Efficient synthesis of novel oxime analogues of the hormone 1α, 25-dihydroxyvitamin D3Paper

Article abstract of DOI:10.3184/174751915X14352521285949

Calcitriol analogues which contained an oxime in the side chain were synthesised in five steps from an intermediate 22-nor Ketone. The key intermediate enones were synthesised by the Wittig-Horner olefination and Wittig olefination respectively. Reduction

Full text of DOI:10.3184/174751915X14352521285949

368 RESEARCH PAPER
VOL. 39 JUNE, 368–372
JOURNAL OF CHEMICAL RESEARCH 2015
Efficient synthesis of novel oxime analogues of the hormone
1α, 25-dihydroxyvitamin D3
Hongliang Li, Zhijie Fang*, Huanran Dai, Hengrui Zhang and Yanan Liu
School of Chemical Engineering, Nanjing University of Science &Technology, Nanjing 210094, P.R. China
Calcitriol analogues which contained an oxime in the side chain were synthesised in five steps from an intermediate 22-nor Ketone. The
key intermediate enones were synthesised by the Wittig–Horner olefination and Wittig olefination respectively. Reduction, oximation,
photoisomerisation and deprotection gave the target compounds with the oxime at C-24.
Keywords: calcitriol, oximation, Wittig–Horner olefination, Wittig olefination
The metabolite of vitamin D, 1α,25-dihydroxyvitamin D3
[1α,25(OH)2D3, calcitriol, 1] (Fig. 1) is well known to regulate
calcium, phosphorus homeostasis in vertebrate organisms1 and
playsaveryimportantroleoncellulardifferentiation,proliferation,
and the functioning of the central nervous system.2 Furthermore,
there is evidence that calcitriol may generate biological responses
through regulation of gene expression by signaling through
the nuclear vitamin D receptor (VDR) transcription factor.3,4
Although calcitriol can play a very important biological role,
the side effects including hypercalciuria, hypercalcinaemia,
nephrocalcinosis, nephrolithiasis and soft tissue calcification,
limit its application.5 Consequently, vitamin D analogues
are being evaluated currently as potential drug candidates to
overcome the side effects of calcitriol.6 Moreover,7,8as the basic
site of the active metabolite, the side chain of vitamin D is
regarded as an important region for modification.1 For example,
analogues with catabolism-blocking side chain modifications
including olefinic,9 acetylenic10 ketonic11 and oxime12 groups have
been developed and their high antiproliferative activity and low
calcium activity has been reported.
Based on our prior work, 19-21 we now report an effective
method for the synthesis of three types of novel oxime analogues
5–7. We suggest that these compounds may have desirable
pharmacological properties (e.g., high metabolic stability) and
biological activity (e.g., lower hypercalcaemia).12
Result and discussion
Synthesis of 5 by Wittig–Horner reaction and photo-
isomerisation
For the synthesis of 5, we started from aldehyde 8 (Scheme 1),
which is readily obtained in large quantities from vitamin D2
using the procedures originally described by Calverley22 modified
by our group.21 Wittig–Horner coupling of 8 with phosphonate
923 was best carried out in THF at room temperature with NaH
as base. Under these conditions, the enone 11a was obtained in
88% yield. Reaction of 11a with Na2S2O4 and NaHCO3 under
phase transfer conditions gave ketone 12a in 67% yield. The
reaction was also carried out with Mg and MeOH as the reducing
agent, but the yield was less than 30%. Subsequently, the ketone
12a was transformed to give the oxime 13a with the yield of
97% by direct reaction with hydroxylamine hydrochloride. In
the final two steps, removal of the silyl protecting groups of
13a with TBAF in THF afforded a 82% yield of triol 14a, and
photoisomerisation of 14a using anthracene(An) as sensitiser
finally gave the target oxime analogue 5 in 63% yield. At the
beginning of our research work, the target oxime analogue 5 was
obtained by photoisomerisation and subsequent deprotection.
The photoisomerisation reaction was incomplete and it was hard
to separate the isomers. The production could not be used directly
in next step. Consequently we carried out the deprotection first,
and then the photoisomerisation. After photoisomerisation, the
products were purified directly by semi-preparative HPLC (10%
H2O/CH3OH).
