Transformation of 20-hydroxyecdysone acetonides into podecdysone B

Article abstract of DOI:10.1023/B:RUJO.0000003183.84168.79

Hydrogenation of 20-hydroxyecdysone 2,3:20,22-diacetonide and 20,22-acetonide over palladium catalyst yields podecdysone B 20,22-acetonide. Acid hydrolysis of the latter affords podecdysone B which is a natural phytoecdysteroid.

Full text of DOI:10.1023/B:RUJO.0000003183.84168.79

Russian Journal of Organic Chemistry, Vol. 39, No. 7, 2003, pp. 952 956. Translated from Zhurnal Organicheskoi Khimii, Vol. 39, No. 7, 2003,
pp. 1013 1017.
Original Russian Text Copyright
2003 by Odinokov, Galyautdinov, Nedopekin, Ves’kina, Khalilov.
Transformation of 20-Hydroxyecdysone Acetonides
into Podecdysone B
V. N. Odinokov, I. V. Galyautdinov, D. V. Nedopekin,
N. A. Ves’kina, and L. M. Khalilov
Institute of Petroleum Chemistry and Catalysis, Academy of Sciences of Bashkortostan Republic,
Ufa Research Center, Russian Academy of Sciences,
pr. Oktyabrya 141, Ufa, 450075 Bashkortostan, Russia
e-mail: ink@anrb.ru
Received October 18, 2002
Abstract Hydrogenation of 20-hydroxyecdysone 2,3: 20,22-diacetonide and 20,22-acetonide over palladium
catalyst yields podecdysone B 20,22-acetonide. Acid hydrolysis of the latter affords podecdysone B which
is a natural phytoecdysteroid.
Ecdysteroids are widely spread in animals; they act
as moulting and metamorphosis hormones of Anthro-
poda species [1]. The concentration of zooecdysteroids
in animals is extremely low, whereas in some plants
the concentration of phytoecdysteroids reaches
1.5 2% [2]. One of the most accessible phytoecdy-
steroids is 20-hydroxyecdysone; it was used as start-
ing compound in the synthesis of a number of phyto-
and zooecdysteroids [3 5].
The signal from the carbonyl carbon atom in the
13C NMR spectrum of III is displaced downfield
(
10 ppm) relative to the corresponding signal of
C
initial compounds I and II due to the lack of conjuga-
tion between the carbonyl group and the double bond.
sp2-Hybridized carbon atoms of the conjugated diene
system give rise to the following signals, C, ppm:
122.2 (C8), 135.5 (C9), 148.0 (C14), and 119.0 (C15).
In the acetal region, only one carbon signal was
While studying chemical transformations of
20-hydroxyecdysone, we have found that 2,3:20,22-
diacetonide I and 20,22-acetonide II derived there-
from are converted into podecdysone B 20,22-aceto-
nide (III) by hydrogenation over palladium catalyst
(10% Pd/C) in chloroform. In both cases, the product
was an equimolar mixture of compounds II and III.
Analogous results were obtained when the reaction
was carried out in methylene chloride and carbon
tetrachloride, whereas no reaction occurred in other
solvents (such as isobutyl alcohol or ethanol). Com-
pounds I and II did not undergo any transformations
over Pd/C in the absence of hydrogen.
present at
106.9 ppm, indicating that the 20,22-
C
acetonide moiety remains unchanged during the reac-
tion; the 2,3-acetonide fragment in diacetonide I
(
108.2 ppm) undergoes hydrogenation. The 1H
NMR spectrum of III contained an olefinic proton
signal at 5.36 ppm (15-H) instead of the 7-H signal
from the initial compound ( 6.07 ppm).
Acid hydrolysis (70% AcOH ZnCl2) of acetonide
III afforded podecdysone B (IV) which is a natural
phytoecdysteroid isolated from plants [6, 7]. Com-
pound IV was also synthesized in a low yield by acid
dehydration of 20-hydroxyecdysone and by enzymatic
hydrolysis of podecdysone B 25-O- -D-glucopyrano-
side isolated from Pfaffia iresinoides roots [8].
The product mixture containing compounds II and
III was separated by column chromatography. The
structure of III follows from its spectral parameters.
