Allopregnanolone (3α-Hydroxy-5α-pregnan-20-one) derivatives with a polar chain in position 16α: Synthesis and activity

Article abstract of DOI:10.1021/jm801454a

The lipophilic nature of allopregnanolone prevents its user-friendly application in human medicine. On inspiration by pReviously prepared allopregnanolone with a 16α -bound tetraethylammonium salt, an attempt was made to produce allopregnanolone analogues

Full text of DOI:10.1021/jm801454a

J. Med. Chem. 2009, 52, 2119–2125
2119
Allopregnanolone (3r-Hydroxy-5r-pregnan-20-one) Derivatives with a Polar Chain in Position
16r: Synthesis and Activity
Barbora Slav´ıkova´,† Zdena Krisˇtof´ıkova´,‡ Hana Chodounska´,† Milosˇ Budeˇsˇ´ınsky´,† Fernando J. Dura´n,§ Adriana S. Veleiro,§
Gerardo Burton,§ and Alexander Kasal*,†
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, CZ16610 Prague 6, Czech Republic, Prague
´
Psychiatric Centre, UstaVn´ı 91, CZ18103 Prague, Czech Republic, and Departamento de Qu´ımica Orga´nica and UMYMFOR
(CONICET-UBA), Facultad de Ciencias Exactas y Naturales, UniVersidad de Buenos Aires, Pabello´n 2, Ciudad UniVersitaria,
C1428EHA, Buenos Aires, Argentina
ReceiVed NoVember 18, 2008
The lipophilic nature of allopregnanolone prevents its user-friendly application in human medicine. On
inspiration by previously prepared allopregnanolone with a 16R-bound tetraethylammonium salt, an attempt
was made to produce allopregnanolone analogues with polar groups introduced into position 16R with the
goal of increasing water solubility, brain accessibility, and potency of neuroactive steroids. The Michael
addition to derivatives of pregn-16-en-20-one was the key reaction step. The link between the steroid skeleton
and the new side chain was either a methylene group (when diethyl malonate was added) or an oxygen
atom (when a hydroxy derivative was added). [35S]TBPS displacement was used to evaluate the products.
Several carbamates (but not their parent alcohols) displaced TBPS from the picrotoxin binding site on GABAA
receptors. Although none of them was more potent than the above ammonium salt, which stimulated this
study, their nonionic nature should not prevent their passage into the brain.
1. Introduction
Of all the bioactive steroids, which have been studied for
almost a century, two groups continue to keep scientists busy:
neuroactive steroids and brassinosteroids. The renewed interest
in neurosteroids and their synthetic analogues, neuroactive
steroids, is inspired both by pure desire to establish the
mechanism of their action and by their potential use in medicine.
Figure 1. Allopregnanolone and some of its analogues.
Many reviews prove that this group of steroids does not act at
are still not seizure-free; sometimes unwanted side effects are
cell nuclei but at receptors contained within cell membranes;
observed, and thus, there is a need to develop new types of
their targets are receptors of some neurotransmitters.1-8
drugs.17,18
One class of neurosteroids activates receptors of γ-aminobu-
Neuroactive steroids are presently studied by organic chemists
tyric acid (GABAa), thus slowing the transmission of neural
who try to recognize the structure-activity relationship of the
signals. The binding sites for this type of compounds at the
compounds.5,19-23 The 3R-hydroxyl is considered essential for
GABA receptor are distinct from the binding sites for benzo-
the neuronal24 but also for other activities.25 We have published
diazepines, barbiturates, and picrotoxin. Specific binding sites
several papers on the synthesis and activity of various analogues
for neurosteroids have not yet been fully identified. Multiple
of 3R-hydroxy-5R-pregnan-20-one (1, “allopregnanolone”; see
binding sites for these compounds were suggested to explain
Figure 1).26,27 Some of the analogues were found active (e.g.,
their electrophysiological properties.9-12 Recent results show
2) when in vitro tests28 were used; many more modifications
that one site spans the M1 and M4 transmembrane domains of
the R subunit and account for the potentiating actions of some
turned out to be inactive.
