- The Synthesis of Chiral Allyl Carbamates via Merger of Photoredox and Nickel Catalysis
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A mild, and versatile, organophotoredox/Ni-mediated protocol was developed for the direct preparation of diverse, enantioenriched allyl carbamates. The reported approach represents a significant departure from classical step-by-step synthesis of allyl carbamates. This dual photoredox/Ni based strategy offers unrivalled capacity for convergent unification of readily available alkyl halides and chiral carbamates derived from 1-bromo-alken-3-ols with high chemoselectivity and efficiency. The reported photoredox/Ni catalyzed cross-coupling reaction is not limited to carbamates, but also to other O-derivatives such as esters, ethers, acetals, carbonates or silyl ethers. To demonstrate the utility of the reported protocol, the resulting allyl carbamates were transformed into functionalized non-racemic allylamines through a sigmatropic rearrangement reaction in enantiospecific manner. This approach allowed for synthesis of enantiomeric allylamines by a simple control of the geometry of a double bond of allyl carbamates. (Figure presented.).
- Garbacz, Mateusz,Stecko, Sebastian
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p. 3213 - 3222
(2020/07/06)
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- The synthesis of non-racemic β-alkyl-β-aryl-disubstituted allyl alcohols and their transformation into allylamines and amino acids bearing a quaternary stereocenter
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A synthesis of non-racemic β-alkyl-β-aryl allyl alcohols and their transformation into allylamines bearing a quaternary stereogenic center is reported. The allyl alcohols were prepared either by Cu-catalyzed enantioselective reduction of enones or by sequ
- Narczyk, Aleksandra,Pieczykolan, Micha?,Stecko, Sebastian
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supporting information
p. 3921 - 3946
(2018/06/08)
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- Ester Synthesis in Water: Mycobacterium smegmatis Acyl Transferase for Kinetic Resolutions
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The acyl transferase from Mycobacterium smegmatis (MsAcT) catalyses transesterification reactions in aqueous media because of its hydrophobic active site. Aliphatic cyanohydrin and alkyne esters can be synthesised in water with excellent and strikingly opposite enantioselectivity [(R);E>37 and (S);E>100, respectively]. When using this enzyme, the undesired hydrolysis of the acyl donor is an important factor to take into account. Finally, the choice of acyl donor can significantly influence the obtained enantiomeric excesses. (Figure presented.).
- de Leeuw, Nicolas,Torrelo, Guzman,Bisterfeld, Carolin,Resch, Verena,Mestrom, Luuk,Straulino, Emanuele,van der Weel, Laura,Hanefeld, Ulf
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p. 242 - 249
(2017/11/16)
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- Chemoenzymatic total synthesis of paecilocin A and 3-butyl-7- hydroxyphthalide
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A highly enantioselective total synthesis of paecilocin A and 3-butyl-7-hydroxyphthalide is described. The key steps involved in this synthesis are enzymatic kinetic resolution and Alder-Rickert reaction.
- Sreelakshmi, Ch.,Bhaskar Rao,Lakshmi Narasu,Janardhan Reddy,Reddy, B.V. Subba
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p. 1303 - 1305
(2014/03/21)
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- One-pot deracemization of sec-alcohols: Enantioconvergent enzymatic hydrolysis of alkyl sulfates using stereocomplementary sulfatases
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Hand in hand: The title transformation was achieved using a pair of sulfatases acting through inversion and retention of configuration on opposite substrate enantiomers. Using Pseudomonas aeruginosa arylsulfatase PAS with alkylsulfatase PISA1 in one-pot l
- Schober, Markus,Toesch, Michael,Knaus, Tanja,Strohmeier, Gernot A.,Van Loo, Bert,Fuchs, Michael,Hollfelder, Florian,Macheroux, Peter,Faber, Kurt
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supporting information
p. 3277 - 3279
(2013/04/23)
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- First stereoselective total synthesis of pectinolide H
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The stereoselective total synthesis of bio-active pectinolide H (1) is described. Midland's asymmetric reduction, Sharpless dihydroxylation reactions are involved in generating the stereogenic centers at C-4′, C-5 and C-1′. Other key steps in the synthesi
- Ramesh,Shekhar,Chantibabu,Rajaram,Ramulu,Venkateswarlu
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scheme or table
p. 1258 - 1260
(2012/03/27)
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- A stereoselective inverting sec -alkylsulfatase for the deracemization of sec -alcohols
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A metallo-β-lactamase-type alkylsulfatase was found to catalyze the enantioselective hydrolysis of sec-alkylsulfates with strict inversion of configuration. This catalytic event, which does not have an analog in chemocatalysis, yields homochiral (S)-configurated alcohols and nonreacted sulfate esters. The latter could be converted into (S)-sec-alcohols as the sole product in up to >99% ee via a chemoenzymatic deracemization protocol on a preparative scale.
