Highly Enantioselective Hydrogenation of α-Dehydroamino Esters and Itaconates with Triphosphorous Bidentate Ligands and the Unprecedented Solvent Effect Thereof
作者:Weicheng Zhang、Xumu Zhang
DOI:10.1021/jo0622429
日期:2007.2.1
coordination in a Pd(II) complex of a phosphine-phosphoramidite ligand 1, which showed excellent enantioselectivity (up to 99.4% ee) in Rh-catalyzed hydrogenation of α-dehydroamino esters in acetone. A dramatic solvent effect was found in the hydrogenation of itaconates, which induces opposite chiralities of the product with the same catalytic system by the use of different solvents (e.g., 99.6% ee (R) in TFE
The present invention is directed to compounds of the formula ##STR1## wherein R.sub.1 is lower alkyl and R.sub.2 is lower alkyl or aryl. Also provided are methods for preparation of these compounds. The compounds of formula I above are useful as plant growth regulants.
A new stereoselective synthetic route to triacetyl-L-erythro-C18-sphingosine has been developed by the combination of diastereoselective addition of thiophenol to chiral olefins and subsequent intramolecular substitution of the corresponding sulfonium group.