Presently, there are three hurdles against the use of neuro-
active steroids in medicine: one is the blood-brain barrier,29,30
which prevents their action in the brain. The other is their low
solubility in aqueous media, which makes the use of injections
necessary. The last is their fast metabolism.31 The solubility
problem prompted us to prepare some more polar analogues
with additional oxo, hydroxy, and carboxy groups. A useful
option was the introduction of a polar substituent situated far
from the sites, which are essential for the receptor binding.1
Such a suitable position seemed to be position 16 not only
because it was used many times in other venues of medicinal
steroids (e.g., refs 32-35) but also because a side chain in
position 16 already led to compounds as active as allopreg-
nanolone (e.g., 3). However, though the 16-susbtituted steroid
3 was active in an in vitro test,36,37 it was inactive in an in vivo
test (the test of epilepsy) probably because of its inability to
cross the hematoencephalic barrier.38,39
steroids. Another site, between the M1 transmembrane domain
of the R subunit and the M3 domain of the ꢀ subunit, is
responsible for the gating of the channel by steroids.13 The
proportion of the subunits was found to be affected by other
steroids in the body.14,15
Neuroactive steroids can be useful as anesthetics, sedatives,
anticonvulsants, and anxiolytics.15,16 These conditions are
presently treated with other potentiators of the GABAA receptor
(e.g., diazepam, carbamazepine, valproate, felbamate). In spite
of the large therapeutic arsenal, about 30% of epileptic patients
* To whom correspondence should be addressed. Phone: (+420) 220
183 314. Fax: (+420) 220 183 582. E-mail: Kasal@uochb.cas.cz.
†
Institute of Organic Chemistry and Biochemistry.
Prague Psychiatric Centre.
Universidad de Buenos Aires.
‡
§
a Abbreviations: GABA, γ-aminobutyric acid; TBAF, tetrabutylammo-
nium fluoride; TBPS, tert-butyl bicyclo[2.2.2]phosphorothionate.
10.1021/jm801454a CCC: $40.75
2009 American Chemical Society
Published on Web 03/16/2009

2120 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7
SlaV´ıkoVa´ et al.
Figure 2. 3R-Hydroxy-5R-pregn-16-en-20-one and some Michael-type adducts.
Scheme 1a
a (i) H2 +Pd/C in MeOH; (ii) p-TsCl in py, then NaNO2 in HMPA, 90 °C; (iii) (CH2OH)2, HC(OEt)3, p-TsOH; (iv) TBSCl, imidazol; (v) LAH, THF; (vi)
COCl2 in toluene, then NH3; (vii) p-TsOH, acetone; (viii) excess of chlorosulfonyl isocyanate, CHCl3; (ix) 1 equiv of chlorosulfonyl isocyanate, CHCl3; (x)
TBAF, THF.
The goal of the present paper was to synthesize and test new
allopregnanolone analogues of increased polarity without aban-
doning the fully covalent nature of the products. Hydroxyl-
containing side chains in the 16R-position were considered the
compounds of choice. Their synthesis was based on the Michael
addition to suitable derivatives of pregn-16-en-20-one (4; see
Figure 2). Diethyl malonate would yield compounds with a
carbon link to the steroid skeleton (e.g., 5), while the oxy
Michael reaction with suitable primary alcohols would produce
compounds with an oxygen link (e.g., 6). Carbamate derivatives
have also shown antiepileptic activity;17 thus, the introduction
of this moiety to the alcohol groups of the additional side chains
appeared as an interesting alternative.
give compound 15. Treatment of 15 with fosgene and ammonia
yielded compound 16. The monoester 12 was also protected at
carbon 20 (by ketalization) and 3 (by silylation), before the LAH
reduction to yield 17. When the 16R-hydroxyethyl derivative
17 was treated with an excess of chlorosulfonyl isocyanate (4.25
equiv), the TBS protecting group at position 3 was cleaved,
giving the dicarbamate 18. When only 1.2 equiv of the reagent
was used, the silylated carbamate 20 was obtained; deprotection
of the 3-hydroxyl gave the monocarbamate 19.
Another carbanion source used for the Michael reaction was
ethyl cyanoacetate, which converted 20-oxopregna-5,16-dien-
3ꢀ-yl acetate 21 (see Scheme 2) into a substituted cyanomalonic
acid 22.40 Decarboxylation led to nitrile 23, which was
hydrogenated (compound 24), hydrolyzed to 3ꢀ-alcohol 25,
inverted at carbon 3 to 3R-alcohol 26, and hydrolyzed to yield
the allopregnanolone analogue 27, with an acetamide group in
position 16R.
