Sharpless asymmetric aminohydroxylations

Sharpless asymmetric aminohydroxylation can also be used for taxol side chain synthesis. For example, using DHQ as a chiral ligand, asymmetric aminohydroxylation of methyl trau.v-cinnamatc provides compound 240 in high enantiomeric excess (Scheme 7-80).37... 

D. Nilov, O. Reiser, The Sharpless Asymmetric Aminohydroxylation - Scope and Limitation, Adv. Synth. Catal. 2002, 344, 1169-1173. 

Angert, K. B. Sharpless, Angew. Chem. Int. Ed. Engl. 1996,35,2813 (c) H. C. Kolb, K. B. Sharpless, Asymmetric Aminohydroxylation in Transition Metals for Organic Synthesis, Vol. 2 M. Beller, C. Bolm (Eds.) WILEY-VCH, Weinheim, 1998,243 - 260 (d) G. Schlingloff, K. B. Sharpless, Asymmetric Aminohydroxylation in Asymmetric Oxidation Reactions A Practical Approach T. Katsuki (Ed.) Oxford University Press, Oxford, in press. 

Sharpless and co-workers first reported the aminohydroxyIation of alkenes in 1975 and have subsequently extended the reaction into an efficient one-step catalytic asymmetric aminohydroxylation. This reaction uses an osmium catalyst [K20s02(OH)4], chloramine salt (such as chloramine T see Chapter 7, section 7.6) as the oxidant and cinchona alkaloid 1.71 or 1.72 as the chiral ligand. For example, asymmetric aminohydroxylation of styrene (1.73) could produce two regioisomeric amino alcohols 1.74 and 1.75. Using Sharpless asymmetric aminohydroxylation, (IR)-N-ethoxycarbonyl-l-phenyl-2-hydroxyethylamine (1.74) was obtained by O Brien et al as the major product and with high enantiomeric excess than its regioisomeric counterpart (R)-N-ethoxycarbonyl-2-phenyl-2-hydroxyethylamine (1.75). The corresponding free amino alcohols were obtained by deprotection of ethyl carbamate (urethane) derivatives. 

O Brien P. Sharpless asymmetric aminohydroxylation scope, limitations, and use in synthesis. Angew. Chem. Int. Ed. 1999 38 326-329. 

Bodkin JA, McLeod MD. The Sharpless asymmetric aminohydroxylation. J. Chem. Soc., Perkin Trans. I 2002,2733-2746. 

The Sharpless asymmetric aminohydroxylation [230] of the electron-deficient 2-vinylfuran 505 gives a 7 1 mixture of semiprotected amino alcohols 506 and 507 (41%). The major product (ee > 86%) is reduced with diisobutylaluminum hydride, giving diol 508 [231], which can be converted into the (3-hydroxyfurylamine derivative 509. This compound is an... 

SCHEME 13.118 Application of the Sharpless asymmetric aminohydroxylation and of the aza-Achmatowicz reaction to the synthesis of a l,5-dideoxy-l,5-iminoalditol. 

Sharpless asymmetric aminohydroxylation One-pot enantioselective synthesis of protected vicinal amino alcohols from simple alkenes. 404... 

Reiser, O. The Sharpless asymmetric aminohydroxylation of olefins. Angew. Chem., Int. Ed. Engl. 1996, 35, 1308-1309. 

Nilov, D., Reiser, O. Recent advances on the sharpless asymmetric aminohydroxylation. Organic Synthesis Highlights V2003, 118-124. 

Chiral amines and K20sC>2(0H)4 are also used to catalyze the Sharpless asymmetric aminohydroxylation. The stoichiometric oxidant in aminohydroxylation is a deprotonated /V-lialoamide, whose mechanistic behavior is very similar to NMO. The reaction proceeds by a mechanism essentially identical to that of Sharpless dihydroxylation. 

The aziridino alcohols that have been prepared and tested as chiral promoters for the catalytic asymmetric dialkylzinc alkylation of imines are shown in Fig. 4. The authors have investigated three different approaches to obtain the ligands in enantiomerically pure form (1) the use of the chiral pool, (2) the Sharpless asymmetric aminohydroxylation, and (3) the Sharpless asymmetric dihydroxylation. The starting materials for the preparation of the aziridino alcohols 30, 31a-h, 32a,b, and 33 were the readily available amino acids L-serine, L-threonine, and aZZo-L-threonine. 

Miscellaneous Reagents. Chloramine-T/Osmium Tetroxide. The Sharpless asymmetric aminohydroxylation system for olefins (4-MeC6H4S02N(Na)Cl/ OsCVcinchona alkaloid derived catalysts)340,341 converts silyl enol ethers into a-(p-tosylamino) ketones in 34-40% yield and 76-92% ee (see Eq. 99).342... 

The Sharpless Asymmetric Aminohydroxylation of Olefins 59 Selectivity [% ee] (yield [%])... 

Aminohydroxylation of Alkenes. Sharpless asymmetric aminohydroxylation (AA) allows for the catalytic and enantios-elective symthesis of protected vicinal aminoalcohols in a single step. This reaction is significant as it applies to the synthesis of a wide variety of biologically active agents and natural products. For example, new monoterpene /3-amino alcohols can effectively be synthesized from (+)-2-carene, (+)-3-carene, (—)-/3-pinene, and... 

Synthesis of the Side Chain by Sharpless Asymmetric Aminohydroxylation... 

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