The absorption maximum in the UV spectrum of
Monitoring of the transformation of diacetonide I
by thin-layer chromatography showed that the initial
compound is converted first into acetonide II via
removal of relatively labile 2,3-acetonide group. The
subsequent transformations are similar for the two
compounds (I and II). As a result, a 1:1 mixture of
II and III is obtained. Our attempts to increase the
acetonide III is located at
244 nm ( = 13200),
indicating the presence of a conjugated diene system
which is typical of podecdysone [6]. In the IR spec-
trum we observed characteristic absorption bands at
1
1650 (C CC C), 1710 (C O), and 3400 cm (OH).
1070-4280/03/3907-0952$25.00 2003 MAIK Nauka/Interperiodica

TRANSFORMATION OF 20-HYDROXYECDYSONE ACETONIDES
953
Scheme 1.
I, R1R2 = Me2C; II, R1 = R2 = H; VII, R3 = H; VIII, IX, R3 = COCF3.
conversion of II into III by prolonging the reaction
led to formation of a complex mixture of by-products.
Under analogous conditions, compound III was
converted into trienone V. The latter was isolated by
column chromatography from a 1:1 mixture with III.
Compound V is 14,15-anhydro-25-hydroxydacryhai-
nansterone 20,22-acetonide (dacryhainansterone has
structure VI [1, 6]). Acetonide V characteristically
showed in the 13C NMR spectrum downfield signals
at
203.85 (C6), 145.45 (C9), 143.83 (C8), 135.23
C
(C14), 131.78 (C11), 128.92 (C15), and 116.29 ppm
(C7), which belong to the oxotriene system.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003

954
ODINOKOV et al.
In keeping with published data [9], the transforma-
121.2 d (C7), 163.7 s (C8), 203.0 s (C6). A mixture
of 0.5 g (0.89 mmol) of diacetonide I, 0.05 g of
the catalyst (10% Pd/C), and 5 ml of chloroform,
methylene chloride, or carbon tetrachloride was stirred
at room temperature under hydrogen until the conver-
sion of initial compound I was complete and the
conversion of intermediate product II was about
50% ( 7 days, TLC monitoring). The mixture was
evaporated, and the residue ( 2 ml) was subjected to
chromatography in a column charged with 20 g of
silica gel (eluent CHCl3 MeOH, 7 : 1) to isolate
0.22 g (48%) of product II and 0.22 g (49%) of III.
tion of enone II into dienone III may be presumed
to involve intermediate formation of 14,15-anhydro
derivative VII. This compound (stachysterone B
20,22-acetonide) was obtained by us previously from
acetonide II [10]. However, conjugated diene VII
was not detected by TLC in the reaction mixture
throughout the transformation of II into III. Our
results are consistent with the data of Galbraith and
Horn [11], according to which acid treatment of
20-hydroxyecdysone is not accompanied by dehydra-
tion of the allylic hydroxy group at C14. On the other
hand, compound VII and its 25-O-trifluoroacetyl
derivative VIII (which was synthesized as described
in [10]) undergo isomerization into compounds III
and IX, respectively. Hence we can conclude that
in the transformation of acetonides I and II into III
the dehydration and isomerization processes occur in
a concerted fashion.
Compound II. Rf 0.4. 13C NMR spectrum (CDCl3),
, ppm: 17.1 q (C18), 20.8 t (C11), 21.9 t (C16), 22.2 q
(C21), 24.1 t (C23), 24.2 q (C19), 29.3 q (C26), 29.3 q
(C27), 29.7 q and 29.9 q (20,22-Me2CO2), 31.4 t
(C12), 31.5 t (C15), 32.2 t (C4), 34.2 d (C9), 37.7 t
(C1), 38.4 s (C10), 41.9 t (C24), 47.6 s (C13), 49.7 d
(C17), 51.1 d (C5), 67.8 d (C3), 67.9 d (C2), 69.1 s
(C25), 82.3 d (C22), 83.9 s (C20), 85.1 s (C14),
EXPERIMENTAL
106.7 s (20,22-Me2CO2), 121.5 d (C7), 165.4 s (C8),
The IR spectra were recorded on a Specord IR75
spectrometer from samples pelleted with KBr. The
UV spectra were measured on a Specord M-40 spec-
trophotometer using CH3OH and CHCl3 as solvents.
