Complete assignments of the 1H and 13C NMR spectra of 15 limonoids

Article abstract of DOI:10.1002/mrc.1159

Unambiguous and complete assignments of ¹H and ¹³C NMR chemical shifts for 15 limonoids, eight of them found in natural sources and seven other synthetic derivatives, are presented. The assignments are based on 2D shift-correlated [<

Full text of DOI:10.1002/mrc.1159

MAGNETIC RESONANCE IN CHEMISTRY
Magn. Reson. Chem. 2003; 41: 206–212
Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/mrc.1159
Spectral Assignments and Reference Data
Complete assignments of the H and 13C
NMR spectra of 15 limonoids
1
23
O
O
2
2
†
2
1
18
2
17
30 13
14
15
0
1
2
1
11
R 19
∗
Benjam ´ı n Rodr ´ı guez
9
1
1
5
0
H 7
H
3
9
Instituto de Qu ´ı mica Org a´ nica, CSIC, Juan de la Cierva 3, E-28006
Madrid, Spain
R2
OR3
O
R
H
H
2
28
Received 10 October 2002; accepted 30 November 2002
1
R1 = R2 = α-OAc, β-H; R3 = Ac
8 R = α-OAc, β-H
R = α-OH, β-H
10 R = O
2 R = α-OH, β-H; R = α-OAc, β-H; R3 = Ac
1
2
9
Unambiguous and complete assignments of 1H and 13
C
1
1
1
1
= α-OAc, β-H; R = α-OH, β-H; R3 = Ac
2
3
4
5
R
R
R
NMR chemical shifts for 15 limonoids, eight of them
found in natural sources and seven other synthetic
derivatives, are presented. The assignments are based
= R = α-OH, β-H; R3 = Ac
2
= R = α-OH, β-H; R3 = H
2
R1
6 R1 = O; R2 = α-OAc, β-H; R = Ac
3
1
1
1
13
on 2D shift-correlated [ H, H-COSY, H, C-gHSQC-
7 R = α-OAc, β-H; R = O; R3 = Ac
2
1
1
13
n
23 O
J(C,H), H, C-gHMBC- J(C,H) (n = 2 and 3)] and NOE
2
1
experiments. Copyright  2003 John Wiley & Sons, Ltd.
R2
O
23
OAc
KEYWORDS: NMR; H NMR; 13C NMR; triterpenoids; limonoids;
1
O
2
2
meliacins; 24,25,26,27-tetranor-apotirucallane derivatives
21
H
2
0
OH
OAc
AcO
H
H
1
2
INTRODUCTION
12 R = O; R = α-H, β-OH
1
O
OAc
H
3 R1 = H, OH; R2 = O
both C-23 epimers)
4 R1 = O, R2 = H2
The limonoids (24,25,26,27-tetranor-apotirucallanes) are a large
group of naturally occurring triterpenoids isolated from several
plants and particularly from those belonging to the Meliaceae
(
1
11
1
,2
and Rutaceae families.
The limonoids occurring in Meliaceae
are also known as meliacins. These compounds display a vast
array of biological activities such as antimalarial, antidiabetic,
anti-inflammatory, insecticidal, bactericidal, spermicidal, vaginal
contraceptive, hypoglycaemic, antifeedant, nematicidal, piscicidal,
RESULTS AND DISCUSSION
Treatment of 3 with acetic anhydride–pyridine gave 1, another
5
constituent of T. havanensis, whereas oxidation of 3 with chromium
3
amoebicidal, larvicidal and several others.
15
5
trioxide–pyridine yielded 7, previously obtained as a synthetic
4
Recently, an extraction of the seed of Trichilia havanen-
15
derivative. Oxidation of 2 provided the 1-ketolimonoid 6, a
sis Jacq. (Meliaceae) was carried out in our laboratories in
order to isolate its meliacin constituents and to test these com-
pounds as antifeedant agents against Leptinotarsa decemlineata
9
substance that had already been obtained as an intermediate for the
synthesis of isoazadirone, although its physical and spectroscopic
data have not been reported. Alkaline hydrolysis of 1 yielded
the new limonoids 4 and 5 (see Experimental). Deacetylation of
(
Say) (Colorado potato beetle) and Spodoptera exigua (H u¨ bner)
larvae. The acetone extract of that seed contained several
11,12
azadirone (8) gave 9, a natural limonoid found in Teclea species
5
–8
previously known limonoids,
including large quantities of
(
Rutaceae), and 9 was transformed into 10 by oxidation with
9
3
,7-di-O-acetyl-14,15-deoxyhavanensin (2), 1,7-di-O-acetyl-14,15-
16
Jones’ reagent. 7-Deacetoxy-7-oxoazadirone (10) has previously
5
5,10
deoxyhavanensin (3) and azadirone
(8). Starting from these
13
been found in Teclea ouabanguiensis. Oxidation of 8 with Jones’
available compounds, the naturally occurring limonoids 1,3,7-tri-
O-acetyl-14,15-deoxyhavanensin (1), 7-deacetylazadirone
7
1
1
16
reagent for a long time (see Experimental) yielded 11 as an unique
5
11,12
(9),
2
1R isomer, whereas both C-21 epimers of 11 have been found in
-deacetoxy-7-oxoazadirone13 (10), isoazadironolide14 (11) and
14
Azadirachta indica as a mixture named isoazadironolide. The 21R
absolute configuration of 11 was now established by application
of the Horeau’s method (see Experimental). Oxidation of 1 with
magnesium monoperoxyphthalate (MMPP) predominantly yielded
˛,3˛, 7˛-triacetoxy-21ꢀ-hydroxy-24,25,26,27-tetranor-apotirucalla-
4,20(22)-dien-23,21-olide5 (12) were synthesized for this work, as
17
well as compounds 4–7, 13 (as a mixture of the C-23 epimers 13a
and 13b) and 14, all of them not hitherto found in natural sources,
5
the ꢁ-hydroxybutenolide 12, previously known as a constituent of
5
,9
although 6 and 7 are previously known as synthetic derivatives.
