- Stereoselective synthesis of (-)-synparvolide B
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The stereoselective synthesis of (-)-synparvolide B, isolated from Syncolostemon parviflorus, has been accomplished from (S)-ethyl lactate. A 1,2-chelation controlled allylation, Sharpless asymmetric epoxidation, Brown asymmetric allylation and RCM reactions were used as the key steps.
- Sabitha, Gowravaram,Rao, Allu Senkara,Yadav, Jhillu Singh
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- Chiral tetraphenylethenes as novel dopants for calamitic and discotic liquid crystals
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Three series of novel chiral tetraphenylethenes have been prepared: citronellyl-derived ethers 1a, b, lactate-derived ethers 2d, g, h, i and lactate-derived esters 3a-c, e-h. Helical twisting powers (HTPs) were determined for those derivatives of 1-3, whi
- Schreivogel, Alina,Dawin, Ute,Baro, Angelika,Giesselmannb, Frank,Laschat, Sabine
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p. 484 - 494
(2010/04/05)
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- Scope and limitations of ether-directed, metal-catalysed aza-Claisen rearrangements; Improved stereoselectivity using non-coordinating solvents
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In an effort to understand and enhance the stereochemical outcome of the MOM-ether directed rearrangement of allylic trichloroacetimidates we have investigated various reaction conditions for this process. A range of Pd(ii) and other metal catalysts have been shown to effectively catalyse the rearrangement providing the subsequent allylic amides in high selectivity (up to 11: 1 ratio of diastereomers). The replacement of THF as a solvent in this reaction with non-coordinating solvents such as toluene has led to an enhancement of the directing effect resulting in a significant increase in the diastereoselective outcome (15: 1 ratio). The reaction was also carried out for the first time, using a highly coordinating ionic solvent which disrupts binding of the Pd(ii)-catalyst to the MOM-ether yielding the allylic amide in only moderate diastereoselectivity. These results provide further evidence for the ether directed aza-Claisen rearrangement of allylic trichloroacetimidates. The Royal Society of Chemistry 2006.
- Jamieson, Andrew G.,Sutherland, Andrew
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p. 2932 - 2937
(2008/02/09)
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- Stereoselective β-hydroxy-α-amino acid synthesis via an ether-directed, palladium-catalysed aza-Claisen rearrangement
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A highly diastereoselective synthesis of (2S,3S)-β-hydroxy-α- amino acids has been developed from enantiopure α-hydroxy acids using a MOM-ether-directed, palladium(II)-catalysed, aza-Claisen rearrangement of allylic acetimidates to effect the key step. This highly stereoselective process gave allylic amides in diastereomeric ratios of up to 14 : 1. Problems associated with the isolation of 1,3-products (anti-Claisen) from sterically demanding substrates via an in situ palladium(0)-catalysed rearrangement process were overcome by the addition of a re-oxidant, p-benzoquinone, leading to cleaner reactions and improved yields of the 3,3-products (Claisen). The target β-hydroxy-α-amino acids are an important class of natural products that are also components of more complex organic compounds with significant biological properties. The Royal Society of Chemistry 2005.
- Fanning, Kate N.,Jamieson, Andrew G.,Sutherland, Andrew
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p. 3749 - 3756
(2007/10/03)
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- A highly stereoselective ether directed palladium catalysed aza-Claisen rearrangement
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A highly stereoselective rearrangement of allylic trichloroacetimidates to allylic trichloroamides has been achieved using adjacent ether groups to direct facial coordination of the palladium(II) catalyst. The Royal Society of Chemistry 2005.
- Jamieson, Andrew G.,Sutherland, Andrew
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p. 735 - 736
(2007/10/03)
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- ALLYLIC ORGANOMETALLIC WAY TO CONTROL ACYCLIC STEREOCHEMISTRY AND ITS APPLICATION TO THE SYNTHESIS OF CARBOHYDRATES
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The Cram/anti-Cram selectivity in the reactions of allylmetals with aldehydes and the erythro/threo selectivity in the reactions of substituted allylic organometallic compounds with other aldehydes can be controlled by the metal (M).Based on both selectiv
- Yamamoto, Yoshinori,Komatsu, Toshiaki,Maruyama, Kazuhiro
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- High Diastereoface Selection in an Ester Enolate Addition to α-Alkoxy Aldehydes: Stereoselective Synthesis of α-Methylene-β-hydroxy-γ-alkoxy Esters
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The aldol-type condensation of β-(dimethylamino)propionates 3 and 4 with a series of α-alkoxy aldehydes proceeds with unprecedented high stereoselectivity (up to 24:1) to give anti α-methylene-β-hydroxy-γ-alkoxy esters.The best results were obtained when the reaction was carried out in diethyl ether and the ester enolate was allowed to equilibrate to the thermodynamically more stable geometric isomer.
- Banfi, Luca,Bernardi, Anna,Colombo, Lino,Gennari, Cesare,Scolastico, Carlo
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p. 3784 - 3790
(2007/10/02)
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