Many examples show the synthetic potential of the hetero
Michael addition.41 The oxy Michael reaction on this type of
steroidal substrate was first observed on the attempted alkaline
hydrolysis of 20-oxopregna-5,16-dien-3ꢀ-yl acetate in
MeOH:42 3ꢀ-hydroxy-16R-methoxypregn-5-en-20-one was in-
advertently formed in a quantitative yield, although the structure
of this product had to be corrected.43 Hydrolysis without side
reactions therefore has to be done differently, e.g., in propan-
2-ol. Higher alcohols, however, are much less prone44 to react
in this way.
2. Results
Chemistry. The Michael reaction between diethyl malonate
and 20-oxopregna-5,16-dien-3ꢀ-yl acetate was recently per-
formed by us.36,37 Acetic acid and its derivatives were then
introduced to position 16R. This time, the primary product, the
steroid substituted dimethyl malonate 7 (see Scheme 1), and
the product of decarboxylation 9 were hydrogenated to a 5R-
pregnane derivatives 8 and 10, respectively The 3ꢀ-hydroxyl
configuration was inverted to the desired 3R. The inversion was
carried out using solvolysis of corresponding 3ꢀ-tosyloxy
intermediates, leading to diester and monoester 11 and 12.
The diester 11 was protected at carbon 20 (by ketalization)
to give 13, which was reduced with LAH and deprotected to
afford the target triol 5. The same diester 13 was also silylated
to a TBS derivative 14, which was reduced and deprotected to
Alkaline conditions are routinely employed for the conjugate
addition of alcohols to unsaturated ketones,45,46 though acids

Allopregnanolone DeriVatiVes with a Polar Chain
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7 2121
Scheme 2a
a (i) NC-CH2COOEt and t-BuOK in t-BuOH; (ii) H2 + Pd/C in MeOH; (iii) KOH in MeOH; (iv) p-TsCl in py, then NaNO2 in HMPA; (v) NaOH and
H2O2 in MeOH.
Scheme 3a
HSQC and H,C HMBC) spectra. The proton and carbon-13
chemical shifts are given in Tables 1 and 2 in Supporting
Information. The configuration at individual centers was con-
trolled by the reaction mechanism involved in each of the
transformations. However, additional proof was required to
establish the configuration at carbons 16 and 17 in the products
of the Michael addition, as these compounds were exposed to
strongly alkaline conditions. The above suggested configurations
were based on circular dichroism of diol 32 (∆ε287nm ) +4.1),
which speaks for the natural configuration of the pregnane
skeleton.54,55 For stereochemical assignment of methylene
protons and determination of the configuration of substituents
at positions 16 and 17, we used 2D H,H ROESY spectra.
Chemical shifts and coupling constants for compound 16 are
shown in Figure 3 (see also Tables 1 and 2 in Supporting
Information). The observed NOE contacts of 18-methyl protons
revealed the stereochemical assignment of ꢀ-oriented H-11,
H-12, and H-15 methylene protons and additional contacts of
18-Me protons to 17-CO-CH3 and H-16, which indicated the
17ꢀ and 16R orientation of the substituents. This is further
supported by observed NOEs of H-17 with H-14, H-15R, and
methine protons of C(16)-substituent. The typical observed
coupling constants pattern of protons in ring D and its
substituents is in agreement with the configurations at C-16 and
a (i) (CH2CH2OH)2+H2SO4 in THF; (ii) (CH2CH2OH)2 + t-BuOK; (iii)
diethyleneglycol + t-BuOK; (iv) glycerol + t-BuOK.
C-17.
