- A general synthesis of homochiral β-hydroxy N-acetylcysteamine thioesters
-
A convenient and efficient route for the enantioselective synthesis of functionalised β-hydroxy N-acetylcysteamine thioesters is described. The route allows the facile incorporation of vicinal 13C labelling to produce intermediates required for biosynthetic studies on a wide range of polyketide metabolites, e.g. 6-MSA, monocerin, colletodiol and strobilurins.
- Le Sann, Christine,Simpson, Thomas J.,Smith, David I.,Watts, Paul,Willis, Christine L.
-
-
Read Online
- Stereoselective synthesis of (S)-dapoxetine: A chiral auxiliary mediated approach
-
An imidazolidin-2-one chiral auxiliary mediated acetate aldol reaction was explored in the enantioselective synthesis of (S)-dapoxetine (SSRI). The diastereoselective aldol adduct was transformed to highly enantiopure (S)-dapoxetine with overall good yield.
- Khatik, Gopal L.,Sharma, Ratnesh,Kumar, Varun,Chouhan, Mangilal,Nair, Vipin A.
-
-
Read Online
- Directed Asymmetric Reduction of a Carbonyl Group via a New Homochiral Boronate Ester
-
Homochiral β-boronate carbonyl derivative 4 directs the asymmetric reduction of the ketone moiety, providing 89percent enantiomeric excess of the (S)-diol 6, using borane-tetrahydrofuran as the reducing agent.
- Mears, Richard J.,Whiting, Andrew
-
-
Read Online
- Lewis base activation of Lewis acids: Vinylogous aldol additions of silyl dienol ethers to aldehydes
-
Highly regioselective vinylogous aldol additions of silyl dienol ethers derived from simple α,β-unsaturated ketones are described. The catalyst system of silicon tetrachloride activated by chiral bisphosphoramide (R,R)-1 effectively promotes the addition
- Denmark, Scott E.,Heemstra Jr., John R.
-
-
Read Online
- Asymmetric catalysis. Asymmetric catalytic intramolecular hydrosilation and hydroacylation
-
Catalysts of the type [Rh(chiral diphosphine)]+ efficiently catalyse the intramolecular hydrosilation of silyl ethers derived from allylic alcohols. The products can be converted to chiral 1,3-diols. High enantiomeric excesses (ee's) are observ
- Barnhart, Richard W.,Wang, Xianqi,Noheda, Pedro,Bergens, Steven H.,Whelan, John,Bosnich
-
-
Read Online
- Copper(I)-Catalyzed Asymmetric Vinylogous Aldol-Type Reaction of Allylazaarenes
-
A vinylogous aldol-type reaction of allylazaarenes and aldehydes is disclosed that affords a series of chiral γ-hydroxyl-α,β-unsaturated azaarenes in moderate to excellent yields with high to excellent regio- and enantioselectivities. With (R,RP)-TANIAPHOS and (R,R)-QUINOXP* as the ligand, the carbon-carbon double bond in the products is generated in (E)-form. With (R)-DTBM-SEGPHOS as the ligand, (Z)-form carbon-carbon double bond is formed in the major product. In this vinylogous reaction, aromatic, α,β-unsaturated, and aliphatic aldehydes are competent substrates. Moreover, a variety of azaarenes, such as pyrimidine, pyridine, pyrazine, quinoline, quinoxaline, quinazoline, and benzo[d]imidazole are well-tolerated. At last, the chiral vinylogous product is demonstrated as a suitable Michael acceptor towards CuI-catalyzed nucleophilic addition with organomagnesium reagents.
- Wang, Si-Qing,Liu, Zong-Ci,Yue, Wen-Jun,Yin, Liang
-
-
Read Online
- Enantioselective synthesis of (+)-sedamine and (-)-allosedamine
-
Two different approaches to the enantioselective syntheses of (+)-sedamine and (-)-allosedamine are described, both using the Sharpless asymmetric epoxidation as the key step. Regioselective reduction of epoxides, chemoselective oxidation of alcohols, ring-closing metathesis, and nucleophilic displacements were the other key steps employed. Georg Thieme Verlag Stuttgart.
