Practical Synthesis of FR195752, the Side Chain of Micafungin, Utilizing a Regioselective Conversion of Diaryl-β-diketone to 3,5-Diarylisoxazole

The practical synthesis of FR195752, the side chain of Micafungin, was established utilizing a highly regioselective conversion of diaryl-β-diketone to 3,5-diarylisoxazole via the corresponding β-keto enamine intermediate whose disfavored regioisomer could be recycled efficiently after its hydrolysis. In addition, the related substance of FR195752 could be strictly controlled by the purification of its intermediate.