Synthesis of 3-(1'-Indanylidene)phthalides via Wittig-Horner Reaction of Dimethyl Phthalide-3-phosphonates and Their Conversion to the BCDE Ring Part of Fredericamycin A
Wittig-Horner reaction of dimethyl phthalide-3-phosphonates with 1-indanones in the presence of bases was investigated. The3-(1'-indanylidene)phthalides obtained above were transformed into dibenzo-1,4-diketospiro[4,4]nonanes, the BCDE ring system of frederocamycin A, by consecutive treatments with diisobutylaluminum hydride and pyridinium dichromate.