- Yadav,Reddy, M. Sridhar,Rao, P. Purushothama,Prasad
-
-
Read Online
- Purification and characterization of a (r)-1-phenyl-1, 3-propanediol- producing enzyme from trichosporon fermentans aj-5152 and enzymatic (r)-1-phenyl-1, 3-propanediol production
-
An (R)-1-phenyl-1, 3-propanediol-producing enzyme was purified from Trichosporon fermentans AJ-5152. It was NADPH-dependent and converted 3-hydroxy-1- phenylpropane-1-one (HPPO) to (R)-1-phenyl-1, 3-propanediol [(R)-PPD] with anti-Prelog's specificity. It
- Kira, Ikuo,Onishi, Norimasa
-
-
Read Online
- A site isolation-enabled organocatalytic approach to enantiopure γ-amino alcohol drugs
-
Solid support-enabled site isolation has previously allowed to use paraldehyde as an acetaldehyde surrogate in aldol reactions. However, only electron-poor aldehydes were tolerated by the system. Herein, we show that the temporary conversion of benzaldehyde into η6-benzaldehyde Cr(CO)3 circumvents this limitation. Asymmetric synthesis of (R)-Phenoperidine, as well as formal syntheses of (R)-Fluoxetine and (R)-Atomoxetine, illustrate the benefits of this strategy.
- Wang, Shoulei,Rodríguez-Escrich, Carles,Fan, Xinyuan,Pericàs, Miquel A.
-
-
Read Online
- Catalyst-Directed Diastereo- and Site-Selectivity in Successive Nucleophilic and Electrophilic Allylations of Chiral 1,3-Diols: Protecting-Group-Free Synthesis of Substituted Pyrans
-
The iridium-catalyzed, protecting group-free synthesis of 4-hydroxy-2,6-cis- or trans-pyrans through successive nucleophilic and electrophilic allylations of chiral 1,3-diols occurs with complete levels of catalyst-directed diastereoselectivity in the absence of protecting groups, premetallated reagents, or discrete alcohol-to-aldehyde redox reactions.
- Shin, Inji,Wang, Gang,Krische, Michael J.
-
-
Read Online
- Enantioselective β-hydroxy thioesters formation via decarboxylative aldol reactions of malonic acid half thioesters with aldehydes promoted by chloramphenicol derived sulfonamides
-
A highly enantioselective synthesis of chiral β-hydroxy thioesters that uses a decarboxylative aldol reaction of malonic acid half thioesters and aldehydes catalyzed by a chloramphenicol base-derived bifunctional organocatalyst is reported. The resulting
- Wang, Yafeng,Huang, Guanxin,Hu, Sha,Jin, Kaijun,Wu, Yan,Chen, Fener
-
-
Read Online
- Direct Deamination of Primary Amines via Isodiazene Intermediates
-
We report here a reaction that selectively deaminates primary amines and anilines under mild conditions and with remarkable functional group tolerance including a range of pharmaceutical compounds, amino acids, amino sugars, and natural products. An anomeric amide reagent is uniquely capable of facilitating the reaction through the intermediacy of an unprecedented monosubstituted isodiazene intermediate. In addition to dramatically simplifying deamination compared to existing protocols, our approach enables strategic applications of iminium and amine-directed chemistries as traceless methods. Mechanistic and computational studies support the intermedicacy of a primary isodiazene which exhibits an unexpected divergence from previously studied secondary isodiazenes, leading to cage-escaping, free radical species that engage in a chain, hydrogen-atom transfer process involving aliphatic and diazenyl radical intermediates.
- Berger, Kathleen J.,Driscoll, Julia L.,Yuan, Mingbin,Dherange, Balu D.,Gutierrez, Osvaldo,Levin, Mark D.
-
supporting information
p. 17366 - 17373
(2021/11/04)
-
- The Catalytic Asymmetric Intermolecular Prins Reaction
-
Despite their significant potential, catalytic asymmetric reactions of olefins with formaldehyde are rare and metal-free approaches have not been previously disclosed. Here we describe an enantioselective intermolecular Prins reaction of styrenes and paraformaldehyde to form 1,3-dioxanes, using confined imino-imidodiphosphate (iIDP) Br?nsted acid catalysts. Isotope labeling experiments and computations suggest a concerted, highly asynchronous addition of an acid-activated formaldehyde oligomer to the olefin. The enantioenriched 1,3-dioxanes can be transformed into the corresponding optically active 1,3-diols, which are valuable synthetic building blocks.