Trichilia havanensis, together with minute amounts of the regioisomer
1
Only partial H NMR spectral data have been published for these
limonoids, except for 6 and the new compounds 4, 5, 13 and 14, and
the C NMR spectra of 2, 4–9 and 12–14 have not been reported
previously. The previous assignments of the C NMR spectra of
13 as a 1.3 : 1 unseparable mixture of the C-23 epimers 13a and 13b.
9
18
Finally, reduction of 12 with sodium borohydride gave the new
limonoid 14.
1
3
1
3
For the complete assignment of the 1H and 13C NMR spectra of
–14, a combination of two-dimensional COSY, HSQC and HMBC
5
5
13
14
1
, 3, 10 and 11 were performed only on the basis of general
1
chemical shift arguments and by comparison with the data reported
for other structurally related triterpenoids. Thus, previous 13C NMR
assignments contain several ambiguities and are not unequivocal.
19
experiments was carried out, together with NOE experiments for
distinguishing the C-2 methylene protons in 1–7 and 12–14, and the
C-12 and C-16 methylene protons in all the compounds. Tables 1–3
show the complete and unambiguous assignments of the H and
NMR spectra of these limonoids.
1
These facts suggested attempting the complete assignment of the H
1
13
C
1
3
and C NMR spectral data of 1–14 in the hope they could be useful
for future assignments of compounds belonging to this biologically
and chemically interesting kind of triterpenoids.
The assignment of both C-6 and C-11 methylene protons in
–14 was evident from the vicinal coupling constant values shown
1
by each of these methylene protons with the H-5˛ and H-9˛ axial
methine protons, respectively (Tables 1 and 2). On the other hand,
in the case of 1–5 and 12–14, the C-2 methylene protons appeared
as a doublet of triplets with identical coupling constants with the
H-1ˇ and H-3ˇ vicinal equatorial protons, whereas in 6 and 7 the
C-2 protons showed double doublet signals, in which the vicinal
coupling values are identical [6: Jꢂ2˛, 3ˇꢃ D Jꢂ2ˇ, 3ˇꢃ D 4.2 Hz] or
very close [7: Jꢂ2˛, 1ˇꢃ D 3.0 Hz, Jꢂ2ˇ, 1ˇꢃ D 4.0 Hz], thus precluding
Ł
Correspondence to: Benjam ´ı n Rodr ´ı guez, Instituto de Qu ´ı mica Org a´ nica,
CSIC, Juan de la Cierva 3, E-28006 Madrid, Spain. E-mail: iqor107@iqog.csic.es
†
Dedicated to the memory of the late Professor Manuel Lora-Tamayo
1904–2002), Complutense University, Madrid.
(
Contract/grant sponsor: Comisi o´ n Asesora de Investigaci o´ n Cient ´ı fica y
T e´ cnica (CAICYT); Contract/grant number: AGL 2001-1652-C02-01.
Copyright  2003 John Wiley & Sons, Ltd.

207
Spectral Assignments and Reference Data
an assignment of the C-2 protons based on these data. Moreover,
H-1ˇ, H-3ˇ, Me-19 and Me-29 axial protons were always observed,
thus establishing that all these hydrogens, including the irradiated
H-2 proton, are on the same side of the plane of the molecule.
Consequently, the other C-2 methylene proton (υ1.91–2.44, dt in
1–5 and 12–14 and dd in 6 and 7) is the 2˛-equatorial hydrogen,
which appeared always upfield shifted with respect to the H-2ˇ
proton. Similarly, when the Me-18 protons signal (υ 0.74–0.92 s)
was irradiated NOE was observed in the cis H-16˛ proton signal (υ
2.38–2.57 ddd), which appeared downfield shifted with respect to
its geminal proton (υ 2.29–2.40 ddd) in all the compounds studied
(1–14). In addition, irradiation at the H-17ˇ proton signal (υ 2.65–2.87
ddd) caused, among others, NOE enhancement in the cis H-16ˇ
the assignment of the C-16 methylene protons of 1–14 is not
unambiguous from the vicinal J values because this methylene is
involved in a cyclopentene ring. Furthermore, in these limonoids
(
1
1–14), the C-12 methylene protons are eclipsed with those of the C-
1 methylene group, as a consequence of a boat conformation (B9,13)
in ring C, and consequently the vicinal JꢂH ꢀ 12, H ꢀ 11ꢃ coupling
values are not reliable data for establishing their configurations.
