furoindoline and pyrrolidinoindoline natural products as demonstrated by the concise formal total syntheses of physovenine and debromoflustramine B. The strategy will likely enable the synthesis of more complex targets such as the communesin alkaloids.
- Schammel, Alex W.,Boal, Ben W.,Zu, Liansuo,Mesganaw, Tehetena,Garg, Neil K.
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supporting information; experimental part
p. 4687 - 4695
(2010/08/06)
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- Remote control of regio- and diastereoselectivity in the hydroformylation of bishomoallylic alcohols with catalytic amounts of a reversibly bound directing group
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(Figure Presented) Remote and reversible! Phosphinites serve as reversibly bound directing groups for the remote control of the regio- and diastereoselective hydroformylation of bishomoallylic alcohols (see scheme; r.r: regioisomer ratio). The distance between the double bond and the functional hydroxy group to which the directing group is reversibly bound is the longest ever reported.
- Gruenanger, Christian U.,Breit, Bernhard
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supporting information; experimental part
p. 967 - 970
(2010/05/02)
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- An interrupted fischer indolization approach toward fused indoline-containing natural products
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An efficient method to access the fused indoline ring system present in a multitude of bioactive molecules has been developed. The strategy involves the condensation of hydrazines with latent aldehydes to ultimately deliver indoline-containing products by way of an interrupted Fischer indolization sequence. Our studies show that the approach will likely be amenable to the synthesis of complex targets, such as the communesin natural products.
- Boal, Ben W.,Schammel, Alex W.,Garg, Neil K.
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supporting information; experimental part
p. 3458 - 3461
(2009/12/07)
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- Synthesis and stereochemistry of the terminal spiroketal domain of the phosphatase inhibitor dinophysistoxin-2
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An expedient synthesis of both axially and equatorially C35 methyl substituted spiroketals representing the C28-C38 domain of the potent and selective protein serine/threonine phosphatase inhibitor dinophysistoxin-2 (DTX-2) was developed to enable comparative stereochemical analyses and a stereochemically correct total synthesis of DTX-2. Comparison of proton and carbon NMR data of the synthetic diastereomers with those published for DTX-2 indicates that DTX-2 possesses the (30S*,34R*,35S*)-relative configuration with an axial C35 methyl substituent.
- Forsyth, Craig J.,Wang, Ce
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p. 3043 - 3046
(2008/12/23)
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- Further explorations on bridged 1,2,4-trioxanes
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Three new bicyclo[3.2.1]-type 1,2,4-trioxanes have been designed and synthesized. One of them demonstrates better tolerance of the intramolecular hemiketals to steric crowding in hydroperoxidation. The other represents a prototype for possible manipulation of the transient radicals generated in cleavage reactions. A new substitution pattern in the bridged system is explored through synthesis of the third molecule. The configurations of all stereogenic centers in the bridged system can be effectively controlled by the chirality of the allyl alcohol as illustrated by the enantioselective synthesis of the fourth molecule. Finally, similar bicyclo[3.3.1]-type 1,2,4-trioxanes are shown very difficult to be synthesized because of the involvement of a conformer with two substituents at axial positions at the same time.
- Zhang, Qi,Wu, Yikang
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p. 10189 - 10201
(2008/02/13)
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- A new 2H-azirin-3-amine as a synthon for α-methyl glutamate
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The synthesis of a novel 2,2-disubstituted 2H-azirin-3-amine 10 as a building block for racemic Glu(2Me) is described. This synthon contains an ester group in the side chain. The reaction of 10 with thiobenzoic S-acid and the amino acid Z-Val-OH yielded the racemic monothiodiamide 17 and the dipeptide 18 as a mixture of diastereoisomers, respectively (Scheme 2). From 18, each of the protecting groups was removed selectively (Scheme 3).
- Hilty, Florentine M.,Brun, Kathrin A.,Heimgartner, Heinz
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p. 2539 - 2548
(2007/10/03)
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- Syntheses and biological evaluation of vinblastine congeners.
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Sixty-two congeners of vinblastine (VLB), primarily with modifications of the piperidine ring in the carbomethoxycleavamine moiety of the binary alkaloid, were synthesized and evaluated for cytotoxicity against murine L1210 leukemia and RCC-2 rat colon cancer cells, and for their ability to inhibit polymerization of microtubular protein at 10(7) M concentrations was found for L1210 inhibition by these compounds, with the most active 1000x as potent as vinblastine.