Side chain oxime analogue 2 and oxime O-methyl ether
3 have been prepared by using Horner-Wadsworth-Emmons
(HWE) coupling of the A-ring with the C,D-ring and possess
better biological activity than calcitriol (1).12 Some 24-oxime
derivatives have been used as antagonists of vitamin D. For
example, the antagonistic bioactivity of 4 is very effective.
This was prepared from the known 24-oxocholesterol acetate.13
Recently, several steroidal natural products with an oxime group
isolated from marine sponges have been shown to have unique
biological activities,14 such as anticancer activity,15 antibacterial
17
activity, 16antihyperglycemic agents,
and potential for the
treatment of rheumatoid arthritis.18 However, there are few
reports of their chemical synthesis.
HO
N
HO
N
R
X
R=
OH
1
Calcitriol
5
H
3CO
HO
N
N
HO
OH
HO
HO
OH
7
6
2
3
,X=NOH
,X=NOCH3
4
Fig. 1 Structures of vitamin D analogues.
* Correspondent. E-mail: zjfang@njust.edu.cn

JOURNAL OF CHEMICAL RESEARCH 2015 369
O
O
R
O
R
O
P
O
O
O
a
c
9
d
b
PPh3
TBSO
O
10
TBSO
OTBS
TBSO
12a:R=
OTBS
OTBS
8
11a:R=
isopropyl
isopropyl
11b:R=
12b:R=
cyclopropyl
cyclopropyl
HO
N
HO
HO
N
N
e
R
R
R
f
HO
OH
TBSO
OTBS
HO
5:R=
OH
13a:R=
13b:R=
14a:R=
14b:R=
isopropyl
cyclopropyl
isopropyl
cyclopropyl
isopropyl
6:R=
cyclopropyl
Scheme 1 Synthesis of compounds 5 and 6.
(a):NaH, THF; (b):DMSO 105°C; (c): Na2S2O4, NaHCO3, (C10H21)3NMeCl, PhCH3, H2O, 80°C; (d):NH2OH·HCl Et3N; (e): n-Bu4NF ,THF,60°C;
(f):An, hv, CH3OH, 20°C.
O
H
3CO
H
3CO
H
3CO
N
N
i
N
h
g
TBSO
OTBS
TBSO
OTBS
TBSO
OTBS
HO
OH
12a
15
16
7
Scheme 2 Synthesis of compound 7.
(g):NH2OCH3·HCl，Et3N; (h):An, hv, toluene, 20°C; (i): n-Bu4NF ,THF,60°C
Synthesis of cyclopropyl oxime analogue 6
Synthesis of oxime O-methyl ether 7
The synthesis of the target compound 6 was similar to that of
the oxime analogue 5 (Scheme 1). Treatment of aldehyde 8
with a molar excess of cyclopropylcarbonylmethylenetriphenyl-
phosphorane(10, readily obtained from cyclopropyl methyl
ketone) in dimethyl sulfoxide at 105°C for 4h led to the isolation of
the pure enone 11b in 54% yield.23 Reaction of 11b with Na2S2O4,
followed by direct reaction with hydroxylamine hydrochloride
gave the oxime 13b. Removal of the silyl protecting group with
TBAF gave triol 14b, which upon reaction with anthracene as
sensitiser in CH3OH at room temperature yielded cyclopropyl
oxime analogue 6. In the last step, we explored the different
catalytic effect between anthracene or 9-acetylanthracene. We
found that the yield of 6 was much higher when anthracene was
used as sensitiser. The crude producti 6 was purified by semi-
preparative HPLC (20% H2O/CH3OH).
As a starting compound for the synthesis of the oxime
O-methyl ether 7 we chose the key intermediate 12a (Scheme
2). The introduction of the oxime O-methyl ether 15 using
hydroxylamine O-methyl ether in anhydrous ethanol proceeded
without destroying the acid-sensitive conjugated triene unit of
this seco-steroid. Then, using anthrancene as triplet-sensitiser
in toluene 15 was converted to the (5Z)-vitamin derivative
16. Removal of the TBS protective groups with TBAF in
THF completed the synthesis of oxime O-methyl ether 7.
In contrast to the last two steps of the route to compounds
5 and 6, the target oxime O-methyl ether 7 was obtained by
photoisomerisation and subsequent deprotection. The reason
was that the photoisomerisation reaction mixture was easily
purified by using silica gel column chromatography easily, to
give the (5Z)-vitamin derivatives 16.

