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Abstract

This review article compiles ¹H and ¹³C NMR signals and specific rotations of reported eremophilane-type sesquiterpenoids. The data presented here are intended to assist chemists in natural products chemistry, synthetic chemistry, and computational chemistry. This review focuses on 71 furanoeremophilanes that contain a C-10 hydroxy group with oxygen functionalities in the skeleton, collected from 40 references. NMR data were collected from the published papers using SciFinder. Eremophilanes featuring 15,6-lactones, 6,15-ethers, and 1-en-10-ols are not included in this chapter. Dihydrofurans, lactols, dimers, nor- and seco-compounds, along with other related structures, will be addressed in separate reviews.

Keywords

sesquiterpenoids eremophilanes specific rotation

Introduction

Isolation of numerous eremophilane type sesquiterpenoids has been reported,^1–3 and the number of new compounds continues to increase. They are biosynthesized through cyclization, rearrangement, functionalization, and elimination from simple small compounds. In the course of our research work, we have encountered many sesquiterpenoids, such as eremophilane, eudesmane, bisabolane, bakkane, and other related sesquiterpenoids.³ The NMR data of known compounds are sometimes not completely listed in the paper. Supporting information is highly useful to identify the compound. Particularly ¹³C NMR data are important for comparison with known compounds.⁴ Recently reviews of eremophilane sesquiterpenoids from Ligularia were published.^2,3 As a part of an ongoing series of reviews,^5–8 data of 71 furanoeremophilane sesquiterpenoids are listed in Tables 1-13. This review focuses on furanoeremophilan-10-ols bearing oxygenated functionalities in the skeleton. NMR data have been compiled from the published papers using SciFinder covering the period from the 1960s to the present; however, due to the inherent limitation of not being able to review all available literature, it does not necessarily encompass all existing data. Compounds and the numberings mentioned in this review are shown in Figures 1-6. 10-Hydroxyfuranoeremophil-1-en-3-ones are not included in this review, but in the following review of alkene part. Dihydrofurans, lactols, dimers, nor- and seco-compounds, and other related compounds will be discussed in separate reviews in the future. In the case of compounds having more than two acyloxy groups, the one substituted in the lower numbered position is numbered with a prime, the next with a double prime, and so on. The coupling constants are sorted from the largest to the smallest; the order of the shapes, d, t, or q, must correspond to the value of the coupling constant. In the case of apparent situation, original data were fixed to the proper order, or the problem with the data pointed out in the footnotes. The data not assigned in the original papers were tentatively listed in the tables without any supporting evidence. The names of skeletons and the numbering system used in this review should refer to the ones used in the previous paper.^5–8 Abbreviations used in this review are as follows^5–8: solvents; A: acetone or acetone-d₆, B: benzene or benzene-d₆, C: chloroform or chloroform-d, D: dimethyl sulfoxide or dimethyl sulfoxide-d₆, E: ethanol, F: dichloromethane, H: hexane, M: methanol or methanol-d_4, P: pyridine or pyridine-d₅, T: carbon tetrachloride. Source of compounds; Ca: Cacalia (current Parasenecio, however original description has been remained), Cr: Cremanthodium, E: Eremophila, F: Farfugium, L: Ligularia, P: Petasites, S: Senecio, V: Valeriana.

Figure 1.

Tetradymol (1) and 10-OR Compounds with Oxygenated Functionalities at C-2, C-3, or C-6, 2-20.

Figure 2.

10-OH Compounds with Oxygenated Functionalities at C-1 and C-6, 21-23.

Figure 3.

10-OH Compounds with Oxygenated Functionalities at C-3 and C-6, 24-40.

Figure 4.

10-OH Compounds with Oxygenated Functionalities at C-3 and C-9, 41-48.

Figure 5.

10-OH Compounds with Oxygenated Functionalities at C-6 and C-9, 49-57.

Figure 6.

10-OH Compounds with Oxygenated Functionalities at C-1, C-3, C-4, C-6, and C-9, 58-71.

Table 1.

NMR Chemical shifts (solvent, δ, multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 1-7.

Compound	1 ^a	1		2	3	4	5	6	7
(solvent)	¹H (C)	¹H (M)	¹³C (M)	¹H (C/T)^b	¹H (C/T)^b	¹H (C/T)^b	¹H (C)	¹H (C)^c	¹H (T)	¹H (B)
1	1.1-1.75 (m)	1.46 (m)	35.1	nd	nd	nd	nd	nd	nd	nd
	1.1-1.75 (m)	1.82 (td, 12.9, 5.0)	—	nd	nd	nd	nd	nd	nd	nd
2	1.1-1.75 (m)	1.59 (m)	23.5	5.00 (m)	5.09 (m)	5.08 (m)	nd	nd	nd	nd
	1.1-1.75 (m)	1.72 (m)	—	—	—	—	nd	nd	nd	nd
3	1.1-1.75 (m)	1.41 (m)	30.4	nd	nd	nd	4.02 (m)	5.06 (quint, 4)	5.20 (m)	5.20 (m)
	1.1-1.75 (m)	1.38 (m)	ー	nd	nd	nd	—	—	—	—
4	nd	1.45 (m)	34.3	nd	nd	nd	nd	nd	nd	nd
5	—	—	42.7	—	—	—	—	—	—	—
6	2.2^d	2.26 (d, 16.3)	28.6	nd	2.53 (br d, 17)	2.30 (m)	nd	nd	nd	nd
	2.4 (q, 9)^e	2.42 (d, 16.3)	—	nd	3.06 (br d, 17)	2.30 (m)	nd	nd	nd	nd
7	—	—	116.2	—	—	—	—	—	—	—
8	—	—	148.7	—	—	—	—	—	—	—
9	2.1 (d, 17)	3.14 (d, 17.4)	34.0	nd	nd	3.02 (br d, 17)	nd	nd	nd	nd
	3.0 (d, 17)	2.36 (d, 17.4)	—	nd	nd	2.54 (br d, 17)	nd	nd	nd	nd
10	—	—	75.6	nd	—	—	—	—	—	—
11	—	—	120.5	—	—	—	—	—	—	—
12	7.04 (s)	7.07 (s)	138.5	6.96 (br s)	6.96 (br s)	6.94 (br s)	7.03 (m)	6.94 (m)	6.93 (m)	6.99 (m)
13	1.88 (d, 1)	1.91 (d, 1.3)	8.1	1.90 (br s)	1.90 (d)	1.89 (br s)	1.89 (d, 1.5)	1.88 (d, 1)	1.90^e	1.75 (d, 1.5)
14	0.95 (s)	0.99 (s)	15.4	1.00 (s)	1.05 (s)	1.02 (s)	1.14 (s)	1.04 (s)	1.08 (s)	1.03 (s)
15	0.80 (d, 7)	0.81 (d, 6.2)	16.5	0.80 (m)	0.80 (m)	0.78 (br d)	1.10 (d, 7)	1.00 (d, 8)	1.05 (d, 6)	1.08 (d, 6)
3′	—	—	—	nd	5.52 (dq, 1, 1)	5.99 (qq, 7, 1)	—	—	5.98 (q, 7)	5.75 (q, 7)
	—	—	—	—	6.09 (br s)	—	—	—	—	—
4'	—	—	—	nd	1.94 (t)	1.96 (dq, 7, 1)	—	—	nd	nd
5'	—	—	—	nd	—	1.89 (dq, 1, 1)	—	—	1.99 (d, 7)	2.02 (d, 7)
OAc	—	—	—	—	—	—	—	1.97 (s)	—	—
[α]_D (solvent)	+56 (nd)	nd		nd	nd	nd	–11 (M)	nd	−13 (E)
Source of compound	Tetradymia glabrata	L. cymbulifera		Euryops tenuisissimus	Euryops abrotanifolius	Euryops tenuisissimus	synthetic	synthetic	F. japonicum
Ref	^9,10	¹¹		¹²	¹²	¹²	¹³	¹³	¹³

Abbreviation: nd, not displayed.

X-ray.

Solvent only described as either CDCl₃ or CCl₄.

Measured at 60 °C.

Multiplicity and J not shown.

J = 9 Hz seems to be unusual.

Table 2.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 8–10.

