22436-06-2Relevant articles and documents
Highly stereoselective α-alkylations, 1,4-additions, and one-pot 1,4-addition/α-methylations achieved on 4-O-acyl and 4-O-crotonyl derivatives of methyl 6-deoxy-2,3-di-O-(t-butyldimethylsilyl)-α-D-glucopyranoside
Totani,Asano,Takao,Tadano
, p. 1772 - 1776 (2001)
Benzylation or methylation of the enolate generated from 4-O-propionyl or 4-O-3-phenyl-propionyl derivatives of methyl 6-deoxy-2,3-di-O-(t-butyldimethylsilyl)-α-D-glucopyranoside provided the respective C-alkylated product stereoselectively. The 1,4-additions of a variety of carbon nucleophiles to the corresponding 4-O-crotonyl derivative provided adducts with high and complementary diastereoselection. The one-pot 1,4-additions of a phenyl nucleophile to the 4-O-crotonyl ester followed by the addition of methyl iodide provided vicinally substituted products with high diastereo- and enantioselectivity, from which diastereomeric α-methyl-β-phenylbutanols were obtained in enantioenriched form after reductive removal of the carbohydrate template.
A drop of enantioselectivity in the Pseudomonas cepacia lipase-catalyzed ester hydrolysis is influenced by the chain length of the fatty acid
Tafi, Andrea,Manetti, Fabrizio,Botta, Maurizio,Casati, Silvana,Santaniello, Enzo
, p. 2345 - 2350 (2004)
A two-step molecular mechanics based computational procedure has been applied to explain the enantioselectivity observed in the hydrolysis of esters of primary alcohols, carried out in the presence of a lipase from Pseudomonas cepacia. This approach proved to be very effective in explaining an unpredictable drop in enantioselectivity, experimentally observed when the chain of the fatty acid was lengthened and to predict the chain length in correspondence of which the effect should have revealed itself.
Diastereoselective Alkylation Reactions Employing a Camphor-Based Chiral Oxazinone Auxialiary
Ahn, Kyo Han,Lim, Ankee,Lee, Seungkyu
, p. 2435 - 2436 (1993)
An almost complete ?-face selectivity is obtained in asymmetric alkylation reactions of lithium enolates derived from imide 2 which contains a camphor-based chiral auxialiary.
Your mother was right, washing matters: An alkyne-analog of ibuprofen reveals unwanted reactivity of aromatic compounds with proteins during copper-catalyzed click chemistry
Cutolo, Giuliano,Pratt, Matthew R.,Shankar, Sahiti N.
, (2021/07/19)
Bioorthogonal chemistry, in particular the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), has enabled the robust identification of covalent protein targets of probes and drugs. Ibuprofen is commonly used pain and fever reducer and is sold as an enantiomeric racemate. Interestingly, the stereoisomers can be enzymatically converted through an ibuprofen-CoA thioester intermediate, which might non-specifically react with protein nucleophiles. Here, we use an alkyne-analog of ibuprofen to make two discoveries. First, we find that ibuprofen likely does not result in notable chemical labeling of proteins. However, we secondly find that aromatic compounds can react with proteins during the CuAAC reaction unless they are appropriately washed out of the mixture. This second discovery of false positive labeling has important technical implications for the application of this approach.
A Water/Toluene Biphasic Medium Improves Yields and Deuterium Incorporation into Alcohols in the Transfer Hydrogenation of Aldehydes
Ruiz-Casta?eda, Margarita,Santos, Lucía,Manzano, Blanca R.,Espino, Gustavo,Jalón, Félix A.
, p. 1358 - 1372 (2021/03/16)
Deuterium labeling is an interesting process that leads to compounds of use in different fields. We describe the transfer hydrogenation of aldehydes and the selective C1 deuteration of the obtained alcohols in D2O, as the only deuterium source. Different aromatic, alkylic and α,β-unsaturated aldehydes were reduced in the presence of [RuCl(p-cymene)(dmbpy)]BF4, (dmbpy=4,4′-dimethyl-2,2′-bipyridine) as the pre-catalyst and HCO2Na/HCO2H as the hydrogen source. Moreover, furfural and glucose, were selectively reduced to the valuable alcohols, furfuryl alcohol and sorbitol. The processes were carried out in neat water or in a biphasic water/toluene system. The biphasic system allowed easy recycling, higher yields, and higher selective D incorporation (using D2O/toluene). The deuteration took place due to an efficient effective M–H/D+ exchange from D2O that allows the inversion of polarity of D+ (umpolung). DFT calculations that explain the catalytic behavior in water are also included.
Highly efficient NHC-iridium-catalyzed β-methylation of alcohols with methanol at low catalyst loadings
Lu, Zeye,Zheng, Qingshu,Zeng, Guangkuo,Kuang, Yunyan,Clark, James H.,Tu, Tao
, p. 1361 - 1366 (2021/06/30)
The methylation of alcohols is of great importance since a broad number of bioactive and pharmaceutical alcohols contain methyl groups. Here, a highly efficient β-methylation of primary and secondary alcohols with methanol has been achieved by using bis-N-heterocyclic carbene iridium (bis-NHC-Ir) complexes. Broad substrate scope and up to quantitative yields were achieved at low catalyst loadings with only hydrogen and water as by-products. The protocol was readily extended to the β-alkylation of alcohols with several primary alcohols. Control experiments, along with DFT calculations and crystallographic studies, revealed that the ligand effect is critical to their excellent catalytic performance, shedding light on more challenging Guerbet reactions with simple alcohols. [Figure not available: see fulltext.].
