Chiral P-aminoalcohols

Another way to obtain achiral or chiral p-aminoalcohol derivatives stereoselec-tively is to use NaBH4 or Zn(BH4)2 to reduce a-hydroxyimines 3.233 or a-trimethyl-... 

The first diastereoselective asymmetric synthesis with ee > 98% seems to be the asymmetric synthesis of aspartic acid of Korean et al in 1968. The chiral auxiliary was a chiral P>aminoalcohoL... 

The chiral ligand (44) was prepared starting from the cyclic a-amino acid (S)-proline80). Recently, similar chiral catalysts and related molybdenum complexes involving optically active N-alkyl-P-aminoalcohols as stable chiral ligands and acetylacetone as a replaceable bidentate ligand, were designed for the epoxidation of allylic alcohols with alkyl hydroperoxides which could be catalyzed by such metal complexes 8,). 

Corma et al have anchored Rh(I), Ru (II), Co(II) and Ni(II) chiral complexes based on p-aminoalcohols such as (L) prolinol onto silica and modified USY-zeolites (scheme 3) to perform enantioselective hydrogenation of the same prochiral alkenes than shown in scheme 2.20,34... 

Vanadium(IV) Schiffsbase complexes derived from P-aminoalcohols 7.62 and vanadyl acetylacetonate have been used to oxidize different substrates to chiral sulfoxides. 

Cyclization by formation of the C4-C5-bond is demonstrated by intramolecular alkylation of the dianion of methylsulfonamide 203 to give sultam 204. This method has been applied towards the synthesis of chiral sultams, which are valuable auxiliaries <03OL4175>. The required P-chloroalkanesulfonamides 203 are easily accessible from p-aminoalcohols via bis-mesylation and displacement of the 0-mesyl group by chloride. 

Chiral boron complexes derived from tartaric acid derivatives and from P-aminoalcohols act as mild Lewis acids and asymmetric catalysts for the reaction of aldehydes (94T979) and methyl glyoxalate (94CC1563) with Danishefsky dienes. The resulting 2,3-dihydropyran-4-ones are obtained in high optic purity. 

Scheme 11.8 Synthesis reaction and chiral N-donor ligands (1 P-aminoalcohol, 2-4 monooxazolines and 5-8 bis(oxazolines) used for the preparation of Ru nanocatalysts. Adapted from Ref [44].

De Vries, A. H. M., Jansen, J. P. G. A. and Feringa, B. L. (1994) Enantioselective conjugate addition of diethylzinc to chalcones catalyzed by chiral NiQI) aminoalcohols complexes. Tetrahedron 50,4479-4491... 

After finishing postdoc with Prof. Ernest L. Eliel at the University of North Carolina at Chapel Hill, K.S. got the position in Tokyo University of Science and became independent in 1981. Then, Oguni reported in 1984 that Et2Zn adds to benzaldehyde to give 1-phenylpropanol with 48% ee using leucinol, a p-aminoalcohol, as a chiral catalyst [15]. As described, we had been dealing with... 

Scheme 2 Enantioselective addition of organometallic reagents to aldehyde using a chiral ligand, P-aminoalcohol derivative...

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 formation of stereogenic C-N bonds by hydrogenation of the enamine structure is not only limited to amino acids. Likewise, chiral 1,2-aminoalcohols or 1,2-diamines can be produced by the enantioselective hydrogenation of dehydro-p-amino alcohols (or their esters) and of dehydro-a-amino aldoximes, respectively (eq 6 and eq 7, Thble 2). Esters and aldoximes thus obtained can be converted into the corresponding alcohols or diamines by standard methods. By this means, simple amines with one aryl group attached to the double bond can also be hydrogenated with high enantioselectivity. ... 

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