Bursera microphylla (Burseraceae) A. Gray has yielded a second component which has demonstrated activity in the cell culture test system of the Cancer Chemotherapy National Service Center (CCNSC). On the basis of NMR, mass, and IR spectrometry, the structure of a new lignan, 3‐(3,4‐methylenedioxybenzyl)‐4‐(3“,4”,5‐trimethoxybenzyl) tetrahydrofuran (named burseran), is proposed. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company