- Diáz-Oviedo, C. David,Maji, Rajat,List, Benjamin
-
supporting information
p. 20598 - 20604
(2021/12/14)
-
- A Catalytic Approach for Enantioselective Synthesis of Homoallylic Alcohols Bearing a Z-Alkenyl Chloride or Trifluoromethyl Group. A Concise and Protecting Group-Free Synthesis of Mycothiazole
-
A protecting group-free strategy is presented for diastereo- and enantioselective routes that can be used to prepare a wide variety of Z-homoallylic alcohols with significantly higher efficiency than is otherwise feasible. The approach entails the merger of several catalytic processes and is expected to facilitate the preparation of bioactive organic molecules. More specifically, Z-chloro-substituted allylic pinacolatoboronate is first obtained through stereoretentive cross-metathesis between Z-crotyl-B(pin) (pin = pinacolato) and Z-dichloroethene, both of which are commercially available. The organoboron compound may be used in the central transformation of the entire approach, an α- and enantioselective addition to an aldehyde, catalyzed by a proton-activated, chiral aminophenol-boryl catalyst. Catalytic cross-coupling can then furnish the desired Z-homoallylic alcohol in high enantiomeric purity. The olefin metathesis step can be carried out with substrates and a Mo-based complex that can be purchased. The aminophenol compound that is needed for the second catalytic step can be prepared in multigram quantities from inexpensive starting materials. A significant assortment of homoallylic alcohols bearing a Z-F3C-substituted alkene can also be prepared with similar high efficiency and regio-, diastereo-, and enantioselectivity. What is more, trisubstituted Z-alkenyl chloride moiety can be accessed with similar efficiency albeit with somewhat lower α-selectivity and enantioselectivity. The general utility of the approach is underscored by a succinct, protecting group-free, and enantioselective total synthesis of mycothiazole, a naturally occurring anticancer agent through a sequence that contains a longest linear sequence of nine steps (12 steps total), seven of which are catalytic, generating mycothiazole in 14.5% overall yield.
- Morrison, Ryan J.,Van Der Mei, Farid W.,Romiti, Filippo,Hoveyda, Amir H.
-
supporting information
p. 436 - 447
(2020/01/09)
-
- Chiral Ion-Pair Organocatalyst-Promoted Efficient Enantio-selective Reduction of α-Hydroxy Ketones
-
The enantioselective reduction of α-hydroxy ketones with catecholborane has been developed employing 5 mol% of an 1,1′-bi-2-naphthol (BINOL)-derived ion-pair organocatalyst. This methodology provides a straightforward access to the corresponding aromatic 1,2-diols in high yields (up to 90%) with excellent enantioselectivities (up to 97%). Furthermore, the α-amino ketones also could be reduced with moderate ee values under mild reaction condition. (Figure presented.).
- Zhang, Yiliang,He, Li,Shi, Lei
-
supporting information
p. 1926 - 1931
(2018/03/27)
-
- Organocatalytic direct asymmetric crossed-aldol reactions of acetaldehyde in aqueous media
-
A new type of diarylprolinol-based catalyst, which contains a dioctylamino group in the presence of a newly developed ionic liquid supported (ILS) benzoic acid as cocatalyst, is shown to be an effective catalytic system for the asymmetric direct crossed-aldol reaction of acetaldehyde in aqueous media using brine. For the reactions studied, the catalyst loading could be reduced to 5 mol %; high yields (up to 97%) and high enantioselectivities (up to 92% ee) were also achieved for a wide variety of aromatic aldehyde.
- Qiao, Yupu,Chen, Qiankun,Lin, Sirong,Ni, Bukuo,Headley, Allan D.
-
supporting information
p. 2693 - 2696
(2013/04/24)
-
- Simple and efficient synthesis of (S)-dapoxetine
-
A refinement in the synthetic strategy for (S)-dapoxetine 1 is described. The key features of synthetic strategy include (a) a Sharpless asymmetric epoxidation reaction and regioselective reductive ring opening of a 2,3-epoxy alcohol to elaborate the hydroxy-bearing stereogenic center at benzylic position; (b) regioselective functionalization of 1-naphthol and amine functionality through Mitsunobu procedures; and (c) Eschweiler-Clarke reductive methylation condition to access the target molecule.
- Sasikumar,Nikalje, Milind D.
-
experimental part
p. 3061 - 3067
(2012/08/27)
-
- Lewis base catalyzed enantioselective additions of an N-silyl vinylketene imine
-
Outside the limits: In the title reaction the nucleophile 1 represents a synthetic equivalent of nucleophilic allylic nitriles and addresses some of the current limitations associated with reactions of allylic nitrile anions. Unsaturated nitriles containi
- Denmark, Scott E.,Wilson, Tyler W.