Biological Evaluation. All the allopregnanolone analogues
described above (compounds 5, 6, 16, 18, 19, 26, 27, 32, and
33) were subjected to preliminary screening using a γ-ami-
can catalyze the reaction by activation of the enone reaction
component.47 Other catalysts (e.g., strong Bronsted acids) were
nobutyric acid (GABAA) receptor test. GABAA receptor activity
also used to promote the addition of higher alcohols to a diene
was evaluated by assaying the effect of the synthetic analogues
system.48-51 High pressure was recommended to increase the
on the binding of [35S]-tert-butylbicyclo[2.2.2]phosphoro-
yields of the addition in sterically congested systems.52 Using
thionate. The binding of this convulsant in the presence of
GABA closely reflects the functional state of GABAA receptors
dehydropregnenolone acetate (21)53 as a model, we found that
ethylene glycol adds in a 1,4-manner under the formation of
and may be useful for characterization of allosteric interactions
compound 29 in the presence of sulfuric acid (see Scheme 3).
between various sites on the receptor. Allopregnanolone (1) was
In this case, acid catalysis gave a better yield (33%, or 63%
used as a positive control to check the viability of the method.
when the recovered compound 28 was accounted for) than
As shown in Table 1, the analogues with a carbamoyloxyethyl
alkaline conditions. The outcome of the transformation was
moiety in position 16R (16, 18, and 19) were positive modulators
1
evident in the H NMR spectrum of the major product, with
of the GABAA receptor. Removal of the carbamoyl moieties in
substantial changes in the signals of the enone system: the 16-
dicarbamate 16 resulted in an inactive compound (5). Other
proton signal lost its vinylic nature, the 21-proton was shifted
structurally related alcohols, e.g., adducts of ethylene glycol,
downfield, and multiplets of four new protons appeared in the
diethylene glycol, or glycerin, were also inactive.
region of H-C-OR signals.
Under the same conditions, however, the overall recovery of
the steroid material was much lower with a 3R-hydroxy
3. Discussion
analogue 30. Eventually, potassium tert-butoxide catalyzed the
addition of ethylene glycol, diethylene glycol, and glycerin to
give the desired 16R-alkoxy products 6, 32, and 33.
Tailoring allopregnanolone analogues to GABAA receptors
with all their complexity and variability is an elusive task.56 In
vitro testing using corresponding receptors is generally useful
for preliminary screening, although its results may be corrected
in later stages by in vivo experiments. The good binding
properties of the 16R-substituted allopregnanolone 3 suggested
a pocket in the receptor that could allow further structural
All the above products were characterized by their 1H NMR
spectra. For selected compounds 5, 11, 13, 16-20, the detailed
1
analysis was done using H and 13C NMR, 2D homonuclear
(H,H COSY and H,H ROESY) and 2D heteronuclear (H,C

2122 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7
SlaV´ıkoVa´ et al.
Figure 3. NOE contacts observed in compound 16 and chemical shifts and coupling patterns of protons of ring D and its substituents.
Table 1. Modulatory Effect of the above Allopregnanolone Analogues on GABAA Receptors
compd
1
3
5
6
16
18
59
300
19
61
750
26
27
32
33
34
Imax(%)a
79
80
19
40
c
c
c
c
26
86
c
c
c
c
c
c
c
c
18
95
IC50 (nM)b
a The maximal suppression of the binding. b The steroid concentration producing a half-maximal inhibition. c Not determined (preliminary screening at
100 nM yielded less than 15% inhibition).
hydrochloric acid or potassium hydrogencarbonate, their concentra-
tion was always 5%; brine was a saturated sodium chloride solution
in water. Prior to evaporation on a rotary evaporator in a vacuum
(0.25 kPa, bath temperature of 40 °C), solutions in organic solvents
were dried over anhydrous MgSO4 or Na2SO4. High resolution mass
spectra (HRMS) were measured on a VG-ZAB mass spectrometer
and on an Agilent LCTOF (2006). The preparation of compounds
8, 9, 21-27 is given in Supporting Information.
modifications in this part of the molecule, without a detrimental
effect on activity. The TBPS binding data of the above analogues
to the receptor (see Table 1) showed that carbamates 16, 18,
and 19 inhibited the binding to the GABAA receptor while
neither the corresponding alcohol 5 nor related alcohols 6, 32,
and 33 were active. The comparison shows that there is more
to a carbamoyloxy group in a molecule than its polarity.57
The position 16 was confirmed now as a suitable region for
structural modifications of allopregnanolone, although the
presence of mere hydroxy groups in the side chain is not a
sufficient precondition. The dicarbamate moiety in compound
16 is also present in commercial felbamate (34), one of
antiepileptic drugs used since its approval in 1993.17,58-60
Although no in vivo studies have been carried out yet, we may
speculate that compound 16 could be an alternative to felbamate
and related drugs whose metabolites have shown some undesired
side effects.
