An oxabicyclo compound, 9, prepared in 47% yield through an isobenzofuran intermediate was converted with excellent regio-and stereocontrol to eight (i)-lignan lactones of the podophyllotoxin series. One of the eight, epiisopicropodophyllin, 36, the 1, 2, 3, 4-cis isomer, previously unknown, was prepared as its methyl ether, 37. A comparative study of the'H NMR spectra of all eight lactones aided by an X-ray crystal structure of a 2, 3-cis lactone, ...