-
p. 3236 - 3239
(2012/05/20)
-
- Synthesis and evaluation of a broad range of new chiral phosphine-carbene ligands for asymmetric hydrogenation
-
A straightforward and gram scale synthesis (six-step synthesis from enantioenriched β-hydroxy esters) of new structurally simple phosphine-carbene ligands bearing a single stereogenic centre has been achieved. Enantioselectivities of up to 60-63% could be achieved in the hydrogenation of methylstilbene and dehydroaminoacids when the reactions were performed under 20-50 bar hydrogen pressure.
- Passays, Johan,Ayad, Tahar,Ratovelomanana-Vidal, Virginie,Gaumont, Annie-Claude,Jubault, Philippe,Leclerc, Eric
-
experimental part
p. 562 - 574
(2011/06/19)
-
- Asymmetric induction by (S)-4-isopropyl-1-phenylimidazolidin-2-thione in titanium-mediated aldol reactions and its application in enantioselective synthesis of (R)-baclofen
-
The usefulness of (S)-4-isopropyl-1-phenylimidazolidin-2-thione as a chiral auxiliary in stereoselective propionate and acetate aldol reactions is discussed. Further, the enantioselective synthesis of (R)-baclofen by acetate aldol reaction using the chiral auxiliary was demonstrated. Georg Thieme Verlag Stuttgart New York.
- Khatik, Gopal L.,Khurana, Ravi,Kumar, Varun,Nair, Vipin A.
-
experimental part
p. 3123 - 3132
(2011/10/31)
-
- Organic metal compound and process for preparing optically-active alcohols using the same
-
The present invention provides an asymmetric reduction catalyst effective in preparing optically-active alcohol compounds having various functional groups, and a process for preparing optically-active alcohol compounds using said asymmetric reduction catalyst. The organic metal compound of the present invention is represented by the following general formula (1): wherein R1 and R2 may be mutually identical or different, and are an alkyl group, a phenyl group, a naphthyl group, a cycloalkyl group, or an alicyclic ring formed by binding R1 and R2, which may have a substituent; R3 is a hydrogen atom or an alkyl group; Cp is a cyclopentadienyl group, which may have a substituent, bound to M1 via a π bond; X1 is a halogen atom or a hydrido group; M1 is rhodium or iridium; and * denotes asymmetric carbon.
- -
-
Page/Page column 7; 12
(2009/04/24)
-
- Asymmetric dehydration of β-hydroxy esters and application to the syntheses of flavane derivatives
-
Catalytic asymmetric dehydration of β-aryl or alkyl substituted β-hydroxy esters via kinetic resolution has been investigated. A brief survey of 10 different chiral ligands is conducted to examine the effects of chiral ligand structure on selectivity of t
- Choi, Eui Ta,Lee, Min Hee,Kim, Yongtae,Park, Yong Sun
-
p. 1515 - 1522
(2008/09/18)
-
- A diarylprolinol in an asymmetric, catalytic, and direct crossed-aldol reaction of acetaldehyde
-
(Chemical Equation Presented) No over-reacting: A diarylprolinol was found to be an effective organocatalyst of the direct, enantioselective aldol reaction of acetaldehyde, affording β-hydroxy α-unsubstituted aldehydes in good yield with excellent enantio
- Hayashi, Yujiro,Itoh, Takahiko,Aratake, Seiji,Ishikawa, Hayato
-
supporting information; experimental part
p. 2082 - 2084
(2009/02/06)
-
- Anthracene cycloadducts as highly selective chiral auxiliaries
-
(Chemical Equation Presented) A new chiral auxiliary was designed and easily prepared from a Diels-Alder cycloadduct of an enantiomerically pure anthracene with maleimide. Excellent diastereoselectivities in Diels-Alder reactions, conjugate additions, and aldol reactions employing these auxiliaries are now reported.
- Liu, Xiang,Snyder, John K.
