16046-10-9Relevant articles and documents
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Soderquist,J.A.,Thompson,K.L.
, p. 237 - 249 (1978)
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β-Keto esters derived from 2-(trimethylsilyl)ethanol: An orthogonal protective group for β-keto esters
Knobloch, Eva,Brueckner, Reinhard
experimental part, p. 2229 - 2246 (2009/04/08)
β-Keto esters derived from 2-(trimethylsilyl)ethanol undergo cleavage and decarboxylation when treated with 0.75 equivalents of tetrabutylammonium fluoride trihydrate in tetrahydrofuran at 50°C, while β-keto esters derived from methanol, tert-butyl alcohol, allyl alcohol, or benzyl alcohol stay intact. Conversely, methyl-, tert-butyl-, allyl-, or benzyl β-keto esters can be cleaved and decarboxylated without the 2-(trimethylsilyl)ethyl β-keto esters being affected. Similarly, mixed bis(β-keto esters) derived from 2-(trimethylsilyl)ethanol and methanol, tert-butyl alcohol, allyl alcohol, or benzyl alcohol can be defunctionalized chemoselectively under the same reaction conditions. Georg Thieme Verlag Stuttgart.
Effects of Volume and Surface Property in Hydrolysis by Acetylcholinesterase. The Trimethyl Site
Cohen, Saul G.,Elkind, Jerome L.,Chishti, S. Bano,Giner, Jose-L. P.,Reese, Heide,Cohen, Jonathan B.
, p. 1643 - 1647 (2007/10/02)
β-Substituted ethyl acetates, XCH2CH2OCOCH3, have been prepared, and their hydrolysis by acetylcholinesterase has been studied.Log of enzymic reactivity, normalized for intrinsic reactivity in hydrolysis by hydroxide, log(kcat/Km)n, rises linearly with increasing refraction volume, MR (or RD25), for substrates with β-X = H, Cl, Br, CH3CH2, (CH3)2CH, (CH3)2S+, (CH3)3N+, and (CH3)3C.Larger substituents may by accommodated, (CH3)3Si and (CH3CH2)3N+, with no further increase in rate.Substrates with β-substituents CH3S, CH3S(O), (CH3)3N+(OH), and CH3S(O2) are less reactive than consistent with the relation with MR by factors of 5-40, indicating that hydrophobic surface and desolvation of the substrate-enzyme interface may be necessary for maximum reactivity correlated with MR.Values of log (kcat/Km)n for substrates with β-substituents X = CH3S, Cl, Br, CH3CH2, (CH3)2CH, (CH3)3C, and (CH3)3Si rise linearly with increasing hydrophobicity, ?, but reactivity of substrates with X = (CH3)3N+ and (CH3)2S+ are more reactive than consistent with a relation to ? by factors of 300 and 40 and with X = CH3S(O2), CH3S(O), and (CH3)2N+(OH), by factors of 7-100.Reactivity appears related to (i) volume of the β-substituent and its fit in its subsite, which is trimethyl rather than anionic, and (ii) the hydrophobicity of its surface.