- Kuehne, Martin E,Bornmann, William G,Marko, Istvan,Qin, Yong,LeBoulluec, Karen L,Frasier, Deborah A,Xu, Feng,Mulamba, Tshilundu,Ensinger, Carol L,Borman, Linda S,Huot, Anne E,Exon, Christopher,Bizzarro, Fred T,Cheung, Julia B,Bane, Susan L
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p. 2120 - 2136
(2007/10/03)
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- Oxidation of ketones to esters using a tin substituted zeolite beta
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Applicants have developed a process for the oxidation of ketones to esters. The process involves contacting the ketone with hydrogen peroxide and a catalyst at oxidation conditions. The catalyst is a molecular sieve represented by the empirical formula: (MwSnxTiySi1?x?y?zGez)O2 where M is a trivalent metal such as aluminum or boron. These molecular sieves have a microporous three dimensional framework structure of at least SiO2and SnO2tetrahedral units, a crystallographically regular pore system and the characteristic x-ray diffraction pattern of zeolite beta.
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- Folding strain stereocontrol in cyclohexane ring formation by means of an intramolecular ester enolate alkylation reaction
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Diastereoselectivity in the cyclization of ethyl 7-bromo-2-methylheptanoates with an additional substituent at various positions in the chain, by LDA treatment, was investigated in connection with the concept of folding strain stereocontrol. Cyclization of 3-, 4-, and 6-methyl-substituted substrates revealed high selectivity, which demonstrates the prevalence of folding strain stereocontrol and the usefulness of this approach for stereoselective ring construction. In particular, reactions of the latter two substrates resulted in the stereodivergent preparation of diastereomeric 1,3-dimethylcyclohexanecarboxylates. In the case of the 5-methyl-substituted substrate, the selectivity of ring closure was only moderate. 1H and 13C NMR spectroscopic data were useful for determining the conformation of 1-methylcyclohexanecarboxylate derivatives. The origin of the diastereoselectivity was examined through the qualitative comparison of the strain in the diastereomeric folding in the transition state. Various factors that might affect stereoselectivity were examined in the cyclization of 5-substituted substrates to better understand this concept. As predicted, the selectivity increased as the substituent became bulkier: Ph Me ≈ Et ≤ i-Pr t-Bu. The effects of other factors - solvent, base counter cation, and leaving group - on selectivity agree with results predicted from the reactivity-selectivity relationship.
- Tokoroyama, Takashi,Kusaka, Hisashi
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p. 2487 - 2502
(2007/10/03)
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- Total Synthesis of Tautomycin
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A convergent stereocontrolled synthesis of the antifungal antibiotic tautomycin, a potent protein phosphatases inhibitor, has been achieved first via key aldol coupling of two large subunits, a right-hand C1-C21 ketone and a left-hand aldehyde (left from C22).The C1-C10 segment was synthesized through a remote stereochemical control process using a spiroketal template.After joining with the C11-C18 segment, the spiroketal moiety was selectively constructed.Then the right-hand C1-C21 ketone was synthesized via Roush asymmetric crotylboration.The left-hand aldehyde was prepared from a C21-C26 segment and a dialkylmaleic anhydride segment.Completely stereoselective assemblage of the two subunits, the right-hand and the left-hand, was achieved by employing the Mukaiyama aldol reaction.Further functional group manipulation including desilylation, oxidation at C2, and deprotection of tert-butyl ester with concomitant anhydride formation provided tautomycin which was identical with the natural product.As a preliminary study, derivatizations and degradation of the natural product were also examined to support the total synthesis.
- Oikawa, Masato,Ueno, Tohru,Oikawa, Hideaki,Ichihara, Akitami
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p. 5048 - 5068
(2007/10/02)
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- Synthetic study on tautomycin. Stereocontrolled synthesis of C(1)-C(18) fragment using a strategy of selective reduction of spiroketal
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A stereocontrolled synthesis of C(1)-C(18) fragment of tautomycin is accomplished employing asymmetric crotylboration, selective reduction of spiroketal, and addition of crotylstannane as the key steps.
