Taxol asymmetric aldol reaction

Several methods have been developed for the synthesis of the taxol side chain. We present here the asymmetric construction of this molecule via asymmetric epoxidation and asymmetric ring-opening reactions, asymmetric dihydroxylation and asymmetric aminohydroxylation reaction, asymmetric aldol reactions, as well as asymmetric Mannich reactions. 

Several other chiral boron reagents are available for asymmetric aldol reactions however, each of these compounds must be synthesized in the laboratory. In certain situations, some will give higher stereocontrol than the Ipc ligands, and hence for a given reaction their application could be pursued. Chiral reagents 53 and 54 have been used in the synthesis of bryostatin 7 [36] and the Taxol side-chain [37], respectively, while bis-sulfonamide 55 has been used in the synthesis of a C24-C35 segment of FK-506 (Scheme 9-18) [38]. 

Commerqon et al.40 developed a method based on an Evans-type auxiliary-controlled aldol reaction. Subsequent treatment of the aldol product with base produced the standard epoxide compound for the asymmetric synthesis of the taxol side chain (Scheme 7-84). 

Shiina I, Saitoh K, Frechard-Ortuno I, Mukaiyama T (1998) Total Asymmetric Synthesis of Taxol by Dehydration Condensation between 7-TES Baccatin III and Protected N-Benzoylphenylisoserines Prepared by Enantioselective Aldol Reaction. Chem Lett 3... 

Two Evans aldol reactions were used to create the C5 and Cl stereocenters in the asymmetric synthesis of a Taxol C-ring with chloroacetyl oxazolidinone 33, giving the Evans syn-aldol 45 as a single diastereomer in 77% yield. ... 

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