The 1H and 13C NMR spectra were obtained on
a Bruker AM-300 instrument operating at 300.13 (1H)
and 75 MHz (13C); CDCl3, CD3OD, and C5D5N were
used as solvents; the chemical shifts were measured
relative to TMS as internal reference. The melting
points were determined on a compact Boetius device.
The specific rotations were measured using a Perkin
Elmer 141 polarimeter. Thin-layer chromatography
was performed on Silufol plates; spots were visualized
by treatment with a solution of 4-hydroxy-3-methoxy-
benzaldehyde in ethanol acidified with sulfuric acid.
Podecdysone B 20,22-acetonide or (20R,22R)-
20,22-O-isopropylidene-2 ,3 ,25-trihydroxy-5 -
cholesta-8,14-dien-6-one (III). a. Diacetonide I was
prepared by the procedure reported in [10] from
20-hydroxyecdysone isolated from Serratula coronata
[12]; mp 234 235 C, [ ]1D5 = +39.4 (c = 1.1, CHCl3);
13C NMR spectrum (CDCl3), C, ppm: 16.9 q (C18),
20.4 t (C11), 21.1 t (C16), 21.8 q (C21), 23.4 q (C19),
23.5 t (C23), 26.5 t (C15), 26.5 q (C26), 26.8 q (C27),
28.4 q and 28.4 q (20,22-Me2CO2), 28.9 q and 29.3 q
(2,3-Me2CO2), 30.8 t (C12), 31.3 t (C4), 34.3 d (C9),
37.5 t (C1), 37.7 s (C10), 41.3 t (C24), 47.2 s (C13),
48.9 d (C17), 50.7 d (C5), 70.3 s (C25), 71.5 d (C3),
72.0 d (C2), 81.9 d (C22), 84.3 s (C20), 84.7 s (C14),
106.9 s (20,22-Me2CO2), 108.2 s (2,3-Me2CO2),
203.3 s (C6).
Compound III. Rf 0.6; mp 120 122 C, [ ]D18
58.3 (c = 0.4, MeOH). IR spectrum (KBr), , cm :
=
1
1650, 1710, 3400. UV spectrum, max, nm: 244 ( =
1
12310). H NMR spectrum (CDCl3), , ppm (J, Hz):
0.93 s (3H, 19-H); 0.99 s (3H, 18-H); 1.17 s (3H,
21-H); 1.19 s and 1.21 s (6H, 26-H, 27-H); 1.27 s and
1.38 s (6H, 20,22-Me2CO2); 0.70 2.74 m (18H, CH,
3
CH2), 3.46 d.d (1H, 22-H, J = 11.7, 2.1); 3.64 m
(1H, 2-H, w1/2 = 17); 3.95 m (1H, 3-H, w1/2 = 6);
5.33 m (1H, 15-H, w1/2 = 4). 13C NMR spectrum
(CDCl3), C, ppm: 17.4 q (C18), 21.2 t (C11), 21.2 q
(C21), 23.7 t (C23), 26.8 q (C19), 28.9 q (C26), 29.1 q
(C27), 29.5 t (C16), 29.5 q and 29.7 q (20,22-Me2CO2),
31.5 t (C4), 36.5 t (C7), 37.3 t (C24), 38.6 t (C12),
41.2 t (C1), 43.0 s (C10), 45.8 s (C13), 52.2 d (C5),
56.0 d (C17), 67.4 d (C3), 68.9 d (C2), 70.4 s (C25),
81.8 d (C22), 83.0 s (C20), 106.9 s (20,22-Me2CO2),
119.0 d (C15), 122.2 s (C8), 135.5 s (C9), 148.0 s
(C14), 213.2 s (C6). Found, %: C 71.96; H 9.36.
C30H46O6. Calculated, %: C 71.68; H 9.22.
b. A mixture of 0.5 g (0.96 mmol) of acetonide II
{mp 223 224 C, [ ]1D8 = +58.5 (c = 0.9, CHCl3);
prepared by the procedure reported in [10] from
20-hydroxyecdysone}, 0.05 g of 10% Pd/C), and 5 ml
of chloroform was stirred at room temperature under
hydrogen until the conversion of II reached 50%
( 7 days, TLC). The mixture was evaporated, and the
residue ( 2 ml) was subjected to column chromatog-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003

TRANSFORMATION OF 20-HYDROXYECDYSONE ACETONIDES
955
raphy on 20 g of silica gel (eluent CHCl3 MeOH,
7:1) to isolate 0.24 g (49%) of initial compound II
(Rf 0.4) and 0.23 g (48%) of III (Rf 0.6). Product III
was identical in the melting point, [ ]D value, and
1H and 13C NMR spectra to a sample prepared as
described in a.