- Schober, Markus,Gadler, Petra,Knaus, Tanja,Kayer, Heidemarie,Birner-Gruenberger, Ruth,Guelly, Christian,MacHeroux, Peter,Wagner, Ulrike,Faber, Kurt
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supporting information; experimental part
p. 4296 - 4299
(2011/10/08)
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- First stereoselective total synthesis of gallicynoic acids G and H
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A stereoselective convergent total synthesis of two acetylenic acids, gallicynoic acid G (1) and H (2), is reported, involving asymmetric reduction of alkynones 3 and 4, respectively, with the Corey- Bakshi-Sibata (CBS) catalyst as a key step (Scheme 3), 3 and 4 being obtained from a common intermediate, the chiral alkynol 12 (Scheme 2). Copyright
- Radha Krishna, Palakodety,Anitha, Kadimi
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p. 1246 - 1253
(2011/09/14)
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- Asymmetric synthesis and sensory evaluation of sedanenolide
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The synthesis and sensory evaluation of enantiomeric sets of sedanenolide (1) and 3-butylphthalide (3) are described. The asymmetric synthesis was achieved via the intramolecular Diels-Alder reaction of chiral propargylester (5) which was prepared from optically active propargyl alcohol (4) and 2,4-pentadienoic acid. The sensory evaluation of these enantiomers revealed that there were distinct differences between their aroma character and odor threshold.
- Oguro, Daichi,Watanabe, Hidenori
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experimental part
p. 1502 - 1505
(2011/11/04)
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- Synthesis and use of stereospecifically deuterated analogues of palmitic acid to investigate the stereochemical course of the Δ11 desaturase of the processionary moth
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Thaumetopoea pityocampa pheromone glands contain desaturases that, after several sequential reactions from palmitic acid, catalyze the formation of a unique enyne fatty acid, which is the immediate sex pheromone precursor. In this article, we describe the synthesis of different stereospecifically deuterium-labeled and isotopically tagged palmitic acid probes needed to decipher the stereochemical course of the T. pityocampa Δ11 desaturase. The synthesis of probes has been carried out by a chemoenzymatic route, in which the key step is the kinetic lipase-catalyzed resolution of racemic mixtures of secondary propargyl alcohols. The presence of the acetylenic bond simplifies the absolute configuration determination of the resolved alcohols. Moreover, it allows the introduction of the isotopic tag by deuteration. By use of the probes thus prepared, experimental evidence is presented that the Δ11 desaturase of T. pityocampa transforms palmitic acid into (Z)-11-hexadecenoic acid by removal of the pro-(R)-hydrogen atoms from both C11 and C12.
- Abad, Jose-Luis,Villorbina, Gemma,Fabrias, Gemma,Camps, Francisco
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p. 7108 - 7113
(2007/10/03)
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- Studies on Pd(II)-catalyzed coupling-cyclization of α- or β-amino allenes with allylic halides
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The palladium-catalyzed coupling-cyclization of α- or β-amino allenes with allylic halides leading to 3-allylic 2,5-dihydropyrroles and 1,2,3,6-tetrahydropyridines, respectively, was studied. The starting materials are easily available. The skeletons of b
- Ma, Shengming,Yu, Fei,Gao, Wenzhong
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p. 5943 - 5949
(2007/10/03)
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- The effect of catechin derivatives on the enantioselectivity of lipase-catalyzed hydrolyses of alkynol benzoate esters
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Polyphenols, such as (+)-catechin and pyrogallol could be used to enhance stereochemical control in the lipase-catalyzed hydrolysis of alkynol benzoate esters, leading to increased enantioselectivities in the kinetic resolution of alkynols with lipase Amano AH.
