Synthesis of N-desmethyl derivatives of 17α-acetoxy-11β(4-N,N- dimethylaminophenyl)-19-norpregna-4,9-diene-3,20-dione and mifepristone: Substrates for the synthesis of radioligands

Article abstract of DOI:10.1016/S0039-128X(98)00086-5

The syntheses of N-desmethyl derivatives of CDB-2914 and the mono-N- desmethyl derivative of Mifepristone are described. We also describe the use of the mono-desmethyl derivatives as substrates for the synthesis of N- tritomethyl derivatives of CDB-2914 a

Full text of DOI:10.1016/S0039-128X(98)00086-5

Steroids 64 (1999) 205–212
Synthesis of N-desmethyl derivatives of 17␣-acetoxy-11␤-
(4-N,N-dimethylaminophenyl)-19-norpregna-4,9-diene-3,20-dione
and mifepristone1
Substrates for the synthesis of radioligands
Pemmaraju N. Raoa,*, C. Kirk Acostaa, James W. Cessaca, Martin L. Bahra, Hyun K. Kimb
aDepartment of Organic Chemistry, Southwest Foundation for Biomedical Research, San Antonio, TX 78245-0549, USA
bNational Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
Received 15 June 1998; accepted 18 September 1998
Abstract
The syntheses of N-desmethyl derivatives of CDB-2914 and the mono-N-desmethyl derivative of Mifepristone are described. We also
describe the use of the mono-desmethyl derivatives as substrates for the synthesis of N-tritomethyl derivatives of CDB-2914 and
Mifepristone with high specific activity (ca. 80 Ci/mmol), which serve as radioligands for radioimmunoassay. © 1999 Elsevier Science Inc.
All rights reserved.
Keywords: Steroids; Synthesis; N-desmethyl; CDB-2914; Mifepristone; Radioligands
Since its discovery in the early 1980s, Mifepristone 1
(RU-38 486) (Fig. 1) remains the most well-studied anti-
progestin of clinical importance to date. Early metabolism
studies [1] have demonstrated that the parent compound 1 is
rapidly converted to mono-desmethyl derivative 2 (RU-42
633) and a non-demethylated propynyl alcohol metabolite 3
(RU-42 698). Further metabolism converts 2 to di-des-
methyl metabolite 4 (RU-42 848). All three metabolites
have been shown to retain powerful antiprogestational and
antiglucocorticoid activity and thus, all contribute to the
overall physiological action of Mifepristone.
In 1986, Cook et al. [2] reported the synthesis of 17␣-
acetoxy-11␤-(4-N,N-dimethylaminophenyl)-19-norprenga-
4,9-diene-3,20-dione 5 (CDB-2914). This compound was
shown to be equipotent to Mifepristone with slightly lower
antiglucocorticoid activity. For clinical trials, a large quantity
of 5 was required, for which we developed a practical large
scale synthesis [3,4]. We anticipated that the metabolism of 5
would be analogous to that of Mifepristone. Therefore, it was
necessary to synthesize authentic reference samples of mono-
and di-desmethyl CDB-2914 6 and 7, respectively. These sam-
ples helped to investigate their role as potential metabolites and
gain insight into the pharmacokinetics of the parent compound.
The di-N-desmethyl derivative of CDB-2914 7 was pre-
pared through copper (I)-catalyzed conjugate addition of a
suitably protected derivative of 4-bromoaniline to the well
know 9(11)-en-5␣,10␣-epoxide. The mono-desmethyl de-
rivative of CDB-2914 6 was obtained in a single step from
the parent compound using a novel oxidative N-demethyl-
ation reaction developed in our laboratories [5]. Similar
oxidative N-demethylation of Mifepristone 1 gave the
mono-N-desmethyl derivative (RU-42 633) 2. The mono-
desmethyl derivatives 6 and 2 were used for the synthesis of
N-tritiomethyl derivatives of CDB-2914 8 and RU-38 486
9.
1. Experimental
Melting points (mp) were determined on a Thomas-
Hoover apparatus and are uncorrected. Nuclear magnetic
resonance spectra were recorded on either a Varian EM-390
(90 MHz) or a General Electric GE-300 (300 MHz) spec-
trometers as deuteriochloroform solutions using tetrameth-
* Corresponding author.
