Synthesis of (2 R ,3 S )-isobutyl phenylisoserinate, the Taxol ® side chain, from ethyl benzoylacetate
摘要:
Reduction of ethyl 2-chloro-3-phenyl-3-oxopropionate with borohydride affords predominately the synchlorohydrin. Resolution of this ester with the lipase MAP-10 gives (2S,3R)-2-chloro-3-hydroxypropionic acid which after esterification with MeOH/HCl is converted to the cis-epoxide with potassium carbonate and DMF. Aminolysis of the epoxide with aqueous ammonia results in ring opening and amide formation. The amide is converted to an ester upon treatment with isobutyl alcohol and HCl(g) at 100 degrees C. Neutralization then affords the Taxol side chain as the free amine. (C) 2000 Published by Elsevier Science Ltd.