Efficient large scale stereoinversion of (R)-ethyl 3-hydroxybutyrate
作者:Andrew J. Carnell、Robert Head、Derek Bassett、Michael Schneider
DOI:10.1016/j.tetasy.2003.12.005
日期:2004.3
A three step method for the large scale preparation of enantiomerically pure ethyl (S)-3-hydroxybutyrate is reported starting from the commercial biopolymer poly[(R)-hydroxybutyrate]. The key step depends on the ability to cleanly invert the stereochemistry of (R)-ethyl 3-hydroxybutyrate via its mesylate ester under neutral conditions, avoiding the competing elimination process. This has been achieved in good (75%) yield on >100 g scale by controlled addition of the mesylate to a stirred slurry of calcium carbonate in water at 80 degreesC. (C) 2003 Elsevier Ltd. All rights reserved.
Iridium-Catalyzed Asymmetric Hydrogenation of Vinyl Ethers
作者:Ye Zhu、Kevin Burgess
DOI:10.1002/adsc.200700546
日期:2008.5.5
A carbene-oxazoline catalyst 1 proved to be an effective catalyst for reduction of an enol ether that the literature suggested could not be hydrogenated effectively by P,N-Ir catalysts. Thus, a series of ester and alcohol substrates were hydrogenated using catalyst 1. Good to excellent enantioselectivities and high conversions were obtained.