370 JOURNAL OF CHEMICAL RESEARCH 2015
Conclusion
chloride (0.150 g,0.310 mmol) were added. The reaction mixture was
stirred vigorously for 3h at reflux under Ar. After being cooled to room
temperature, the reaction mixture was extracted with ethyl acetate
(3×20 mL). The organic layer was washed with water (2×30 mL), brine
(2×30 mL) and dried over sodium sulfate. The solvent was removed by
rotary evaporation. The resulting white solid was chromatographed on
silica gel, eluting with a gradient of Et2O in PE (PE: Et2O = 100:3), to
In conclusion, we have synthesised three kinds of novel oxime
analogues of the hormone 1α,25-dihydroxyvitamin D3, oxime
analogue 5, cyclepropyl oxime analogue 6 and oxime O-methyl
ether 7 by oximation reaction without destroying the acid-
sensitive conjugated triene unit of this seco-steroid. The total
yield of three target compounds 5, 6 and 7 were 29%, 19% and
27%,respectively. The successful synthesis of these products
can provide an experimental foundation for modifying the side
chain of vitamin D to develop bioactive molecules, and hence
the discovery of new drugs. The study of the biological activity
of compounds 5, 6 and 7 has been carried out in our group.
21
give the desired product 12a (0.204 g, 66.9%) as white solid. m.p.
1
76–78°C (lit.21 76–78°C); H NMR (500 MHz, CDCl3) δ 6.46 (d, J =
11.4 Hz, 1H), 5.82 (d, J = 11.5 Hz, 1H), 4.96 (d, 2H), 4.54 (dd, J = 9.2,
4.2 Hz, 1H), 4.22 (d, J = 2.4 Hz, 1H), 2.87 (d, J = 13.1 Hz, 1H), 1.09
(m, 7H), 0.54 (s, 3H), 0.08–0.04 (m, 12H). ppm; 13C NMR (126 MHz,
CDCl3): δ 215.5, 153.8, 143.4, 135.6, 121.8, 116.6, 106.7, 70.3, 67.3,
56.5, 46.0, 44.0, 41.0, 40.7, 37.4, 36.6, 35.8, 29.9, 29.1, 27.7, 26.0, 25.9,
23.6, 22.4, 18.7, 18.5, 18.4, 18.2, 12.1, –4.7, –4.8 ppm.
Experimental
All the reactions were performed in oven-dried glassware under an
atmosphere of ultra high purity argon. Anhydrous THF was distilled
from sodium metal immediately prior to use. All chemicals were
purchased from commercial suppliers and used without further
purification unless otherwise noted. Column chromatography was
performed using silica gel (300–400 mesh).1H and 13C NMR spectra
were recorded at 500 MHz and 126 MHz with a Bruker Avance III
500 NMR spectrometer in CDCl3. Chemical shifts (δ) are reported
downfield from internal Me4Si (δ 0.00). HRMS spectra analyses
were performed on an Agilent 6540Q-TOF MS. HPLC was carried
out using a LC-6AD equipped with one 6 mL/min preparative
pump head using Shim-pack PERP-ODS(H) KIT 10 mm×250mm
(semipreparative) columns packed with C-18-bonded silica and a SPD-
20A UV-C variable-wavelength detector set at 254 nm. TLC plates
were visualised by observation under UV lamp. Melting points were
determined in capillaries and without correction.
1(S),3(R)-Bis(tert-butyldimethylsilyloxy)-20(R)-(3’-isopropyl-3’-
hydr-oxyiminopropyl)-9,10-secopregna-5(E),7(E), 10(19)–triene
N-oxide (13a): A 50 mL round-bottom flask was charged with 12a
(0.500 g, 0.777 mmol) dissolved in 25 mL of anhydrous alcohol.