Compound	8	9	10 ^a	10	10	10	10
(solvent)	¹H (T)	¹H (T)	¹H (C)	¹H (B)	¹H (P)	¹³C (C)^b	¹³C (B)^b
1	nd	nd	nd	nd	nd	33.6	34.7
2	nd	nd	nd	nd	nd	22.6	22.7
3	nd	nd	nd	nd	nd	29.1	29.3
4	—	—	nd	nd	nd	33.6	33.9
5	—	—	—	—	—	44.9	45.1
6	nd	nd	4.52 (s)	4.41 (d, 7.5)	nd	69.2	69.0
7	—	—	—	—	—	119.3	119.8
8	—	—	—	—	—	149.1	149.3
9	nd	nd	3.21 (d, 17.8)	2.94 (d, 17.8)	3.25 (d, 17.8)	34.6	33.5
	nd	nd	2.53 (d, 17.8)	2.42 (d, 17.8)	2.83 (d, 17.8)	—	—
10	—	—	—	—	—	76.6	76.3
11	—	—	—	—	—	118.5	119.4
12	6.96 (m)	6.92 (m)	7.08 (m)	7.00 (m)	nd	138.4	138.5
13	1.87 (d, 1.5)	1.84 (d, 1.5)	2.03 (d, 1.5)	1.95 (d, 1.5)	2.11 (d, 1.5)	7.8	7.9
14	0.92 (s)	1.04 (s)	1.22 (s)	1.11 (s)	1.45 (s)	10.5	10.7
15	0.94 (d, 7)	1.01 (d, 7)^c	0.78 (d, 5.5)	0.55 (d, 5.5)	0.75 (d, 5.5)	15.8	15.8
6-OH	—	—	—	2.72 (d, 7.5)	—	—	—
10-OH	—	—	—	2.93 (s)	—	—	—
[α]_D (solvent)	+10 (M)	nd	+58 (E)	+33 (E)	nd	nd	nd
Source of compound	synthetic	synthetic	L. japonica	L. japonica	L. japonica	Unidentified Ligularia	Unidentified Ligularia
Ref	¹³	¹³	¹⁴	¹⁵	^14,15	¹⁶	¹⁶

Abbreviation: nd, not displayed.

The data of specific rotation was revised to +33 (E) in ref.¹⁵

Tentative.

Obtained after the deuterium exchange experiment.

Table 3.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 11 and 12.

Compound	11			11		11		12		12
(solvent)	¹H (T)	¹H (C)	¹H (P)	¹H (C)	¹³C (C)	¹H (B)	¹³C (B)	¹H (B)	¹³C (B)	¹H (C)^a	¹³C (C)
1	nd	nd	nd	1.48 (m)	33.7	1.56 (dt, 14.0, 4.4)	34.3	1.56 (br d, 12.9)	34.3	1.50 (ddd, 13.2, 4.9, 1.9)	33.6
	nd	nd	nd	1.74 (td, 13.2, 5.2)	—	1.88 (td, 14.0, 4.4)	—	1.86 (td, 12.9, 4.9)	—	1.75 (dt, 13.5, 4.9)	—
2	nd	nd	nd	1.70 (m)	22.6	1.14 (m)	22.8	1.12 (m)	22.8	1.69 (m)	22.6
	nd	nd	nd	1.44 (m)	—	1.41 (m)	—	1.42 (m)	—	1.45 (m)	—
3	nd	nd	nd	1.25 (m)	28.8	0.92 (m)	29.1	0.94 (m)	29.1	1.25 (m)	28.8
	nd	nd	nd	1.36 (qd, 12.6, 4.9)	—	1.15 (m)	—	1.16 (m)	—	1.36 (m)	—
4	nd	nd	nd	1.12 (m)	33.6	0.91 (m)	33.9	0.92 (m)	33.8	1.14 (m)	33.7
5	—	—	—	—	45.4	—	45.7	—	45.6	—	45.3
6	4.05 (s)	4.19 (s)	4.25 (s)	4.13 (s)	79.1	3.99 (s)	79.3	4.09 (s)^b	77.8	4.22 (s)	77.4
7	—	—	—	—	116.1	—	116.4	—	117.0	—	116.7
8	—	—	—	—	151.1	—	152.0	—	151.9	—	151.0
9	3.01 (d, 17.8)	3.18 (d, 17.8)	3.20 (d, 17.8)	2.70 (d, 18.1)	34.5	3.06 (d, 16.5)	35.3	3.03 (d, 18.0)	35.3	2.70 (d, 18.1)	34.5
	2.59 (d, 17.8)	2.73 (d, 17.8)	2.87 (d, 17.8)	3.13 (d, 18.1)	—	2.93 (d, 16.5)	—	2.93 (d, 18.0)	—	3.13 (d, 18.1)	—
10	—	—	—	—	75.0	—	74.9	—	74.9	—	75.1
11	—	—	—	—	119.4	—	119.6	—	119.5	—	119.3
12	7.02 (m)	7.22 (m)	nd	7.14 (q, 1.1)	138.2	6.99 (s)	138.4	6.99 (q, 1.2)	138.4	7.12 (q, 1.1)	138.1
13	1.99 (d, 1.5)	2.07 (d, 1.5)	2.06 (d, 1.5)	2.05 (d, 1.1)	8.6	1.76 (s)	8.5	1.78 (d, 1.2)	8.6	2.03 (d, 1.1)	8.6
14	1.12 (s)	1.22 (s)	1.30 (s)	1.20 (s)	10.9	1.29 (s)	11.3	1.29 (s)	11.3	1.21 (s)	11.0
15	0.70 (d, 5.5)	0.73 (d, 5.5)	0.66 (d, 5.5)	0.73 (d, 6.6)	15.6	0.53 (d, 6.6)	15.7	0.56 (d, 6.6)	15.7	0.72 (d, 6.6)	15.6
1'	3.28 (s)	3.39 (s)	3.27 (s)	3.35 (s)	57.5	2.93 (s)	56.8	3.03 (dq, 8.5, 7.0)	65.2	3.42 (dq, 8.5, 6.9)	65.4
	—	—	—	—	—	—	—	3.36 (dq, 8.5, 7.0)	—	3.62 (dq, 8.5, 6.9)	—
2'	—	—	—	—	—	—	—	0.87 (t, 7.1)	15.4	1.17 (t, 6.9)	15.5
OH	4.30 (s)	4.99 (s)	—	4.94 (s)	—	5.06 (s)	—	5.20 (br s)^b	—	5.18 (s)	—
[α]_D (solvent)	+5 (E)			nd		nd		nd		+141.5 (C)
Source of compound	L. japonica			F. japonicum		F. japonicum		L. kanaitzensis		L. kanaitzensis
Ref	^14,15			¹⁶		¹⁶		¹⁷		¹⁶

Abbreviation: nd, not displayed.

Tentative.

H-6 and OH not shown in ref.¹⁷

Table 4.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 13–16.

Compound	13			13		14	15		16
(solvent)	¹H (C)	¹H (B)	¹H (P)	¹H (B)	¹³C (B)	¹H (C)	¹H (B)	¹³C (B)	¹H (C)
1	nd	nd	nd	1.45 (dd, 14.1, 3.0)	33.5	nd	1.48 (br d, 13.5)	33.5	nd
	nd	nd	nd	1.72 (m)	—	nd	1.74 (m)	—	nd
2	nd	nd	nd	1.09 (m)	22.3	nd	1.09 (m)	29.2	nd
	nd	nd	nd	1.36 (m)	—	nd	1.35 (m)	—	nd
3	nd	nd	nd	0.94 (m)	29.2	nd	0.94 (m)	22.3	nd
	nd	nd	nd	1.07 (m)	—	nd	1.06 (m)	—	nd
4	nd	nd	nd	1.00 (m)	33.8	nd	1.02 (m)	34.1	nd
5	—	—	—	—	45.5	—	—	45.6	—
6	6.17 (s)	6.34 (s)	6.46 (s)^a	6.37 (s)	70.5	3.2 (s)	6.44 (s)	70.3	nd
7	—	—	—	—	115.6	—	—	115.8	—
8	—	—	—	—	151.9	—	—	151.9	—
9	2.65 (d, 17.8)	2.69 (d, 17.8)	2.83 (d, 17.8)	2.71 (d, 17.4)	34.1	2.75 (d, 17)	3.00 (d, 17.9)	33.9	nd
	3.20 (d, 17.8)	2.99 (d, 17.8)	3.13 (d, 17.8)	2.99 (d, 17.4)	—	3.06 (d, 17)^b	2.74 (d, 17.9)	—	nd
10	—	—	—	—	75.0	—	—	75.1	—
11	—	—	—	—	119.6	—	—	119.5	—
12	7.08 (m)	6.94 (m)	nd	6.94 (q, 1.1)	139.1	6.98 (s)	6.94 (q, 1.2)	139.2	nd
13	1.91 (d, 1.5)	1.89 (d, 1.5)	1.96 (d, 1.5)	1.92 (d, 1.1)	8.2	1.85 (d, 1)	1.95 (d, 1.2)	8.2	nd
14	1.05 (s)	1.04 (s)	1.20 (s)	1.05 (s)	10.0	1.05 (s)	1.10 (s)	16.0	nd
15	0.88 (d, 5.5)	0.72 (d, 5.5)	0.95 (br)	0.72 (d, 6.0)	16.1	0.95 (d, 7)	0.72 (d, 7.4)	10.2	1.14 (d, 7)
1'	—	—	—	—	169.5	—	—	175.2	—
2'	—	—	—	—	20.2	2.45 (m)	2.03 (sextet, 6.6)	41.5	2.34 (m)
3'	—	—	—	—	—	1.07 (d, 7)	1.21 (dq, 13.7, 6.6)	26.9	nd
	—	—	—	—	—	—	1.59 (dq, 13.7, 6.6)	—	nd
4'	—	—	—	—	—	1.3 (d, 7)	0.73 (t, 7.4)	11.7	0.88 (t, 5.5)
5'	—	—	—	—	—	—	0.98 (d, 6.8)	16.9	nd
OH	3.21 (s) OH	3.22 (br) OH	—	—	—	—	—	—	—
OAc	2.05 (s)	1.50 (s)	1.99 (s)	—	—	—	—	—	—
[α]_D (solvent)	nd			−39.4 (E)		−56.1 (M)	−33.0 (E)		nd
Source of compound	synthetic			L. kanaitzensis		Tetradymia glabrata	L. kanaitzensis		L. japonica
Ref	^14,15			¹⁷		¹⁰	¹⁷		¹⁴

Abbreviation: nd, not displayed.

