dimethyl (3'aR,6'R,6'aR)-2',2'-dimethyl-6'-(trityloxymethyl)spiro[2H-1,2-oxazole-3,4'-6,6a-dihydro-3aH-furo[3,4-d][1,3]dioxole]-4,5-dicarboxylate 生成 dimethyl (1S,5S,6S,8R,9R)-8-ethyl-11,11-dimethyl-4,7,10,12-tetraoxa-3-azatricyclo[7.3.0.02,6]dodec-2-ene-5,6-dicarboxylate