1Presented in part at the Xth International Congress on Hormonal
Steroids. Quebec City, Quebec, Canada. June 1998:17–21.
0039-128X/99/$ – see front matter © 1999 Elsevier Science Inc. All rights reserved.
PII: PII S0039-128X(98)00086-5

206
P.N. Rao et al. / Steroids 64 (1999) 205–212
Fig. 1. Metabolites and radioligands.
ylsilane (TMS) as an internal standard (␦ ϭ 0.0). Infrared
(IR) spectra were recorded on a Perkin-Elmer model 1600
FTIR instrument equipped with a diffuse reflectance acces-
sory using a KBr matrix. Mass spectral analyses(EI) were
conducted by Dr Susan Weintraub of the University of
Texas Health Science Center at San Antonio using a Finni-
gan-MAT model 4615. Combustion analyses were per-
formed by Midwest Microlabs Ltd. (Indianapolis, IN,
USA). Flash-column chromatography was performed on
32–63 ␮M silica gel obtained from Scientific Absorbents
Inc. (Atlanta, GA, USA). Thin-layer chromatography (TLC)
analyses were carried out on silica gel GF (Analtech) glass
plates (2.5 ϫ 10 cm with 250 ␮M and prescored).
better and were used without further purification. Anhy-
drous tetrahydrofuran (THF) was obtained via distillation of
reagent grade material from the sodium benzophenone ke-
tyl.
The reactions with H methyl iodide on CDB-3877 and
RU-42,633 were performed by American Radiolabeled
Chemicals, Inc. (ARC) of St. Louis, MO, USA.
3
1.2. 4-Bromo-N,N-bis-(trimethylsilyl)aniline 12
Compound 12 was prepared according to the procedure
of Bock et al. [6] NMR (90 MHz) ␦ 0.1 (s, 18 H), 6.6 and
7.35 (d, J ϭ 9 Hz, AA’BB’ of aromatic protons) ppm. FTIR:
Most chemicals and solvents were ACS reagent grade or
␯
2953, 1479, 1251, 1218 cmϪ1
.
max

P.N. Rao et al. / Steroids 64 (1999) 205–212
207
MS(m/e): Mϩ ϭ 317.
added dropwise over 10 min. The system was sealed and
stirred overnight at 4°C. The mixture was diluted with
methylene chloride (60 ml) and washed sequentially with
10% sodium sulfite solution, saturated sodium bicarbonate
solution, and brine. The organic fractions were combined,
dried over sodium sulfate, filtered, and concentrated in
vacuo to give 1.6 g of a stable foam. NMR analysis indi-
cated the crude material contained 62% of the desired ␣-ep-
oxide 15.
Analysis: For C12H22BrNSi2 Calc: C 45.56; H 7.01; Br
25.25. Found: C 46.83; H 7.34: Br 22.50. Note: NMR and
mass spectral analyses indicate the presence of a contami-
nant which was determined to be 4-trimethylsilyl-N,N-bis-
(trimethylsilyl) aniline which is not removed during distil-
lation.
2.2. 4-Bromo-N-methyl-N-trimethylsilylaniline 13
NMR (90 MHz) ␦ 0.77 (s, C-18 CH3), 1.36 (s, C-21
CH3), 3.75–4.3 (m, 8 H, ketal methylenes), 5.85 (br. m,
11-CH, ␤-epoxide), 6.04 (br. m, 11-CH, ␣-epoxide) ppm.
Under nitrogen, a solution of N-methylaniline (22 ml,
203 mmol); methanol (0.8 ml, 19.8 mmol); and tetrameth-
ylammonium bromide (3.13 g, 20.3 mmol) in methylene
chloride (200 ml) was cooled in an ice bath. A solution of
bromine (11 ml, 213.5 mmol) in methylene chloride (200
ml) was added dropwise with stirring at such a rate to
maintain the reaction temperature below 10°C (ca. 45 min
for the addition). During the addition, the brown color
disappears instantaneously. The end of the reaction is de-
termined by the persistency of a slight brown coloration. At
that point, triethylamine (30 ml, 215.7 mmol) was added
and the solution allowed to warm to room temperature. The
methylene chloride was removed under a stream of dry
nitrogen with slight warming. The residue was subjected to
vacuum distillation (bp 72–76°C @ 1 mm Hg) to afford
4-bromo-N-methylaniline 11 (26 g, 69%).