3r-Hydroxy-16r-bis(methoxycarbonyl)methyl-5r-pregnan-
20-one (11). 4-Toluenesulfonyl chloride (6.0 g, 31.2 mmol) was
added to a solution of 3ꢀ-alcohol 8 (6.0 g, 13.37 mmol) in pyridine
(60.0 mL).61,62 After 48 h, the mixture was diluted with brine (150
mL). The precipitate was extracted with CHCl3, and the extract
was washed with water and a solution of hydrochloric acid and
potassium hydrogencarbonate and dried over anhydrous sodium
sulfate. Evaporation of the solvent in a vacuum to dryness afforded
tosylate, which was solvolyzed with sodium nitrite (22 g, 32.10
mmol) in HMPA (115.0 mL) at 90 °C h under nitrogen for 2 h.
The mixture was poured into water, and the product was extracted
with ethyl acetate. The extract was subsequently washed with water,
dilute hydrochloric acid, water, a solution of potassium hydrogen
carbonate, and water. After evaporation of the solvent, the product
was purified using flash chromatography with a column of silica
gel (400.0 mL). Elution with toluene/ethyl acetate (85:15) yielded
white crystals of compound 11 (3.15 g, 52%). Mp 149-151 °C
(acetone/heptane), [R]D +67 (c 0.25). IR (CHCl3): 3617, 1000 (OH);
4. Experimental Section
Chemistry. General Methods. Melting points were determined
on a Boetius micromelting point apparatus (Germany) and a Fisher-
Johns apparatus and are uncorrected. Optical rotations were
measured at 25 °C in CHCl3 solution using an Autopol IV (Rudolf
Research Analytical, Flanders). [R]D values are given in 10-1 deg
cm2 g-1. Infrared spectra (wavenumbers in cm-1) were recorded
on a Bruker IFS 88 spectrometer or on a Nicolet Magna 550 FT-
IR spectrophotometer. 1H NMR spectra were taken on Bruker
AVANCE-400 (at 400 MHz) in CDCl3 at 23 °C. For selected
compounds 5, 11, 13, 16-20 a detailed NMR analysis was done
using 1D and 2D NMR spectra measured on a Bruker AVANCE-
500 instrument (1H at 500.13 MHz, 13C at 125.77 MHz). Proton
and carbon chemical shifts are referenced to TMS and CHCl3,
respectively, and are given in ppm (δ scale); coupling constants
(J) and width of multiplets (W) are given in Hz. Multiplicity
determinations and 2D spectra were obtained using standard Bruker
software. The homogeneity of all compounds was confirmed by
thin-layer chromatography (TLC), which was performed on silica
gel G (ICN Biochemicals, detection by spraying with concentrated
sulfuric acid was followed by heating). Preparative thin-layer
chromatograms (PLC) were detected by inspection in a UV light
after spraying with a methanolic solution of morin (0.02%). For
column chromatography, silica gel 60 (Merck, 63-100 µm) was
used. When solutions were washed with aqueous solutions of
1
1751, 1729, 1232, 1161, 1029 (COOCH3); 1702 (CdO). For H
and 13C NMR data, see Tables 1 and 2 in Supporting Information.
Anal. (C26H40O6) C, H.
3r-Hydroxy-16r-methoxycarbonylmethyl-5r-pregnan-20-
one (12). Analogously, alcohol 10 was isomerized into the 3R-
alcohol 12. Mp 112.115 °C. [R]D +62 (c 0.30). IR (CHCl3): 1729,
1700 (CdO); 1438 (OCH3); 1232, 1161 (C-O). 1H NMR (CDCl3,
400 MHz): δ 0.63 (s, 3H, H-18); 0.78 (s, 3H, H-19); 2.12 (s, 3H,
H-21); 2.40 (d, J ) 8.6, 1H, H 17); 2.97 (m, W ) 46, 1H, H-16);
3.62 (s, 3H, OCH3); 4.05 (m, W ) 16, 1H, H-3). Anal. (C24H38O4)
C, H.
