An alternative approach to (S)- and (R)-2-methylglycidol O-benzyl ether derivatives
摘要:
This report describes the gram scale synthesis of (S)- and (R)-2,2,4-trimethyl-4-(hydroxymethyl)-1,3-dioxolanes using the Sharpless asymmetric dihydroxylation (AD) of the Weinreb amide of 2-methyl-2-propenoic acid. The 2-methylglycerol acetonides resultant from protection of the AD products were used as starting materials in the synthesis of O-benzyl ethers of the valuable C4-chiral building blocks (S)- and (X)-2-methylglycidol. (C) 2001 Elsevier Science Ltd. All rights reserved.
Asymmetric Dihydroxylation of Esters and Amides of Methacrylic, Tiglic, and Angelic Acid: No Exception to the Sharpless Mnemonic!
作者:Fabian Weber、Reinhard Brückner
DOI:10.1002/ejoc.201403622
日期:2015.4
are contradictory and partly in conflict with the Sharpless mnemonic. We systematically screened the SAD of esters and amides of angelic, tiglic, and methacrylic acid. Enantiocontrol arose in 14 of the 15 reactions, culminating at 99 % ee for the Weinreb amide of tiglicacid. The absolute configurations of all the nonracemic products were established by (stereo)chemical correlations. Without exception
Asymmetric dihydroxylation (AD) of N,N-dialkyl and N-methoxy-N-methyl α,β- and β,γ-unsaturated amides
作者:Youssef L. Bennani、K.Barry Sharpless
DOI:10.1016/s0040-4039(00)60350-7
日期:1993.3
The asymmetricdihydroxylation of α,β- and β,γ-unsaturated amides affords the corresponding diols in good yields and excellent enantiomeric excesses. However, both N,N-diakyl and N-methoxy-N-methyl α,β and β,γ-unsaturated amides require a Modified-AD-mix™ formulation to achieve good catalytic turnover rates
Enantioselective Total Syntheses of (<i>R</i>)- and (<i>S</i>)-Naphthotectone, and Stereochemical Assignment of the Natural Product
作者:Guillermo A. Guerrero-Vásquez、Flávia A. D. Galarza、José M. G. Molinillo、Carlos Kleber Z. Andrade、Francisco A. Macías
DOI:10.1002/ejoc.201501479
日期:2016.3
core of the final products was obtained by a late-stage anodic treatment. (R)-Naphthotectone was obtained in six steps from leuconaphthazarin with an overall yield of 38 % and an enantiomeric excess of 86 %. This compound was found to have the same absolute configuration as the natural product at its C-3′ stereogenic center. (S)-Naphthotectone was obtained in five steps from leuconaphthazarin with an
S<sub>N</sub>2 vs. E2 on quaternary centres: an application to the synthesis of enantiopure β<sup>2,2</sup>-amino acids
作者:Alberto Avenoza、Jesús H. Busto、Francisco Corzana、Gonzalo Jiménez-Osés、Jesús M. Peregrina
DOI:10.1039/b400282b
日期:——
SN2 and E2 competing reactions in cyclic sulfamidates can be modulated by the change of an amide group to an ester group attached to the quaternary carbon activated for the nucleophilic attack, allowing an easy approach to enantiopure α,α-disubstituted β-amino acids.
An efficient synthesis of the 1,6-dioxaspiro[4.4]nonan-2-one motif of the immunosuppressive triterpenoid Phainanoid F
作者:Chen-Lu Zhang、Fa-Jun Nan
DOI:10.1016/j.tetlet.2017.09.091
日期:2017.11
We describe an efficient synthesis of the 1,6-dioxaspiro[4.4]nonan-2-one motif of the immunosuppressive triterpenoid Phainanoid F and its C4 epimer. A furan oxidative spirocyclization for constructing the spiro center was used as the key step. Other important reactions involved Sharpless asymmetric dihydroxylation, Weinreb ketone synthesis and Yamaguchi esterfication. The synthesis was achieved in