77877-25-9Relevant articles and documents
Stereoselective synthesis of oxazolidin-2-ones via an asymmetric aldol/curtius reaction: Concise total synthesis of (?)-cytoxazone
Choi, Hosam,Choi, Joohee,Jang, Hanho,Lee, Kiyoun
, (2021/06/14)
Herein, we are reporting an efficient approach toward the synthesis of 4,5-disubstituted oxazolidin-2-one scaffolds. The developed approach is based on a combination of an asymmetric aldol and a modified Curtius protocol, which uses an effective intramolecular ring closure to rapidly access a range of oxazolidin-2-one building blocks. This strategy also permits a straightforward and concise asymmetric total synthesis of (?)-cytoxazone. Consisting of three steps, this is one of the shortest syntheses reported to date. Ultimately, this convenient platform would provide a promising method for the early phases of drug discovery.
Synthesis of γ-Lactones via the kowalski homologation reaction: Protecting-group-free divergent total syntheses of eupomatilones-2,5,6, and 3- epi-eupomatilone-6
Choi, Hosam,Jang, Hanho,Kim, Hyoungsu,Lee, Kiyoun
supporting information, p. 7857 - 7862 (2019/10/11)
A highly efficient synthesis of functionalized chiral γ-butyrolactone scaffolds has been described. The basis of the approach is the Kowalski ester homologation that is modified for our proposed transformation. The newly developed methodology combines a d
Lithium Amino Alkoxide-Evans Enolate Mixed Aggregates: Aldol Addition with Matched and Mismatched Stereocontrol
Jermaks, Janis,Tallmadge, Evan H.,Keresztes, Ivan,Collum, David B.
supporting information, p. 3077 - 3090 (2018/03/08)
Building on structural and mechanistic studies of lithiated enolates derived from acylated oxazolidinones (Evans enolates) and chiral lithiated amino alkoxides, we found that amino alkoxides amplify the enantioselectivity of aldol additions. The pairing of enantiomeric series affords matched and mismatched stereoselectivities. The structures of mixed tetramers showing 2:2 and 3:1 (alkoxide-rich) stoichiometries are determined spectroscopically. Rate and computational studies provide a viable mechanistic and stereochemical model based on the direct reaction of the 3:1 mixed tetramers, but they raise unanswered questions for the 2:2 mixed aggregates.
Application of the silicon-tether strategy for controlling the regioselectivity and diastereoselectivity of intramolecular nitrone cycloadditions for aminopolyol synthesis
Ishikawa, Teruhiko,Kudo, Takayuki,Shigemori, Kazunori,Saito, Seiki
, p. 7633 - 7637 (2007/10/03)
Highly regioselective and diastereoselective intramolecular chiral nitrone cycloaddition reactions with a vinyl group tethered by a silicon atom have been developed as a general method for the synthesis of stereodefined amino polyols. This strategy featur
An Activated Germanium Metal-Promoted, Highly Diastereoselective Reformatsky Reaction
Kagoshima, Hirotaka,Hashimoto, Yukihiko,Oguro, Dai,Saigo, Kazuhiko
, p. 691 - 697 (2007/10/03)
Activated germanium metal, prepared by the reduction of germanium(II) iodide with potassium metal, was found to promote the Reformatsky reaction effectively under mild conditions. In the presence of activated germanium metal, the reactions of α-bromo ketones 2a and 2b and α-bromo imides 2e and 2f with benzaldehyde (1a) proceeded smoothly to give the corresponding β-hydroxy carbonyl compounds 3a, 3b, 3e and 3f, respectively, in good yields and with good syn diastereo- selectivity. The activated germanium metal-promoted, asymmetric Reformatsky reaction of enantiomerically pure-oxazolidinone derivatives 2g-j with various aldehydes 1a-d was also examined; the highest diastereoselectivity was achieved when (1S,2R)-2-amino-1,2-diphenylethanol- derived 2j was used as the Reformatsky donor. The excellent diastereoselectivity could be explained in terms of the formation of a chairlike, six-membered transition state between the aldehyde and enolate as in the Zimmerman-Traxler model. A single recrystallization of the Reformatsky adducts, followed by hydrolysis and subsequent esterification, led to enantiomerically pure methyl 3-hydroxy- 2-methylalkanoates 10j-m, with almost quantitative recovery of the enantiomerically pure 2-oxazolidinone 14.
