155320-73-3Relevant academic research and scientific papers
Highly enantioselective synthesis of syn- and anti-propionate aldols without diastereoselection in the chiral oxazaborolidinone-promoted aldol reaction with a silyl ketene acetal derived from ethyl 2- (methylthio)propionate
Hena, Mostofa Abu,Terauchi, Saori,Kim, Chul-Sa,Horiike, Michio,Kiyooka, Syun-Ichi
, p. 1883 - 1890 (1998)
A mixture of syn- and anti-aldol products containing an α-methylthio group were obtained in good yields with high enantioselectivities in the chiral oxazaborolidinone-promoted aldol reactions of a novel silyl ketene acetal, derived from ethyl 2-(methylthio)propionate, with aldehydes. Subsequent desulfurization resulted in an effective preparation of essentially enantiopure syn- and anti-propionate aldols which were separable.
A practical synthesis of essentially enantiopure syn-propionate aldols using a chiral oxazaborolidinone-promoted asymmetric aldol reaction coupled with radical reduction
Kiyooka, Syun-ichi,Shahid, Kazi A.,Hena, Mostofa A.
, p. 6447 - 6449 (1999)
Essentially enantiopure syn-propionate aldols (>98% ee) were prepared by a chiral oxazaborolidinone-promoted asymmetric aldol reaction, followed by a diastereoselective radical reduction with Bu3SnH and Et3B, which was carried out un
Biotransformation of aromatic ketones and ketoesters with the non-conventional yeast Pichia glucozyma
Contente, Martina Letizia,Molinari, Francesco,Zambelli, Paolo,De Vitis, Valerio,Gandolfi, Raffaella,Pinto, Andrea,Romano, Diego
supporting information, p. 7051 - 7053 (2015/02/02)
The non-conventional yeast Pichia glucozyma CBS 5766 has been used for the biotransformation of different aromatic ketones and ketoesters. The growth and biotransformation conditions were optimised for the reduction of acetophenone and under optimised conditions, propiophenone, butyrophenone and valerophenone were reduced to the corresponding (S)-alcohols with high yields and enantioselectivity. Ketoreductase(s) of Pichia glucozyma showed high catalytic activities also towards aromatic β- and γ-ketoesters, being often competitive with esterase(s). These concurrent activities allowed for the preparation of hydroxyesters, hydroxyacids and lactones often in a very selective manner.
Diastereoselective radical debromination approach toward divergent syntheses of syn- and anti-propionate units, coupled with enantioselective and/or diastereoselective Lewis acid-promoted aldol reactions
Kiyooka, Syun-Ichi
, p. 2897 - 2910 (2007/10/03)
A practical methodology directed to the enantioselective synthesis of polypropionate backbones, available for the synthesis of polyketide natural products, has been developed by iterative enantio- and diastereoselective Lewis acid-promoted aldol reactions, followed by diastereoselective radical debromination reactions. A chiral oxazaborolidinone-promoted aldol reaction of a racemic aldehyde, derived from 2-methyl-1,3-propanediol, with a silylketene acetal from ethyl 2-bromopropionate, resulted in highly enantioselective formation of the corresponding bromo aldol adduct, followed by radical debromination with Bu3SnH in the presence of Et3B to divergently give syn- and anti-propionate aldols, which are versatile stereotriads. Furthermore, elongation of the propionate units has also been achieved: the BF3·OEt2-promoted aldol reaction of chiral syn- and anti-α-methyl-β-protected-oxy aldehydes with the silyl nucleophile proceeded with essentially complete syn-selectivity while the TiCl4-promoted aldol reaction resulted in fairly good anti-selectivity. The resulting bromo aldol adducts were divergently debrominated by the radical reduction to give a complete set of stereotetrads.
Enantio- and diastereoselective reductive aldol reactions with iridium-pybox catalysts
Zhao, Cun-Xiang,Duffey, Matthew O.,Taylor, Steven J.,Morken, James P.
, p. 1829 - 1831 (2007/10/03)
(formula presented) A catalytic amount of [(cod)IrCl]2 and indane-pybox converts diethylmethylsilane, methyl acrylate, and certain aldehydes to the derived reductive aldol adduct with good enantio- and diastereocontrol.