NMR (CCl4, 90 MHz) ␦ 2.7 (s, NCH3), 3.65 (br.s, NH),
6.85 (d of d, J ϭ 75.6 Hz, J’ ϭ 9.0 Hz, 4 aromatic H) ppm.
Under nitrogen, a solution of 4-bromo-N-methylaniline
11 (15 g, 81.06 mmol) in dry THF (100 ml) was chilled to
Ϫ78°C. Butyllithium (1.5 M/hexanes, 54 ml, 81 mmol) was
added via a syringe and the mixture was allowed to warm to
Ϫ30°C for about 5 min. The resulting slurry was cooled
back to Ϫ78°C and chlorotrimethylsilane (11 ml, 86.7
mmol) was added. The mixture was stirred at Ϫ78°C for 30
min. and then allowed to warm to room temperature. The
solvent was removed under a stream of dry nitrogen with
occasional warming. The resulting liquid was filtered
through a pad of Celite and the filtrate was concentrated in
vacuo to give 20.3 g. Vacuum distillation (92–96°C @ 1
mm Hg) gave 16.2 g (77%) of 13.
2.4. 3,20-bis-Ethylenedioxy-5␣,17␣-dihydroxy-11␤-(4-
aminophenyl)-19-norpregn-9-ene 16a
Magnesium (410 mg, 16.7 mmol) was weighed into a
100-ml round bottom, three-neck flask equipped with a
reflux condenser, addition funnel, a magnetic stir bar, and a
rubber septum. A single crystal of iodine was added and the
system was flushed with dry nitrogen. The entire system
was flame dried under a positive pressure of nitrogen. After
cooling, dry ether (20 ml) and a catalytic amount of 1,2-
dibromoethane were added via a syringe. An ether (5.0 ml)
solution of p-bromo-N,N-bis(trimethylsilyl)aniline 12 (5.3
g, 16.7 mmol) was prepared and 1.0 ml of this solution was
added. The mixture was heated to reflux and the remaining
bromo-aniline solution was added dropwise over 1 h. After
refluxing for 5 h, the reaction mixture was allowed to cool
to room temperature and stirred overnight. Dry THF (20 ml)
was added followed by the addition of copper(I) chloride
(166 mg, 1.67 mmol) and the mixture was stirred at room
temperature for 30 min. After cooling to 0°C, a THF (10 ml)
solution of epoxide 15 (1.0 g, 2.39 mmol) was added via a
syringe and the mixture was stirred at 0°C for 15 min. The
mixture was then allowed to warm to room temperature and
stirred for 2 h. Saturated ammonium chloride solution (30
ml) was added slowly. Air was bubbled through the mixture
for 30 min and then diluted with water. The aqueous mix-
ture was extracted with methylene chloride (3x). The meth-
ylene chloride extracts were washed with water (2x) and
brine. The combined extracts were dried over sodium sul-
fate, filtered, and evaporated in vacuo to give 5.5 g of a dark
oil. The oil was loaded onto a column (Si) and eluted with
10% acetone/methylene chloride to afford 700 mg as a
stable foam. Recrystallization of this material from methyl-
ene chloride/methanol (containing a trace of pyridine) gave
180 mg of 16a as a high melting solid (no melt up to 310°C
in a sealed tube).
NMR(CCl4, 90 MHz) ␦ 0.13 (s, 9 H, -Si(CH3)3), 2.7 (s,
-NCH3), 6.88 (d of d, J ϭ 48.6 Hz, J’ ϭ 9 Hz, 4 H,
aromatic) ppm.
