Aminoalcohols norephedrine

Carpentier and coworkers studied the asymmetric transfer hydrogenation of /f-keloeslers using chiral ruthenium complexes prepared from [(// -p-cyrriene)-RuC12]2 and chiral aminoalcohols based on norephedrine. During this study, these authors became aware of substrate inhibition when ketoesters carrying 4-halo-substituents were used. It transpired that this was caused by formation of a complex between the substrate and the catalyst [28]. 

The vicinal aminoalcohol D,L-norephedrine (47) is cleaved to benzoic acid (67 %) and benzaldehyde (25%) in 0.1 M potassium hydroxide (10 °C). Under less alkaline conditions (pH 7.5) the cleavage reaction is suppressed, but now a greater number of products with an azomethine, probably 48, as major component (37 %) is obtained. 

Reagents that encompass both the alcohol and the amine functional groups of a commercially available aminoalcohol are very usefirl. Ephedrine 1.61 (R = Me), pseudoephedrine 1.78, norephedrine 1.61 (R=H) and their Aralkyl and N-acyl derivatives are commonly used, [253, 290, 320-324], as are aminoalcohols 1.79. Also popular are aminoalcohols formed from the natural aminoadds (S)-alaninol... 

A few of these ligands are illustrated, including the camphor-derived ligand (6.03) (which was the first one to give high enantioselectivies), the norephedrine-derived aminoalcohol (6.04), the praline-derived ligand (6.05), aminoalcohols with axial chirality such as binaphthyl (6.06) and ferrocene-based aminoalcohols such as (6.07). ... 

Itsuno has described the first enantioselective allylation of aldehydes using crosslinked polymer-supported A-sulfonylated aminoalcohols as chiral ligands [146], Polymer-supported ligands 220 and 221 were prepared by copolymerisation of the norephedrine-derived monomer 218 or D-camphor-derived 219 with styrene and divinylbenzene (DVB) in a [chiral monomer]/[styrene]/[DVB] molar ratio of 1/8/1 (Scheme 90). 

Optically active allylboronates bearing chiral auxiliary located at the boron atom found widespread applications in asymmetric synthesis. Enantiomerically enriched a-alkylidene-y-lactones and lactams can also be synthesized following such a synthetic approach. VUlieras et al. (41, 45] demonstrated the potential of chiral allylboronates derived from 2-phenyl-2,3-bomanediol, ephedrine, or norephedrine for this purpose. Chiral allylboronates 46a,b were obtained in a sequence of reactions involving transformation of achiral precursors 32 into the corresponding boronic acids 44 followed by their esterification with enantiomerically pure diol or 1,2-aminoalcohol 45 (Scheme 4.10). In the case of methyl-substituted derivatives 32b (R = Me), initial composition of E- and Z-isomers was transferred to the target allylboronates 46b. Importantly, the isomeric mixture was separated by means of the column chromatography. 

Preparation of Acylated Oxazolidinones The Evans diastereoselective alkylation precursors are generally prepared in two steps starting from the corresponding p-aminoalcohols, which are themselves prepared by reduction of the related optically active a-amino acids (typically valine, phenylalanine, and phenylglycine) or available from natural sources such as norephedrine (Scheme 2.43). The reaction between the... 

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