GIAO ¹³C NMR calculation of 1.

Position	Exp. δC	Cal. δCa	Δδ (cal. − exp.)
1	86.2	88.0	1.8
2	160.3	161.0	0.7
3	128.7	128.4	−0.3
4	171.9	169.4	−2.5
4a	143.7	144.8	1.1
6	164.4	162.6	−1.8
6a	100.9	100.0	−0.9
7	164.7	163.0	−1.7
8	101.7	99.2	−2.5
9	166.6	164.4	−2.2
10	104.7	102.9	−1.8
10a	134.2	133.6	−0.6
10b	121.7	122.7	1.0
1-CH3	26.2	24.8	−1.4
3-OCH3	60.9	56.7	−4.2
9-OCH3	55.9	53.2	−2.7
1′	97.3	96.4	−0.9
2′	30.7	31.8	1.1
3′	25.4	26.8	1.4
4′	48.8	49.9	1.1
		MAE	1.59
		RMSD	1.82

^aCal. δ_C was scaling corrected from calculated shielding tensor (σ) using the formula δ_C = (186.5242 − σ)/1.0533.