20,20-Ethylenedioxy-16r-bis(methoxycarbonyl)methyl-5r-
pregnan-3r-ol (13). A mixture of ketone 11 (700 mg, 1.56 mmol),
ethylene glycol (13.5 mL), p-toluenesulfonic acid monohydrate
(1.13 mg, mmol), ethyl O-formate (2.7 mL), and benzene (4.5 mL)
was allowed to stand 2 days at 50 °C. The mixture was poured
into ethyl acetate, washed with a solution of potassium hydrogen
carbonate, water, and dried over magnesium sulfate. Evaporation
of the solvent afforded a colorless oil of compound 13. Yield 292

Allopregnanolone DeriVatiVes with a Polar Chain
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7 2123
1
mg (38%). [R]D -2 (c 0.24). IR (CHCl3): 3616, 1000 (OH); 1749,
1703 (CdO). For H and 13C NMR data, see Tables 1 and 2 in
1728, 1437, 1244, 1234, 1162 (COOCH3). HRMS (FAB), M+ calcd,
Supporting Information. Anal. (C26H42O6N2) C, H, N.
1
493.316 529; found, 493.317 259. For H and 13C NMR data, see
3r-tert-Butyldimethylsilyloxy-16r-ethyl-20,20-ethylenedioxy-
5r-pregnan-16b-ol (17). Functional groups in compound 12 (800
mg, 2.05 mmol) were protected by ketalization and silylation as
above, and the product was reduced with LAH in THF. Alcohol
17 (434 mg, 41%) was obtained. Mp 112-115 °C (ethyl acetate).
[R]D +2 (c 0.30). IR (CHCl3): 3622, 3471 (OH); 1472
((CH3)3C-Si); 1254 ((CH3)2Si); 1373 (CH3). For 1H and 13C NMR
data, see Tables 1 and 2 in Supporting Information.
16r-Ethyl-20-oxo-5r-pregnane-3r,16b-diyl Dicarbamate (18).
To a solution of the silyloxy derivative 17 (43 mg, 0.08 mmol) in
1.0 mL of CHCl3, chlorosulfonyl isocyanate (48.8 mg, 0.34 mmol)
was added.63 The reaction mixture was stirred at room temperature
under nitrogen. After 90 min, THF (0.5 mL) was added, followed
by a saturated aqueous solution of sodium hydrogen carbonate (1.0
mL). After being stirred for an additional 1 h at room temperature,
the mixture was concentrated to a third of its volume. Water was
added to the residue and then extracted with dichloromethane and
ethyl acetate. The organic layer was washed with water and dried
with sodium sulfate, and the solvent was evaporated under vacuum.
The resulting solid was purified by flash chromatography on silica
gel (ethyl acetate/hexane, 1:1) to give dicarbamate 18 (19 mg, 57%)
as a white solid. Mp 170-172 °C (ethyl acetate). IR (CHCl3): 3353,
3205, 2930, 1701, 1603, 1401, 1356, 1333, 1261, 1042, 750. For
1H and 13C NMR data, see Tables 1 and 2 in Supporting
Information. HRMS (ESI), [M + 1]+ calcd for C25H41N2O5,
449.2937; found, 449.3015.
16r-Carbamoyloxyethyl-3r-hydroxy-5r-pregnan-20-one (19).
Alcohol 17 (40.0 mg, 0.076 mmol) was treated with chlorosulfonyl
isocyanate (13.0 mg, 0.092 mmol) as above. The resulting solid
was purified by flash chromatography on silica gel (ethyl acetate/
hexane, 1:1) to give carbamate 20 (24.0 mg, 60%) as an amorphous
solid. For 1H and 13C NMR data, see Tables 1 and 2 in Supporting
Information.
Deprotection of the silyloxy derivative was carried out by
treatment with TBAF (36 mg, 0.126 mmol) in THF (2.0 mL) at
room temperature. After 18 h, the solvent was evaporated. The
residue was purified by flash chromatography on silica gel (CH2Cl2)
and PLC (ethyl acetate/hexane, 8:2) to give 19 (10.0 mg, 33%) as
a white solid. Mp 164-166 °C (ethyl acetate). IR (CHCl3): 3470,
3204, 2931, 2852, 1706, 1602, 1399, 1260, 1037, 750. For 1H and
13C NMR data, see Tables 1 and 2 in Supporting Information.