The assignment of both C-2 methylene protons in 1–7 and 12–14
(Tables 1 and 2) was supported by NOE experiments. On irradiation
at the H-2 proton signal appearing at υ 2.18–3.26 (dt in 1–5 and 12–14
and dd in 6 and 7) strong NOE enhancement in the signals of the
Table 1. 1H NMR chemical shifts, υ (ppm), and coupling constants, J(H,H) (Hz), for 1–7a
Proton
1
2
3
4
5
6
7
1
2
2
3
5
6
6
7
9
1
1
1
1
1
1
1
1
ˇ
4.61 t
3.48 t
4.84 t
3.55 t
3.49 t
—
5.03 dd
2.44 dd
3.01 dd
—
˛
1.99 dt
2.16 dt
4.69 t
1.83 mb
2.29 dt
4.92 t
1.93 dt
2.26 dt
3.36 t
1.91 dt
2.20 dt
3.51 t
1.92 dt
2.19 dt
3.54 t
2.24 dd
3.26 dd
5.03 t
ˇ
ˇ
˛
2.26 dd
1.78 mb
1.78 mb
5.19 t
2.00 dd
1.74 dt
1.82 mb
5.20 dd
2.67 dd
1.79 mb
1.49 mb
1.85 mb
1.49 mb
5.31 dd
2.41 ddd
2.30 ddd
2.75 ddd
0.82 s
2.11 dd
1.78 mb
1.84 ddd
5.21 t
2.13 dd
1.72 ddd
1.83 ddd
5.19 dd
2.67 dd
1.72 mb
1.50 mb
1.83 mb
1.51 mb
5.30 dd
2.40 ddd
2.29 ddd
2.74 ddd
0.79 s
2.31 dd
1.76 mb
1.79 mb
3.94 t
2.10 dd
1.73 ddd
1.96 ddd
5.16 dd
2.50 dd
2.23 dddd
1.42 dddd
1.88 ddd
1.61 ddd
5.35 dd
2.39 ddd
2.31 ddd
2.78 ddd
0.88 s
2.38 dd
1.78 mb
1.94 ddd
5.22 dd
2.50 dd
1.41 dddd
1.58 mb
1.79 mb
1.58 mb
5.36 dd
2.38 ddd
2.31 ddd
2.77 ddd
0.74 s
˛
ˇ
ˇ
˛
2.58 dd
1.28 dddd
1.52 mb
1.77 mb
1.53 mb
5.36 dd
2.41 ddd
2.32 ddd
2.77 ddd
0.79 s
2.47 dd
1.27 mb
1.52 dddd
1.74 mb
1.55 mb
5.35 dd
2.39 ddd
2.31 ddd
2.76 ddd
0.76 s
2.65 dd
1.70 mb
1.51 mb
1.80 mb
1.51 mb
5.55 dd
2.56 ddd
2.39 ddd
2.80 ddd
0.83 s
1˛
1ˇ
2˛
2ˇ
5
6˛
6ˇ
7ˇ
Me-18
Me-19
0.97 s
0.91 s
0.96 s
0.88 s
0.88 s
1.30 s
1.16 s
21
22
23
7.22 dt
6.26 dd
7.36 t
7.22 dt
6.27 dd
7.35 t
7.21 ddd
6.25 dd
7.36 t
7.21 dt
6.26 dd
7.34 t
7.23 dt
6.27 dd
7.36 t
7.22 dt
6.28 dd
7.36 t
7.21 dt
6.24 dd
7.35 t
Me-28
Me-29
Me-30
0.80 s
0.78 s
0.93 s
0.89 s
1.00 s
0.81 s
1.03 s
0.91 s
0.90 s
0.85 s
0.82 s
0.85 s
1.12 s
1.05 s
1.16 s
1.15 s
1.15 s
1.14 s
1.11 s
1.18 s
1.20 s
1˛-OAc
3˛-OAc
7˛-OAc
2.00 s
—
2.06 s
—
—
—
1.99 s
2.00 s
2.09 s
—
—
—
2.03 s
—
1.99 s
1.98 s
1.99 s
1.97 s
—
1.95 s
1.96 s
J(H,H)
1ˇ,2˛
1ˇ,2ˇ
2˛,2ˇ
2˛,3ˇ
2ˇ,3ˇ
5˛,6˛
5˛,6ˇ
6˛,6ˇ
6˛,7ˇ
6ˇ,7ˇ
9˛,11˛
9˛11ˇ
3.0
3.0
2.9
2.9
3.1
3.1
2.7
2.7
2.8
2.8
—
—
3.0
4.0
16.4
16.0
16.2
15.1
15.3
14.4
17.0
3.0
3.0
4.8
2.9
2.9
3.1
3.1
2.7
2.7
2.8
2.8
6.3
9.2
4.2
4.2
—
—
3.2
3.4
2.7
2.4
1.7
10.8
12.8
14.4
3.2
12.2
14.8
2.8
12.9
14.8
3.4
13.2
14.4
3.6
10.7
14.3
3.6
b
b
2.8
2.8
2.9
2.9
7.5
2.4
2.8
2.4
2.0
2.4
6.6
6.8
6.4
7.2
5.4
5.5
11.8
11.6
11.6
11.2
11.4
11.8
11.7
Copyright  2003 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2003; 41: 206–212

208
Spectral Assignments and Reference Data
Table 1. (Continued)
Proton
1
2
3
4
5
6
7
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
1˛,11ˇ
1˛,12˛
1˛,12ˇ
1ˇ,12˛
1ˇ,12ˇ
2˛,12ˇ
5,16˛
5,16ˇ
13.1
3.6
13.2
14.0
4.6
14.1
5.1
b
b
5.6
9.6
9.4
b
b
9.6
2.8
9.4
b
b
b
b
5.4
b
13.6
1.7
1.9
3.4
1.6
3.6
1.9
3.3
1.6
3.6
1.4
3.5
1.6
3.6
3.4
6˛,16ˇ
6˛,17ˇ
6ˇ,17ˇ
7ˇ,21
1,22
15.2
10.8
7.6
15.2
11.2
7.2
15.2
10.8
7.6
15.1
10.9
7.4
15.4
11.2
7.3
15.2
10.8
7.5
15.2
10.9
7.6
0.8
0.8
0.7
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
1,23
1.6
1.6
1.7
1.7
1.7
1.6
1.6
2,23
1.6
1.6
1.7
1.7
1.7
1.6
1.6
a
In CDCl3 solution. All these assignments were in agreement with COSY, HSQC and HMBC spectra, and NOE experiments.
