620172-41-0Relevant articles and documents
Homo-Roche ester derivatives by asymmetric hydrogenation and organocatalysis
Khumsubdee, Sakunchai,Zhou, Hua,Burgess, Kevin
, p. 11948 - 11955 (2014/01/06)
Asymmetric hydrogenation routes to homologues of The Roche ester tend to be restricted to hydrogenations of itaconic acid derivatives, that is, substrates that contain a relatively unhindered, 1,1-disubstituted alkene. This is because in hydrogenations mediated by RhP2 complexes, the typical catalysts, it is difficult to obtain high conversions using the alternative substrate for the same product, the isomeric trisubstituted alkenes (D in the text). However, chemoselective modification of the identical functional groups in itaconic acid derivatives are difficult; hence, it would be favorable to use the trisubstituted alkene. Trisubstituted alkene substrates can be hydrogenated with high conversions using chiral analogs of Crabtree's catalyst of the type IrN(carbene). This paper demonstrates that such reactions are scalable (tens of grams) and can be manipulated to give optically pure homo-Roche ester chirons. Organocatalytic fluorination, chlorination, and amination of the homo-Roche building blocks was performed to demonstrate that they could easily be transformed into functionalized materials with two chiral centers and α,ω-groups that provide extensive scope for modifications. A synthesis of (S,S)- and (R,S)-γ-hydroxyvaline was performed to illustrate one application of the amination product.
Highly enantioselective rhodium-catalyzed hydrogenation of 2-(2-methoxy-2-oxoethyl)acrylic acid - A convenient access of enantiomerically pure isoprenoid building blocks
Ostermeier, Markus,Brunner, Bernhard,Korff, Christian,Helmchen, Guenter
, p. 3453 - 3459 (2007/10/03)
Asymmetric catalytic hydrogenation of 2-(2-methoxy-2-oxoethyl)acrylic acid (5) to give (2S)-4-methoxy-2-methyl-4-oxobutanoic acid [(S)-6] was studied. An enantiomeric excess of 99.7% ee was achieved with a catalyst formed in situ from [Rh(COD)2]BF4 and the chiral phosphite L2 in 1,2-dichloroethane as solvent. In addition, enzyme-catalyzed semi-saponification of dimethyl 2-methylsuccinate was investigated. Mono ester (S)-6 was transformed into a few compounds which can serve as C 5-building blocks in natural product syntheses. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