-
p. 2935 - 2938
(2008/09/19)
-
- Lewis base activation of Lewis acids: Catalytic, enantioselective vinylogous aldol addition reactions
-
(Chemical Equation Presented) The generality of Lewis base catalyzed, Lewis acid mediated, enantioselective vinylogous aldol addition reactions has been investigated. The combination of silicon tetrachloride and chiral phosphoramides is a competent catalyst for highly selective additions of a variety of α,β-unsaturated ketone-, 1,3-diketone-, and α,β- unsaturated amide-derived dienolates to aldehydes. These reactions provided high levels of γ-site selectivity for a variety of substitution patterns on the dienyl unit. Both ketone- and morpholine amide-derived dienol ethers afforded high enantio- and diastereoselectivity in the addition to conjugated aldehydes. Although α,β-unsaturated ketone-derived dienolate did not react with aliphatic aldehydes, α,β-unsaturated amide-derived dienolates underwent addition at reasonable rates affording high yields of vinylogous aldol product. The enantioselectivities achieved with the morpholine derived-dienolate in the addition to aliphatic aldehydes was the highest afforded to date with the silicon tetrachloride-chiral phosphoramide system. Furthermore, the ability to cleanly convert the morpholine amide to a methyl ketone was demonstrated.
- Denmark, Scott E.,Heemstra Jr., John R.
-
p. 5668 - 5688
(2008/02/10)
-
- More than a protective group: Synthesis and applications of a new chiral silane
-
Enantiomerically pure (-)-(R)- and (+)-(S)-(1-methoxy-2,2,2-triphenylethyl) dimethylsilanes (MOTES-H) were synthesized from triphenylacetaldehyde in five synthetic steps and with 60% overall yield. MOTES-protected α- and β-hydroxycarbonyl compounds were used in Grignard and Diels Alder reactions in the presence of MgBr2 to afford addition products with 87-98% yield and selectivities of up to >120:1 dr. With this method, the pine beetle pheromone (-)-frontalin (67%, 98.5% ee) and naturally occurring (-)-(R)-octane-1,3-diol (90%, >99% ee) were synthesized.
- Campagna, Maurizio,Trzoss, Michael,Bienz, Stefan
-
p. 3793 - 3796
(2008/02/12)
-
- Novel phosphorus-containing prodrug
-
Novel cyclic phosphoramidate prodrugs of parent drugs MH of formula I their use in delivery of drugs to the liver, their use in enhancing oral bioavailability, and their method of preparation are described.
- -
-
Page/Page column 63
(2010/11/08)
-
- Phosphoramidate and phosphate prodrugs of (-)-β-D-(2R,4R)-dioxolane- thymine: Synthesis, anti-HIV activity and stability studies
-
A series of phosphoramidate and phosphate prodrugs of DOT were synthesized via dichlorophosphate or H-phosphonate chemistry and evaluated for their anti-HIV activity against LAI M184V mutants in PBM cells as well as for their cytotoxicity. The antiviral and cytotoxic profiles of the prodrugs were compared with that of the parent compound (DOT), and it was found that four aryl phosphoramidates 5, 18, 20, and 26 showed a significant enhancement (8- to 12-fold) in anti-HIV activity without cytotoxicity. Chemical stability of these prodrugs was evaluated in phosphate buffer at pH values of biological relevance (i.e., pH 2.0 and 7.4). Enzymatic hydrolysis was also studied in esterase or lipase in buffer solution. Chemical stability studies indicate that the phosphoramidates have good chemical stability at pH 2.0 and at pH 7.4 phosphate buffer. Phosphoramidate prodrugs were hydrolyzed in vitro by esterase or lipase and found to be better substrates for lipases than for esterases. 1,3-Diol cyclic phosphates showed potent anti-HIV activity without increasing the cytotoxicity compared with that of DOT and have good chemical and enzymatic stability. Long-chain lipid phosphates, although showed potent anti-HIV activity, exhibited increased cytotoxicity.
- Liang, Yuzeng,Narayanasamy, Janarthanan,Schinazi, Raymond F.,Chu, Chung K.
-
p. 2178 - 2189
(2007/10/03)
-
- Candida Rugosa lipase-catalyzed kinetic resolution of β-hydroxy- β-arylpropionates and δ-hydroxy-δ-aryl-β-oxo-pentanoates
-
A simple and convenient method was reported for the preparation of optically active β-hydroxy-β-arylpropionates, δ-hydroxy-δ- aryl-β-oxo-pentanoates and their butyryl derivatives via CRL-catalyzed hydrolysis. The optically active products are potential precursors of some chiral pharmaceuticals and natural products.
- Xu, Chengfu,Yuan, Chengye
-
p. 2169 - 2186
(2007/10/03)
-
- Identification of potent type I MetAPs inhibitors by simple bioisosteric replacement. Part 2: SAR studies of 5-heteroalkyl substituted TCAT derivatives
-
Systematic SAR studies on the thiazole ring 5-substituent of TCAT derivatives revealed that the introduction of a β-alkoxy or an amino group enhanced the inhibitory activity significantly. The present compounds are representative of specific Co(II)-MetAP1 inhibitors. Before the physiologically relevant metal ions for MetAPs are established, these small molecular compounds could be used as tools for detailed biological studies.