b
Overlapped or partially overlapped signal; υ values were measured from the HSQC spectra.
Table 2. 1H NMR chemical shifts, υ (ppm), and coupling constants, J(H,H) (Hz), for 8–14a
Proton
8
9
10
11
12
13ab
13bb
14
1
2
2
3
5
6
6
7
9
1
1
1
1
1
1
1
1
ˇ
7.14 d
5.83 d
—
7.11 d
5.80 d
—
7.12 d
5.89 d
—
7.13 d
5.86 d
—
4.64 t
4.59 t
4.57 t
4.60 t
c
c
c
c
˛
1.98 dt
2.20 dt
4.69 t
1.98 dt
2.18 dt
4.68 t
ˇ
ˇ
—
—
—
—
4.68 t
5.17 t
4.68 t
5.17 t
2.18 mc
1.80 mc
1.95 mc
5.25 dd
2.18 mc
1.97 mc
1.78 mc
1.93 mc
1.81 mc
5.39 dd
2.48 ddd
2.35 ddd
2.87 ddd
0.92 s
1.18 s
6.01 ddd
—
2.24 dd
1.78 mc
1.78 mc
5.17 t
c
c
c
c
c
c
2.23 dd
1.78 mc
1.78 mc
5.17 t
˛
2.18 dd
1.77 ddd
1.90 ddd
5.26 dd
2.21 dd
1.88 mc
1.68 mc
1.84 mc
1.63 mc
5.36 dd
2.41 ddd
2.31 ddd
2.79 ddd
0.77 s
1.18 s
7.22 ddd
—
2.39 dd
1.85 mc
1.88 mc
4.01 t
2.09 dd
2.39 dd
2.88 t
—
˛
ˇ
ˇ
c
c
c
c
c
c
c
c
c
c
˛
2.20 dd
1.93 mc
1.75 dddd
1.89 mc
1.60 ddd
5.58 dd
2.56 ddd
2.40 ddd
2.83 ddd
0.78 s
1.16 s
7.24 dt
—
2.12 dd
1.94 mc
1.88 mc
1.85 ddd
1.69 ddd
6.06 dd
2.57 ddd
2.40 ddd
2.82 ddd
0.77 s
1.36 s
7.24 dt
—
2.51 dd
1.31 mc
1.54 mc
1.76 mc
1.72 mc
5.37 dd
2.45 ddd
2.33 ddd
2.84 ddd
0.92 s
2.52 dd
1.31 dddd
1.51 mc
1.70 mc
1.52 mc
5.35 dd
2.44 ddd
2.34 ddd
2.65 dddd
0.90 s
1˛
1ˇ
2˛
2ˇ
5
5.32 dd
5.31 dd
c
c
c
c
6˛
6ˇ
7ˇ
2.77 mc
0.87 s
0.97 s
—
2.77 mc
0.90 s
0.96 s
—
Me-18
Me-19
0.97 s
6.00 ddd
0.95 s
2
2
2
2
1A
1B
2
4.66 ddd
4.77 dd
5.86 td
—
—
—
—
6.26 dd
7.36 t
6.27 dd
7.36 t
6.27 dd
7.36 t
1.14 s
1.11 s
1.42 s
—
5.91 dd
—
5.88 dd
—
6.92 t
6.07 d
0.79 s
0.91 s
1.15 s
6.90 t
6.12 d
0.79 s
0.91 s
1.15 s
3
Me-28
Me-29
Me-30
1.06 s
1.06 s
1.21 s
—
1.14 s
1.08 s
1.16 s
—
1.07 s
1.07 s
1.22 s
—
0.80 s
0.79 s
0.91 s
0.91 s
1.16 s
1.14 s
c
c
c
c
c
c
1˛-OAc
3˛-OAc
7˛-OAc
2.01 s
2.02 s
—
—
—
—
2.04 s
2.00 s
1.94 s
—
—
1.95 s
1.99 s
1.99 s
(continued overleaf)
Copyright  2003 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2003; 41: 206–212

209
Spectral Assignments and Reference Data
Table 2. (Continued)
Proton
8
9
10
11
12
13ab
13bb
14
2
1-OH
—
—
—
4.22 de
4.92 de
—
—
—
—
J(H,H)
1
1
1
2
2
2
5
5
6
6
6
9
9
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
,2
10.2
—
10.2
—
10.2
—
10.4
—
—
—
ˇ,2˛
—
—
—
—
—
3.0
3.0
3.0
3.0
2.9
ˇ,2ˇ
—
—
—
3.0
3.0
2.9
16.6
2.9
c
c
˛,2ˇ
—
—
—
16.5
3.0
˛,3ˇ
—
—
—
3.0
3.0
3.0
3.0
ˇ,3ˇ
—
—
—
3.0
2.9
c
c
c
c
c
c
c
˛,6˛
2.4
13.2
14.8
3.3
2.2
6.0
3.4
2.6
14.5
14.5
—
4.7
6.0
c
c
˛,6ˇ
11.9
c
11.0
10.4
c
c
˛,6ˇ
˛,7ˇ
2.9
2.9
3.2
2.0
2.8
2.8
6.0
2.8
2.8
2.8
2.8
2.8
2.8
ˇ,7ˇ
—
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
˛,11˛
˛,11ˇ
1˛,11ˇ
1˛,12˛
1˛,12ˇ
1ˇ,12˛
1ˇ,12ˇ
2˛,12ˇ
5,16˛
5,16ˇ
6˛,16ˇ
6˛,17ˇ
6ˇ,17ˇ
7ˇ,21A
7ˇ,22
1A,21B
1,21(OH)
1A,22
1B,22
1,22
7.1
5.8
6.6
12.0
c
11.9
11.8
c
12.5
11.8
13.6
2.8
c
14.0
c
c
c
c
c
c
c
c
c
c
c
3.6
7.4
9.6
3.4
13.2
1.6
3.6
15.4
11.2
7.1
0.8
0
4.0
10.0
2.0
13.2
1.6
3.5
15.6
11.0
7.3
0.8
0
6.4
c
c
c
1.6
3.5
15.4
11.2
7.4
0.8
0
1.8
3.4
1.8
3.5
15.5
10.5
7.0
0
1.5
3.4
15.2
10.4
7.2
1.0
0.4
17.4
—
15.6
10.5
7.2
0
—
—
1.6
—
8.2e
1.5
—
7.5e
1.2
1.2
