A component $F,;C_{20}H_{30}O_4,;M^+;(m/e);334,;mp;258{sim}260^{circ},;[{alpha}]D=-133.25^{circ};(C=0.2,;EtOH)$, was isolated from Siegesbeckia pubescens $M_{AKINO}$. This compound was identified as $16{eta}-(-)-kauran-17$, 19-dioic acid, using spectroscopies and synthesizing various derivatives of the compound F.