36060-85-2Relevant articles and documents
Chemo- and Enantioselective Pd/B Hybrid Catalysis for the Construction of Acyclic Quaternary Carbons: Migratory Allylation of O-Allyl Esters to α- C-Allyl Carboxylic Acids
Fujita, Taiki,Yamamoto, Tomohiro,Morita, Yuya,Chen, Hongyu,Shimizu, Yohei,Kanai, Motomu
supporting information, p. 5899 - 5903 (2018/05/14)
We describe herein the asymmetric synthesis of α-allyl carboxylic acids containing an α-quaternary stereocenter by a chiral hybrid catalyst system comprising palladium and boron complexes. The reaction proceeded through palladium-catalyzed ionization of α,α-disubstituted O-allyl esters for the generation of chiral π-allyl palladium complex as an electrophile, boron-catalyzed enolization of the carboxylate part for the generation of chiral α,α-disubstituted carboxylic acid-derived enolates as a nucleophile, and enantioselective coupling between the thus-generated nucleophile and electrophile. Proper combinations of chiral ligands for the boron and palladium catalysts were crucial. The reaction proceeded chemoselectively at the α-position of the carboxylic acid group.
Chiral 1,2,4-triazoles: stereoselective acylation and chlorination
Katritzky, Alan R.,Fedoseyenko, Dmytro,Kim, Myong S.,Steel, Peter J.
experimental part, p. 51 - 57 (2010/04/24)
Acyl groups are transferred from diverse N- and O-acyl derivatives of chiral 3,5-bis-(1-hydroxyethyl)-[1,2,4]-triazole to amino acid esters enantioselectively, with 7% to 68% ee, depending on the temperature conditions and nature of the reagents. Thionyl
An efficient synthesis of new 2-aminomethyl-1,3,4-oxadiazoles from enantiomeric phenylglycine hydrazides
Kudelko, Agnieszka,Zieliński, Wojciech
experimental part, p. 1200 - 1206 (2009/04/10)
New derivatives of 2-aminomethyl-1,3,4-oxadiazole were synthesized in the reactions of N-protected phenylglycine hydrazides and triethyl orthoesters (orthoformate, orthoacetate, orthopropionate, orthobenzoate) in the presence of glacial acetic acid. Studies on the cleavage reactions of the acid-sensitive N-BOC and N-Ac 1,3,4-oxadiazoles are presented. Spectral characteristics of the compounds and attempts to elucidate the racemization phenomenon observed in products are also discussed.
Lipase activity of Lecitase Ultra: characterization and applications in enantioselective reactions
Mishra, Mithilesh Kumar,Kumaraguru, Thenkrishnan,Sheelu, Gurrala,Fadnavis, Nitin W.
experimental part, p. 2854 - 2860 (2010/04/05)
The general properties of Lecitase Ultra, a phospholipase manufactured and marketed by Novozymes, Denmark, have been studied after purification by ultrafiltration. The enzyme has a molecular mass of 35 KD, pH-optimum of 8.5, and appears to possess a single active site which exhibits both the lipase and phospholipase activities that increase in the presence of Ca2+ and Mg2+ ions. The enzyme is inhibited by heavy metal ions and surfactants, and does not accept p-nitrophenyl acetate and glycerol triacetate. Substrates, such as glycerol tributyrate and p-nitrophenyl palmitate, esters of N-acetyl-α-amino acids and α-hydroxy acids are readily accepted. Amino acids with aliphatic residues, such as alanine, isoleucine, and methionine, are hydrolyzed with high enantioselectivity for the l-enantiomer (E >100), but amino acids with aromatic residues such as phenylalanine and phenylglycine, and esters of α-hydroxy acids are hydrolyzed with low enantioselectivity (E = 1-5). Immobilization of the enzyme in a gelatin matrix (gelozyme) leads to a marginal improvement in the enantioselectivity for these substrates. However, a dramatic improvement in enantioselectivity is observed for ethyl 2-hydroxy-4-oxo-4-phenylbutyrate (E value increases from 4.5 to 19.5 with S-selectivity). Similarly, glycidate esters, such as ethyl trans-(±)-3-phenyl glycidate and methyl trans-(±)-3-(4-methoxyphenyl) glycidate, are selectively hydrolyzed with a remarkable selectivity towards the (2S,3R)-enantiomer providing unreacted (2R,3S)-glycidate esters (ee >99%, conversion 52-55%) by the immobilized enzyme.