Multiplicity not shown, but must be “s”.

Multiplicity shown as “q”, but must be “d” (AB quartet).

Table 5.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 17–21.

Compound	17 ^a		18 ^b	19		20	21				21
(solvent)	¹H (C)^c	¹³C (C)	¹H (C/T)^d,e	¹H (T)^e	¹H (B)^e	¹H (T)	¹H (C)^e,f	¹H (P)^e	¹H (D)^e	¹H (M)^e	¹³C (D)
1	nd	33.2	nd	nd	nd	nd	3.93	4.30	3.65 (m)	3.86	71.0^g
2	nd	29.3	nd	nd	nd	nd	nd	nd	nd	nd	28.5^h
3	nd	22.5	nd	nd	nd	nd	nd	nd	nd	nd	30.8^h
4	nd	34.1	nd	nd	nd	nd	nd	nd	nd	nd	32.7
5	nd	45.6	nd	nd	nd	nd	nd	nd	nd	nd	44.7
6	6.26 (s)	70.2	nd	6.07 (s)	6.57 (s)	6.15 (br s)	4.44	4.66	4.18 (d, 8)	4.36	68.2^g
7	—	115.4	—	—	—	—	—	—	—	—	118.9
8	—	151.5	—	—	—	—	—	—	—	—	149.1
9	2.63 (d, 17.6)	33.8	nd	2.55 (d, 19)	2.87 (d, 19)	3.12 (d, 17.5)	3.00	3.25	2.82 (d, 18)	2.92	28.5
	3.18 (d, 17.6)	—	nd	3.08 (d, 19)	3.07 (d, 19)	2.55 (d, 17.5)	2.78	3.33	2.62 (d, 18)	2.72	—
10	—	75.2	—	—	—	—	—	—	—	—	78.7
11	—	119.5	—	—	—	—	—	—	—	—	119.2
12	7.08 (s)	139	—	6.96 (m)	7.09 (m)	6.98 (br s)	7.12	7.22	7.22	7.12	137.9
13	1.90 (s)	8.4	nd	1.89	2.01	1.88 (d, 1)	2.04 (d, 1)	2.12	1.94	1.99	7.6
14	1.03 (s)	15.8	nd	0.98 (s)	1.14 (s)	1.00 (s)	1.23 (s)	1.46 (s)	1.06 (s)	1.17 (s)	11.0
15	0.87 (d, 7.0)	10.2	nd	0.95 (m)	0.82 (m)	0.91 (br d, 7)	0.79	0.77	0.68 (d, 5)	0.75	15.2
1'	—	167	—	—	—	—	—	—	—	—	—
2'	—	127.6	2.19 (m)	5.58 (m)	5.56 (m)	5.55 (tq)	—	—	—	—	—
3'	6.01 (m)	138.7	1.65	—	—	—	—	—	—	—	—
4'	1.92 (d, 7.0)	16.2	0.93 (d)	1.89 (m)	1.47 (d, 1)	2.15 (br q, 7)	—	—	—	—	—
5'	1.81 (s)	20.7	0.93 (d)	2.17 (d, 1)	2.14 (d, 1)	1.08 (t, 7)	—	—	—	—	—
6'	—	—	—	—	—	2.17 (d, 1)	—	—	—	—	—
OH	—	—	—	—	—	—	—	—	4.39 (d, 8)	—	—
OH	—	—	—	—	—	—	—	—	4.43 (d, 5)	—	—
10-OH	—	—	—	—	—	—	—	—	5.06 (s)	—	—
[α]_D (solvent)	nd		nd	−68 (M)		−86 (C)	nd				nd
Source of compound	L. macrophylla		Othonna amplexicaulis	F. japonicum		synthetic	Euryops tenuissimus				synthetic
Ref	¹⁸		¹⁹	²⁰		²¹	²²				²³

Abbreviation: nd, not displayed.

X-ray.

Compounds 18 is a mixture with 19.

Tentative.

Solvent C or T, not shown.

Multiplicity and J not complete.

Measured at 80 °C.

May be interchanged.

Table 6.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 22–25.

Compound	22			23		24		24		25
(solvent)	¹H (C)^a	¹H (B)^a	¹H (P)^a	¹H (D)	¹³C (D)	¹H (C)	¹³C (C)	¹H (B)	¹³C (B)	¹H (C)	¹H (D)
1	—	—	—	4.28 (br s)	28.2	1.45-1.53 (m)	29.8	1.43 (m)	30.2	nd	nd
	—	—	—	—	—	1.94-2.06 (m)	—	2.06 (br s)	—	nd	nd
2	nd	nd	nd	1.95-2.00 (m)	36.1	1.77-1.88 (m)	28.2	1.70 (m)	27.5	nd	nd
	nd	nd	nd	1.65-1.71 (m)	—	—	—	1.39 (m)	—	nd	nd
3	nd	nd	nd	1.65-1.71 (m)	51.8	4.87 (s)	73.0	4.79 (br s)	72.4	4.99^a	5.14^a
4	nd	nd	nd	1.40-1.50 (m)	73.7	—	36.8	—	36.6	—	—
5	nd	nd	nd	2.30-2.40 (m)	147.0	1.28-1.39 (m)	45.1	1.18 (br s)	45.4	1.6	nd
6	—	—	—	6.67 (d, 2.4)	136.1	4.17 (s)	76.9	4.09 (s)	77.0	6.15 (s)	6.14 (s)
	—	—	—	—	—	—	—	—	—	—	—
7	—	—	—	—	36.1	—	116.6	—	116.5	—	—
8	—	—	—	—	80.3	—	150.8	—	151.0	—	—
9	3.6	2.83	3.78	2.00-2.10 (m)	122.0	2.77 (d, 18.3)	34.4	2.85 (br s)	34.9	3.11 (d, 18)	nd
	2.84	2.37	2.96	1.80-1.90 (m)	—	3.18 (br d, 18.3)	—	2.85 (br s)	—	2.72 (d, 18)	nd
10	—	—	—	—	147.0	—	74.7	—	74.2	—	—
11	—	—	—	—	8.7	—	119.3	—	118.9	—	—
12	7.12	6.7	nd	7.65 (s)	10.0	7.13^a	138.3	6.98 (s)	138.0	7.10 (q, 1.3)	7.15 (q, 1.3)
13	2.22	2.14	2.23	1.84 (s)	18.0	2.02^a	8.6	1.81 (d, 0.7)	7.9	1.89 (d, 1.3)	1.80 (d, 1.3)
14	0.98	0.96	1.20	1.21 (s)	166.6	1.43 (s)	13.0	1.55 (s)	13.0	0.98 (s)	1.05 (s)
15	0.89	0.64	0.84	0.85 (d, 6.3)	142.1	0.82 (d, 6.9)	11.8	0.75 (d, 6.6)	11.1	1.20 (d, 7)	1.03 (d, 7)
1'	—	—	—	—	125.5	—	65.5	—	168.9	—	—
2'	—	—	—	—	60.9	—	15.4	—	20.2	—	—
1''	—	—	—	—	—	—	170.7	—	65.2	—	—
2''	—	—	—	—	—	—	21.4	—	14.8	—	—
[α]4_D (solvent)	nd			–10 (C)		+7.7 (M)		+11.5 (E)		nd
Source of compound	synthetic			L. sagitta		L. oligonema		unidentified Ligularia		synthetic
Ref	²²			²⁴		²⁵		¹⁶		²⁶

Abbreviation: nd, not displayed.

Multiplicity and J not shown.

Table 7.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 26–34.