2.3 3,20-bis-Ethylenedioxy-17␣-hydroxy-5␣,10␣-epoxy-19-
norpregn-9(11)-ene 15 [2]
Hexafluoroacetone trihydrate (1.42 g, 6.45 mmol), hy-
drogen peroxide (30 wt%, 0.8 ml, 7.76 mmol), and meth-
ylene chloride (10 ml) were combined in a 100 ml flask
equipped with a magnetic stir bar and a polyethylene stop-
per. The system was flushed with nitrogen and the mixture
was stirred in an ice bath for 30 min. A solution of 3,20-
bisethylenedioxy-17␣-hydroxy-19-norpregna-4,9-diene 14
(2.0 g, 4.97 mmol) in methylene chloride (10 ml) was then
NMR (90 MHz) ␦ 0.48 (s, 18-CH3), 1.35 (s, 21-CH3),
3.75–4.05 (br. m, 8 H, 3,20-diketal), 4.2 (br. d, 11␤-H),
6.55 and 7.15 (d, J ϭ 9 Hz, AA’BB’, 4 H) ppm.
FTIR: ␯
3553, 3357, 2942, 1621, 1512 cmϪ1
.
max
MS (m/e): Mϩ ϭ 511.
Analysis: for C30H41NO 6 Calc: C 70.42; H 8.08; N 2.74.
Found: C 70.49; H 8.16; N 2.84.

208
P.N. Rao et al. / Steroids 64 (1999) 205–212
2.5. 11␤-(4-Aminophenyl)-17␣-hydroxy-19-norpregna-4,9-
diene-3,20-dione 17a
2.7. 17␣-Acetoxy-11␤-(4-aminophenyl)-19-norpregna-4,9-
diene-3,20-dione 7
The acetamide-acetate 18a (650 mg, 1.19 mmol) was
suspended in 35% aqueous methanol (100 ml) and treated
with potassium hydrogen carbonate (10 g). The mixture was
stirred at room temperature for 18 h and monitored by TLC
(10% acetone/methylene chloride). The solvent was re-
moved in vacuo and the residue was taken up in water. The
aqueous mixture was extracted with methylene chloride
(3x). The organic extracts were washed with water (2x),
brine, and combined. After filtering, the filtrate was evapo-
rated in vacuo and the residue was purified via flash chro-
matography (10% acetone/methylene chloride) to afford
425 mg of 7 along with 60 mg of starting material 18a. The
desired product 7, obtained above, was combined with sim-
ilar materials from previous experiments and the combined
materials (550 mg) were recrystallized from methylene
chloride/ether two times to yield 440 mg, (no true melt at
temperatures up to 310°C in a sealed tube. However, dis-
coloration/decomposition began at 290°C).
A mixture of ethanol (50 ml) and 8.5% sulfuric acid (5
ml) was sparged with nitrogen for 30 min. Grignard product
16a (2.6 g, 5.1 mmol) was added as a solid and the mixture
was placed in an oil bath preheated to 95°C for 30 min. The
mixture was cooled in an ice bath and quenched with the
addition of saturated potassium carbonate (ca. pH ϭ 10).
The ethanol was removed in vacuo and the residue diluted
with water. The resulting solid was filtered, washed with
water (2x), and dried in vacuo. The material was purified via
preparitive HPLC (Waters LC 2000 system, Prep Pak 500
silica cartridge, 3% isopropanol/methylene chloride with
0.1% triethylamine, 20 ml/min) to afford 1.23 g of 17a,
mp ϭ 268–270°C (sealed tube).
NMR (300 MHz) ␦ 0.46 (s, 18-CH3), 2.25 (s, 21-CH3),
4.33 (d, 11␣-H), 5.75 (s, C-4 H), 6.57 and 6.91 (d, J ϭ 9 Hz,
AA’BB’ for aromatic H) ppm.
FTIR: ␯
3367, 3257, 2932, 1703, 1643, 1583, 1512
max
cmϪ1
.
NMR (300 MHz) ␦ 0.35 (s, 18-CH3), 2.08 (s, 17-OAc),
2.12 (s, 21-CH3), 4.40 (d, 11␣-H), 5.78 (s, C-4 H), 6.5 and
7.05 (d, J ϭ 9 Hz, AA’BB’ of 4 aromatic H) ppm.
MS (m/e): Mϩ ϭ 405.