Hydroxylamine hydrochloride (1.100 g, 15.540 mmol, 20 equiv.) and
triethylamine (5 mL) were added, and the reaction was brought to reflux
for 3h at which point TLC analysis showed complete consumption of
starting material and the appearance of a new, more polar product
13a(0.496 g, 97%). This material was purified directly using silica gel
column chromatography (10% ethyl acetate/PE) to give a white solid.
m.p.109–112°C;1H NMR (500 MHz, CDCl3): δ 6.46 (d, J = 9.8 Hz,
1H), 5.84 (d, J = 11.4 Hz, 1H), 4.99 (s, 1H), 4.94 (s, 1H),4.52 (m, 1H),
4.31–3.93 (m, 1H), 3.04 -2.74 (m, 1H), 0.55 (s, 3H), 0.17–0.03 (m, 11H)
ppm; 13C NMR (126 MHz, CDCl3) δ 166.02, 153.58, 143.23, 135.30,
121.68, 116.38, 106.53, 77.21, 76.96, 76.70, 70.16, 67.18, 56.37, 56.26,
55.97, 45.87, 43.88, 40.47, 36.70, 36.49, 33.58, 31.70, 28.89, 27.57, 25.81,
25.75, 23.48, 23.35, 22.21, 20.06, 19.97, 18.52, 18.19, 18.02, 11.96,
–4.82, –4.96 ppm; HRMS (ESI Positive) calcd for C39H71NO3Si2Na,
[M+Na]+680.4870, found 680.4870.
20(R)-(3’-isopropyl-3’-hydroxyiminopropyl)-1(S),3(R)-dihydroxy-
9,10-secopregna-5(E),7(E),10(19)- triene N-oxide (14a): A solution
of 13a (0.080 g,0.122 mmol) was dissolved in tetrahydrofuran (25 mL)
and then 1M tetrabutylammonium fluoride solution in tetrahydrofuran
(1.5 mL) was added. The reaction mixture was heated to 60°C for
1.5h. After being cooled to room temperature, the reaction mixture
was poured into water (100 mL). The aqueous layer was extracted
with ethyl acetate (3×50 mL). The organic layer was washed with
water (2×50 mL), brine (2×50 mL) and dried over sodium sulfate. The
residue was purified by chromatography (silica gel, PE:EA=1:1)to
give 14a (0.043 g,82.2%)as a colourless solid. m.p.77-80°C;1H NMR
(500 MHz, CDCl3): δ 6.55 (d, J = 11.3 Hz, 1H), 5.87 (d, J = 11.4 Hz,
1H), 5.24-4.98 (m, 1H), 4.95 (s, 1H), 4.58-4.39 (m, 1H), 4.32-4.02 (m,
1H), 3.05-2.62 (m, 2H), 0.71-0.37 (m, 3H) ppm; 13C NMR (126 MHz,
CDCl3) δ 166.28, 145.05, 132.83, 123.14, 115.91, 109.65, 77.22, 76.97,
76.72, 71.01, 65.70, 56.40, 55.92, 45.88, 41.82, 40.34, 36.60, 33.58,
31.70, 28.99, 27.49, 23.47, 23.17, 22.23, 20.08, 20.00, 18.51, 12.06 ppm;
HRMS (ESI Positive) calcd for C27H43NO3Na, [M+Na]+ 452.3141,
found 452.3140.
The starting aldehyde 8 was obtained from vitamin D2 as described
1
previously. Aldehyde 821: m.p. 111–113°C,(lit.22113–115°C); H NMR
(500 MHz, CDCl3) δ 9.59 (d, J = 3.2 Hz, 1H), 6.45 (d, J = 11.4 Hz,
1H), 5.84 (d, J = 11.4 Hz, 1H), 4.97 (d, 2H), 4.63–4.47 (m, 1H), 4.22
(s, 1H), 2.94–2.84 (m, 1H), 2.56 (dd, J = 14.1, 5.1 Hz, 1H), 1.12 (t, 4H),
0.59 (s, 3H), 0.10–0.04 (m, 12H). ppm;13C NMR(75 MHz, CDCl3):
δ 204.9, 153.6, 142.2, 135.9, 121.5, 116.8, 106.6, 70.1, 67.1, 55.6, 51.3,
49.7, 46.2, 43.8, 40.2, 36.5, 28.8, 26.4, 25.8, 25.7, 23.3, 22.6, 18.2, 18.0,
13.5, 12.4,–4.8, –5.0 ppm; MS (ESI, m/z) [M+H]+:573.56.