Compound	26		27		28		29		30, 31, 32 ^a	33, 34 ^b
(solvent)	¹H (C)	¹³C (C)	¹H (C)	¹³C (C)	¹H (C)	¹³C (C)	¹H (B)	¹³C (B)	¹H (B)^c	¹H (T)
1	nd	29.4	nd	29.5	1.55 (m)	29.7	1.37 (m)	30.5	1.7-1.9 (m)	nd
	nd	—	nd	—	1.96 (m)	—	1.37 (m)	—	1.7-1.9 (m)	nd
2	nd	29.7	nd	29	1.85 (m)	28.9	1.44 (m)	27.4	1.7-1.9 (m)	nd
	nd	—	nd	—	1.90 (m)	—	1.71 (m)	—	1.7-1.9 (m)	nd
3	4.97 (br s)	72.6	4.96 (br s)	72.6	4.97 (br s)	72.6	4.88 (br s)	72.4	4.92 (m)	4.99 (m)
4	nd	37.0	nd	37.1	1.60 (m)	37.1	1.33 (m)	37.2	nd	nd
5	—	45.2	—	45.1	—	45.2	—	45.7	—	—
6	6.16 (s)	69.5	6.16 (s)	69.5	6.22 (s)	69.2	6.34 (s)	69.9	4.43 (br s)	6.17 (br s)
7	—	114.8	—	114.9	—	115	—	115.7	—	—
8	—	150.8	—	150.8	—	150.8	—	151.5	—	—
9	2.75 (d, 18.1)	34.0	2.75 (d, 18.1)	33.6	2.73 (d, 18.1)	33.6	2.77 (br d, 18.0)	34.6	2.46 (br d)	nd
	3.13 (br d, 18.1)	—	3.13 (br d, 18.1)	—	3.08 (br d, 18.1)		2.67 (d, 18.0)	—	2.72 (br d)	nd
10	—	74.9	—	74.9	—	74.8	—	74.8	—	—
11	—	119.2	—	119.1	—	119.3	—	119.6		—
12	7.11 (br s)	138.9	7.11 (s)	138.9	7.08 (s)	139.0	6.95 (s)	139.2	6.98 (br s)	6.99 (br s)
13	1.89 (s)	8.1	1.90 (s)	8.1	1.89 (s)	8.1	1.93 (s)	8.1	1.91 (d, 1)	1.85 (d, 1)
14	1.26 (s)	11.7	1.27 (s)	12.1	1.27 (s)	12.3	1.35 (s)	12.8	1.39 (s)	1.25 (s)
15	0.99 (d, 7.3)	12.0	0.98 (d, 6.8)	12.0	0.98 (d, 6.8)	11.8	0.91 (d, 6.6)	11.6	0.79 (d, 7)	1.02 (d, 7)
1'	—	175.8	—	175.4	—	166.7	—	171.6	—	—
2'	2.56 (sept, 6.8)	34.4	2.36 (m)	41.4	—	127.2	1.95 (d, 6.7) 2H	43.4	—	—
3'	1.16 (d, 7.3)	19.0	nd	26.7	6.05 (qq, 6.8, 1.4)	138.9	2.04 (tsept, 6.7)	25.6	6.13 (dq, 1, 1)^d	6.05 (br s)
	—	—	—	—	—	—	—	—	5.27 (dq, 1, 1)	5.49 (dq)
4'	1.19 (d, 7.3)	19.2	0.88 (t, 7.5)	11.7	1.95 (dq, 6.8, 1.4)	15.6	0.81 (d, 6.7)	22.2	1.87 (t, 1)	1.93 (br s)
5'	—	—	1.16 (d, 7.3)	16.9	1.84 (s)	20.5	0.81 (d, 6.7)	22.3	—	—
OH	—	—	5.36 (s)	—	—	—	—	—	—	—
OAc	2.08 (s)	170.3	2.08 (s)	170.3	2.05 (s)	170.4	1.69 (s)	169.2	—	—
OAc	—	21.4	—	21.4	—	21.3	—	20.6	—	—
[α]0_D (solvent)	−30 (C)		−21 (C)		−56 (C)		+5.6 (E)		nd	−32 (C)^e
Source of compound	L. oligonema		L. oligonema		L. dictyoneura		L. stenoglossa		Lopholaena platyphylla	synthetic
Ref	²⁷		²⁷		²⁸		¹⁶		²⁹	²¹

Abbreviation: nd, not displayed.

Compounds 30, 31, and 32 are a mixture. For 31; 6.12 (qq, 7, 1), 1.99 (dq, 7, 1), 1.92 (dq, 1, 1), and for 32; 5.76 (qq, 1, 1), 2.13 (d, 1), 1.87 (d, 1).

Compouonds 33 and 34 are a mixture. For 34; 6.37 (qq, H-3'’), 1.83 (br s, H-4'’), 1.83 (br s, H-5'’); J not shown.

Measured at 75˚C.

Shown only as “13”, but most probably “6.13”.

Measured at 436 nm.

Table 8.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 35–38.

Compound	35 ^a		35 ^a		36 ^a		37 ^a		38 ^a
(solvent)	¹H (C)	¹³C (C)	¹H (B)	¹³C (B)	¹H (B)	¹³C (B)	¹H (B)	¹³C (B)	¹H (B)	¹³C (B)
1	1.96 (m)	34.0	1.26 (m)	34.1	1.65 (m)	34.1	1.67 (ddd, 13.4, 7.7, 1.4)	34.1	1.54 (ddd, 13.6, 7.4, 1.6)	33.1
	2.19 (td, 13.2, 6.6)	—	1.74 (td, 13.4, 6.3)	—	2.01 (td, 13.6, 6.2)	—	2.04 (td, 13.4, 6.6)	—	1.92 (m)	—
2	2.45 (m)	37.7	2.11 (m)	37.5	1.76 (ddd, 13.9, 13.6, 7.7)	37.5	1.76 (ddd, 15.4, 13.4, 7.7)	37.6	1.75 (ddd, 15.4, 13.6, 7.4)	37.3
	2.49 (dt, 13.4, 6.3)	—	1.71 (dt, 13.4, 6.3)	—	2.14 (ddd, 13.9, 6.2, 2.6)	—	2.16 (ddd, 15.4, 6.0, 1.4)	—	2.14 (ddd, 15.4, 5.9, 1.6)	—
3	—	210.4	—	208.2	—	208.4	—	208.5	—	207.6
4	2.27 (q, 6.6)	48.0	1.67 (q, 6.8)	47.6	1.61 (m)	47.7	1.64 (q, 6.0)	47.7	1.64 (q, 6.7)	47.6
5	—	46.3	—	46.3	—	47.1	—	47.0	—	46.9
6	4.50 (d, 6.6)	68.9	4.16 (d, 6.9)	68.9	3.73 (s)	78.7	3.87 (s)	77.2	6.16 (s)	69.7
7	—	118.2	—	118.7	—	116.1	—	116.6	—	115.4
8	—	148.7	—	149.1	—	151.6	—	151.5	—	151.5
9	3.42 (d, 17.9)	34.0	2.82 (d, 17.6)	34.1	2.95 (d, 18.3)	35.2	2.95 (d, 18.1)	35.2	2.88 (d, 17.8)	34.1
	2.90 (d, 17.9)	—	2.50 (d, 17.6)	—	2.89 (d, 18.3)	—	2.94 (d, 18.1)	—	2.73 (d, 17.8)	—
10	—	75.4	—	75.1	—	74.0	—	73.9	—	74.0
11	—	119.3	—	119.8	—	119.6	—	119.5	—	119.7
12	7.16 (s)	139.0	6.97 (s)	138.9	6.94 (s)	138.9	6.95 (s)	138.8	6.91 (s)	139.5
13	2.05 (s)	7.9	1.88 (s)	7.8	1.68 (s)	8.4	1.71 (s)	8.5	1.85 (s)	8.1
14	1.18 (s)	13.2	0.98 (s)	13.1	1.13 (s)	13.6	1.15 (s)	13.7	0.92 (s)	12.5
15	0.94 (d, 6.6）	7.7	0.79 (d, 6.8)	8.2	0.70 (d, 6.9)	8.1	0.80 (d, 6.9)	8.1	0.97 (d, 6.7)	8.4
1'	—	—	—	—	—	—	2.92 (dq, 15.4, 6.9)	65.6	—	169.2
	—	—	—	—	—	—	3.25 (dq, 15.4, 6.9)		—	—
2'	—	—	—	—	—	—	0.79 (t, 6.9)	15.2	1.42 (s)	20.0
6-OH	2.66 (d, 6.6)	—	2.30 (d, 6.9)	—	—	—	—	—	—	—
10-OH	3.60 (s)	—	2.99 (br s)	—	—	—	5.30 (br s)	—	3.30 (s)	—
OMe	—	—	—	—	2.80 (s)	57.2	—	—	—	—
[α] _D (solvent)	−6.4 (E)		−6.4 (E)		−1.7 (E), −10.4 (C)		nd		−40.4 (E)
Source of compound	L. stenoglossa		L. stenoglossa		L. stenoglossa		L. stenoglossa		L. stenoglossa
Ref	¹⁶		¹⁶		¹⁶		¹⁶		¹⁶

Abbreviation: nd, not displayed.

CD measured.

Table 9.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 39–46.

