Asymmetric aminohydroxylation protocols

The Sharpless regioreversed asymmetric aminohydroxylation protocol was used as a key step in the total synthesis of ustiloxin D by M.M. Joullie and co-workers.The ( )-ethyl cinnamate derivative was subjected to in situ generated sodium salt of the N-Cbz chloroamine in the presence of catalytic amounts of the anthraquinone-based chiral ligand to afford the desired A/-Cbz protected (2S,3R)-(3-hydroxy amino ester in good yield and with good diastereoselectivity. 

The anticancer drugs Taxol and Taxotere feature a (2R, 35)-V-benzoyl phenylisoserine as side chain. A number of stereoselective syntheses of this moiety have been reported. Among them, the preparation based on the catalytic asymmetric aminohydroxylation protocol recently developed by Sharpless and reported in Fig. 26 seems particularly attractive [77]. 

In the asymmetric aminohydroxylation (AA) an olefin is converted into a vicinal amino alcohol by means of an osmium(VIII)-mediated suprafacial addition of a nitrogen and an oxygen atom to the double bond. Like the AD, the AA has been developed by modifying an originally stoichiometric, achiral version. Although the first aminohydroxylations were reported in 1976 [70], the asymmetric catalytic protocol is still underdevelopment [71]. 

Since the discovery of the catalytic AD in 1987, there have been numerous attempts in the Sharpless group to render the old catalytic aminohydroxylation process asymmetric [7]. Until recently, the obvious approach of adding the AD s chiral ligands, but otherwise staying close to the original protocol [3] led to extremly slow catalyst turnover. The initial breakthrough [8] was not due to a sudden con-... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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