- Cui, Yong-Mei,Huang, Qing-Qing,Xu, Jie,Chen, Ling-Ling,Li, Jing-Ya,Ye, Qi-Zhuang,Li, Jia,Nan, Fa-Jun
-
p. 4130 - 4135
(2007/10/03)
-
- Lewis base catalyzed enantioselective aldol addition of acetaldehyde-derived silyl enol ether to aldehydes
-
Chiral phosphoramide catalyzed-enantioselective aldol addition of an acetaldehyde-derived trialkylsilyl enol ether to aromatic aldehydes provides protected aldol products in good yields with good to excellent enantioselectivities. Preliminary studies show that the aldolization intermediate (a chlorohydrin adduct) can be trapped with tert-butyl isocyanide to form an α-hydroxy lactone with good selectivity in a singlepot operation.
- Denmark, Scott E.,Bui, Tommy
-
p. 10190 - 10193
(2007/10/03)
-
- Lewis base activation of Lewis acids: Catalytic, enantioselective addition of silyl ketene acetals to aldehydes
-
The concept of Lewis base activation of Lewis acids has been reduced to practice for catalysis of the aldol reaction of silyl ketene acetals and silyl dienol ethers with aldehydes. The weakly acidic species, silicon tetrachloride (SiCl4), can b
- Denmark, Scott E.,Beutner, Gregory L.,Wynn, Thomas,Eastgate, Martin D.
-
p. 3774 - 3789
(2007/10/03)
-
- Prodrugs for liver specific drug delivery
-
The present invention is directed towards novel cyclic phosph(oramid)ate prodrugs of alcohol, amine-, and thiol-containing drugs, their preparation, their synthetic intermediates, and their uses. Another aspect of the invention is the use of the prodrugs
- -
-
-
- Enantioselective Hydrogenation of β-Keto Esters using Chiral Diphosphine-Ruthenium Complexes: Optimization for Academic and Industrial Purposes and Synthetic Applications
-
Enantioselective hydrogenation using chiral complexes between atropisomeric diphosphines and ruthenium is a powerful tool for producing chiral compounds. Using a simple and straightforward in situ catalyst preparation, the conditions were optimized using molecular hydrogen for both academic and industrial purposes. This led to the best conditions and the lowest catalytic ratio required for the pressure used. Hydrogenation of various β-keto esters was efficiently performed at atmospheric and higher pressures, leading to the use of very low catalyst-substrate ratios up to 1/20,000. Asymmetric hydrogenations were used in key-steps towards the total synthesis of corynomycolic acid, Duloxetine and Fluoxetine.
- Ratovelomanana-Vidal,Girard,Touati,Tranchier,Ben Hassine,Genet
-
p. 261 - 274
(2007/10/03)
-
- Chiral ligand-controlled catalytic asymmetric epoxidation of α,β-unsaturated carbonyl compounds with peroxide
-
Asymmetric epoxidation reaction of α,β-unsaturated carbonyl compounds with alkylperoxide was catalyzed by an external chiral tridentate aminodiether-lithium peroxide giving epoxides with good enantiomeric excess. Slow addition of alkylhydroperoxide was beneficial for a catalytic asymmetric reaction. Lone pair electron-differentiating coordination of a carbonyl oxygen to lithium is another critical factor for high enantioselectivity.
- Tanaka, Yoshihito,Nishimura, Katsumi,Tomioka, Kiyoshi
-
p. 4549 - 4556
(2007/10/03)
-
- Lewis base activation of Lewis acids. Vinylogous aldol reactions
-
A highly regioselective vinylogous aldol reaction catalyzed by SiCl4 and a chiral phosphoramide (R,R)-5, providing δ-hydroxy enones for a variety of aldehyde and dienol ether structures, has been developed. Low catalyst loadings (1 mol %) can b
- Denmark, Scott E.,Beutner, Gregory L.
