- Evaluation of gem-Diacetates as Alternative Reagents for Enzymatic Regio-and Stereoselective Acylation of Alcohols
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Geminal diacetates have been used as sustainable acyl donors for enzymatic acylation of chiral and nonchiral alcohols. Especially, it was revealed that geminal diacetates showed higher reactivity than vinyl acetate for hydrolases that are sensitive to acetaldehyde. Under optimized conditions for enzymatic acylation, several synthetically relevant saturated and unsaturated acetates of various primary alcohols were obtained in very high yields up to 98% without E/Z isomerization of the double bond. Subsequently, the acyl donor was recreated from the resulting aldehyde and reused constantly in acylation. Therefore, the developed process is characterized by high atomic efficiency. Moreover, it was shown that acylation using geminal diacetates resulted in remarkable regioselectivity by discriminating among the primary and secondary hydroxyl groups in 1-phenyl-1,3-propanediol providing exclusively 3-acetoxy-1-phenyl-propan-1-ol in good yield. Further, enzymatic kinetic resolution (EKR) and chemoenzymatic dynamic kinetic resolution (DKR) protocols were developed using geminal diacetate as an acylating agent, resulting in chiral acetates in high yields up to 94% with enantiomeric excesses exceeding 99%.
- Koszelewski, Dominik,Brodzka, Anna,Madej, Arleta,Trzepizur, Damian,Ostaszewski, Ryszard
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p. 6331 - 6342
(2021/05/06)
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- Hypervalent Iodine-Based Activation of Triphenylphosphine for the Functionalization of Alcohols
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The use of hypervalent iodine reagents as a general tool for the activation of PPh 3 and its application to the functionalization of alcohols is reported. Combination of PPh 3 with PhICl 2 or TolIF 2 gives dihalophosphoranes that are characterized by 31 P NMR, however, with PhIOAc 2, PhI(OTFA) 2, or the cyclic chloro(benzoyloxy)iodane, no phosphoranes were observed. Reaction of these iodanes with PPh 3 in the presence of primary, secondary, or tertiary alcohols results in either halogenation or acyl-transfer products in moderate to high yield.
- Eljo, Jasmin,Carle, Myriam S.,Murphy, Graham K.
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supporting information
p. 2871 - 2875
(2017/10/06)
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- An efficient one-pot synthesis of unsymmetrical ethers: A directly reductive deoxygenation of esters using an InBr3/Et3SiH catalytic system
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(Chemical Equation Presented) This study describes a novel one-pot procedure for a directly reductive conversion of the carbonyl function of esters to the corresponding ethers by Et3SiH in the presence of a catalytic amount of InBr3.
- Sakai, Norio,Moriya, Toshimitsu,Konakahara, Takeo
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p. 5920 - 5922
(2008/02/09)
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- Scandium(III) trifluoromethanesulfonate catalyzed aromatic nitration with inorganic nitrates and acetic anhydride
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The rare earth metal(III) trifluoromethanesulfonate (rare earth metal(III) triflate, RE(OTf)3) was found to be an efficient catalyst for aromatic nitration with carboxylic anhydride-inorganic nitrate as the nitrating agent. In the presence of a catalytic amount of RE(OTf)3, the nitration of substituted benzenes proceeded to afford the corresponding nitrobenzenes. Especially, scandium(III) trifluoromethanesulfonate (scandium(III) triflate, Sc(OTf)3) is the most active catalyst among our tested Lewis acids. It was also found that acetic anhydride-Al(NO 3) · 9H2O is the most active nitrating agent in this system.