1(S),3(R)-Bis(tert-butyldimethylsilyloxy)-20(R)-(3’-isopropyl-3’-
oxypropyl-1’(E)-enyl)-9,10-secopregna-5(E),7(E),10(19)–triene(11a):
Sodium hydride (60%, 0.241 g, 6.02 mmol) was added to anhydrous
THF (20 mL) under argon atmosphere, diethylphosphono-3-methyl-2-
butanone (9, 1.782 g, 8.02 mmol) was added dropwise to the reaction
mixture. The reaction mixture was stirred for 1 h at room temperature
under Ar. Then aldehyde 8 (2.200 g, 3.839 mmol) in dry THF (10 mL)
was added. The reaction mixture was heated to reflux for another 2h
with an argon flow, cooled to room temperature, and treated with
water (100 mL). The aqueous layer was extracted with ethyl acetate
(3×50 mL), which was in turn washed with saturated brine (3×50
mL) and water (2×50 mL) and dried over sodium sulfate. After
removal of solvent, the residue was purified by chromatography (SiO2,
21
PE: Et2O = 100:3) to give 11a (2.186 g, 87.7%) as white solid. m.p.
20(R)-(3’-isopropyl-3’-hydroxyiminopropyl)-1(S),3(R)-dihydroxy-
9,10-secopregna-5(Z),7(E),10(19)- triene N-oxide (5): Oxime 14a
(0.024 g, 0.100 mmol), anthracene (0.020 g) and triethylamine (2
mL) in methanol (35 mL) was stirred at room temperature under Ar.
The reaction mixture was then irradiated using a 500W high pressure
UV lamp through a brown uranium quartz filter for 10h. The solution
was concentrated under reduced pressure. The residue mixture
was purified directly using reverse phase HPLC chromatography
(10% H2O/methanol) to give 0.015 g of 5 as colourless foam
(62.5%).1H NMR (500 MHz, CDCl3): δ 6.40 (d, J = 11.2 Hz, 1H),6.04
(d, J =11.2Hz, 1H), 5.42 (s, 1H), 5.01 (s, 1H), 4.54-4.36 (m, 1H),
4.36–4.13 (m, 1H), 2.93–2.71 (m, 1H), 0.65 (s, 3H) ppm; 13C NMR
(126 MHz, CDCl3) δ 166.68, 147.64, 143.04, 132.85, 124.91, 117.00,
111.64, 77.18, 76.92, 76.67, 70.75, 66.80, 56.27, 55.98, 45.87, 45.22,
42.83, 40.40, 36.61, 33.54, 31.81, 29.61, 29.00, 27.46, 23.51, 23.16,
1
105–106°C，(lit.21 105–106°C) ; H NMR (500 MHz, CDCl3): δ 6.73
(dd, J = 15.7, 9.0 Hz, 1H), 6.46 (d, J = 11.4 Hz, 1H), 6.09 (d, J = 15.7
Hz, 1H), 5.83 (d, J = 11.4 Hz, 1H), 4.97 (d, 2H), 4.66–4.45 (m, 1H),
4.23 (s, 1H), 2.98–2.71 (m, 2H), 2.57 (dd, J = 14.1, 4.9 Hz, 1H), 2.29
(t, 2H), 2.10–1.84 (m, 3H), 1.82–1.64 (m, 4H), 1.11 (m, 10H), 0.86 (m,
20H), 0.59 (s, 3H), 0.07 (s, 12H) ppm;13C NMR (126 MHz, CDCl3): δ
204.6, 153.7, 152.4, 142.8, 135.8, 126.4, 121.7, 116.8, 106.8, 70.3, 67.3,
56.3, 55.5, 46.2, 44.0, 40.5, 40.4, 38.4, 36.7, 29.0, 27.6, 26.0, 25.9, 23.6,
22.4, 19.6, 18.7, 18.6, 18.4, 18.2, 12.4, –4.7, –4.8 ppm.
1(S),3(R)-Bis(tert-butyldimethylsilyloxy)-20(R)-(3’-isopropyl-3’-
oxypropyl)-9,10-secopregna-5(E),7(E), 10(19)–triene(12a): Enone
11a(0.304 g, 0.474 mmol)was dissolved in toluene (15 mL) and distilled
water (15 mL) and sodium bicarbonate (0.790 g, 9.405 mmol), sodium
dithionite (1.630 g, 9.405 mmol) and methyltridecylammonium

JOURNAL OF CHEMICAL RESEARCH 2015 371
22.21, 20.06, 19.97, 18.97, 18.52, 11.92, 0.92, –0.10 ppm; HRMS (ESI
Positive) calcd for C27H43NO3Na, [M+Na]+ 452.3141, found 452.3141.
