- Strategic vinyl sulfone nucleophile β-substitution significantly impacts selectivity in Vinylogous Darzens and aza-Darzens reactions
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Vinylogous Darzens and aza-Darzens reactions employing a benzothiophene 1,1-dioxide nucleophile are reported. These new [2 + 1] annulation reactions, which proceed under mild reaction conditions, are γ-selective, affording trans-epoxides selectively and favoring trans-aziridines. The reactions are base-dependent, with KOtBu and Cs2CO3 being optimal for aldehyde and imine annulations, respectively. Comparison of the benzothiophene nucleophile to its acyclic counterpart reveals superior performance in the case of aldehydes, while the outcome varies depending on the sulfonamide imine used.
- Delost, Michael D.,Njardarson, Jon T.
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supporting information
p. 6917 - 6921
(2020/09/12)
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- Biocatalytic reduction of α,β-unsaturated carboxylic acids to allylic alcohols
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We have developed robust in vivo and in vitro biocatalytic systems that enable reduction of α,β-unsaturated carboxylic acids to allylic alcohols and their saturated analogues. These compounds are prevalent scaffolds in many industrial chemicals and pharmaceuticals. A substrate profiling study of a carboxylic acid reductase (CAR) investigating unexplored substrate space, such as benzo-fused (hetero)aromatic carboxylic acids and α,β-unsaturated carboxylic acids, revealed broad substrate tolerance and provided information on the reactivity patterns of these substrates. E. coli cells expressing a heterologous CAR were employed as a multi-step hydrogenation catalyst to convert a variety of α,β-unsaturated carboxylic acids to the corresponding saturated primary alcohols, affording up to >99percent conversion. This was supported by the broad substrate scope of E. coli endogenous alcohol dehydrogenase (ADH), as well as the unexpected CC bond reducing activity of E. coli cells. In addition, a broad range of benzofused (hetero)aromatic carboxylic acids were converted to the corresponding primary alcohols by the recombinant E. coli cells. An alternative one-pot in vitro two-enzyme system, consisting of CAR and glucose dehydrogenase (GDH), demonstrates promiscuous carbonyl reductase activity of GDH towards a wide range of unsaturated aldehydes. Hence, coupling CAR with a GDH-driven NADP(H) recycling system provides access to a variety of (hetero)aromatic primary alcohols and allylic alcohols from the parent carboxylates, in up to >99percent conversion. To demonstrate the applicability of these systems in preparative synthesis, we performed 100 mg scale biotransformations for the preparation of indole-3-aldehyde and 3-(naphthalen-1-yl)propan-1-ol using the whole-cell system, and cinnamyl alcohol using the in vitro system, affording up to 85percent isolated yield.
- Aleku, Godwin A.,Leys, David,Roberts, George W.
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p. 3927 - 3939
(2020/07/09)
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- Enantioselective α-Benzylation of Acyclic Esters Using π-Extended Electrophiles
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The first asymmetric cooperative Lewis base/palladium catalyzed benzylic alkylation of acyclic esters is reported. This reaction proceeds via stereodefined C1-ammonium enolate nucleophiles. Critical to its success was the identification of benzylic phosphate electrophiles, which were uniquely reactive. Alkylated products were obtained with very high levels of enantioselectivity, and this method has been applied toward the synthesis of the thrombin inhibitor DX-9065a.
- Schwarz, Kevin J.,Yang, Chao,Fyfe, James W. B.,Snaddon, Thomas N.
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supporting information
p. 12102 - 12105
(2018/09/11)
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- Preliminary SAR on indole-3-carbinol and related fragments reveals a novel anticancer lead compound against resistant glioblastoma cells
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The prognosis for glioblastoma patients is, at best, poor, with the median time of survival after diagnosis measured in months. As such, there is much need for the rapid development of potent and novel treatments. Herein, we report our preliminary findings on the SAR of a series of indole-3-carbinol and related fragments and reveal a potent lead with low micromolar activity against a particularly resistant glioblastoma cell culture, providing a new platform for future development of a new therapy in this area.
- Sherer, Christopher,Tolaymat, Ibrahim,Rowther, Farzana,Warr, Tracy,Snape, Timothy J.