Analysis: for C26H31NO3 Calc: C 77.01; H 7.70; N 3.43.
Found: C 76.82; H 7.54; N 3.54.
FTIR: ␯
3466, 3378, 2964, 1730, 1708, 1665, 1599,
.
max
1512, 1261 cmϪ1
MS (m/e): Mϩ ϭ 447.
2.6. 11␤-(4-N-Trifluoroacetamidophenyl)-17␣-acetoxy-19-
norpregna-4,9-diene-3,20-dione 18a
Analysis: for C28H33NO4 Calc: C 75.14; H 7.43; N 3.13.
Found: C 72.61; H 7.27; N 3.05.
Trifluoroacetic anhydride (1.39 ml, 9.86 mmol) and ace-
tic acid (0.56 ml, 9.86 mmol) were added to methylene
chloride (10 ml) and stirred at room temperature for 30 min.
The mixture was chilled to 0°C in an ice bath and treated
with p-toluenesulfonic acid (86.3 mg, 0.45 mmol). The
mixed anhydride was added to a pre-cooled (0°C) mixture
of amino-alcohol 17a (200 mg, 0.49 mmol) in methylene
chloride (20 ml) and the mixture was stirred at 0°C for 2 h.
The mixture was quenched with the cautious addition of
saturated potassium carbonate (to pH ϭ 10). After diluting
with water, the mixture was extracted with methylene chlo-
ride (3x). The methylene chloride extracts were washed
with water (2x), brine, combined, and dried over sodium
sulfate. The mixture was filtered and the filtrate was con-
centrated in vacuo to afford 280 mg. The crude material was
recrystallized from acetone/ether to yield 155 mg of a white
solid, mp ϭ 187–189°C (sealed tube).
2.8. 11␤-(4-N-Methylaminophenyl)-17␣-hydroxy-19-
norpregna-4,9-diene-3,20-dione 17b
Magnesium (0.8 g, 32.9 mmol) was weighed into a
100-ml round bottom 2-neck flask. The flask was fitted with
a reflux condenser, magnetic stir bar, and a rubber septum.
A small crystal of iodine was added and the system was
flushed with nitrogen. The entire system was flame dried
and then allowed to cool to room temperature under a
positive pressure of nitrogen. THF was added, followed by
the addition of dibromoethane (ca. 0.1 ml) the mixture was
stirred at room temperature until there was evidence of
reaction on the surface of the magnesium. A solution of
4-bromo-N-methyl-N-trimethylsilylaniline 13 (7.7 g, 29.8
mmol) in dry THF (10 ml) was added via a syringe. The
mixture was stirred and heated to reflux for 4 h. The mixture
was cooled to room temperature and solid copper(I) bro-
mide-dimethyl sulfide complex (0.68 g, 3.3 mmol) was
added and the mixture was stirred at room temperature for
30 min. The epoxide 6 (1.6 g, assume 4.97 mmol) as a THF
(15 ml) solution was added and the mixture was stirred for
2 h. Saturated ammonium chloride solution (5.0 ml) was
added and the mixture was stirred at room temperature
while air was bubbled through the mixture. The mixture was
diluted with water and extracted with methylene chloride.
The methylene chloride extracts were washed with water
NMR (300 MHz) ␦ 0.3 (s, 18-CH3), 2.08 (s, 17-OAc),
2.15 (s, 21-CH3), 4.45 (d, 11␣-H), 5.8 (s, C-4 H), 7.06 and
7.7 (d, J ϭ 9 Hz, AA’BB’ of 4 aromatic H), 9.28 (s,
-NHCOCF3) ppm.
FTIR: ␯
3291, 2953, 1730, 1708, 1659, 1240, 1158
max
cmϪ1
.
MS (m/e): Mϩ ϭ 543.
Analysis: for C30H22F3NO5 Calc: C 66.29; H 5.93; N
2.58. Found: C 65.21; H 6.10; N 2.42.

P.N. Rao et al. / Steroids 64 (1999) 205–212
209
(2x) and brine. The combined methylene chloride extracts
were dried over sodium sulfate, filtered, and evaporation of
the solvent gave 11.2 g of a dark oil.