1(S),3(R)-Bis(tert-butyldimethylsilyloxy)-20(R)-(3’-isopropyl-
3’-methyliminopropyl)-9,10-secopregna-5(E),7(E),10(19)–triene
N-oxide (15): Ketone 12a (0.300 g, 0.466 mmol) was slowly added
with stirring to a solution of methoxylamine hydrochloride (1.558 g,
18.64 mmol) and triethylamine(5 mL) in anhydrous alcohol (50 mL)
at r.t., The mixture was stirred at 80°C for 8h. Ethyl acetate and water
were added, and the organic phase was washed with brine, dried
with Na2SO4, and evaporated. The residue was dissolved in CH2Cl2,
applied on a silica column, and washed with PE/diethyl ether (200:1)
to produce 15(0.297 g, 94.6%) as a white solid. m.p.85–87°C;1H NMR
(500 MHz, CDCl3): δ 6.48 (d, J = 11.4 Hz, 1H), 5.85 (d, J = 11.4 Hz,
1H), 4.98 (d, 2H), 4.56 (m, 1H), 4.24 (s, 1H), 3.81 (s, 4H), 2.85 (m, 1H),
0.57 (s, 4H), 0.18–0.03 (m, 16H) ppm; 13C NMR (126 MHz, CDCl3)
δ 165.73, 153.57, 143.19, 135.30, 121.66, 116.38, 106.55, 77.21, 76.96,
76.71, 70.18, 67.17, 60.94, 60.85, 56.37, 55.93, 45.85, 43.89, 40.45,
36.68, 36.51, 36.26, 33.63, 32.15, 28.88, 27.61, 27.50, 27.38, 27.18,
25.80, 25.74, 23.47, 23.40, 22.20, 20.19, 20.10, 19.18, 18.62, 18.53,
18.18, 18.01, 11.94, –4.83, –4.97 ppm; HRMS (ESI Positive) calcd for
C40H73NO3Si2, [M+H]+ 672.5207, found 672.5204.
1(S),3(R)-Bis(tert-butyldimethylsilyloxy)-20(R)-(3’-isopropyl-3’-
methyliminopropyl)-9,10-secopregna-5(Z), 7(E), 10(19)–triene N-oxide
(16): A solution of oxime ether 15 (0.160 g, 2.38 mmol), anthracene
(0.200 g) and triethylamine (5 mL) in toluene was irradiated for
8h with a 500W high pressure mercury arc lamp in an analogous
manner as was described above for 5. The solution was concentrated
under vacuum, and the residue was applied to a silica column, and
washed with PE/diethyl ether (200:1) to produce 16 (0.124 g,77.5%)
as colourless foam. 1H NMR (500 MHz, CDCl3): δ 6.24 (d, J = 11.2
Hz, 1H), 6.02 (d, J = 11.2 Hz, 1H), 5.18 (s, 1H), 4.87 (d, J = 1.5 Hz,
1H), 4.34 (m, 1H), 4.30–4.06 (m, 1H), 3.79 (d, J = 1.9 Hz, 4H), 2.80
(m, 1H), 0.54 (s, 4H), 0.26–0.05 (m, 17H) ppm; 13C NMR (126 MHz,
CDCl3) δ 165.77, 148.27, 140.86, 134.94, 123.09, 117.87, 111.11, 77.20,
76.95, 76.69, 71.99, 67.47, 60.95, 60.85, 56.27, 55.93, 45.98, 45.71, 44.77,
40.52, 36.71, 36.28, 33.63, 33.19, 32.17, 28.80, 27.63, 27.53, 27.43, 27.19,
25.79, 23.43, 22.11, 20.19, 20.10, 19.18, 18.64, 18.54, 18.17, 18.07, 11.90,
-4.74, -4.84, -5.14 ppm; HRMS (ESI Positive) calcd for C40H73NO3Si2,
[M+H]+ 672.5207, found 672.5195.
