Table 1.

¹H (400 MHz, CDCl₃) and ¹³C (100 MHz, CDCl₃) NMR data, ¹H–¹H COSY and HMBC correlations for diterpenoid 1.

Position	δΗ (J in Hz)	δC, Mult.	1H–1H COSY	HMBC (H→C)
1a	1.69 m	40.6, CH2	H-1b, H2-2	C-10
1b	1.91 m		H-1a, H2-2	C-9
2a	1.45 m	18.6, CH2	H2-1, H-2b, H2-3	n.o.
2b	1.63 m		H2-1, H-2a, H2-3	n.o.
3a	1.16 dd(13.6, 4.0)	41.7, CH2	H2-2, H-3b	C-4, -17
3b	1.39 m		H2-2, H-3a	n.o.
4		33.4, C
5	0.92 dd (9.6, 2.0)	56.1, CH	H2-6	C-4, -6, -10
6a	1.29 m	19.9, CH2	H-5, H-6b, H2-7	C-8, -10
6b	1.72 m		H-5, H-6a, H2-7	C-5, -8, -10
7a	0.94 m	39.8, CH2	H2-6, H-7b	C-6
7b	1.78 br d (11.6)		H2-6, H-7a	C-8
8		82.5, C
9	1.38 m	60.6, CH	H2-11	C-8, -10, -11, -20
10		39.2, C
11a	1.51 m	22.1, CH2	H-9, H-11b, H2-12	C-9
11b	1.94 m		H-9, H-11a, H2-12	C-8, -9
12a	2.22 m	29.3, CH2	H2-11, H-12b, H-14	C-13, -14
12b	2.91 ddd (13.6, 3.2, 2.4)		H2-11, H-12a	n.o.
13		169.3, C
14	5.82 br s	117.0, CH	H-12a	C-12, -13, -15, -16
15		170.6, C
16	6.07 s	100.9, CH		C-8, -13, -14, -15
17	0.89 s	33.4, CH3		C-3, -4, -5, -18
18	0.80 s	21.4, CH3		C-3, -4, -5, -17
19	1.25 s	22.3, CH3		C-7, -8, -9
20	0.78 s	15.6, CH3		C-1, -5, -9, -10

n.o. = not observed.