Studies on the Constituents of the Seeds of Hernandia ovigera L. IV. Syntheses of β-Peltatin-A and-B Methyl Ethers from Desoxypodophyllotoxin

Two kinds of 4-aryltetralin type lignans, β-peltatin-A methyl ether (I-A) and β-peltatin-B methyl ether (I-B), were synthesized from desoxypodophyllotoxin (DPT), which is available in large quantities from the seeds of Hernandia ovigera L. (Hernandiaceae). The syntheses were achieved via demethylene-DPT (IV), 8-bromo-demethylene-DPT (V) and 8-bromo-DPT (VI). Methylenation of V was carried out successfully by using cesium fluoride and methylene iodide in DMF. Compound I-B was readily obtained by the reaction of VI with cuprous iodide and sodium methoxide in the presence of pyridine. Synthesis of I-A was only achieved by the reaction of lithiated VI with nitrobenzene at-100°C in the presence of tetramethylethylene diamine, and I-A was obtained in low yield, together with I-B.