31.8 t (C16), 33.1 t (C4), 39.7 t (C7), 38.0 t (C12),
38.3 t (C1), 42.3 t (C24), 44.2 s (C10), 47.3 s (C13),
54.0 d (C5), 57.6 d (C17), 68.6 d (C3), 70.0 d (C2),
71.3 s (C25), 77.4 s (C20), 78.6 d (C22), 120.3 d (C15),
123.7 s (C8), 136.6 s (C9), 149.5 s (C14), 215.7 s (C6).
(20R,22R)-2 ,3 ,25-Trihydroxy-20,22-O-iso-
propylidene-5 -cholesta-7,9,14-trien-6-one (V).
A mixture of 0.1 g (0.2 mmol) of compound III,
0.05 g of 10% Pd/C, and 5 ml of chloroform was
stirred at room temperature under hydrogen until the
conversion of III reached 50% ( 3 days, TLC).
The mixture was evaporated, and the residue ( 2 ml)
was subjected to chromatography in a column charged
with 5 g of silica gel (eluent CHCl3 MeOH, 7:1) to
isolate 48 mg (48%) of initial compound III (Rf 0.6)
c. Compound VII was synthesized by the proce-
dure described in [10]; mp 124 125 C, [ ]1D7 = 9.0
13
(c = 0.7, MeOH); C NMR spectrum* (CD3OD),
,
C
ppm: 19.9 q (C18), 22.3 t (C11), 24.1 q (C19), 24.1 q
(C21), 25.1 t (C23), 27.3 t (C12), 29.0 q (C26), 29.3 q
(C27), 29.3 q and 29.7 q (20,22-Me2CO2), 32.8 t (C4),
36.9 t (C16), 39.4 t (C1), 39.8 d (C9), 40.0 s (C10),
42.0 t (C24), 51.5 d (C5), 58.8 d (C17), 68.6 d (C2),
68.6 d (C3), 71.3 s (C25), 83.1 d (C22), 84.8 s (C20),
108.2 s (20,22-Me2CO2), 121.1 d (C7), 130.2 d (C15),
and 49 mg (49%) of compound V (Rf 0.8), [ ]D18
=
113.0 (c = 0.8, CH3OH). 1H NMR spectrum
(CDCl3), , ppm (J, Hz): 0.87 s (3H, 19-H); 1.02 s
(3H, 18-H); 1.16 s (3H, 21-H); 1.20 s and 1.22 s (6H,
26-H, 27-H); 1.27 s and 1.40 s (6H, 20,22-Me2CO2);
0.71 2.86 m (14H, CH, CH2), 3.39 4.12 m (3H,
22-H, 2-H, 3-H); 6.08 s (1H, 7-H); 6.25 m (1H, 15-H,
w1/2 = 4); 6.30 m (1H, 11-H, w1/2 = 3). 13C NMR
spectrum (CDCl3), C, ppm: 19.6 q (C18), 20.8 q
158.9 s (C8), 150.4 s (C14), 206.1 s (C6). Following
the procedure described above in b, from 0.2 g
(0.4 mmol) of compound VIIc we obtained (after
chromatographic separation in a column charged with
8 g of silica gel, eluent CHCl3 MeOH, 7:1) 98 mg
(49%) of initial compound VII (Rf 0.5) and 94 mg
(47%) of compound III (Rf 0.6) which was identical
to a sample prepared as described in a.
(C21), 24.4 t (C23), 26.7 q (C19), 28.8 q (C26), 29.2 q
Podecdysone B or (20R,22R)-2 ,3 ,20,22,25-
pentahydroxy-5 -cholesta-8,14-dien-6-one (IV).