-
p. 7800 - 7801
(2007/10/03)
-
- Inter- and intramolecular differentiation of enantiotopic dioxane acetals through oxazaborolidinone-mediated enantioselective ring-cleavage reaction: Kinetic resolution of racemic 1,3-alkanediols and asymmetric desymmetrization of meso-1,3-polyols
-
Acetals derived from racemic 1,3-alkanediols undergo kinetic resolution in chiral oxazaborolidinonemediated ring-cleavage reaction with nucleophiles such as enol silanes and allylic silanes. Enantioselectivity of the reaction is affected by nucleophiles, the N-sulfonyl groups of oxazaborolidinones, and the substituents attached to the acetal carbon. For disubstituted acetals rac-1 and for trisubstituted acetal rac-2, derived from syn-2,4-dimethyl-1,3-pentanediol, satisfactory enantioselectivity is obtained by using methallylsilane 7b,c as a nucleophile in combination with N-mesyloxazaborolidinone 4a. On the other hand, enantioselective reaction of trisubstituted acetal rac-3b, derived from anti-2,4-dimethyl-1,3-pentanediol, is realized by using silyl ketene acetal 5e in combination with N-tosyloxazaborolidinone 4b. The reaction conditions optimized for the kinetic resolution, or enantiomer differentiating reaction, of the racemic acetals are successfully applied to asymmetric desymmetrization of meso-1,3-polyols through intramolecular differentiation of the enantiotopic acetal moieties of the bis-acetal derivatives. The utility of the ring-cleavage reaction as a method for enantioselective terminal differentiation of prochiral polyols is demonstrated in convergent asymmetric synthesis of pentol derivative 35 corresponding to the C(19)-C(27) ansachain of rifamycin S.
- Harada, Toshiro,Egusa, Takayuki,Igarashi, Yasuto,Kinugasa, Motoharu,Oku, Akira
-
p. 7080 - 7090
(2007/10/03)
-
- Chiral diazaborolidine-mediated enantioselective aldol reactions of phenylthioacetate esters
-
Methodology is described for the enantioselective conversion of achiral aldehydes by anti-selective aldol reaction to chiral β-hydroxy-α-phenylthio esters and aldehydes. (C) 2000 Elsevier Science Ltd.
- Corey,Choi, Soongyu
-
p. 2769 - 2772
(2007/10/03)
-
- Methods for treating depression and other disorders using optically pure R (-) fluoxetine and monoamine oxidase inhibitor
-
A method and composition are utilizing the pure R(-) isomer of fluoxetine which is a potent antidepressant and appetite suppressant substantially free of adverse effects. In addition, a method and composition are disclosed utilizing the pure R(-) isomer of fluoxetine which is useful to treat migraine headaches, pain, in particular chronic pain, psychoactive substance abuse disorders and obsessive compulsive disorders.
- -
-
-
- Stereoselective synthesis of 4-alkoxy-3-methylidenealkanols using reactions between 2-(1-alkoxyalkyl)propenylstannanes and aldehydes: X-ray crystal structure of (1R,4R)-3-methylidene-1-(4-nitrophenyl)-pentane-1,4-diol
-
The 2-(1-hydroxy- and 1-alkoxy-alkyl)propenylstannanes 9 and 11-15, react with aldehydes to form 4-hydroxy- and 4-alkoxy-3-methylidenealkanols 23, 24 and 36-53. The stereoselectivity of these reactions has been investigated. If the reactions are carried out by transmetallation of the stannane using a tin(IV) halide before addition of the aldehyde, modest stereoselectivity in favour of the 1,4-anti-products 23, 36 and 37 is observed for the hydroxystannane 9, whereas the alkoxystannanes 11-15 give rise preferentially to the 1,4-syn-diastereoisomers 47-53, selectivity 75-85:25-15. It should be noted that these stereochemical assignments are the reverse of those reported in the preliminary communication on this work. The structure of the 1,4-anti-product 36 from the reaction between the hydroxystannane 9 and p-nitrobenzaldehyde was established by X-ray diffraction. The stereoselectivity of BINOL-titanium(IV) catalysed reactions of the (R)-SEM-stannane (R)-12 with benzaldehyde is controlled by the configuration of the BINOL and can be used to synthesize either the 1,4-anti- or 1,4-syn-isomers 40 and 47.
- Almendros, Pedro,Gruttadauria, Michelangelo,Helliwell, Madeleine,Thomas, Eric J.
-
p. 2549 - 2560
(2007/10/03)
-
- Highly efficient enzymatic resolution of homoallyl alcohols leading to a simple synthesis of optically pure fluoxetine and related compounds
-
A practical method for enzymatic resolution of homoallyl alcohols and its utility in the synthesis of optically pure fluoxetine and related compounds is reported.