A divergent synthesis of essentially enantiopure syn- and anti-propionate aldol adducts based on the chiral 1,3,2-oxazaborolidin-5-one-promoted asymmetric aldol reaction followed by diastereoselective radical reduction
Kiyooka,Shahid
, p. 1485 - 1495 (2007/10/03)
Essentially, enantiopure syn- and anti-propionate aldol adducts were divergently synthesized using a novel strategy which utilizes both the highly enantioselective 1,3,2-oxazaborolidin-5-one-promoted aldol reaction with a ketene silyl acetal derived from ethyl 2-bromo propionate and a highly diastereoselective radical debromination reaction. These procedures provide yields that increase to a level available for practical synthesis.
Superior substrate control on diastereoselection in boric Lewis acid-promoted aldol reactions. Asymmetric synthesis of a 3,4-syn homologous series of ethyl 3,5-dihydroxy-2,4-dimethyl-5-phenylpentanoates
Kiyooka, Syun-ichi,Shahid, Kazi A.,Murai, Kazunori,Li, Yong-Nan,Okazaki, Momotoshi,Shuto, Yoshihiro
, p. 2343 - 2349 (2007/10/03)
The BF3·OEt2-promoted aldol reaction of chiral syn- and anti-α-methyl-β-siloxy aldehydes with a silyl ketene acetal resulted in essentially complete syn Felkin selection. Even in the asymmetric aldol reaction using chiral oxazaboroli
Synthesis of W-propionylated (S)-(-)-2-(pyrrolidin-2-yl)propan2-ol and its use as a chiral auxiliary and selectivity marker in asymmetric aldol reactions
Hedenstroem, Erik,Andersson, Fredrik,Hjalmarsson, Mats
, p. 1513 - 1518 (2007/10/03)
The N-propionylated pyrrolidine derivative and chiral auxiliary, (S)-(-)-2-(pyrrolidin-2-yl)propan-2-ol, was synthesised and used in stereoselective aldol reactions with benzaldehyde. Differences in stereoselectivity were investigated as a function of temperature, solvent, chelating agent and the amount of the chelating agent used by monitoring the 1H NMR spectra of the aldol adducts that were obtained. Among the additives that were investigated, Cp2ZrCl2 induced higher syn-selectivity, while SnCl2 induced higher syn-selectivity respectively. TMSCl was found to induce high selectivity for one syn- and one anti-diastereomer. Varying the ligand sets on titanium additives was found to induce differences in selectivity, with (i-PrO)3TiCl exhibiting syn-selectivity and Cp2TiCl2 exhibiting anti-selectivity. Differences in reactivity and stereoselectivity were also found to depend upon the amount of Lewis acid that was added. Methods for removal of the auxiliary were also investigated. Acidic hydrolysis was used successfully to obtain the desired 3-hydroxy-2-methyl-3-phenylpropionic acids, but was found to give low yields and resulted in a large amount of epimerisation. Furthermore, the ethyl esters of these hydroxy acids are easy to separate into pure syn- and anti-diastereomers by LC. The Royal Society of Chemistry 2000.
Enantioselective aldol reaction using bornane-2,3-diol-aluminum complex as a chiral Lewis acid
Shimizu, Makoto,Kawamoto, Manabu,Yamamoto, Yasushi,Fujisawa, Tamotsu
, p. 501 - 502 (2007/10/03)
β-Hydroxy ester was formed in high enantiomeric excess by the reaction of ketene silyl acetal with aldehyde in the presence of a chiral Lewis acid prepared from diethylaluminum chloride and chiral diol derived from (+)-camphor.
Chelation-Controlled Protocol for the Diastereoselective Reduction of Ketones
Sarko, Christopher R.,Guch, Ian C.,DiMare, Marcello
, p. 705 - 706 (2007/10/02)
A new chelation-controlled, α-chiral ketone reduction protocol is presented based on titanium tetrachloride and a wide variety of reducing agents.Features of the proposed intermediate titanium chelates necessary to obtain high diastereoselectivity are dis