Compound	39 ^a		40 ^a		41	42	43	44 ^b	45	46
(solvent)	¹H (B)	¹³C (B)	¹H (B)	¹³C (B)	¹H (C/T)	¹H (C/T)	¹H (C)	nd	¹H (T)	¹H (B)
1	1.57 (dt, 13.5, 7.6)	33.1	1.46 (td, 13.5, 5.6)	33.8	nd	nd	nd		nd	nd
	1.94 (m)	—	1.02 (ddd, 13.5, 7.3, 1.6)	—	nd	nd	nd		nd	nd
2	1.76 (m)	37.4	2.06 (m)	37.0	nd	nd	nd		nd	nd
	2.15, (dt, 15.5, 5.9)	—	2.33 (td, 13.5, 7.3)	—	nd	nd	nd		nd	nd
3	—	207.6	—	208.3	4.02 (m)	5.10 (m)	5.25 (m)		5.20 (m)	—
4	1.68 (q, 7.3)	47.6	2.86 (q, 7.2)	48.3	nd	nd	nd		nd	nd
5		46.9		49.8	—	—	—		—	—
6	6.22 (s)	69.5	6.03 (s)	69.3	2.15 (d, 17)	nd	nd		nd	nd
	—	—	—	—	2.53 (d, 17)	nd	nd		nd	nd
7	—	115.6	—	116.2	—	—	—		—	—
8	—	151.5	—	149.1	—	—	—		—	—
9	2.92 (d, 18.0)	34.2	2.27 (d, 16.2)	36.5	4.47 (br s)	5.65 (m)	5.70 (m)		—	—
	2.77 (d, 18.0)	—	2.56 (dd, 16.2, 1.6)	—	—	—	—		—	—
10	—	74.1	—	74.0	—	—	—		—	—
11	—	119.6	—	120.0	—	—	—		—	—
12	6.93 (br s)	139.6	6.84 (s)	139.5	7.12 (q, 1.2)	7.08 (d, 1)	7.05 (d, 1)		7.37 (br s)	7.48 (q, 1)
13	1.90 (s)	8.2	1.82 (s)	9.3	1.90 (d, 1.2)	1.92 (d, 1)	1.92 (d, 1)		2.00 (s)	1.97 (d, 1)
14	0.98 (s)	12.7	1.07 (s)	14.0	1.21 (s)	1.13 (s)	1.11 (s)		0.98 (s)	1.05 (s)
15	0.98 (d, 7.3)	8.4	1.11 (d, 7.2)	9.5	1.10 (d, 6.5)	1.05 (d, 7)	1.11 (d, 7)		1.08 (d, 7)	1.33 (d, 7.5)
1'	—	171.4	—	171.7	—	—	—		—	—
2'	1.76 (m)	43.0	2.05 (d, 6.8)	43.6	—	—	—		—	—
	1.76 (m)	—	2.05 (d, 6.8)	—	—	—	—		—	—
3'	1.93 (m)	25.5	2.16 (tsept, 6.8)	24.9	—	—	—		—	—
4'	0.71 (d, 6.9)	22.2	0.86 (d, 6.8)	22.7	—	—	—		—	—
5'	0.72 (d, 6.9)	22.3	0.87 (d, 6.8)	22.8	—	—	—		—	—
OAc	—	—	—	—	—	2.10 (s)	2.19 (s)		2.00 (s)
OAc	—	—	—	—	—	2.00 (s)	2.00 (s)		—
OH	—	—	—	—	—	—	—		—	3.73 (s)
[α]_D (solvent)	−5.5 (E)		+4.1 (E)		−5 (M)	nd	nd	−18 (M)	nd	nd
Source of compound	L. stenoglossa		L. stenoglossa		synthetic	synthetic	synthetic	synthetic	synthetic	synthetic
Ref	¹⁶		¹⁶		¹³	¹³	¹³	¹³	¹³	¹³

Abbreviation: nd, not displayed.

CD measured.

Only [α]_D shown.

Table 10.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 47–55.

Compound	47	48		49	50	51	52 ^a	53	54 ^a	55
(solvent)	¹H (B)	¹H (T)^b	¹H (B)	¹H (D)	¹H (C)	¹H (C)	¹H (C)	¹H (T)	¹H (C)	¹H (T)
1	nd	nd	nd	nd	nd	nd	nd	nd	nd	nd
2	nd	nd	nd	nd	nd	nd	nd	nd	nd	nd
3	5.30 (m)	5.20 (m)	5.22 (m)	nd	nd	nd	nd	nd	nd	nd
4	—	—	—	nd	nd	nd	nd	nd	nd	nd
5	nd	nd	nd	nd	nd	nd	nd	nd	nd	nd
6	nd	nd	nd	nd	—	6.01 (s)	6.54 (d, 1.5)	6.74 (s)	6.48 (d, 1.5)	6.67 (s)
7	nd	nd	nd	—	—	—	—	—	—	—
8	—	—	—	—	—	—	—	—	—	—
9	4.31 (br s)	5.70 (m)	6.05 (m)	4.54 (br s)	—	—	4.84 (br s)	—	4.84 (br s)	—
10	—	—	—	—	—	—	—	—	—	—
11	—	—	—	—	—	—	—	—	—	—
12	7.05 (m)	7.04 (m)	6.92 (m)	7.12 (br s)	7.48 (q, 1)	7.42 (q, 1)	7.11 (br s)	7.37 (q, 1)	7.11 (br s)	7.37 (q, 1)
13	1.73 (d, 1)	1.90	1.65 (d, 1)	2.00 (d, 1)	2.28 (d, 1)	2.03 (d, 1)	1.83 (d, 1)	1.90 (d, 1)	1.83 (d, 1)	1.90 (d, 1)
14	1.17 (s)	1.18 (s)	1.31 (s)	0.90 (s)	1.20 (s)	0.85 (s)	1.08 (s)	0.93 (s)	1.08 (s)	0.93 (s)
15	1.10 (m)	1.06 (m)	nd	1.05 (d, 7)	1.01 (d, 7)	0.85 (d, 7)	1.12 (d, 7)	1.14 (d, 7)	1.12 (d, 7)	1.14 (d, 7)
2'	—	—	—	—	—	—	—	—	5.72 (tq)	—
3'	5.80 (q, 7)	5.95	5.72 (q, 8)	—	—	—	6.13 (qq)	nd	—	—
4'	2.05 (d, 7)	1.98	1.99 (d, 8)	—	—	—	2.02 (dq)	nd	2.18 (q)	—
5'	1.95 (m)	1.90	1.90^b	—	—	—	1.92 (dq)	nd	1.09 (t)	—
6'	—	—	—	—	—	—	—	—	2.20 (br s)	—
2''	—	5.65 (m)	5.55 (m)	—	—	—	—	—	—	—
3''	—	—	—	—	—	—	—	—	—	—
4''	—	1.90	1.31 (d, 1.5)	—	—	—	—	—	—	—
5''	—	2.18	2.07 (m)	—	—	—	—	—	—	—
[α]_D (solvent)	nd	+79 (E)		nd	nd	nd	−51 (C)	nd	−51 (C)	nd
Source of compound	synthetic	F. japonicum		synthetic	synthetic	synthetic	synthetic	synthetic	synthetic	synthetic
Ref	¹³	¹³		²¹	³⁰	³⁰	²¹	²¹	²¹	²¹

Abbreviation: nd, not displayed.

Compounds 52 and 54 are a mixture. The value of [α]_D is for the mixture.

Multiplicity and J not complete.

Table 11.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 56–61.

Compound	56 ^a	57 ^a	58	59	60		61
(solvent)	¹H (T)	¹H (T)	¹H (D)^b	¹H (C)^b	¹H (C)	¹³C (C)	¹H (C)	¹³C (C)
1	nd	nd	4.00	5.45	3.83 (dd, 8.9, 2.5)	73.3	3.92 (t. 3.0)	62.1
2	nd	nd	nd	nd	1.63 (m)	31.2	1.72-1.76 (m)	24.4
	nd	nd	nd	nd	2.08 (m)	—	2.57-2.65 (m)	—
3	nd	nd	3.64	5.09	1.25 (m)	29.2	2.42-2.45 (m)	23.4
4	nd	nd	—	—	1.47 (m)	35.0	1.40-1.43 (m)	32.0
5	nd	nd	1.16	1.65	1.51 (m)	48.1	1.61-1.65 (m)	50.2
6	6.42 (dd, 1.5, 1.5)	6.50 (dd, 1.5, 1.5)	4.17	6.08	4.49 (s)	68.1	7.04 (s)	68.3
7	—	—	—	—	—	139.5	—	139.6
8	—	—	—	—	—	144.4	—	146.1
9	5.94 (d, 1.5)	5.87 (d, 1.5)	2.85	3.00	—	188.0	—	186.4
	—	—	2.60	3.00	—	—	—	—
10	—	—	—	—	—	79.9	—	80.5
11	—	—	—	—	—	121.9	—	121.8
12	7.04 (br s)	7.04 (br s)	7.19	7.13	7.50 (s)	146.9	7.47 (s)	147.4
13	1.80 (d, 1)	1.80 (d, 1)	1.93	1.90	2.11 (s)	7.4	1.92 (s)	8.5
14	1.10 (s)	1.10 (s)	0.81	0.97	1.27 (s)	11.2	1.03 (s)	16.0
15	1.14 (d, 7)	1.14 (d, 7)	1.33	1.33	0.81 (d, 5.4)	15.3	1.13 (d, 7.2)	16.0
1'	—	—	—	—	—	—	—	176.5
2'	5.74 (tq)	—	—	—	—	—	2.66-2.71 (m)	34.2
3'	—	6.14 (qq)	—	—	—	—	1.23 (d, 7.2)	18.6
4'	2.18 (q)	2.01 (dq)	—	—	—	—	1.26 (d, 7.2)	19.5
5'	1.10 (t)	1.91 (dq)	—	—	—	—	—	—
6'	2.20 (br s)	—	—	—	—	—	—	—
2''	—	5.74 (tq)	—	—	—	—	—	—
3''	6.14 (qq)	—	—	—	—	—	—	—
4''	2.01 (dq)	2.18 (q)	—	—	—	—	—	—
5''	1.91 (dq)	1.10 (t)	—	—	—	—	—	—
6''	—	2.20 (br s)	—	—	—	—	—	—
1-OH	—	—	4.41 (d, 7.5)	—	—	—	—	—
3-OH	—	—	4.41 (d, 7.5)	—	—	—	—	—
6-OH	—	—	4.31 (d, 8)	—	—	—	—	—
10-OH	—	—	5.01 (s)	—	—	—	—	—
OAc	—	—	—	2.06 (s)	—	—	—	—
OAc	—	—	—	2.10 (s)	—	—	—	—
OAc	—	—	—	2.10 (s)	—	—	—	—
[α]_D (solvent)	nd	nd	nd	nd	+203.9 (F)		+52 (C)
Source of compound	Othonna heterophylla	Othonna heterophylla	synthetic	synthetic	S. nemorensis		L. virgaurea
Ref	²¹	²¹	²⁶	²⁶	³¹		³²

Abbreviation: nd, not displayed.