- Oikawa,Oikawa,Ichihara
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p. 4797 - 4800
(2007/10/02)
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- Synthesis of γ- and δ-Lactones by Free-Radical Annelation of Se-Phenyl Selenocarbonates
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A general method for the synthesis of γ- and δ-lactones through the intramolecular addition of alkoxycarbonyl radicals, formed by reaction of Se-phenylselenocarbonates with n-Bu3SnH, onto carbon-carbon multiple bonds is described.This free-radical cyclization is characterized by high regioselectivity favoring exo addition and by a high ratio of cyclization to reduction.Monocyclic, fused bicyclic, and spirocyclic lactones are formed in good to excellent yield.Use of allyltri-n-butyltin as a chain-transfer agent in the place of n-Bu3SnH affords the corresponding 3-butenyl lactones.
- Bachi, Mario D.,Bosch, Eric
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p. 4696 - 4705
(2007/10/02)
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- Oxidation of acetals, an orthoester, and ethers by dioxiranes through α-CH insertion
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Dimethyldioxirane (1a) and methyl(trifluoromethyl)dioxirane (1b) efficiently afford cleavage of acetals and of ketals to carbonyl products under mild, neural conditions. Dialkyl ethers are cleaved to alcohols, aldehydes and/or carboxylic acids, whereas reaction of dioxiranes 1a,b with medium-ring cyclic ethers transforms the latter into lactones, via the corresponding hemiacetals, with no appreciable formation of ring-opened products. The products can be accounted for on grounds of a remarkably selective O-atom insertion by the dioxirane into C-H bonds α to the ether functionality.
- Curci,D'Accolti,Fiorentino,Fusco,Adam,Gonzalez-Nunez,Mello
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p. 4225 - 4228
(2007/10/02)
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- The Conformational Behaviour of 10-Substituted Spirodecanes
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The conformational behaviour of 10-X-substituted 1,4-dioxa- and 1,4,6-trioxaspirodecanes 1-4 has been studied by 13C-, 19F- and 1H-NMR spectroscopy.Two X-ray analyses of (2a,e) are presented, and their implications to cleavage reactions of chiral acetals are discussed.Participation of twist boat forms in the conformeric equilibrium of at least 1c has been made plausible by observing 13C, 19F-NMR coupling constants.The ratios of axial to equatorial conformers in 1-4 have been calculated by molecular mechanics.
- Wolff, J. Jens,Frenking, Gernot,Harms, Klaus
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p. 551 - 561
(2007/10/02)
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- HIGHLY REGIOSELECTIVE RING-OPENING OF α-SUBSTITUTED CYCLIC ACID ANHYDRIDES CATALYZED BY LIPASE
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Lipase Amano P irreversibly catalyzed a ring-opening of α-substituted cyclic acid anhydrides 1 preferentially at the less hindered carbonyl group to give monoesters with high regioselectivity.
- Hiratake, Jun,Yamamoto, Kazuyoshi,Yamamoto, Yukio,Oda, Jun'ichi
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p. 1555 - 1556
(2007/10/02)
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- Synthesis of vinblastine and vincristine type compounds
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A new process for the stereospecific synthesis of alkaloids of the vinblastine and vincristine type including the synthesis of vinblastine and vincristine as well novel alkaloids which are active as anti-tumor agents.
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- Macrocyclic lactone HMG-CoA reductase inhibitors
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Novel 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors which are useful as antihypercholesterolemic agents and are represented by the following general structural formula (I): STR1 are disclosed. Also disclosed are pharmaceutical compositions and methods of use of the compounds of formula (I).
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- Acid-Catalyzed Hydrolysis of a (γ-Hydroxyalkyl)ketene Dithioacetal. A Cyclic Intermediate and Product Distribution
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2-(Hydroxyalkylidene)-1,3-dithiane 1a undergoes acid-catalyzed hydrolysis.Disappearance of 1a is faster than formation of the products thio ester 5a and lactone 5a'.The product distribution changes with pH in a similar way to that of hydrolysis of the cyclic intermediate 3a.Hydrolysis of 1a must proceed mostly through 3a, accompanying its accumulation.In comparison with the reference substrate 1b, anchimeric assistance by the internal hydroxyl group was not observed in wholly aqueous solution, but it becomes apparent in aqueous acetonitrile solutions at high organic concentration.Neighboring hydroxyl participation is considered to occur by internal solvation, and the carbocation 2a can exist as a discrete intermediate of the hydrolysis.
