Enantioselective Sharpless Dihydroxylations and Aminohydroxylations

3-epi-daunosamine (i-xylo) SCHEME 13.115 Total syntheses of 3-amino-2,3,6-trideoxyhexoses. 

Applying the same route, d- and L-mannose were obtained in a five-step synthesis (39% overall yield) from furfural. Similarly, the same methodology was extended to the preparation of d- and L-gulose and d- and L-talose (19% yield) [229]. 

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 13.116 Total asymmetric syntheses of tetritol and tetrose derivatives. 

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. 

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In 1975, Sharpless et al. reported that imino-osmium trioxides underwent aminohydroxylation (Scheme 54).208,209 t0 perform aminohydroxylation with high efficiency, regio-, chemo-, and enantioselectivity must be addressed. This had made the practical realization of aminohydroxylation difficult. However, the development of asymmetric dihydroxylation, as described in the preceding section, propelled the study of asymmetric aminohydroxylatyion forward and, in 1996, Sharpless et al. reported a highly enantioselective version of catalytic aminohydroxylation... 

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