20(R)-(3’-isopropyl-3’-methyliminopropyl)-1(S),3(R)-dihydroxy-
9,10-secopregna-5(Z),7(E),10(19)- triene N-oxide (7): The protected
analogue 16(0.100 g, 0.15 mmol) was dissolved in THF (30 mL),
and TBAF (1M in THF, 2 mL) was added. The reaction mixture was
refluxed to 60°C for 2h. The reaction was quenched with H2O and
extracted with ethyl acetate (3×50 mL), dried over Na2SO4, and
filtered. The filtrate was concentrated in vacuum to give the crude
product which was purified by column chromatography (50% ethyl
acetate in PE) to afford 7(0.042 g,63.5%) as colourless foam. 1H NMR
(500 MHz, CDCl3): δ6.36 (d, J = 11.2 Hz, 1H), 6.01 (d, J = 11.1 Hz,
1H), 5.31 (s, 1H), 4.98 (s, 1H), 4.38 (s, 1H), 4.21 (d, J = 3.0 Hz, 1H),
3.78 (d, J = 2.7 Hz, 4H), 2.81 (d, J = 14.2 Hz, 1H), 0.54 (s, 3H) ppm;
13C NMR (126 MHz, CDCl3) δ 165.92, 147.57, 142.96, 132.96, 124.82,
117.02, 111.70, 77.23, 76.97, 76.72, 70.69, 66.72, 60.96, 60.85, 56.27,
55.89, 45.84, 45.16, 42.78, 40.38, 36.64, 33.60, 32.13, 28.99, 27.42,
27.21, 23.51, 23.34, 22.22, 20.19, 20.09, 19.17, 18.51, 11.92 ppm; HRMS
(ESI Positive) calcd for C28H45NO3Na, [M+Na]+ 466.3297, found
466.3293.
1(S),3(R)-Bis(tert-butyldimethylsilyloxy)-20(R)-(3’-cyclopropyl-
3’-oxypropyl-1’(E)-enyl)-9,10-secopregna-5(E),7(E),10(19) –
triene(11b): Obtained by Wittig coupling of aldehyde 8(8 g, 0.014mol)
with phosphorane 10 (12 g, 0.035 mol) in dimethyl sulfoxide (50 mL).
The reaction mixture was refluxed to 105°C for 4h.The enone was
purified on a silica column, using a PE/diethyl ether (50:1) solvent
system, to give enone 11b (4.8 g) 22 in 53.7% yield as a white solid. m.p.
123–124°C，(lit.22 123–124°C); 1H NMR (500 MHz, CDCl3): δ 6.79
(dd, J = 15.7, 8.9 Hz, 1H), 6.48 (d, J = 11.4 Hz, 1H), 6.19 (d, J = 15.7
Hz, 1H), 5.85 (d, J = 11.4 Hz, 1H), 5.01 (s, 1H), 4.97 (s, 1H),4.56 (dd, J
= 9.1, 4.0 Hz, 1H), 4.24 (s, 1H), 3.00–2.73 (m, 1H), 2.58 (dd, J = 14.1,
5.1 Hz, 1H), 2.38–2.26 (m, 2H), 0.61 (s, 3H), 0.15–0.03 (m, 13H) ppm.
1(S),3(R)-Bis(tert-butyldimethylsilyloxy)-20(R)-(3’-cyclopropyl-3’-
oxypropyl)-9,10-secopregna-5(E),7(E),10(19)–triene (12b): Starting
with 11b(1.200 g, 1.88 mmol), a hydrogenation procedure similar to
that used to make 12a was used to obtain 12b22 (0.824 g, 68.4%) as
a white solid. m.p. 93–94°C，(lit.22 93–94°C); 1H NMR (500 MHz,
CDCl3): δ6.46 (d, J = 11.4 Hz, 1H), 5.83 (d, J = 11.4 Hz, 1H), 4.98
(s, 1H), 4.94 (s, 1H),4.59–4.38 (m, 1H), 4.16 (s, 1H), 2.83 (m, 1H),
0.65–0.38 (m, 3H), 0.09–0.04 (m, 9H) ppm.