HRMS (ESI), [M + 1]+ calcd for C24H40NO4, 406.2879; found,
406.2885.
3ꢀ-Hydroxy-16r-(2′-hydroxyethoxy)-pregn-5-en-20-one (29).
Sulfuric acid (5 drops, i.e., 122 mg, 1.24 mmol) was mixed with
ethylene glycol (30 drops, 670 mg, 10.7 mmol), and a solution of
20-oxopregna-5,16-dien-3ꢀ-yl acetate (21, 34 mg, 0.095 mmol) in
warm THF was added. The mixture was briefly shaken to ease the
dissolution of the solid and then kept at 50 °C for 72 h. Sulfuric
acid was partly neutralized with potassium hydrogen carbonate (300
mg, 2.17 mmol), and THF was removed on a rotary evaporator.
Steroid material was precipitated with brine (4.0 mL), and the vessel
was put in a refrigerator. The precipitate was filtered off using a
paper filter. The product was dissolved in CHCl3, and the solution
was concentrated in a vacuum and applied on a preparative thin
layer of silica gel. PLC plates were developed with benzene/ether/
2-propanol, 3:3:0.1. The lipophilic zone was eluted to yield 3ꢀ-
hydroxypregna-5,16-dien-20-one (28, 16 mg, 53%) as a colorless
oil. Mp 209-212 °C (MeOH-water) (ref 64 gives 210-212 °C).
1H NMR (CDCl3, 400 MHz): δ 0.92 (s, 3H, H-18); 1.05 (s, 3H,
H-19); 2.26 (s, 3H, H-21); 3.53 (m, W ) 35, 1H, H-3); 5.36 (m, W
) 21, H-6); 6.71 (s, W ) 17, 1H, H-16).
Tables 1 and 2 in Supporting Information. Anal. (C28H44O7) C, H.
3r-Hydroxy-16r-bis(hydroxymethyl)methyl-5r-pregnan-20-
one (5). Lithium aluminum hydride (50 mg) was added to a solution
of compound 13 (70 mg, 0.14 mmol) in THF (2.0 mL). The mixture
was heated to reflux under nitrogen for 2 h. The mixture was cooled,
and excess reagent was decomposed with brine. Inorganic material
was filtered off and washed with ether. The filtrate was washed
with a solution of hydrochloric acid, water, and a solution of
potassium hydrogen carbonate. After evaporation of the solvent in
vacuo, the residue was purified by PLC on silica gel (CHCl3/2-
propanol, 9:1). White crystals of compound 5 (25 mg, 45%) were
crystallized from MeOH/acetone. Mp 181-183 °C. [R]D +60 (c
0.14). IR (KBr): 3434, 1027, 1002 (OH); 1694 (CdO). For 1H and
13C NMR data, see Tables 1 and 2 in Supporting Information. Anal.
(C24H40O4) C, H.
3r-tert-Butyldimethylsilyloxy-20,20-ethylenedioxy-16r-bis-
(methoxycarbonyl)methyl-5r-pregnane (14). tert-Butyldimeth-
ylsilyl chloride (723 mg, 4.80 mmol) was added to a solution of
3R-alcohol 13 (790 mg, 1.60 mmol) and imidazole (653 mg, 9.60
mmol) in N,N-dimethylformamide (13.0 mL). The reaction mixture
was allowed to stand at room temperature for 72 h, then diluted
with ether (200.0 mL) and washed successively with 5% aqueous
citric acid (3×), water (3×), a solution of potassium hydrogen
carbonate (2×) and water. The solvent was evaporated, and the
residue was purified by PLC on silica gel (toluene/ether, 7/3).
Compound 14 (618 mg, 63%) failed to crystallize from common
solvents. [R]D -5 (c 0.14). IR (CHCl3): 1746, 1728, 1244, 1164,
1026 (COOCH3); 1462, 1361 ((CH3)3C-Si); 1407, 1250 (CH3Si).
