It should be noted that compound B 1 b is the first example of a 8,15-epoxypimarane-type diterpenoid possessing a 14,16-ether bridge, and compound B 2 b is the second member of a rare class of 10,19-epoxyrosane-type diterpenoid (Figure 1). The NOESY correlations of H-3/H-2 I i , H-2 I i /H-19 I i , H-2 I i /H-1 I i , H-19 I i /H-6 I i , H-6 I i /H SB 3 sb -20, and H SB 3 sb -20/H-12 I i revealed that these protons were cofacial and they were in I i -configuration (Figure 3). Fraction E5H1B was separated on a silica gel CC (CH SB 2 sb Cl SB 2 sb /EtOAc, 4/1), followed by a silica gel CC ( I n i -hexane/acetone, 10/1) to obtained three fractions, E5H1B1-E5H1B3. Fraction E5H1B1 was purified by a silica gel CC ( I n i -hexane/acetone, 10/1) to yield Compound B 1 b (1.7 mg). [Extracted from the article]