Bifunctional chiral auxiliaries 7: Aldol reactions of enolates derived from 1,3-diacylimidazolidine-2-thiones and 1,3-diacylimidazolidin-2-ones
Davies,Edwards,Evans,Mortlock
, p. 6621 - 6642 (2007/10/02)
Dibutylboron enolates of 1,3-diacylimidazolidine-2-thiones and 1,3-diacylimidazolidin-2-ones undergo highly syn-stereoselective aldol reactions with aldehydes to allow elaboration of both acyl sidechains. The reaction is proposed to occur via sequential e
Asymmetric Aldol Reactions. Use of the Titanium Enolate of a Chiral N-Acyloxazolidinone To Reverse Diastereofacial Selectivities
Nerz-Stormes, Maryellen,Thornton, Edward R.
, p. 2489 - 2498 (2007/10/02)
Aldol reactions of the titanium enolate of (S)-N-propionyl-4-isopropyl-2-oxazolidinone (readily derived from L-valine) with representative aldehydes give high diastereofacial selectivities for the syn aldol adducts expected from chelation control.This represents a remarkable reversal in selectivity compared with the corresponding boron enolate, thus permitting either enantiomeric form of β-hydroxy-α-methyl carboxylic acids to be made from a single, readily available oxazolidinone simply by changing the metal.A lithium interference effect is shown to be easily prevented by use of excess titanium.Use of diethyl ether as solvent rather than THF significantly enhances the stereoselectivity.Mechanistically, the observed stereochemical reversal constitutes very strong evidence that chelation is operative with titanium, presumably through a chelated chairlike transition structure.In this transition structure, the conformation would be rigidly locked by chelation and the titanium would be at least hexacoordinate, resulting in a "superaxial" ligand, thus nicely explaining the high stereocontrol.
Bifunctional chiral auxiliaries 3: Synthesis of homochiral 1,3-diols via asymmetric aldol reactions of dialkylboron enolates of 1,3-dipropionyl-trans-4,5-diphenyl-imidazolidin-2-one and aldehydes
Davies,Mortlock
, p. 1001 - 1004 (2007/10/02)
Dibutylboron enolates derived from both racemic and homochiral 1,3-dipropionyl-trans-4,5-diphenylimidazolidin-2-one 3 react with aldehydes in highly diastereoselective dialdol reactions to give, after reductive cleavage of the acyl sidechain, substituted 1,3 diols.
HIGHLY STEREOSELECTIVE REFORMATSKY REACTIONS OF 3-(2-BROMOPROPIONYL)-2-OXAZOLIDONE DERIVATIVES WITH VARIOUS ALDEHYDES
Ito, Yoshio,Terashima, Shiro
, p. 2821 - 2834 (2007/10/02)
The Reformatsky reactions of 3-(2-bromopropionyl)-2-oxazolidone derivatives with various aldehydes were investigated to elucidate the effects of substituents in the 2-oxazolidone moieties on their diastereoselectivities.The highest 2,3-syn-diastereoselect
ASYMMETRIC ALDOL REACTIONS. MECHANISM OF SOLVENT EFFECT ON STEREOSELECTIVITY IS SPECIFIC, STOICHIOMETRIC BINDING OF TETRAHYDROFURAN TO A CHIRAL TITANIUM ENOLATE
Shirodkar, Shailaja,Nerz-Stormes, Maryellen,Thornton, Edward R.
, p. 4699 - 4702 (2007/10/02)
Solvent plays an important role in aldol reactions of an acyloxazolidinone-derived titanium enolate.Diethyl ether produces nearly fivefold higher diastereofacial selectivity than THF.We now show that this strong solvent effect arises from stoichiometric binding, most probably to the titanium, of THF in the transition structure, whereas ether is not bound.These mechanistic results indicate that THF lowers the selectivity by interfering with chelation control, which is highly preferred in ether.Implications include the possibility of using other ethers to improve chelation/nonchelation control still more, or even use of chiral ethers as chiral controller groups or adjuncts.
