Fig. 2. Key 1 H– 1 H in Pimarane, abietane, and labdane diterpenoids from Euphorbia pekinensis Rupr. and their anti-tumor activities

Fig. 2. Key 1 H– 1 H COSY (red bold lines) and HMBC (blue→) of compounds 5 (a1) and 16 (a2), NOSEY correlation (blue→) of compounds 5 (b1) and 16 (b2), The ORTEP drawing of compounds 5 (c1) and 16 (c2). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)