摘要:
We describe an efficient, six-stage synthesis of 2-methyl-4-deoxyisopicropodophyllotoxin, which proceeds via a Diels-Alder cycloaddition between 2-methylmaleic anhydride and the orthoquinodimethane generated by treatment of 5-[1-acetoxy-1-(3',4',5'-trimethoxyphenyl)methyl]-6-trimethyl-silylmethyl-1,3-benzodioxole with silica gel at 60-degrees-C. The podophyllin was converted into a number of 4'-ester derivatives. This procedure was also used to prepare a diazapodophyllin via the use of 4-phenyl-1,2,4-triazoline-3,5-dione as dienophile.