- Okuyama, Tadashi,Fueno, Takayuki
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p. 1405 - 1408
(2007/10/02)
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- Novel HMG-CoA reductase inhibitors
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Novel 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors which are useful as antihypercholesterolemic agents and are represented by the following general structural formulae (I) or (II): STR1 wherein: n is 1 to 5; R is hydrogen or STR2 R1 is hydrogen or methyl; R2 is hydrogen or methyl; and R3 is hydrogen, C1-5 alkyl or C1-5 alkyl substituted with a member of the group consisting of phenyl, dimethylamino, or acetylamino; and the dotted lines at a, b and c represent optional double bonds and pharmaceutically acceptable salts of the compounds (II) in which R3 is hydrogen are disclosed.
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- Ruthenium Complex Catalyzed Regioselective Dehydrogenation of Unsymmetrical α,ω-Diols
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Ruthenium complex catalyzed regioselective dehydrogenation of unsymmetrically substituted 1,4- and 1,5-diols in the presence of such a hydrogen acceptor as α,β-unsaturated ketone gave predominantly β-substituted γ-lactones and γ-substituted δ-lactones, respectively.Among the ruthenium complexes, RuH2(PPh3)4 was the most active and selective catalyst and showed high catalytic activity even at 20 deg C.For example, 2,2-dimethyl-1,4-butanediol was quantitatively converted to dihydro-4,4-dimethyl-2(3H)-furanone and dihydro-3,3-dimethyl-2(3H)-furanone in a ratio of 99.6/0.4 in the presence of 4-phenyl-3-buten-2-one (hydrogen acceptor) and a catalytic amount of RuH2(PPh3)4 at 20 deg C.The proposed main factor controlling the regioselectivity is the steric constraints produced by the substituent(s) of a diol at the coordination step of alkoxy group to ruthenium.
- Ishii, Youichi,Osakada, Kohtaro,Ikariya, Takao,Saburi, Masahiko,Yoshikawa, Sadao
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p. 2034 - 2039
(2007/10/02)
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- Regioselective Hydrogenation of Unsymmetrically Substituted Cyclic Anhydrides Catalyzed by Ruthenium Complexes with Phosphine Ligands
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Regioselective hydrogenation of unsymmetrically substituted cyclic anhydrides catalyzed by ruthenium complexes with mono-, di-, or triphosphine ligands produced the corresponding two isomeric lactones, where the regioselectivity was influenced by the bulkiness of substituent(s) on the anhydrides and of the phosphine ligands of catalyst.
- Ikariya, Takao,Osakada, Kohtaro,Ishii, Youichi,Osawa, Shoichi,Saburi, Masahiko,Yoshikawa, Sadao
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p. 897 - 898
(2007/10/02)
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- BAEYER-VILLIGER OXIDATION WITH Me3SiOOSiMe3 UNDER ASSISTANCE OF SnCl4 OR BF3-OEt2.
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Treatment of ketones with bis(trimethylsilyl) peroxide and Lewis acid such as SnCl//4 or BF//3-OEt//2 in dichloromethane at room temperature affords esters in fair to excellent yields. Jasmine lactone is synthesized from 2- left bracket (Z)-pentenyl right bracket cyclopentanine by means of Me//3SiOOSiMe//3-BF//3-OEt//2 system without any protection of the carbon-carbon double bond. The oxidation of enol acetates of ketones to alpha -hydroxy (or alpha -acetoxy) ketones with Me//3SiOOSiMe//3-FeCl//3 system is also disclosed.
- Matsubara,Takai,Nozaki
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p. 2029 - 2032
(2007/10/02)
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- CATALYTIC REGIOSELECTIVE DEHYDROGENATION OF UNSYMMETRICAL α,ω-DIOLS USING RUTHENIUM COMPLEXES
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Ruthenium complex catalyzed regioselective dehydrogenation of unsymmetrically substituted 1,4- and 1,5-diols in the presence of α,β-unsaturated ketone as a hydrogen acceptor and triethylamine gave β-substituted γ-lactones and γ-substituted δ-lactones as major products, respectively.
- Ishii, Youichi,Osakada, Kohtaro,Ikariya, Takao,Saburi, Masahiko,Yoshikawa, Sadao
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p. 2677 - 2680
(2007/10/02)
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