Table 1.

NMR data for compound 1 (¹H 500 MHz, ¹³C 125 MHz, δ ppm) in methanol-d₄

position	δC	δH mult. (J in Hz)	1H-1H COSY	HMBC
1	127.5 CH	7.80 m	H-2	C-3, C-4a, C-13
1a	138.0 C
2	135.0 CH	7.82 m		C-1a, C-4
3	125.8 C
4	119.2 CH	8.54 d (1.2)	H-2	C-4a, C-1a, C-2, C-3
4a	144.1 C
6	125.3 CH	9.26 d (6.8)	H-7	C-12b, C-4a, C-7a, C-7
7	118.7 CH	8.77 d (6.8)		C-12a, C-7b, C-6, C-12b
7a	137.5 C
7b	121.9 C
8	124.8 CH	8.43 d (8.4)	H-9, H-10	C-11a, C-10, C-7b
9	124.0 CH	7.49 dd (8.4, 7.6)	H-10	C-10, C-7b, C-11
10	134.6 CH	7.83 m	H-11	C-11a, C-8, C-9
11	114.5 CH	7.82 m		C-11a, C-9
11a	147.5 C
12a	132.4 C
12b	145.0 C
13	79.6 C
14	51.6 CH2	4.16 d (18.4)		C-15, C-12b, C-1a, C-13
15	206.7 C	4.26 d (18.4)
16	30.4 CH3	1.99 s		C-15, C-14, C-13