Water-accelerated organometallic chemistry: Alkyne carboalumination - Sulfinimine addition and asymmetric synthesis of allylic amines
Wipf, Peter,Nunes, Ruth L.,Ribe, Seth
, p. 3478 - 3488 (2007/10/03)
Carboalumination of alkynes in the presence of catalytic CP2ZrCl2 and H2O affords vinyl-alane intermediates, which serve as nucleophiles in the subsequent addition to enantiomerically enriched (tertbutyl)- and (para-tolyl)
Efficient and selective cleavage of t-butoxycarbonyl group from carbamates and amides by CeCl3·7H2O-NaI
Yadav,Subba Reddy,Reddy, K. Srinivasa
, p. 468 - 470 (2007/10/03)
A highly selective cleavage of the t-butoxycarbonyl group has been achieved in high yields using CeCl3·7H2O-NaI in acetonitrile at ambient temperature under neutral conditions. This method is mild and compatible with a wide range of
On the economic application of DuPHOS rhodium(I) catalysts: A comparison of COD versus NBD precatalysts
Cobley, Christopher J,Lennon, Ian C,McCague, Raymond,Ramsden, James A,Zanotti-Gerosa, Antonio
, p. 7481 - 7483 (2007/10/03)
The effectiveness of cyclooctadiene and norbornadiene precatalysts of the type [Rh(DuPHOS)(diolefin)]BF4 in catalytic asymmetric hydrogenation of various prochiral olefins has been examined. In some of the systems studied, the NBD complex gave
Metal-catalyzed acyl transfer reactions of enol esters: Role of Y5(OiPr)13O and (thd)2Y(OiPr) as transesterification catalysts
Lin, Mei-Huey,RajanBabu
, p. 997 - 1000 (2007/10/03)
(equation presented) Primary and secondary alcohols react with vinyl or isopropenyl acetate at room temperature in the presence of catalytic amounts (0.05-1 mol percent) of Y5(OiPr)13O to give the corresponding esters. In selected cases, the yttrium catalyst promotes the selective O-acylation of amino alcohols without the formation of the amide. Enol esters also react with α-amino acid esters in the absence of a catalyst, at room temperature, to give the corresponding amides.
Pronase catalysed peptide syntheses
Lobell, Mario,Schneider, Manfred P.
, p. 319 - 325 (2007/10/03)
A mixture of proteases from Streptomyces griseus (pronase), displaying a very broad substrate tolerance in the hydrolysis of peptides, has been studied for the first time systematically regarding their substrate specificity in peptide synthesis. It is demonstrated that pronase can be employed successfully for the formation of dipeptides with yields up to 95%. Pronase has also been employed successfully as catalyst for the enzyme assisted synthesis of a hexapeptide.
Rational de novo design of NADH mimic for stereoselective reduction based on molecular orbital calculation
Eguchi, Tadashi,Fukuda, Miki,Toyooka, Yumiko,Kakinuma, Katsumi
, p. 705 - 714 (2007/10/03)
The methodology of rational design of NADH mimics in stereoselective reduction of carbonyl and imino groups based on molecular orbital calculation was described. The designed NADH mimics 1a and 1b were subjected to the reduction of benzoylformate and acetyliminophenylacetate. As expected from the calculations of the transition-states, the reduction with 1a proceeded with high stereoselectivity in both substrates, while 1b showed much lower chirality transfer.