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
1.8
1.8
—
—
—
—
—
—
1.0
1.7
1.7
0.8
1.7
1.7
0.8
1.7
1.7
1.0
—
1.0
—
1,23
—
2,23
—
—
1.2
1.2
—
a
b
c
In CDCl3 solution. All these assignments were in agreement with COSY, HSQC and HMBC spectra, and NOE experiments.
It was not possible to assign all the proton signals for 13a and 13b owing to the complexity of the spectra of the mixture of the two C-23 epimers.
Overlapped signal; υ values were measured from the HSQC spectra.
Collapsed into a d (J D 1.0 Hz) after addition of D2O.
d
e
Disappeared after addition of D2O.
proton signal always greater than that exhibited for the trans H-
6˛ proton. Moreover, both C-12 methylene protons were easily
showed HSQC correlation with the olefinic C-15 carbon (υ 118.21
d and 119.01 d, respectively), whereas the H-7ˇ proton (υ 5.20 in 2
and 5.26 in 8, both dd) was connected with the C-7 carbon (υ 75.03
d and 74.42 d, respectively). In the case of 1 and 12, the HMBC
connectivities observed between the H-1ˇ proton (υ 4.61 t and 4.64
t, respectively) and the C-9, C-10 and C-19 carbons (υCꢀ1 35.50 d
and 35.40 d, υCꢀ10 40.19 s and 40.16 s, and υCꢀ19 15.88 q and 15.90 q,
respectively), and between the H-3ˇ proton (υ 4.69 t in both 1 and 12)
and the C-4 and C-29 carbons (υCꢀ4 35.96 s and 35.97 s, υCꢀ29 21.68 q
and 21.64 q, respectively) were in agreement with this reassignment.
1
distinguished (Tables 1 and 2) because on irradiation at the H-17ˇ
proton signal, NOE was observed in the signal of the cis H-12ˇ
proton and not in that of its geminal H-12˛ proton.
1
The H NMR assignments for 1–14 (Tables 1 and 2) are in
1
5,9,10–14
agreement with the partial H NMR data published before
for the previously known compounds (1–3 and 7–12), although in
9
,10
2
and 8 the previous assignment
the H-7ˇ sp proton must be reversed, as well as for the assignment
of the H-1ˇ and H-3ˇ protons in 1 and 12. These reassignments were
for the olefinic H-15 proton and
3
5
13
5
5
13
14
The previous C NMR assignments for 1, 3, 10 and 11
strongly supported by HSQC and HMBC experiments, because the
are, in general, in good agreement with those shown in Table 3.
H-15 olefinic proton of 2 and 8 (υ 5.31 dd and 5.36 dd, respectively)
However, the use of 2D experiments (HSQC and HMBC) in the
Copyright  2003 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2003; 41: 206–212

210
Spectral Assignments and Reference Data
Copyright  2003 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2003; 41: 206–212

211
Spectral Assignments and Reference Data
present work allowed the assignment of the acetyl groups in 1 and 3
(24), 319 (100), 283 (22), 159 (14), 145 (14), 105 (15), 91 (19), 81 (23),
69 (13), 55 (17), 43 (24). Found: C 75.39, H 9.07. C26H38O4 requires
C 75.32, H 9.24%. For H and C NMR spectra, see Tables 1 and 3,
respectively.
5
,13,14
and the C-Me groups in 10, not achieved previously,
the unambiguous assignment for several carbons of 10 and the
and also
1
3
1
13
1
4
correct reassignment for the C-28 and C-29 carbons of 11.