Compounds 56 and 57 are a mixture.

Multiplicity and J not complete.

Table 12.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 62–64.

Compound	62		63 ^a		64
(solvent)	¹H (nd)^b	¹H (B)^c	¹H (C)	¹³C (C)	¹H (C)
1	4.77 (br dd, 2.5, 2.5)	5.02 (t, 2.5)	4.07 (d, 2.0, 2.0)^d	62.0	4.84 (br s)
2	1.64 (br d, 13)	1.64 (br d, 13)	1.73 (m)	24.4	1.70 (m)
	2.29 (m)	2.29 (dddd, 13, 13, 3.5, 2.5)	2.63 (m)	—	2.32 (m)
3	2.29 (m)	2.52 (dddd, 13, 13, 3.5)^e	2.54 (m)	23.3	2.32 (m)
	1.43 (br d, 13)	1.37 (br d, 13)	1.46 (m)	—	2.32 (m)
4	1.72 (br qd, 7, 3)	1.81 (m)	1.78 (m)	31.9	1.70 (m)
5	—	—	—	50.0	—
6	7.02 (br s)	7.15 (br s)	7.02 (s)	67.9	7.05 (s)
7	—	—	—	139.7	—
8	—	—	—	145.9	—
9	—	—	—	186.2	—
10	—	—	—	80.4	—
11	—	—	—	121.8	—
12	7.47 (q, 1)	6.83 (q, 1)	7.51 (s)	147.4	7.43 (br s)
13	1.97 (d, 1)	1.68 (d, 1)	1.98 (d)^f	8.1	1.92 (br s)
14	1.03 (s)	1.12 (s)	1.28 (s)	16.2	1.00 (s)
15	1.20 (d, 7)	1.26 (d, 7)	1.16 (d, 7.4)	5.9	1.18 (d, 7)
1'	—	—	—	166.9	—
2'	2.03 (dq, 15, 7.5)	1.83 (dq, 15, 7.5)	—	141.9	—
	1.84 (dq, 15, 7.5)	1.70 (dq, 15, 7.5)	—	—	—
3'	0.85 (dd, 7.5, 7.5)	0.77 (dd, 7.5, 7.5)	6.26 (qq, 7.2, 1.3)	126.6	5.95 (qq, 7, 1.5)
4'	—	—	1.94 (dq, 7.2, 1.3)	15.9	1.54 (dq, 7, 1.5)
5'	—	—	2.08 (q, 1.3)	20.5	1.90 (dq, 1.5, 1.5)
OAc	—	—	—	—	nd
[α]d_D (solvent)	−40 (C)		−48.3 (E)		−27 (C)
Source of compound	S. collinus		S. nemorensis		S. dryophyllus
Ref	³³		^34,35		³⁶

Abbreviation: nd, not displayed.

CD shown in ref.³⁵

Solvent not shown, but may be CDCl₃ by analogy.

Measured at 70˚C.

Multiplicity must be “dd”.

One J missing.

J not shown.

Table 13.

NMR Chemical Shifts (Solvent, d, Multiplicity, and J (Hz)), Specific Rotations, Source of Compounds, and References of Compounds 65–71.

Compound	65 ^a		66 ^b		67	68	69	70	71 ^b
(solvent)	¹H (C)	¹³C (C)	¹H (C)	¹³C (C)	¹H (C)	¹H (C)	¹H (C)	¹H (C)	¹H (C)	¹³C (C)
1	4.88 (br s)	74.6	3.94 (br s)	62.0	3.98 (dd, 2.0)	nd	nd	1.3-1.9 (m)	3.64 (d, 5.5)	74.0
2	1.64-1.67 (m)	21.1	1.76 (dd, 14.0, 2.0)	24.3	1.75-2.52 (m)	nd	nd	1.3-1.9 (m)	2.27 (m)	23.8
	2.21-2.29 (m)	—	2.59 (t, 14.0)	—	1.75-2.52 (m)	nd	nd	1.3-1.9 (m)	1.76 (m)	—
3	2.32-2.38 (m)	23.8	1.44 (d, 13.6)	23.3	1.75-2.52 (m)	4.79 (m)	5.06 (m)	1.3-1.9 (m)	2.36 (m)	26.0
	—	—	—	—	1.75-2.52 (m)	—	—	1.3-1.9 (m)	—	—
4	1.43-1.52 (m)	31.8	2.47 (t, 14.0)	31.9	1.75-2.52 (m)	—	—	—	1.41 (m)	39.8
5	1.68-1.74 (m)	51.0	1.65 (m)	50.1	—	2.88 (qd, 7, 2.5)	2.70 (qd, 7, 3)	—	1.94 (m)	56.7
6	6.97 (s)	66.9	7.06 (s)	68.2	7.18 (s)	—	—	7.05 (s)	4.81 (s)	78.5
7	—	138.7	—	139.6	—	—	—	—	—	149.0
8	—	146.3	—	145.9	—	—	—	—	—	146.9
9	—	185.9	—	186.3	—	—	—	—	—	186.2
10	—	79.2	—	80.5	—	—	—	—	—	87.6
11	—	120.8	—	121.8	—	—	—	—	—	120.0
12	7.28 (s)	146.5	7.50 (s)	147.4	7.46 (s)^c	7.52 (q, 1)	7.44 (q, 1)	7.14 (q, 1)	7.50 (s)	146.9
13	1.91 (s)	8.4	1.94 (s)	8.5	1.98 (s)	2.29 (d, 1)	2.24 (d, 1)	1.93 (d, 1)	2.12 (s)	7.5
14	1.05 (s)	15.8	1.05 (s)	16.0	1.07 (s)	1.21 (s)	1.32 (s)	1.19 (s)	0.73 (s)	15.4
15	0.85 (d, 6.8)	15.2	1.14 (d, 7.6)	15.9	1.16 (d, 7.4)	1.18 (d, 7)	1.21 (d, 7)	1.00 (s)	1.21 (d, 7.4)	19.0
1'	—	165.2	—	176.5	—	—	—	—	—	—
2'	—	130.5	2.73 (qq, 7.2, 7.2)	34.1	—	—	—	—	—	—
3'	7.95 (dd, 8.2, 1.0)	129.1	1.28 (d, 7.2)	18.6	6.27 (m)	—	—	5.95 (qq, 7, 1)	—	—
4'	7.41-7.46 (m)	128.3	1.30 (d, 7.2)	19.5	1.92 (dq, 7.2, 1.3)	—	—	2.20 (dq, 7, 1)	—	—
5'	7.54-7.61 (m)	132.4	—	—	2.08 (q, 1.3)^d	—	—	1.90 (dq, 1, 1)	—	—
6'	7.41-7.46 (m)	128.3	—	—	—	—	—	—	—	—
7'	7.95 (dd, 8.2, 1.0)	129.1	—	—	—	—	—	—	—	—
1''	—	170.6	—	—	—	—	—	—	—	—
2''	2.19 (s)	20.8	—	—	—	2.07 (s)	2.07 (s)	2.19 (s)	—	—
OH	4.18 (s)	—	4.01 (s)	—	—	—	—	—	4.25 (s)	—
[α]_D (solvent)	+31.4 (E)		+0.9 (M)		nd	nd	nd	nd	+165.3 (F)
Source of compound	Acanthopanax leucorrhizus		L. atroviolacea		synthetic	synthetic	synthetic	S. fistulosus	S. nemorensis
Ref	³⁷		^38,39		³⁵	³⁰	³⁰	⁴⁰	³¹

Abbreviation: nd, not displayed.

Numbering changed.

X-ray.

Assigned to H-2 in ref,³⁵ but must be H-12.

Not assigned, but must be H-5’ (“q” should be “quint”).

The data of tetradymol (1),^9–11 10-angeloyloxyfuranoeremophilan-2β-ol (2),¹² 2β-(2-methylacryloyloxy)furanoeremophilan-10β-ol (3),¹² 2β-angeloyloxyfuranoeremophilan-10β-ol (4),¹² and furanoeremophilane-3β,10β-diol (5),¹³ its 3-O-acetyl 6,¹³ and its 3-O-angeloyl 7¹³ (Figure 1) are listed in Table 1. The structure of tetradymol (1) was established by X-ray.⁹ The configuration of C-10 of compound 2 was not determined, presumably because the NOE method was not popular at that time. Compounds 3 and 4 are 2β-substituted, however, 5-7 are 3β-subsutituted. Unfortunately, the solvent used for compounds 2-4, either CDCl₃ or CCl₄, was not specified. The H-6 of tetradymol (1)^9,10 seems to be unusual; the data in ref¹¹ is believed to be more reliable. The data of compound 6 were obtained at 60 °C. Most of the data were reported in 1970s, and it is desirable that measurements be recorded with a modern equipment in the near future.