1(S),3(R)-Bis(tert-butyldimethylsilyloxy)-20(R)-(3’-cyclopropyl-
3’-hydroxyiminopropyl)-9, 10-secopregna-5(E),7(E),10(19)–triene
N- oxide (13b): Using the procedure for the synthesis of 13a from
12a, 13b (0.051 g, 0.078 mmol) was obtained from 12b (0.050 g, 0.078
mmol) in 100% yield as a white solid. m.p. 118–120°C; 1H NMR (500
MHz, CDCl3): δ6.46 (d, J = 11.3 Hz, 1H), 5.83 (d, J = 11.3 Hz, 1H),
4.98 (s, 1H), 4.94 (s, 1H),4.54 (d, J = 5.1 Hz, 1H), 4.22 (s, 1H), 2.85
(m, 1H), 2.59–2.47 (m, 1H), 0.79–0.61 (m, 5H), 0.54 (d, J = 8.1 Hz,
3H), 0.16–0.01 (m, 14H) ppm; 13C NMR (126 MHz, CDCl3) δ 163.00,
161.92, 153.59, 143.22, 135.33, 132.28, 121.66, 116.39, 114.20, 106.54,
99.94, 77.20, 76.94, 76.69, 75.17, 70.17, 67.17, 60.01, 56.36, 56.17, 56.02,
45.87, 43.88, 40.46, 36.49, 36.44, 36.12, 33.08, 31.83, 28.88, 27.56,
25.80, 25.74, 23.72, 23.47, 22.19, 18.53, 18.19, 18.02, 14.06, 11.96,
8.28, 5.09, 5.03, –4.83, –4.97 ppm; HRMS (ESI Positive) calcd for
C39H69NO3Si2 Na, [M+Na]+678.4714, found 678.4713.
20(R)-(3’-cyclopropyl-3’-hydroxyiminopropyl)-1(S),3(R)-dihydroxy-
9,10-secopregna-5(E),7(E),10(19)- triene N-oxide (14b): Using the
procedure for the synthesis of 14a from 13a, compound 14b (0.047
g, 0.110 mmol) was obtained from 13b(0.050 g, 0.156 mmol) in 70.5%
yield as a white solid. m.p. 97–110°C; 1H NMR (500 MHz, CDCl3):
δ6.54 (d, J = 11.0 Hz, 1H), 5.87 (d, J = 11.1 Hz, 1H), 5.09 (s, 1H), 4.95
(s, 1H), 4.47 (s, 1H), 4.15 (m, 1H), 2.79 (m, 3H), 0.77–0.61 (m, 4H),
0.59–0.42 (m, 4H) ppm; 13C NMR (126 MHz, CDCl3) δ 162.96, 151.60,
144.92, 132.93, 123.08, 115.96, 109.64, 77.23, 76.98, 76.73, 70.98, 65.66,
56.40, 56.15, 55.98, 45.88, 41.84, 40.35, 36.61, 36.35, 36.07, 31.79, 29.62,
28.99, 27.49, 23.47, 22.23, 18.54, 14.05, 12.07, 5.01 ppm; HRMS (ESI
Positive) calcd for C27H41NO3Na, [M+Na]+450.2984, found 450.2977.
20(R)-(3’-cyclopropyl-3’-hydroxyiminopropyl)-1(S),3(R)-dihydroxy-
9,10-secopregna-5(Z),7(E),10(19)- triene N-oxide(6): Prepared from
oxime 14b by following the same procedure described for 7. Compound
6 (0.010 g, 0.024 mmol) from 14b (0.047 g, 0.011 mmol) as colourless
foam in 72.3% yield. 1H NMR (500 MHz, CDCl3): δ6.38 (d, J = 11.3
Hz, 1H), 5.98 (d, J = 11.3 Hz, 1H), 5.33 (s, 1H), 5.00 (s, 1H), 4.44
(s, 1H), 4.23 (s, 1H), 2.94–2.73 (m, 1H), 2.60 (d, J = 10.3 Hz, 1H),
1.08–0.94 (m, 3H), 0.55 (s, 3H) ppm; 13C NMR (126 MHz, CDCl3) δ
163.41, 147.62, 143.04, 132.84, 124.93, 117.00, 111.67, 77.18, 76.93,
76.67, 70.77, 66.81, 56.27, 56.02, 45.87, 45.22, 42.83, 40.40, 36.34,
31.89, 29.62, 29.01, 27.46, 23.67, 23.51, 22.21, 18.53, 13.93, 11.94,
5.11, 5.03, -0.09 ppm; HRMS (ESI Positive) calcd for C27H41NO3Na,
[M+Na]+ 450.2984, found 450.2961.
Financial support from the prospective joint project of
Production, Education and Research in Jiangsu Province, China
(grant no. BY2013004-02) is gratefully acknowledged.
Electronic Supplementary Information
1H NMR, 13C NMR, HRMS data can be found in the ESI
available through stl.publisher.ingentaconnect.com/content/stl/
jcr/supp-data.
Received 13 March 2015; accepted 2 June 2015
Paper 1503245 doi: 10.3184/174751915X14352521285949
Published online: 29 June 2015
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