- Master, Hosang E.,Newadkar,Rane,Kumar, Ashok
-
p. 9253 - 9254
(2007/10/03)
-
- Effective 1,5-asymmetric induction in tin(IV) chloride promoted reactions between aldehydes and (4-alkoxy-2-alkenyl)tributylstannanes
-
Transmetallation of (S)-4-benzyloxy-2-pentenyl(tributyl)stannane (1) using tin(IV) chloride generates an allyltin trichloride which reacts in situ with aldehydes to give 1-substituted syn-(3Z)-5-benzyloxyhexenols with excellent stereoselectivity. With chiral aldehydes, the stereoselectivity of the reaction is dominated by the reagent, except for 2-alkoxyaldehydes which show matching and mismatching consistent with preferred Felkin-Anh diastereofacial selectivity.
- McNeill,Thomas
-
p. 322 - 334
(2007/10/02)
-
- Methods and compositions for treating depression using optically pure fluoxetine
-
A method and composition are disclosed utilizing the pure S(+) isomer of fluoxetine, which is a potent antidepressant substantially free of adverse toxic or psychological effects, having a rapid onset of action and a high response rate.
- -
-
-
- Highly enantioselective routes to Darzens and acetate aldol products from achiral aldehydes and t-butyl bromoacetate
-
New methodology is described for the enantioselective coupling of t-butyl bromoacetate with aldehydes to give anti-α-bromo β-hydroxy esters (1), useful precursors of chiral glycidic esters (2), acetate aldols (3), β-amino acid esters (4) and α-amino acid
- Corey,Choi
-
p. 2857 - 2860
(2007/10/02)
-
- ALDOL REACTIONS IN POLYPROPIONATE SYNTHESIS: HIGH ?-FACE SELECTIVITY OF ENOL BORINATES FROM α-CHIRAL METHYL AND ETHYL KETONES UNDER SUBSTRATE CONTROL.
-
Use of (c-C6H11)2BCl in the anti-selective aldol reaction of the α-chiral ethylketone 2 leads to high stereoselectivity (>94percent) for the 1,2-anti-2,4-anti isomer 7.The related α-chiral methylketone aldol reaction, 8 9, proceeds with 84-93percent d
- Paterson, Ian,Goodman, Jonathan M.,Isaka, Masahiko
-
p. 7121 - 7124
(2007/10/02)
-
- Asymmetric Synthesis of Both Enantiomers of Tomoxetine and Fluoxetine. Selective Reduction of 2,3-Epoxycinnamyl Alcohol with Red-Al.
-
Both enantiomers of tomoxetine 7a,7b and fluoxetine 8a,8b (as their hydrochloride salts) have been synthetized from cinnamyl alkohol by asymmetric epoxidation, and their absolute configurations have been established.Optimal conditions for regioselective Red-Al reduction at C-2 of 2,3-epoxycinnamyl alcohol are discussed.
- Gao, Y.,Sharpless, K. B.
-
p. 4081 - 4084
(2007/10/02)
-
- ELUCIDATION OF STEREOSPECIFITY OF A SELENIUM-CONTAINING HYDROGENASE FROM METHANOCOCCUS VANNIELLII - SYNTHESIS OF (R)- AND (S)--3,4-DIHYDRO-7-HYDROXY-1-HYDROXYETHYLQUINOLINE
-
To elucidate the stereospecifity of the selenium-containing hydrogenase from Methanococcus vannielii, (R)- and (S)--3,4-dihydro-7-hydroxy-1-hydroxyethylquinoline were syntheside as authentic samples for comparison with the compound which was deri
- Teshima, Tadashi,Nakaji, Akira,Shiba, Tetsuo,Tsai, Lin,Yamazaki, Shigeko
-
p. 351 - 354
(2007/10/02)
-
- ASYMMETRIC REDUCTION OF PROCHIRAL HYDROXY KETONES WITH A CHIRAL REDUCING AGENT PREPARED FROM TIN(II) CHLORIDE, A CHIRAL DIAMINE, AND DIISOBUTYLALUMINUM HYDRIDE
-
Asymmetric reduction of prochiral α- and β-hydroxy ketones with a reagent, generated from tin(II) chloride, a chiral diamine, and diisobutylaluminum hydride, afforded the corresponding dihydroxy compounds in good chemical and optical yields.Optical yields depended on the nature of the protective groups of hydroxyl function.
- Mukaiyama, Teruaki,Tomimori, Koji,Oriyama, Takeshi
-
p. 1359 - 1362
(2007/10/02)
-