Table 2 shows the data of 4αH-10β-hydroxyfuranoeremophilan-3-one (8),¹³ 4βH-10β- hydroxyfuranoeremophilan-3-one (9),¹³ and furanoeremophilane-6β,10β-diol (10)^14–16 (Figure 1). Compounds 8 and 9 are C-4 epimers. The coupling constant (J = 7 Hz) for H₃-15 of compound 9 was obtained after deuterium labeling. The authors described that the compound 8 adopted steroid-like conformation, and 9 non-steroid-like conformation.⁸

The data of 6β-methoxyfuranoeremophilan-10β-ol (11)^14–16 and 6β-ethoxyfuranoeremophilan-10β-ol (12)^16,17 (Figure 1) are displayed in Table 3. These are methyl- and ethyl-ether of compound 10. Because the H-6 and OH-6 chemical shifts were not shown in ref,¹⁷ they were collected from our own original charts on this occasion. The data collected in CDCl₃ were also included here.¹⁶

Table 4 illustrates the data of 6β-acetoxyfuranoeremophilan-10β-ol (13),^14,15,17 6β-(2-methylpropanoyloxy)furanoeremophilan-10β-ol (14),¹⁰ and 6β-(2-methylbutanoyloxy)furanoeremophilan-10β-ols (15 and 16).^14,17 Compound 13 is the acetate of compound 10. Compounds 14-16 are 6-O-acyl derivatives of 10. The absolute configuration of 2′-methyl group of 15 was established by comparing the two data of the synthetic compounds (2′-S and 2′-R).¹⁷ Unfortunately, the data of 2′-R compound are not described.

The data of four 6β-acyloxyfuranoeremophilan-10β-ols (17−20)^18–21 (Figure 1) and furanoeremophilane-1α,6β,10β-triol (21)^22,23 (Figure 2) are tabulated in Table 5. Compounds 18 is a mixture with 19, while, 19 was isolated in pure. The solvent used for 18, either CDCl₃ or CCl₄, was not specified. The structure of 17 was established by X-ray.¹⁸ The NMR spectrum of compound 21 was measured in CDCl₃ at 80 °C.²² Some coupling patterns and J values of compounds 18-20 are not shown. Detailed NMR data of compound 21 is highly expected in the near future.

Table 6 shows the data of 10β-hydroxyfuranoeremophilane-1,6-dione (22),²² 6β-(2-hydroxymethylacryloyloxy)furanoeremophilane-1β,10β-diol (23),²⁴ (Figure 2) 3β-acetoxy-6β-ethoxyfuranoeremophilan-10β-ol (24),^16,25 and 3β,6β-diacetyloxyfuranoeremophilan-10β-ol (25)²⁶ (Figure 3). Some coupling patters and J values of compounds 22, 24, and 25 were not reported.^22,25,26 The H-1 of compound 23 appeared at δ 4.28 as a broad singlet, meaning that this compound adopted a steroid-like conformation.⁸

The data of four 3β-acetoxy-6β-acyloxyfuranoeremophilan-10β-ols, 26−29,^16,27,28 the mixture of three 3β-acyloxyfuranoeremophilane-6β,10β-dols, 30-32,²⁹ and the mixture of two 3β,6β-diacyloxyfuranoeremophilan-10β-ols, 33 and 34²¹ (Figure 3) are accumulated in Table 7. The former four compounds have acetoxy groups at C-3β position. Compounds 30-32 were not separated, and the data shown in Table 7 correspond to compound 30; the data for the other two acyl groups being shown in the footnote. In the footnote of Table 2 for compound 30 in ref,²⁹ the resonance H-3′ is listed as “13”, but it is most likely “6.13”. Compounds 33 and 34 are a mixture. The data of compound 33 were shown in Table 7, and those of 34 in the footnote. Compound 28 has an angelate group, while, 34 a tiglate group. It is very interesting to note that only compound 29 shows the positive sign of the specific rotation among other 8 compounds in Table 7.

Table 8 provides the data of four 10β-hydroxyfuranoeremophilan-3-ones, 35−38¹⁶ (Figure 3). Compound 35 is keto diol, and others are its 6-metoxy, ethoxy, and acetoxy derivatives. CD spectra of compounds 35−38 were measured.

The data of two 6β-acyloxy-10β-hydroxyfuranoeremophilan-3-ones, 39¹⁶ and 40¹⁶ (Figures 3), furanoeremophilane-3β,9β,10β-triol (41),¹³ its diacetate 42,¹³ the 9α-acetate 43 (C-9 epimer of 42),¹³ 3β,10β-dihydroxyfuranoeremophilan-9-one (44),¹³ its acetate 45,¹³ and 10β-hydroxyfuranoeremophilane-3,9-dione (46)¹³ (Figure 4) are given in Table 9. Compound 40 has 4βH as in the case of compound 9. Compounds 42 and 43 are C-9 epimers. The solvent for 41 and 42 are either CDCl₃ or CCl₄, not specified. The NMR data of compound 44 were not reported.¹³ The CD spectra of compounds 39 and 40 were measured.¹⁶

Table 10 presents the data of two 3β-acyloxyfuranoeremophilan-10β-ols, 47 and 48¹³ (Figure 4), furanoeremophilane-6β,9β,10β-triol (49),²¹ its 6-O-acyl derivatives, 52 and 54,²¹ and 10β-hydroxyfuranoeremophilan-9-ones, 50,³⁰ 51,³⁰ 53,²¹ and 55²¹ (Figure 5). Compounds 52 and 54 are a mixture; the value of the specific rotation being for the mixture. Compound 51 has a trans-fused decalin system and a 6α-acetoxy substituent; H-6 resonating at slightly higher field. Some of the data of compound 48 are not described in detail.¹³ Compounds 52 and 54 differ only in the acyl group, similar to the case of compounds 53 and 55.

The data of two 6β,9β-diacyloxyfuranoeremophilan-10β-ols, 56 and 57²¹ (Figure 5), two 1,3,6-trioxygenated furanoeremophilan-10β-ols, 58 and 59,²⁶ 1α,6β,10β-trihydroxyfuranoeremophilan-9-one (60),³¹ and 1β,10α-dihydroxy-6β-(2-methylpropanoyloxy)furanoeremophilan-9-one (61)³² (Figure 6) are shown in Table 11. Compounds 56 and 57 are a mixture. Compound 59 is a diacetate of 58. The configuration of compound 61 at C-1 and C-10 are different from those of 58–60. Compound 60 seems to adopt a steroid-like conformation judged from the coupling pattern of H-1.³¹ However, it is uncertain whether compounds 58 and 59 adopt a steroid-like conformation, as the coupling patterns and J values have not been reported.²⁶

Table 12 illustrates the data of two 1,6-diacyloxy-10β-hydroxyfuranoeremophilan-9-ones, 62 and 64,^33,36 and 6β-angeloyloxy-1α,10β-dihydroxyfuranoeremophilan-9-one (63)^34,35 (Figure 6). Compound 64 corresponds to the acetate of compound 63. The multiplicity of H-1 in compound 63 is listed as “d”, but it should be “dd”, since two J couplings are indicated. The solvent for compound 62 was not shown, but probably CDCl₃ by analogy, and measurement in C₆D₆ was carried out at 70˚C. The CD data of compound 63 was published in ref.³⁵ The C-1 position of compound 62 was substituted by a propanoyl group, which is rather rare.

The data of bezoylated compound 65,³⁷ two chlorinated compounds, 66^38,39 and 67,³⁵ two 6,9-diones, 68 and 69,³⁰ 1,6-diacyloxy-4α-hydroxyfuranoeremophilan-9-one 70,⁴⁰ and highly distorted intramolecular ether 71³¹ (Figure 6) are shown in Table 13. Benzoylated natural product 65 is relatively rare, and the numbering system of compound 65 has been modified. The structure of compound 66 was established by X-tray.³⁸ Compounds 66 and 67 contain chlorine atoms at the C-1 position. The chemical shifts of H-1 of compounds 66 and 67 are slightly shifted to the higher region than those of compounds bearing a hydroxy group, as expected. The resonance of δ 7.46 for 67 was assigned to H-2 in ref,³⁵ but it should be H-12.³⁵ The signal at δ 2.08 must be for H-5′, although it was not assigned; the pattern “q” should be “quintet”.³⁵ It is interesting to note that compounds 68 and 69 are C-10 epimers; cis and trans fused decalins with a 1,4-diketone moiety. The structure of compound 71 was established by X-ray.³¹ Compounds 60 and 71 were isolated from the same plant.³¹

Conclusion

This review focuses on 71 furanoeremophilanes that contain a C-10 hydroxy group with oxygen functionalities in the skeleton. The simplest compound is tetradymol (1), which has no functional group. One or several oxygenated functional groups are substituted at C-1, C-2, C-3, C-4, C-6, and C-9 positions; among the compounds described here, most possessed one or two substituents, whereas those with three were very few. The papers discussed here are not limited to a specific time period; however, many of the older publications lack complete signal assignments, while most of the more recent studies, benefiting from improved instrumentation, provide full assignments. Nevertheless, many synthetic papers still only list chemical shifts without detailed assignments.