- Kawada, Atsushi,Takeda, Shigemitsu,Yamashita, Kazumi,Abe, Hitoshi,Harayama, Takashi
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p. 1060 - 1065
(2007/10/03)
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- 2-Arylindoles as gonadotropin releasing hormone (GnRH) antagonists: Optimization of the tryptamine side chain
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A series of 2-arylindoles containing novel heteroaromatic substituents on the tryptamine tether, based on compound 1, was prepared and evaluated for their ability to act as gonadotropin releasing hormone (GnRH) antagonists. Successful modifications of 1 included chain length variation (reduction) and replacement of the pyridine with heteroaromatic groups. These alterations culminated in the discovery of compound 27kk which had excellent in vitro potency and oral efficacy in rodents.
- Young, Jonathan R.,Huang, Song X.,Walsh, Thomas F.,Wyvratt Jr., Matthew J.,Yang, Yi Tien,Yudkovitz, Joel B.,Cui, Jisong,Mount, George R.,Ren, Rena Ning,Wu, Tsuei-Ju,Shen, Xiaolan,Lyons, Kathryn A.,Mao, An-Hua,Carlin, Josephine R.,Karanam, Bindhu V.,Vincent, Stella H.,Cheng, Kang,Goulet, Mark T.
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p. 827 - 832
(2007/10/03)
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- Chemical compounds
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A novel class of protecting compounds, particularly for amino acids, is based on 2,2 di nitrophenyl ethan- groups, particularly the groups wherein the nitro is in the para position. The ethyl group may be substituted, e.g. by an alkyl group, in the l- position. Preferred compounds include the alcohol or halide which are suitable for protecting acid functional groups, and esters, including activated and substituted esters, particularly the succinimidyl ester, for protecting amine groups. The invention includes methods of manufacture and use, together with protected amino acids.
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- Substituent Effects. XVI. Acetolysis of 2-Phenylethyl Tosylates
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The acetolysis rates of 2-arylethyl tosylates were determined for a series of aryl substituents.The non-linear substituent effect was reasonably accounted for on the basis of two linear LArSR relationships; one for the aryl-assisted (FkΔ) and one for the unassisted (Ks) process, respectively.A precise dissection of the apparent substituent effect into individual effects for both processes was achieved in this manner.The substituent effect on the ks process can be described as a linear function of ?0 with a small ρs of -0.19, and that on the FkΔ process in terms of the LArSR Eq., with a ρΔ=-3.87 and an rΔ=0.631.The use of ?+ for the FkΔ process failed to give any reasonable dissection.The r value for this FkΔ process is essentially identical to that for the neophyl solvolysis.The unique r value oh 0.6 is concluded to be characteristic of β-aryl-assisted ionization processes in general.
- Fujio, Mizue,Funatsu, Kimito,Goto, Mutsuo,Seki, Yoji,Mishima, Masaaki,Tsuno, Yuho
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p. 1091 - 1096
(2007/10/02)
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- Nucleotide. XIV. Substituierte β-Phenylaethyl-Gruppen. Neue Schutzgruppen fuer Oligonucleotid-Synthesen nach dem Phosphorsaeuretriester-Verfahren
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Various o- and p-substituted β-phenylethanols (2-10) have been synthesized and investigated as blocking groups in the phosphotriester approach.A large number of 5'-O-tritylated thymidine-3'-phosphotriesters (13-36) with two different phosphate protecting groups have been prepared, characterized, and studied according to their chemical stability and usefullness for oligonucleotide syntheses.The combination of a 5'-O-monomethoxytrityl- and a 3'-(2,5-dichlorophenyl, p-nitrophenylethyl)-phosphate function as in 18 turned out to possess optimal properties as a monomeric nucleotide building block due to the fact that these blocking groups can be quantitatively and selectively be removed without harming each other by trifluoroacetic acid in chloroform to 41, by oximate to 42, and by DBU to 43.The base-catalyzed removal of the monosubstituted phenylethyl groups by DBU or DBN respectively as well as the disubstituted phenylethyl groups by triethylamine in aprotic solvents is a β-elimination process leading to phosphodiesters without attack on the P-center.
- Uhlmann, Eugen,Pfleiderer, Wolfgang
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p. 1688 - 1703
(2007/10/02)
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