- Nakamura, Kaoru,Takenaka, Keishi
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p. 415 - 422
(2007/10/03)
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- Synthesis of chiral 3-substituted phthalides via rhodium(I)-catalyzed crossed alkyne cyclotrimerisation
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3-Substituted phthalides were synthesized for the first time by crossed alkyne cyclotrimerisations with Wilkinson's catalyst. Esterification of propiolic acids with chiral propargylic alcohols by either the DCC/DMAP or the Mitsunobu method allows the synt
- Witulski, Bernhard,Zimmermann, Axel
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p. 1855 - 1859
(2007/10/03)
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- Mutation of cysteine-295 to alanine in secondary alcohol dehydrogenase from thermoanaerobacter ethanolicus affects the enantioselectivity and substrate specificity of ketone reductions
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The mutation of Cys-295 to alanine in Thermoanaerobacter ethanolicus secondary alcohol dehycrogenase (SADH) was performed to give C295A SADH, on the basis of molecular modeling studies utilizing the X-ray crystal structure coordinates of the highly homologous T. brockii secondary alcohol dehydrogenase (YKF.PDB). This mutant SADH has activity for 2-propanol comparable to wild-type SADH. However, the C295A mutation was found to cause a significant shift of enantioselectivity toward the (S)-configuration in the reduction of some ethynylketones to the corresponding chiral propargyl alcohols. This result confirms our prediction that Cys-295 is part of a small alkyl group binding pocket whose size determines the binding orientation of ketone substrates, and, hence, the stereochemical configuration of the product alcohol. Furthermore, C295A SADH has much higher actifity towards t-butyl and some α-branched ketones than does wild-type SADH. The C295A mutation does not affect the thioester reductase activity of SADH. The broader substrate specificity and altered stereoselectivity for C295A SADH make it a potentially useful tool for asymmetric reductions. Copyright
- Heiss, Christian,Laivenieks, Maris,Zeikus,Phillips, Robert S.
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p. 1659 - 1666
(2007/10/03)
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- Asymmetric synthesis of umuravumbolide1
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(equation presented) This first asymmetric synthesis of enantiopure desacetylumuravumbolide and umuravumbolide via asymmetric reduction, allylboration, and ring-closing metathesis confirms their revised structures and configurations. A convenient procedure to upgrade the enantiopurity of α,β-acetylenic alcohols is also described.
- Venkat Ram Reddy,Rearick, John P.,Hoch, Nyssa,Veeraraghavan Ramachandran
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- Optically active propargylic and allylic alcohols with a difluoromethyl group at the terminal carbon
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Enantioselective esterification of α-substituted propargylic alcohols was found to proceed very smoothly in the presence of a catalytic amount of lipase (Nobozym 435) to yield the corresponding (R)-alcohols and (S)-acetates with high enantiomeric excess. Further, the preparation of optically active propargylic and allylic alcohols with a difluoromethyl group at the terminal carbon is described.
- Xiao, Ling,Kitazume, Tomoya
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p. 3597 - 3601
(2007/10/03)
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- Highly stereoselective total syntheses of (+)-allopumiliotoxins 267A and 339A via intramolecular nickel(II)/chromium(II)-mediated cyclization
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Remarkably high regio- and stereoselective approaches for the syntheses of dendrobatid alkaloids (+)allopumiliotoxin 267A and 339A have been develop. As a model study for these alkaloids, we initially undertook intramolecular chromium(II)-mediated cycliza
- Aoyagi, Sakae,Wang, Tzu-Chueh,Kibayashi, Chihiro
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p. 11393 - 11409
(2007/10/02)
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