- MnO2as a terminal oxidant in Wacker oxidation of homoallyl alcohols and terminal olefins
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Efficient and mild reaction conditions for Wacker-type oxidation of terminal olefins of less explored homoallyl alcohols to β-hydroxy-methyl ketones have been developed by using a Pd(ii) catalyst and MnO2 as a co-oxidant. The method involves mild reaction conditions and shows good functional group compatibility along with high regio- and chemoselectivity. While our earlier system of PdCl2/CrO3/HCl produced α,β-unsaturated ketones from homoallyl alcohols, the present method provided orthogonally the β-hydroxy-methyl ketones. No overoxidation or elimination of benzylic and/or β-hydroxy groups was observed. The method could be extended to the oxidation of simple terminal olefins as well, to methyl ketones, displaying its versatility. An application to the regioselective synthesis of gingerol is demonstrated.
- Fernandes, Rodney A.,Ramakrishna, Gujjula V.,Bethi, Venkati
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p. 6115 - 6125
(2020/10/27)
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- Aldolase Cascade Facilitated by Self-Assembled Nanotubes from Short Peptide Amphiphiles
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Early evolution benefited from a complex network of reactions involving multiple C?C bond forming and breaking events that were critical for primitive metabolism. Nature gradually chose highly evolved and complex enzymes such as lyases to efficiently facilitate C?C bond formation and cleavage with remarkable substrate selectivity. Reported here is a lipidated short peptide which accesses a homogenous nanotubular morphology to efficiently catalyze C?C bond cleavage and formation. This system shows morphology-dependent catalytic rates, suggesting the formation of a binding pocket and registered enhancements in the presence of the hydrogen-bond donor tyrosine, which is exploited by extant aldolases. These assemblies showed excellent substrate selectivity and templated the formation of a specific adduct from a pool of possible adducts. The ability to catalyze metabolically relevant cascade transformations suggests the importance of such systems in early evolution.
- Afrose, Syed Pavel,Das, Dibyendu,Reja, Antara
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supporting information
p. 4329 - 4334
(2020/02/05)
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- Breaking the Dogma of Aldolase Specificity: Simple Aliphatic Ketones and Aldehydes are Nucleophiles for Fructose-6-phosphate Aldolase
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d-Fructose-6-phosphate aldolase (FSA) was probed for extended nucleophile promiscuity by using a series of fluorogenic substrates to reveal retro-aldol activity. Four nucleophiles ethanal, propanone, butanone, and cyclopentanone were subsequently confirmed to be non-natural substrates in the synthesis direction using the wild-type enzyme and its D6H variant. This exceptional widening of the nucleophile substrate scope offers a rapid entry, in good yields and high stereoselectivity, to less oxygenated alkyl ketones and aldehydes, which was hitherto impossible.
- Roldán, Raquel,Sanchez-Moreno, Israel,Scheidt, Thomas,Hélaine, Virgil,Lemaire, Marielle,Parella, Teodor,Clapés, Pere,Fessner, Wolf-Dieter,Guérard-Hélaine, Christine
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supporting information
p. 5005 - 5009
(2017/04/18)
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- The effect of the hydrophobic environment on the retro-aldol reaction: Comparison to a computationally-designed enzyme
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Recent work on a computationally-designed retroaldolase RA-61 suggested that most of the rate-acceleration brought about by this enzyme was due to non-specific interactions with the aromatic substrate. To provide a benchmark for the role of non-specific interactions in this system, we measured the second-order rate constant for the amine-catalysed retro-aldol reaction of methodol in the presence of non-specific hydrophobic pockets such as micelles. We found that a simple micellar system, that consists of a positively-charged surfactant and a long-chain amine, can accelerate the retro-aldol reaction of methodol by 9500-fold. This effect rivals the 105-fold rate acceleration of RA-61. Similar results were obtained with BSA used as the catalyst, implying that the retro-aldol reaction of methodol can be greatly accelerated by non-specific hydrophobic pockets that contain an amino group.
- Schmidt, Joshua,Ehasz, Clayton,Epperson, Michael,Klas, Kimberly,Wyatt, Justin,Hennig, Mirko,Forconi, Marcello
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p. 8419 - 8425
(2013/12/04)
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- Aldolase activity of serum albumins
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Bovine and human serum albumins catalyze the aldol reaction of aromatic aldehyedes and acetone, with saturation kinetics and moderate and opposite enantioselectivity. The reaction occurs at the binding site in domain IIa, and is inhibited by warfarin. Kin
- Benedetti, Fabio,Berti, Federico,Bidoggia, Silvia
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supporting information; experimental part
p. 4417 - 4420
(2011/07/31)
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- A fluorogenic aldehyde bearing a 1,2,3-triazole moiety for monitoring the progress of aldol reactions
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We have developed a new type of fluorogenic aldehyde bearing a 1,2,3-triazole moiety that is useful for monitoring the progress of aldol reactions through an increase in fluorescence. Whereas 6-methoxy-2naphthaldehyde was highly fluorescent, the fluorogenic aldehyde, 4-formylbenzene connected to the 6-methoxy-2-naphthyl group through a 1,2,3-triazole moiety, was essentially nonfluorescent in aqueous solutions. We suggest that the 4-formylphenyl group acts as a quencher to suppress the fluorescence of the 6-methoxy-2- naphthyltriazole moiety. The product of the aldol reaction of this aldehyde does not have a quenching moiety and showed more than 800-fold higher fluorescence than the aldehyde. Assay systems using the fluorogenic aldehyde were validated by screening of aldol catalysts, ranking of the activities of the catalysts, and evaluation of reaction conditions.
- Guo, Hai-Ming,Tanaka, Fujie
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supporting information; experimental part
p. 2417 - 2424
(2009/07/18)
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- Direct organocatalytic aldol reactions in buffered aqueous media
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Organocatalytic cross-aldol reactions catalyzed by cyclic secondary amines in aqueous media provide a direct route to a variety of aldols including carbohydrate derivatives and may warrant consideration as a prebiotic route to sugars.
- Cordova, Armando,Notz, Wolfgang,Barbas III, Carlos F.
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p. 3024 - 3025
(2007/10/03)
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- Process research and structural studies on nabumetone
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A short, simple and economical process for large-scale preparation of nabumetone has been developed. The single-crystal structures of nabumetone and one of its key intermediates have been determined by X-ray diffraction studies. Two impurities have been isolated and characterised.
- Prabhakar,Reddy, C. Bakki,Reddy, Ch. Maheedhara,Nageshwar,Devi, A. Sivalakshmi,Babu, J. Moses,Vyas,Sarma,Reddy
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p. 121 - 125
(2013/09/08)
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