84.21 mmol) was added and the mixture was stirred at 0°C
for 1 h. The mixture was filtered and the filter pad was
washed with methanol. The filtrate was diluted with 10%
sodium thiosulfate solution and the aqueous mixture was
extracted with methylene chloride (3x). The methylene
chloride extracts were washed with water and brine, com-
bined, and dried over sodium sulfate. Evaporation of the
solvent gave 9.72 g of a stable brown foam. The material
was chromatographed (10% acetone/methylene chloride) to
afford 3.88 g (50%) of CDB-3877 6. A sample was recrys-
tallized from methylene chloride/hexanes to provide an an-
alytical sample, mp ϭ 239–240°C (dec.).
The crude material from above was diluted with ethanol
(100 ml) and 10% sulfuric acid (20 ml) was added and the
mixture was heated to reflux for 1 h. The solvent was
removed in vacuo, diluted with water, and made basic with
concentrated ammonium hydroxide. The mixture was ex-
tracted with methylene chloride. The methylene chloride
extracts were washed with water (3x), brine, combined, and
dried over sodium sulfate. After filtering, evaporation of the
solvent gave 7.3 g of a black oil. The crude material was
purified via flash chromatography (5% acetone/methylene
chloride) to afford 0.4 g of 17b as a green foam. The
material was recrystallized from ethyl acetate to give 0.25 g
(12%), mp ϭ 81–83°C.
NMR (300 MHz) ␦ 0.37 (s, 18-CH3), 2.10 (s, 17␣-OAc),
2.17 (s, COCH3), 2.87 (s, NHCH3), 4.45 (d, J ϭ 11 Hz,
11␣-H), 5.83 (s, C-4 H), 6.57 and 7.02 (d, J ϭ 9 Hz,
AA’BB’ of aromatic H) ppm.
NMR (90 MHz) ␦ 0.43 (s, 18-CH3), 2.23 (s, 21-CH3),
2.78 (s, -NHCH3), 4.40 (br. d, J ϭ 7.5 Hz, 1 H, 11-CH),
5.78 (s, 1 H, 4-CH), 6.76 (d of d, J ϭ 39 Hz, J’ ϭ 9 Hz, 4
H) ppm.
FTIR (KBr, diffuse reflectance): 3417, 2891, 1729, 1708,
1660, 1604, 1581 cmϪ1
.
MS (m/z): 461 (Mϩ), 120, 107 (base).
Analysis: for C29H35NO4⅐0.2 CH2Cl2 Calc: C 73.31; H
7.41; N 2.93. Found: C 73.13 H 7.60; N 3.08.
Note: Prolonged drying at elevated temperatures failed to
remove traces of methylene chloride.
FTIR: ␯
3537, 3408, 3294, 2952, 1730, 1704, 1657,
.
max
and 1642 cmϪ1
2.9. 17␣-Acetoxy-11␤-(4-N-acetyl, N-methylaminophenyl)-
19-norpregna-4,9-diene-3,20-dione 18b
2.11. 17␤-Hydroxy-17␣-propynyl-(4-N-methylamino-
phenyl)-estra-4,9-dien-3-one (RU-42 633) 2 [6]
In dry glassware, trifluoroacetic anhydride (1.3 ml, 9.2
mmol) and glacial acetic acid (0.5 ml, 8.7 mmol) were
added to dry methylene chloride (4.0 ml). The mixture was
stirred at room temperature for 30 min. Solid p-toluenesul-
fonic acid monohydrate (0.082 g, 0.43 mmol) was added
and the mixture was chilled to 0°C. A solution of the steroid
17b (0.2 g, 0.43 mmol) in dry methylene chloride (1.0 ml)
was added and the mixture was stirred at 0°C for 20 min.
Saturated potassium carbonate solution (ca. 3.0 ml) was
added dropwise until cessation of CO2 evolution was ob-
served. The mixture was diluted with water and extracted
with methylene chloride. The organic extracts were washed
with water (2x), brine, combined, dried (Na2SO4), filtered
and concentrated in vacuo to give 0.22 g of an oil. NMR
analysis indicated this material to be diacetate 18b. Tritu-
ration of the residue with pentane gave 0.15g of a solid
(69.3%).
