Table 3.

Chemical shifts of the ¹³C-NMR signals of OTB-GSH and OTB-NAC in comparison with OTA (see Fig. 1 for structure and numbering) (NMR measurements were performed in d₄-methanol/D₂O/d₂-formic acid (70/30/0.1, v/v/v))

No. C	OTB-GSH	OTB-NAC	OTA
	δ 13C (ppm)	δ 13C (ppm)	δ 13C (ppm)
1	171.6	171.6	171.1
3	77.8	77.8	77.6
4	33.9	34.0	32.9
4a	149.4	149.0	143.5
5	123.2	124.1	124.2
6	144.8	144.3	138.6
7	120.5	120.5	120.9
8	161.4	161.2	159.7
8a	111.3	111.2	111.6
9	165.3	165.1	164.7
10	20.9	20.8	20.7
1′	175.9	174.7	174.7
2′	56.5	55.6	55.5
3′	38.4	38.2	38.1
4′	138.0	137.5	137.3
5′ and 9′	130.5	130.4	130.4
6′ and 8′	129.5	129.5	129.5
7′	127.9	128.1	128.1
1″	37.4	37.8	−
2″	53.8	53.5	−
4″	175.3	173.6	−
5″	32.7	22.5	−
6″	27.5	164.9	−
7″	55.3	−	−
8″	174.1	−	−
9″	172.7	−	−
11″	42.5	−	−
12″	173.9	−	−