Chromium trioxide–pyridine oxidation of 2 to give 6
To a solution of 2 (320 mg) in pyridine (17 ml) was added a mixture
of CrO3 (1.7 g) and pyridine (17 ml) and the reaction mixture was left
at room temperature for 24 h (Sarett oxidation procedure ). Then,
the reaction mixture was poured into water (100 ml) and extracted
with Et2O (5 ð 25 ml). The extracts were dried (Na2SO4) and evap-
orated to dryness, and the residue (260 mg) was chromatographed
EXPERIMENTAL
General experimental procedures
1
5
Melting-points were determined on a Kofler block and are uncor-
rected. Optical rotations were measured on a Perkin-Elmer 241 MC
polarimeter. IR spectra were obtained on a Perkin-Elmer Spectrum
One spectrophotometer. UV spectra were recorded on a Perkin-
Elmer Lambda 2 UV/VIS spectrophotometer. Mass spectra were
registered in the positive electron ionization (EI) mode on a Hewlett-
Packard model 5973 instrument (70 eV). Elemental analyses were
made with a Carlo Erba EA 1108 apparatus. Merck silica gel No. 7734
[
silica gel column, 50 g, EtOAc–petroleum ether (1 : 1) as eluent],
giving 210 mg (66%) of 6 (3˛,7˛-diacetoxy-21,23-epoxy-24,25,26,27-
tetranor-apotirucalla-14,20,22-trien-1-one): colourless needles, m.p.
2
2
218–219
°
C (EtOAc–n-hexane); [˛]D
ꢀ44.6° (c 0.399, CHCl ); IR
3
(
70–230 mesh) was used for column chromatography. Merck 5554
Kieselgel 60 F254 sheets were used for thin-layer chromatographic
TLC) analysis.
(KBr), ꢄmax 3160, 1504, 873 (furan), 1727, 1249 (acetate), 1708 (ketone),
ꢀ
1
2967, 1435, 1378, 1031, 950, 787, 600 cm ; EI-MS, m/z (rel. int., %)
C
(
496 [M] (49), 481 (4), 436 (31), 421 (32), 376 (30), 361 (34), 343 (77),
2
79 (45), 225 (24), 197 (23), 137 (30), 81 (28), 43 (100). Found: C 72.56,
1
13
H 8.39. C30H40O6 requires C 72.55, H 8.12%. For H and C NMR
spectra, see Tables 1 and 3, respectively.
NMR spectroscopy
All experiments were performed on a Varian INOVA-400 spectrom-
9
This compound (6) had previously been obtained as an
1
eter equipped with 5 mm inverse detection z-gradient probe. H and
intermediate for the preparation of isoazadirone, although its
1
3
C NMR spectra (at 400 and 100 MHz, respectively) were measured
9
physical and spectroscopic data were not determined.
at room temperature (22–23 °C) using CDCl3 as solvent. Chemical
shifts are given on the υ scale and were referenced to residual CHCl3
at 7.25 ppm for proton and to the solvent at 77.00 ppm for carbons.
Chromium trioxide–pyridine oxidation of 3 to give 7
1
13
One-dimensional H and C NMR spectra were acquired with stan-
dard conditions. The pulse programs of the gHSQC and gHMBC
experiments were taken from the Varian software library. The data
for the HSQC spectra were collected in a 1024 ð 256 matrix with a
spectral width of 2485 Hz in the proton domain and 10 000 Hz in the
carbon domain and processed in a 1024 ð 512 matrix. The null time
following the BIRD pulse was 400 ms. The HMBC experiments were
optimized for long-range coupling constants of 8 Hz and the data
were processed using parameters very similar to those used in the
HSQC experiments. The NOE data were recorded using the double
Compound 3 (400 mg) was treated with CrO3 –pyridine, as described
above for 2, yielding 7 (350 mg, 87.8%), identical in all respects (m.p.
5
[˛] , IR and mass spectra) with the synthetic product described
D
1
13
previously. For H and C NMR spectra, see Tables 1 and 3,
respectively.
Preparation of 7-deacetoxyazadirone (9) from azadirone (8)
To a solution of 8 (890 mg) in EtOH (35 ml) was added an ethanolic
solution of KOH (10%, v/w, 50 ml) and the reaction mixture was
°
1
9
heated at 60 C for 6 h. Water (200 ml) was added to the reaction
pulsed field gradient spin-echo (DPFGSE)-NOE experiment with a
mixing time of 600 ms, a recycle delay of 2 s and 128–256 transients
per spectrum.
and the mixture extracted with CH2Cl2 (4 ð 60 ml). The extracts
were dried (Na2SO4), filtered and the solvents removed in vacuo,
yielding a residue of 9 (760 mg, after crystallization from EtOAc–n-
hexane, 94.5% yield): m.p., [˛]D, UV and IR spectra identical with
Samples of limonoids
11,12
1
13
those reported
for the natural compound. For H and C NMR
Large quantities of 2, 35 and 85,10 were available from a previous
9
spectra, see Tables 2 and 3, respectively.
4
5
work. Compound 1 (1,3,7-tri-O-acetyl-14,15-deoxyhavanensin)
was obtained from 3 by treatment with acetic anhydride–pyridine
Preparation of 7-deacetoxy-7oxoazadirone (10) from 9
in the usual manner.
