methyl 2-[(3-methyl-2'-oxospiro[furo[3,2-f][1,2]benzisoxazole-5,3'-indol]-1'(2'H)-yl)methyl]-1,3-oxazole-4-carboxylate 、
methyl 5-[(2'-oxo-5,6-dihydrospiro[benzo[1,2-b:5,4-b']difuran-3,3'-indol]-1'(2'H)-yl)methyl]furan-2-carboxylate 以2-[(3-methyl-2′-oxospiro[furo[3,2-f][1,2]benzisoxazole-5,3′-indol]-1′(2′H)-yl)methyl]-1,3-oxazole-4-carboxylic acid was obtained (69%) as a colorless solid的产率得到2-[(3-methyl-2'-oxospiro[furo[3,2-f][1,2]benzisoxazole-5,3'-indol]-1'(2'H)-yl)methyl]-1,3-oxazole-4-carboxylic acid