3[[[(4-nitrophenyl)oxy]-carbonyl]amino]benzeneacetic acid, methylester 、
(3R-trans)-4-amino-3,4-dihydro-3-hydroxy-2,2-dimethyl-2H-1-benzopyran-6-carbonitrile 以
乙腈 为溶剂,
以63.9%的产率得到(3S-trans)-3-[[[(6-cyano-3,4-dihydro-3-hydroxy-2,2-dimethyl-2H-1-benzopyran-4-yl) amino]carbonyl]amino]benzeneacetic acid, methyl ester