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supporting information
p. 1561 - 1565
(2017/03/16)
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- Umpolung of protons from H2O: A metal-free chemoselective reduction of carbonyl compounds: Via B2pin2/H2O systems
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H2O is routinely described as a proton donor, however, in the presence of diboron compounds, the umpolung reaction of H2O under metal-free conditions was successfully developed, which could afford hydride species, leading to a highly efficient and chemoselective reduction of CO bonds. This strategy exhibits excellent chemoselectivities toward carbonyl groups in the presence of ester, olefin, halogen, thioether, sulfonyl, cyano as well as heteroaromatic groups.
- Xuan, Qingqing,Zhao, Cong,Song, Qiuling
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supporting information
p. 5140 - 5144
(2017/07/11)
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- Simplifying nickel(0) catalysis: An air-stable nickel precatalyst for the internally selective benzylation of terminal alkenes
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The synthesis and characterization of the air-stable nickel(II) complex trans-(PCy2Ph)2Ni(o-tolyl)Cl is described in conjunction with an investigation of its use for the Mizoroki-Heck-type, room temperature, internally selective coupling of substituted benzyl chlorides with terminal alkenes. This reaction, which employs a terminal alkene as an alkenylmetal equivalent, provides rapid, convergent access to substituted allylbenzene derivatives in high yield and with regioselectivity greater than 95:5 in nearly all cases. The reaction is operationally simple, can be carried out on the benchtop with no purification or degassing of solvents or reagents, and requires no exclusion of air or water during setup. Synthesis of the precatalyst is accomplished through a straightforward procedure that employs inexpensive, commercially available reagents, requires no purification steps, and proceeds in high yield.
- Standley, Eric A.,Jamison, Timothy F.
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supporting information
p. 1585 - 1592
(2013/03/14)
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- Palladium-catalyzed asymmetric benzylation of azlactones
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Asymmetric benzylation of prochiral azlactone nucleophiles enables the catalytic introduction of a benzyl group towards the synthesis of α,α-disubstituted amino acids. Herein, we report an enantioselective palladium-catalyzed process using chiral bis(diphenylphosphinobenzoyl)diamine (dppba) ligands. Naphthalene- and heterocycle-based methyl carbonates react with a number of azlactones derived from both natural and unnatural amino acids. Monocyclic benzylic electrophiles, for which the barrier to ionization is higher, must employ a phosphate leaving group in order to react. Reaction conditions for electron-rich and -neutral benzylic electrophiles have been developed, and the scope of the reaction has been explored with respect to both reaction partners. The high levels of asymmetric induction, as well as the reactivity pattern of the electrophiles, suggest an η3-benzyl intermediate that arises through two distinct pathways. Attack on benzyl: Palladium-catalyzed asymmetric benzylation methodology is demonstrated on prochiral azlactone nucleophiles. The use of naphthyl, heterocyclic, and monocyclic benzylic electrophiles demonstrates the wide reaction scope (see scheme; Cp=cyclopentadienyl). The benzylation products are readily converted into enantioenriched α,α-disubstituted amino acids.
- Trost, Barry M.,Czabaniuk, Lara C.
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supporting information
p. 15210 - 15218
(2013/11/06)
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- Bacterial dioxygenase- and monooxygenase-catalysed sulfoxidation of benzo[b]thiophenes
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Asymmetric heteroatom oxidation of benzo[b]thiophenes to yield the corresponding sulfoxides was catalysed by toluene dioxygenase (TDO), naphthalene dioxygenase (NDO) and styrene monooxygenase (SMO) enzymes present in P. putida mutant and E. coli recombinant whole cells. TDO-catalysed oxidation yielded the relatively unstable benzo[b]thiophene sulfoxide; its dimerization, followed by dehydrogenation, resulted in the isolation of stable tetracyclic sulfoxides as minor products with cis-dihydrodiols being the dominant metabolites. SMO mainly catalysed the formation of enantioenriched benzo[b]thiophene sulfoxide and 2-methyl benzo[b]thiophene sulfoxides which racemized at ambient temperature. The barriers to pyramidal sulfur inversion of 2- and 3-methyl benzo[b]thiophene sulfoxide metabolites, obtained using TDO and NDO as biocatalysts, were found to be ca.: 25-27 kcal mol-1. The absolute configurations of the benzo[b]thiophene sulfoxides were determined by ECD spectroscopy, X-ray crystallography and stereochemical correlation. A site-directed mutant E. coli strain containing an engineered form of NDO, was found to change the regioselectivity toward preferential oxidation of the thiophene ring rather than the benzene ring.