A solution of 9 (180 mg) in Me2CO (10 ml) was treated with an
1
6
excess of Jones’ reagent at 0 °C for 10 min. Work-up in the usual
Alkaline hydrolysis of 1 to give 4 and 5
manner yielded 10 (153 mg, after crystallization from EtOAc–n-
hexane, 85.4% yield): m.p., [˛]D, IR and UV spectra identical with
To a solution of 1 (2 g) in EtOH (30 ml) was added an ethanolic
solution of KOH (10%, v/w, 20 ml) and the reaction mixture was
13
1
13
those reported for the natural product. For H and C NMR
heated at 60 °C for 3 h. Then, water (150 ml) was added and the
spectra, see Tables 2 and 3, respectively.
reaction mixture was extracted with CH2Cl2 (4 ð 50 ml). The extracts
were dried (Na2SO4), filtered and the solvents removed, giving a
residue which was subjected to column chromatography [silica gel,
Oxidation of azadirone (8) to give 11
300 g, CH2Cl2 –EtOAc (9 : 1) as eluent], collecting fractions of 30 ml.
A solution of 8 (680 mg) in Me2CO (30 ml) was treated with
1
6
The residue obtained from fractions 12–24 was crystallized from
EtOAc–n-hexane yielding 850 mg of 4 (50.3%). Fractions 37–53
gave, after evaporation of the solvents and crystallization from
EtOAc–n-hexane, pure 5 (680 mg, 44.3%).
an excess of Jones’ reagent at room temperature for 3 h. Then
water (150 ml) was added and the mixture was extracted with
CH2Cl2 (4 ð 40 ml). The extracts were dried (Na2SO4), filtered
and the solvents removed in vacuo giving a residue (600 mg).
This residue was subjected to column chromatography [silica
gel 60 g, EtOAc–petroleum ether (1 : 1) as eluent] yielding 11
(305 mg, after crystallization from EtOAc–n-hexane, 41.8% yield).
Compound 11 [7˛-acetoxy-21R-hydroxy-3-oxo-24,25,26,27-tetranor-
apotirucalla-1,14,20(22)-trien-23,21-olide]: colourless prisms, m.p.
Compound 4 (7-O-acetyl-14-15-deoxyhavanensin): colourless
1
6
prims, m.p. 195–196 °C; [˛] ꢀ19.5° (c 0.709, CHCl3); IR (KBr),
D
ꢄmax 3480 (OH), 3133, 1503, 874 (furan), 1705, 1269 (acetate), 2956,
ꢀ
1
1
629, 1458, 1377, 1075, 1028, 957, 806, 600 cm ; EI-MS, m/z (rel. int.,
C
%
) 456 [M] (31), 441 (3), 396 (20), 378 (42), 360 (51), 345 (100), 279
2
2
(
22), 171 (12), 159 (13), 145 (17), 131 (15), 105 (17), 91 (19), 81 (27), 43
274–276 °C; [˛]D C 55.6° (c 0.792, CHCl ); UV (MeOH), ꢅ
max
211 nm
3
(
51). Found: C 73.74, H 9.01. C28H40O5 requires C 73.65, H 8.83%.
(log ε 4.21); IR (KBr), ꢄ
3434 (OH), 1766 (ꢁ-lactol), 1734, 1249
max
1
13
For H and C NMR spectra, see Tables 1 and 3, respectively.
(acetate), 1650 (˛,ˇ-unsaturated ketone), 2950, 1451, 1380, 1125, 1030,
ꢀ
1
C
Compound 5 (14,15-deoxyhavanensin): colourless fine needles,
959, 894, 822 cm ; EI-MS, m/z (rel. int., %) 468 [M] (20), 450 (24),
435 (2), 408 (42), 390 (45), 375 (35), 339 (16), 259 (48), 241 (35), 150 (47),
137 (49), 121 (96), 105 (33), 93 (49), 91 (48), 79 (29), 69 (28), 55 (19), 43
(100). Found: C 71.75, H 7.99. C28H36O6 requires C 71.77, H 7.74%.
m.p. 292–294 °C; [˛]1 ꢀ32.0° (c 0.441, CHCl3 –MeOH, 3 : 2); IR (KBr),
6
D
ꢄmax 3550, 3400 (OH), 3120, 1500, 875 (furan), 2930, 1630, 1442, 1386,
ꢀ
1
1
089, 1074, 1041, 1030, 788, 599 cm ; EI-MS, m/z (rel. int., %) 414
C
1
13
[
M] (47), 399 (17), 396 (6), 378 (13), 363 (23), 360 (15), 345 (67), 332
For H and C NMR spectra, see Tables 2 and 3, respectively.
Copyright  2003 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2003; 41: 206–212

212
Spectral Assignments and Reference Data
Compound 11 had previously been isolated from a natural source
as a mixture of the C-21 epimers.
Acknowledgement
1
4
This work was supported by funds from the Comisi o´ n Asesora
de Investigaci o´ n Cient ´ı fica y T e´ cnica (CAICYT), grant No. AGL
Application of Horeau’s method17 to 11
2001-1652-C02-01.
Compound 11 (54 mg, 0.115 mmol) and (š)-˛-phenylbutyric anhy-
dride (92.2 mg, 0.297 mmol) in pyridine solution (2.0 ml) for 18 h at
room temperature: ˛1 D C1.959, ˛2 D C1.650, ˛1 ꢀ 1.1˛2 D C0.144;
configuration 21R.
REFERENCES
1
. Connolly JD, Hill RA. Dictionary of Terpenoids vol. 2. Chapman
and Hall: London, 1991; 1206–1240.