Footnotes

Acknowledgements

The author thanks laboratory staff members engaged in these projects acquiring NMR data. Special thanks are due to Dr Yasuko Okamoto and Prof. Masakazu Sono, Tokushima Bunri University, Prof. Yoshinosuke Usuki, Osaka Metropolitan University, and Emeritus Prof. Chiaki Kuroda, Rikkyo University, for their help to check the references appeared in this review.

ORCID iD

Motoo Tori

Ethical Considerations

Ethical approval is not applicable for this review.

Funding

The author received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

References

Pinder

. The chemistry of the eremophilane and related sesquiterpenes. Prog Chem Org Nat Prod. 1977;34:81-186.

Liao

Liu

Jia

Sun

. Eremophilane sesquiterpenes from the genus Ligularia. Chem Biodivers. 2016;13(6):645-671.

Tori

Kuroda

. Chemical constituents of Ligularia Species (Asteraceae) and their diversity in east Asia. Prog Chem Org Nat Prod. 2020;113:1-247.

Wehrli

Nishida

. The use of carbon-13 nuclear magnetic resonance spectroscopy in natural products chemistry. Prog Chem Org Nat Prod. 1979;36:1-229.

Tori

. Cumulative data of ¹H and ¹³C NMR signals and specific rotations of Eremophilane Sesquiterpenoids. 1. Bicyclic eremophilanes (1). Nat Prod Commun. 2022;17(8). DOI: https://doi.org/10.1177/1934578X221109527

Tori

. Cumulative data of ¹H and ¹³C NMR signals and specific rotations of Eremophilane Sesquiterpenoids. 2. Bicyclic eremophilanes (2). Nat Prod Commun. 2022;17(12). DOI: https://doi.org/10.1177/1934578X221141172

Tori

. Cumulative data of ¹H and ¹³C NMR signals and specific rotations of Eremophilane Sesquiterpenoids. 3. 10H-Furanoeremophilanes without 3-O functionality. Nat Prod Commun. 2023;18(6). DOI:1934578X231180710

Tori

. Cumulative data of ¹H and ¹³C NMR signals and specific rotations of Eremophilane Sesquiterpenoids. 4. 10H-3-O-furanoeremophilanes. Nat Prod Commun. 2024;19(5). DOI:https://doi.org/10.1177/1934578X241250240

Jennings

Reeder

Hurley

. Isolation and structure determination of one of the toxic constituents from Tetradymia glabrata. J Org Chem. 1974;39(23):3392-3398.

10.

Jennings

Hurley

Reeder

, et al. Isolation and structure determination of the second toxic constituent from Tetradymia glabrata. J Org Chem. 1976;41(26):4078-4081.

11.

Chen

Zheng

Zhang

Aisa

Hao

. Phytotoxic terpenoids from Ligularia cymbulifera roots. Front Plant Sci. 2017;7:2033.

12.

Bohlmann

Zdero

Grenz

. Über die inhaltsstoffe der Gattung Euryops. Chem Ber. 1974;107(8):2730-2759.

13.

Nagano

Takahashi

. 3(-Angeloyloxy-10(-hydroxy-9(-senecioyloxyfuranoeremophilane And 3(-angeloyloxy-10(-hydroxyfuranoeremophilane. New furanoeremophilane derivatives from Farfugium japonicum Kitamura. Bull Chem Soc Jpn. 1978;51(11):3335-3340.

14.

Tada

Moriyama

Tanahashi

Takahashi

. New furanosesquiterpenes from Ligularia japonica less. Furanoeremophilane-6(,10(-diol, 10(-hydroxy-6(-methoxyfuranoeremophilane and 10(-hydroxyfuranoeremophilan-6(-yl 2′ξ-methylbutanoate. Tetrahedron Lett. 1971(43):4007-4010.

15.

Tada

Moriyama

Tanahashi

Takahashi

. Furanoeremophilane-6(,10(-diol and its derivatives. New furanosesquiterpenes from Ligularia japonica less. Bull Chem Soc Jpn. 1974;47(8):1999-2002.

16.

Tori

. unpublished results. unpublished data.

17.

Tori

Watanabe

Matsuo

, et al. Diversity of Ligularia kanaitzensis in sesquiterpenoid composition and neutral DNA sequences. Tetrahedron. 2008;64(19):4486-4495.

18.

Cantrell

Duke

Fronczek

, et al. Phytotoxic eremophilanes from Ligularia macrophylla. J Agric Food Chem. 2007;55(26):10656-10663.

19.

Bohlmann

Zdero

Grenz

. Neue sesquiterpene der Gattung Othonna. Chem Ber. 1974;107(12):3928-3945.

20.

Nagano

Tanahashi

Moriyama

Takahashi

. New furanoeremophilane derivatives from Farfugium japonicum Kitamura. Bull Chem Soc Jpn. 1973;46(9):2840-2845.

21.

Bohlmann

Suwita

. Weitere Furanoeremophilane aus Othonna-Arten. Chem Ber. 1976;109(4):1230-1238.

22.

Eagle

Rivett

DEA

Williams

Wilson

. The structure of euryopsonol, a furanoeremophilane from Euryops species. Tetrahedron. 1969;25(21):5227-5233.

23.

Vhalmers

Coleman

Rivett

DEA

Woolard

. Carbon-13 nuclear magnetic resonance spectroscopy of euryopsonol and euryopsol. South African J Chem. 1980;33(1):1-3.

24.

Jia

. A new triterpene and new sesquiterpenes from the roots of Ligularia sagitta. Helv Chim Acta. 2008;91(9):1717-1727.

25.

Kuroda

Inagaki

Okamoto

, et al. Chemical diversity in Ligularia oligonema. Nat Prod Commun. 2017;12(8):1161-1164.

26.

Novotny

Krojidlo

Samek

Kohoutova

Sorm

. Terpenes. CCXXIII. Structure of nemosenins A, B, C, D, and senemorin, new furoeremophikane derivatives from Senecio nemorensis subspecies fuchsii. Collection Czechoslov Chem Commun. 1973;38(3):739-755.

27.

Nagano

Matsushima

Yamada

, et al. Two new furanoeremophilane sesquiterpenoids from Ligularia oligonema. Nat Prod Commun. 2010;5(1):1-4.

28.

Nagano

Iwazaki

Matsushima

, et al. High diversity of Ligularia dictyoneura in chemical composition and DNA sequence. Chem Biodivers. 2007;4(12):2874-2888.

29.

Bohlmann

Zdero

Mahanta

. Neue Eremophilan-derivate aus Lopholaena-Arten. Phytochemistry. 1977;16(11):1769-1771.

30.

Yamakawa

Satoh

Ohba

, et al. Studies on the terpenoids and related alicyclic compounds-XXII. Stereochemical study on the angular hydroxylation of polycylic ketones using benzeneseleninic anhydride. Tetrahedron. 1981;37(3):473-479.

31.

Shi

Jiang

Chou

Wang

. A novel furanoeremophilane with an unusual oxygen bridge from Senecio nemorensis. Fitoterapia. 2013;84:11-14.

32.

Liu

Wei

Shi

. Novel sesquiterpenes from Ligularia virgaurea spp. oligocephala. Helv Chim Acta. 2007;90(9):1802-1810.

33.

Bohlmann

Castro

Zdero

King

Robinson

. New furanoeremophilanes from Senecio species. Rev Latinoamer Quim. 1984;14(3):101-103.

34.

Chen

Gao

Yang

. Studies of chemical constituents of Senecio nemorensis L. Chem J Chin Univ. 1992;13(6):781-783.

35.

Chen

Gao

Niu

. Studies on the absolute configurations of two 10-hydroxy-9-oxo-furoeremophilanes using CD spectra. Chem J Chin Univ. 1993;14(3):363-365.

36.

Dupre

Grenz

Jakupovic

Bohlmann

Niemeyer

. Eremophilane, germacrane and shikimic acid derivatives from Chilean Senecio species. Phytochemistry. 1991;30(4):1211-1220.

37.

Zhang

. Sesquiterpenoids from the root bark of Acanthopanax leucorrhizus and their biological activities. Helv Chim Acta. 2014;97(9):1283-1288.

38.

Wang

Sun

Huang

, et al. Phytochemical investigation and cytotoxic evaluation of the components of the medicinal plant Ligularia atroviolacea. Chem Biodivers. 2009;6(7):1053-1065.

39.

Shi

Zhao

Zhang

Huang

. Furanoeremophilanes from Ligularia atroviolacea. Fitoterapia. 2008;79(6):476-478.

40.

Villarroel

Torres

. A new furanoeremophilane from Senecio fistulosus. J Nat Prod. 1985;48(5):841-842.

Cumulative Data of 1 H and 13 C NMR Signals and Specific Rotations of Eremophilane Sesquiterpenoids. 5. Furanoeremophilanes Containing an Oxygenated Functionality at C-10

Abstract

Keywords

Introduction

Conclusion

Footnotes

Acknowledgements

ORCID iD

Ethical Considerations

Funding

Declaration of Conflicting Interests

References