Enantiodivergent Synthesis of Halofuginone by Candida Antarctica Lipase B (CAL-B)-catalyzed Kinetic Resolution in Cyclopentyl Methyl Ether (CPME)

The synthesis of both enantiomers of a key intermediate in the synthesis of halofuginone was accomplished by Candida antarctica lipase B-catalyzed kinetic resolution of the corresponding racemate. When the resolution was carried out in the versatile and eco-friendly solvent cyclopentyl methyl ether (CPME) using PCPB (p-chlorophenylbutyrate) as the acylating reagent, the highest enantiomeric ratio (E) values were measured and highly enantioenriched (95% ee) compounds could be obtained in a single iteration. As an example, one of the two enantiomers was used as a starting material to prepare (+)-halofuginone in a three-step procedure.