Similar treatment of RU-38 486 with iodine-calcium
oxide in THF-methanol, as described above, gave RU-42
633 2 in 82% yield as a stable foam.
NMR (300 MHz) ␦ 0.552 (s, 18-CH3), 1.894 (s, ϵ
CCH3), 2.813 (s, -NCH3), 4.340 (d, J ϭ 6.6 Hz, 11␣-H),
5.756 (s, C-4 H), 6.545 and 6.971 (d, AA’BB’ of aromatic
H) ppm.
FTIR (KBr, diffuse reflectance): 3380, 2945, 1656, 1614,
1518 cmϪ1
.
MS (m/e): 415 (Mϩ), 266, 120, 107 (base).
Analysis: for C28H33NO2⅐0.3 CH2Cl2 Calc: C 77.06; H
7.68; N 3.18. Found: C 77.28; H 7.97; N 3.33.
Note: Prolonged drying at elevated temperatures failed to
remove traces of methylene chloride.
2.12. 17␣-Acetoxy-11␤-(4-N-methyl, N-tritiomethyl-
aminophenyl)-19-norpregna-4,9-dien-3-one 8
NMR (90 MHz) ␦ 0.3 (s, 18-CH3), 2.10, 2.13, and 2.23
(s, 3 H, 21-CH3, -OAc, or NAc), 3.23 (s, NCH3), 4.53 (br.
d, J ϭ 6.7 Hz, 1 H, 11-CH), 5.83 (s, 1 H, 4-CH), 7.21 (d of
d, J ϭ 13.5 Hz, J’ ϭ 9 Hz, 4 H) ppm.
A solution containing CDB-3877 6 (2.0 mg, 4.8 nmol),
3
DMF (0.5 ml), and H methyl iodide (100 mCi, in 0.15 ml
FTIR: ␯
2946, 1730, 1711, 1664, and 1604 cmϪ1
.
of THF; specific activity 80 Ci/mmol) was heated with
stirring at 70°C for 90 h in a 1.0 ml sealed tube. After
max
3
2.10. 17␣-Acetoxy-11␤-(4-N-methylaminophenyl)-19-
norpregna-4,9-dien-3-one (CDB-3877) 6 [5]
removal of unreacted methyl iodide H under vacuum, the
reaction mixture was first purified by prep TLC (silica gel)
using hexane/acetone (3:1) as the solvent system. The band
corresponding to N-tritiomethyl CDB-2914 was identified
by exposing the TLC plate to X-ray film. The correct band
was cut from the plate and eluted from the silica gel using
ethanol to give 10 mCi. The product was further purified via
Calcium oxide (8.03 g, 143.14 mmol) was added to a
well stirred THF/methanol (100 ml) solution of CDB-2914
5 (8.0 g, 16.84 mmol) and the mixture was chilled in an ice
bath. A THF/methanol (20 ml) solution of iodine (21.37 g,

210
P.N. Rao et al. / Steroids 64 (1999) 205–212
Fig. 2. Synthesis of di-N-desmethyl derivative.
prep HPLC (Zorbax XDB-C18, 3.5 micron 4.6 ϫ 150 mm,
acetonitrile/0.03% TEAA 1:1). Final yield of N-tritiomethyl
CDB-2914 was 5.5 mCi, specific activity 80 Ci/mmol, ra-
diochemical and chemical purity was 97%.
3. Results and discussion
The synthesis of the N-desmethyl derivatives (Fig. 2)
was dependent upon the preparation of protected derivatives
of 4-bromoaniline 10a and 4-bromo-N-methylaniline 10b
(Fig. 3), which would allow for the successful formation of
Grignard reagents. Attempts to form Grignard reagents di-
rectly from 10a and 10b were met with failure. 4-Bromo-
bis-N,N- trimethylsilylaniline 12 was prepared using a step-
wise silylation according to the procedure of Bock et al. [6].