Oxidation of 1 to give 12 and 13
To a solution of 1 (600 mg) in MeOH (50 ml) was added magnesium
2
3
. Connolly JD, Hill RA. Nat. Prod. Rep. 2001; 18: 131; 2002; 19: 494.
. Akhila A, Rani K. In Progress in the Chemistry of Organic
Natural Products, vol. 78, Herz W, Falk H, Kirby GW, Moore RE,
Thamm Ch (eds). Springer: Vienna, 1999; 48–149.
monoperoxyphthalate (MMPP, 2.2 g) at 0 °C, then the reaction
mixture was stirred at room temperature for 7 days. After partial
elimination of the solvent in vacuo, the reaction mixture was diluted
with CH2Cl2 (100 ml) and successively washed with an aqueous
saturated solution of NaHCO3 and water. The organic extracts
were dried (Na2SO4), filtered and the solvents removed, giving a
residue (410 mg) which was chromatographed [silica gel column,
4
. L o´ pez-Olgu ´ı n JF. PhD Thesis, Polytechnic University, Madrid,
1998; 29–97.
5. Arenas C, Rodr ´ı guez-Hahn L. Phytochemistry 1990; 29: 2953.
6. Chan WR, Gibbs JA, Taylor DR. J. Chem. Soc., Chem. Commun.
1967; 720.
6
0 g, petroleum ether–EtOAc (3 : 2) as eluent], yielding 12 (210 mg,
3
3%, less polar compound) and minute amounts (2.3 mg, 0.36%) of
the mixture of the C-23 epimers 13.
7. Chan WR, Gibbs JA, Taylor DR. J. Chem. Soc., Perkin Trans 1:
973; 1047.
Compound 12 [1˛,3˛, 7˛-triacetoxy-21ꢀ-hydroxy-24,25,26,27-
tetranor-apotirucalla-14,20(22)-dien-23,21-olide] showed physical
1
8
. Rodr ´ı guez-Hahn L, C a´ rdenas J, Arenas C. Phytochemistry 1996;
43: 457.
(
m.p.) and spectroscopic (IR and mass spectra) data identical with
5
1
those reported for a constituent of Trichilia havanensis. For H and
1
3
9. Adesogan EK, Okorie DA, Taylor DAH. J. Chem. Soc. C 1970; 205.
0. Lavie D, Levy EC, Jain MK. Tetrahedron 1971; 27: 3927.
C NMR spectra, see Tables 2 and 3, respectively
1
The epimeric mixture 13 [in a 1.3 : 1 ratio: 1˛,3˛, 7˛-triacetoxy-
3ꢀ-hydroxy-24,25,26,27-tetranor-apotirucalla-14,20(22)-dien-21,
2
2
11. Ayafor JF, Okogun JI. J. Nat. Prod. 1982; 45: 182.
12. Ayafor JF, Sondengam BL, Connolly JD, Rycroft DS, Okogun JI.
J. Chem. Soc., Perkin Trans 1: 1981; 1750.
1
3-olide] showed only one spot on TLC with several eluents. For H
1
3
and C NMR spectra of the two epimers (13a and 13b), see Tables 2
and 3, respectively.
13. Ayafor JF, Sondengam BL, Bilon AN, Connolly JD. J. Nat. Prod.
1
986; 49: 583.
Conversion of 12 into compound 14
1
1
4. Siddiqui BS, Faizi GS, Rasheed M. J. Nat. Prod. 1999; 62: 1006.
5. Poos GI, Arth GE, Beyler RE, Sarett LH. J. Am. Chem. Soc. 1953;
A stirred solution of 12 (190 mg) in MeOH (15 ml) was treated with an
excess of NaBH4 at room temperature for 2 h. Work-up in the usual
manner yielded 142 mg (76.8%, after crystallization from EtOAc–n-
hexane) of 14 [1˛,3˛, 7˛-triacetoxy-24,25,26,27-tetranor-apotirucalla-
7
5: 422.
6. Bowers A, Halsall TG, Jones ERH, Lemin AJ. J. Chem. Soc. 1953;
548.
1
2
1
[
4,20(22)-dien-23,21-olide]: colourless needles, m.p. 227–228 °C;
2
2
17. Horeau A, Nouaille A. Tetrahedron Lett. 1971; 12: 1939.
18. Tsai TYR, Minta A, Wiesner K. Heterocycles 1979; 12: 1397.
19. Stott K, Keeler J, Van QN, Shaka AJ. J. Magn. Reson. 1997; 125:
302.
˛]D ꢀ40.8° (c 0.887, CHCl3); UV (MeOH), ꢅmax 209 nm (log ε
4
.37); IR (KBr), ꢄmax 1781, 1760, 1627 (˛,ˇ-unsaturated ꢁ-lactone),
ꢀ
1
1
729, 1259 (acetates), 2953, 1377, 1171, 1051, 890 cm ; EI-MS, m/z
C
(
rel. int., %) 556 [M] (3), 496 (3), 436 (10), 421 (2), 394 (3), 376 (100),
3
61 (84), 334 (16), 279 (13), 209 (9), 157 (11), 145 (11), 119 (13), 105
(
13), 91 (11), 43 (86). Found: C, 68.94, H 8.10. C32H44O8 requires C
1
13
69.04, H 7.97%. For H and C NMR spectra, see Tables 3 and 4,
respectively.
Copyright  2003 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2003; 41: 206–212