- Boyd, Derek R.,Sharma, Narain D.,McMurray, Brian,Haughey, Simon A.,Allen, Christopher C. R.,Hamilton, John T. G.,McRoberts, W. Colin,More O'Ferrall, Rory A.,Nikodinovic-Runic, Jasmina,Coulombel, Lydie A.,O'Connor, Kevin E.
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scheme or table
p. 782 - 790
(2012/02/05)
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- Discrete iron complexes for the selective catalytic reduction of aromatic, aliphatic, and α,β-unsaturated aldehydes under water-gas shift conditions
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Iron-catalyzed reductions: Selective iron-catalyzed reduction of aldehydes with hydrogen generated in situ by the water-gas shift reaction is presented (see scheme). The generality and selectivity of this mild procedure are demonstrated by the efficient reduction of various aromatic, aliphatic and α,β-unsaturated aldehydes.
- Tlili, Anis,Schranck, Johannes,Neumann, Helfried,Beller, Matthias
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p. 15935 - 15939
(2013/02/21)
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- Structure-activity relationships for a novel series of dopamine D2-like receptor ligands based on N-substituted 3-aryl-8-azabicyclo[3.2.1]octan-3-ol
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Discovering dopamine D2-like receptor subtype-selective ligands has been a focus of significant investigation. The D2R-selective antagonist 3-[4-(4-chlorophenyl)-4-hydroxypiperidinyl]methylindole (1, L741,626; K i(D2R/D3R) = 11.2:163 nM) has previously provided a lead template for chemical modification. Herein, analogues have been synthesized where the piperidine was replaced by a tropane ring that reversed the selectivity seen in the parent compound, in human hD2LR- or hD3R-transfected HEK 293 cells (31, Ki(D2R/D3R) = 33.4: 15.5 nM). Further exploration of both N-substituted and aryl ring-substituted analogues resulted in the discovery of several high affinity D2R/D3R ligands with 3-benzofurylmethyl-substituents (e.g., 45, Ki(D2R/D3R) = 1.7:0.34 nM) that induced high affinity not achieved in similarly N-substituted piperidine analogues and significantly (470-fold) improved D3R binding affinity compared to the parent ligand 1. X-ray crystallographic data revealed a distinctive spatial arrangement of pharmacophoric elements in the piperidinol vs tropine analogues, providing clues for the diversity in SAR at the D2 and D3 receptor subtypes.
- Paul, Noel M.,Taylor, Michelle,Kumar, Rakesh,Deschamps, Jeffrey R.,Luedtke, Robert R.,Newman, Amy Hauck
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experimental part
p. 6095 - 6109
(2009/10/01)
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- PIPERIDINONES USEFUL IN THE TREATMENT OF INFLAMMATION
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There is provided compounds of formula (I): wherein R1, R2, R3, R4, R5, R6, R7, m and n have meanings given in the description, and pharmaceutically acceptable derivatives thereof, which compounds are useful in the treatment of diseases and conditions associated with inflammation.
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Page/Page column 110-111
(2008/12/07)
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- Piperidine derivatives having anxiolytic effect
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Piperidine compounds having the general formula (I), STR1 wherein R 1 is a group having general formula (II), STR2 wherein X is CHR 10, O, S, SO, SO 2 or NR 10, Z 1 is CH 2, O, or S; Z 2 and Z 3 are independently (CH 2) n, n being 0 or 1, O or S or Z 1 and Z 2 may together represent a group --CH CH--; or when Z 3 is (CH 2) n wherein n is 0, Z 1 and Z 2 may together represent a 3-membered divalent group; show potent sigma receptor activity. Furthermore they show effect in animal models indicative of anxiolytic properties. Accordingly they are useful as medicines for the treatment of anxiety, psychosis, epilepsy, convulsion, movement disorders, motor disturbances, amnesia, cerebrovascular diseases, senile demential of the Alzheimer type or Parkinson''s disease.
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