A mixture of 0.1 g (0.2 mmol) of compound III, 1 ml
of 70% acetic acid, and 94 mg of zinc chloride was
stirred for 4 h at room temperature. The mixture was
diluted with water (3 ml) and extracted with butyl
alcohol (3 10 ml). The organic layer was washed
with a saturated solution of NaCl (30 ml), dried over
MgSO4, and evaporated. The solid residue was sub-
jected to chromatography in a column charged with
5 g of silica gel (eluent CHCl3 MeOH, 7:1) to isolate
60 mg (60%) of initial compound III (Rf 0.6) and
35 mg (38%) of compound IV (Rf 0.3), mp 124
126 C, [ ]1D5 = 15.5 (c = 1.5, MeOH) (cf. [6, 7]).
(C27), 30.0 t (C16), 29.5 q and 29.7 q (20,22-Me2CO2),
31.8 t (C4), 38.7 t (C12), 41.0 t (C1), 42.0 t (C24),
43.8 s (C10), 45.7 s (C13), 49.4 d (C5), 57.0 d (C17),
66.9 d (C3), 67.5 d (C2), 70.3 s (C25), 81.6 d (C22),
82.9 s (C20), 106.9 s (20,22-Me2CO2), 116.3 d (C7),
128.9 d (C15), 131.7 d (C11), 135.2 s (C14), 143.8 s
(C8), 145.4 s (C9), 203.8 s (C6). Found, %: C 72.23;
H 8.97. C30H44O6. Calculated, %: C 71.97; H 8.86.
Podecdysone B 20,22-acetonide 25-trifluoro-
acetate or (20R,22R)-2 ,3 -dihydroxy-20,22-O-iso-
propylidene-25-trifluoroacetoxy-5 -cholesta-8,14-
dien-6-one (IX). Compound VIII was synthesized by
the procedure described in [10]; mp 104 106 C,
1
[ ]1D5 = 150.3 (c = 1.7, CHCl3); 13C NMR spectrum
(CDCl3), , ppm (J, Hz): 19.0 q (C18), 20.5 t (C11),
IR spectrum (KBr), , cm : 1650, 1710, 3400. UV
1
spectrum:
244 nm ( = 14150). H NMR spec-
max
trum (CD3OD), , ppm (J, Hz): 1.00 s (3H, 19-H);
1.04 s (3H, 18-H); 1.20 s (3H, 21-H); 1.27 s and
1.30 s (6H, 26-H, 27-H); 0.82 2.70 m (18H, CH,
CH2), 3.63 m (1H, 22-H, w1/2 = 5); 3.84 m (1H, 2-H,
w1/2 = 10); 3.94 m (1H, 3-H, w1/2 = 4); 5.44 m
(1H, 15-H, w1/2 = 3). 13C NMR spectrum (CD3OD),
21.1 q (C21), 23.1 t (C23), 23.2 q (C19), 25.0 q (C26),
25.8 q (C27), 26.7 t (C12), 26.7 q and 28.8 q (20,22-
Me2CO2), 31.6 t (C4), 36.4 t (C16), 38.1 t (C1), 38.4 d
(C9), 38.5 s (C10), 39.5 t (C24), 47.5 s (C13), 49.7 d
(C5), 57.7 d (C17), 67.2 d (C3), 67.7 d (C2), 80.8 d
(C22), 83.0 s (C20), 88.7 s (C25), 107.1 s (20,22-
C, ppm: 18.4 q (C18), 20.8 q (C21), 23.8 t (C11),
27.3 t (C23), 28.9 q (C19), 29.8 q (C26), 29.9 q (C27),
____________
1
Me2CO2), 114.3 q (CF3CO2, JCF = 286.0), 120.6 d
(C7), 128.4 d (C15), 148.9 s (C14), 155.6 s (C8),
2
156.0 q (CF3CO2, JCF = 41.4), 203.6 s (C6). A mix-
*
The signal from C13 is overlapped by the solvent multiplet
(
49 ppm).
ture of 0.2 g (0.33 mmol) of compound VIII, 0.05 g
C
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003

956
ODINOKOV et al.
of 10% Pd/C, and 5 ml of chloroform was stirred at
room temperature under hydrogen until the conversion
of VIII reached 50% ( 7 days, TLC). The mixture
was evaporated, and the residue ( 2 ml) was subjected
to column chromatography on 8 g of silica gel using
CHCl3 MeOH (10:1) as eluent. We isolated 96 mg
(48%) of initial compound VIII (Rf 0.5) and 93 mg
(47%) of compound IX (Rf 0.6); mp 112 114 C;
[ ]1D8 = 35.4 (c = 1.1, CHCl3). IR spectrum (KBr),
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003