Thus, reaction of 10a with chlorotrimethylsilane, in trieth-
ylamine, gave 4-bromo-N-trimethylsilylaniline 11. Subse-
quent reaction of 11 with butyllithium, followed by the
addition of chlorotrimethylsilane afforded 12. In a similar
fashion, 4-bromo-N-methyl-N-trimethylsilylaniline 13 was
obtained using the butyl lithium/chlorotrimethylsilane pro-
cedure.
2.13. 17␤-Hydroxy-17␣-propynyl-11␤-(4-N-methyl, N-
tritiomethylaminophenyl)-estra-4,9- dien-3-one (3H RU-38
486)
A solution containing RU-42 633 2 (2.0 mg, 4.8 nmol),
3
DMF (0.5 ml), and H methyl iodide (100 mCi, in 0.15 ml
of THF; specific activity 80 Ci/mmol) was heated with
stirring at 70°C for 90 h in a 1.0 ml sealed tube. After
3
removal of unreacted methyl iodide H under vacuum, the
reaction mixture was first purified by prep TLC (silica gel)
using hexane/acetone (3:1) as the solvent system. The band
corresponding to mifepristone (methyl 3H) was identified by
exposing the TLC plate to X-ray film. The correct band was
cut from the plate and eluted from the silica gel using
ethanol to give 10 mCi. The product was further purified via
prep HPLC (Zorbax XDB-C18, 3.5 micron 4.6 ϫ 150 mm,
acetonitrile/0.03% TEAA 1:1). Final yield of tritiomethyl
mifepristone was 5.5 mCi, specific activity 80 Ci/mmol,
radiochemical and chemical purity 97%.
The regioselective 5,10-epoxidation of 3,20-bis-ethyl-
enedioxy-17␣-hydroxy-19-nor-pregna-5(10),9(11)-diene 14
[7] was achieved using hexafluoroacetone hydroperoxide
generated in situ from hexafluoroacetone and hydrogen per-
oxide following the general procedure of Teutsch et al. [8].
Fractional crystallization of the epoxide mixture gave the
Fig. 3. Synthesis of protected 4-bromoanilines.

P.N. Rao et al. / Steroids 64 (1999) 205–212
211
Fig. 4. Synthesis of mono-desmethyl and N-tritiomethyl derivatives.
pure 5␣,10␣-isomer 15 in 50% yield. Copper (I) catalyzed
conjugate addition of the Grignard reagents, prepared from
aryl bromides 12 and 13, gave the Grignard adducts 16a and
16b. Acid hydrolysis of Grignard adducts 16a and 16b gave
4,9-dien-3,20-diones 17a and 17b. Acetylation of 17a and
17b with the mixed anhydride, generated from the reaction
of trifluoroacetic anhydride and acetic acid, gave 17-acetate,
N-trifluoroacetate 18a and 17-acetate, N-acetate 18b. Care-
ful hydrolysis of 18a using 10% potassium bicarbonate gave
di-N-desmethyl derivative 7. Attempts to selectively hydro-
lyze the N-acetate in 18b were not successful.
Demethylation of CDB-2914 5 was accomplished using
iodine-calcium oxide in THF-methanol to afford N-des-
methyl CDB-2914 6 [5]. Similar treatment of RU-38 486 1
and other 20-ketopreganes, with the 11␤-N,N-dimethyl-
aminophenyl group, consistently gave N-dealkylated prod-
ucts.
the parent compounds. While the synthesis of N-tritiom-
ethyl RU-38 486 1 has been reported by Mais et al. [9], their
synthesis of the substrate RU-42 633 2 was achieved
through a multi-step sequence, rendering the process more
cumbersome.
Acknowledgments
This work was supported by Contract Nos. NO1-HD-1–
3137 and NO1-HD-6–3255 from the National Institute of
Child Health and Human Development, National Institutes
of Health.
References
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of 5 proved to be the only viable approach to obtain des-
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of 17b gave 17-acetate-N-acetate 18b and we were unable
to selectively hydrolyze the N-acetate in 18b to give 6.
The ease with which the N-desmethyl derivatives of
CDB-2914 and RU-38 486 can be obtained, made possible
the facile synthesis of the N-tritiomethyl derivatives (Fig.
4). Thus, the reaction of the N-desmethyl derivatives 6 and
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