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.
Acylation of alkyl halides and amino aldehydes with a phosphane oxide-based d1-synthon
Bruenjes, Marco,Kujat, Christof,Monenschein, Holger,Kirschning, Andreas
, p. 1149 - 1160 (2007/10/03)
Alkyl iodides and α-amino aldehydes can be homologated to the corresponding methyl esters and β-amino methyl esters, including β-amino-α-hydroxy methyl esters, using lithiated (dimethoxymethyl) diphenylphosphane oxide. The primary α,α-(dimethoxy) diphenylphosphane oxides obtained by this Horner-Wittig type process collapse to give the target esters under proton-catalyzed conditions in the presence of water. Detailed and carefully conducted mechanistic studies revealed that the diphenylphosphane oxide group is activated by protonation, and acts as the initial leaving group in this process. In the cases of adducts derived from the reaction of the phosphane oxide-stabilized anion with α-amino aldehydes, homologation to the β-amino- and β-amino-α-hydroxy methyl esters can be achieved by KOtBu-mediated elimination to the intermediate O,O-ketene acetals. These may either be allowed to react with water under acidic conditions to yield the β-amino methyl esters, or may be treated under the Sharpless asymmetric dihydroxylation conditions to directly furnish the β-amino-α-hydroxy methyl esters. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
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.
