Rapid continuous photoflow synthesis of naturally occurring arylnaphthalene lignans and their analogs.

Naturally occurring arylnaphthalene lignans (ANLs) are subclass of lignans in many dietary or medicinal plants. The progressing interest of ANLs is due to their diversified biological activities. Herein, we developed a convenient method for the preparation of naturally occurring ANLs and their analogs through the continuous photoflow intramolecular Diels-Alder reaction in several minutes under mild conditions with good yields and regioselectivities.