1H NMR (CDCl3, 400 MHz): δ 0.05 (s, 6H, (CH3)2Si); 0.74 (s,
3H, H-18); 0.80 (s, 3H, H-19); 0.90 (s, 9H, (CH3)3CSi); 1.33 (s,
3H, H-21); 1.91 (d, J ) 8.0, 1H, H-17); 2.76 (m, W ) 36, 1H,
H-16); 3.71 (s, 3H, OCH3) and 3.75 (s, 3H, OCH3); 3.92 (m, 4H,
OCH2CH2O); 3.96 (d, J ) 4, 1H, H-16a); 4.03 (m, W ) 16, 1H,
H-3). HRMS (FAB), M+ calcd, 607.403 008; found, 607.402 002.
3r-tert-Butyldimethylsilyloxy-20,20-ethylenedioxy-16r-bis(hy-
droxymethyl)methyl-5r-pregnane (15). Lithium aluminum hy-
dride (200 mg) was added to the solution of compound 14 (760
mg, 1.25 mmol) in THF (25.0 mL). The mixture was allowed to
stand at room temperature for 4 h. The reaction mixture was poured
into a saturated aqueous solution of ammonium chloride (75.0 mL),
and the product was extracted with ether. Evaporation of the solvent
afforded 560 mg (81%) of diol 15 as a colorless oil. [R]D -4 (c
0.25). IR (CHCl3): 3626, 3463, 1031 (OH); 1463, 1362
((CH3)3C-Si); 1406, 1253 (CH3Si). 1H NMR (CDCl3, 400 MHz):
δ 0.05 (s, 6H, (CH3)2Si); 0.74 (s, 3H, H-18); 0.79 (s, 3H, H-19);
0.90 (s, 9H, (CH3)3CSi); 1.33 (s, 3H, H-21); 1.82 (d, J ) 8.0, 1H,
H-17); 2.76 (m, W ) 36, 1H, H-16); 3.77 (m, 4H, 2xCH2O); 3.92
(m, 4H, OCH2CH2O); 4.05 (m, W ) 16, 1H, H-3). HRMS (FAB),
M+ calcd, 573.395 124; found, 573.393 566.
16r-Bis(carbamoyloxymethyl)methyl-3r-hydroxy-5r-pregnan-
20-one (16). A solution of diol 15 (250 mg, 0.45 mmol),
dimethylaniline (0.552 mL), and toluene (1.8 mL) was cooled to
-10 °C, and a solution of COCl2 in toluene (1.09 M, 5.1 mL) was
added. The mixture then was kept at -5 to +5 °C for 20 h. The
mixture was washed with a solution of hydrochloric acid, dried
over sodium sulfate, and saturated with ammonia. Heating at reflux
for 7 min, filtration, and evaporation of the solvent gave a yellow
oil residue, which was treated with p-toluenesulfonic acid (200 mg,
1.05 mmol) in acetone (20.0 mL). After standing for 18 h at
laboratory temperature, the acid was neutralized with a solution of
potassium hydrogen carbonate (105 mg, 1.05 mmol) in water (2.0
mL). The reaction mixture was concentrated to a quarter of its
volume in a vacuum. The product was extracted with CHCl3 and
washed with water, and the solvent was evaporated. The residue
was chromatographed on three preparative plates (CHCl3/MeOH,
9:1). The major zone was eluted to afford dicarbamate 16 (37 mg,
17%) as white crystals. Mp 181-183 °C (CHCl3/MeOH). [R]D +61
(c 0.26). IR (CHCl3): 3617, 999 (OH); 3547, 3433 (NH2); 1727,
The polar zone yielded the title compound 29 (12 mg, 33%, or
63% when the recovered compound 28 was calculated for) as white
crystals. Mp 167-168 °C (acetone). [R]D -15 (c 0.20). IR (CHCl3):
3608, 3474, 1048 (OH); 1702, 1359, 595 (COCH3); 1667, 809
(CdC). H NMR (CDCl3, 400 MHz): δ 0.64 (s, 3H, H-18); 1.00
(s, 3H, H-19); 2.19 (s, 3H, H-21); 2.58 (d, J ) 6.6, 1H, H-17);
3.39 (m, W ) 20, 1H), 3.50 (m, W ) 20, 1H) and 3.68 (m, W )
1

2124 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7
SlaV´ıkoVa´ et al.
36, 2H, -O-CH2CH2OH); 3.75 (m, W ) 36, 1H, H-3); 4.54 (t, J )
6.5, 1H, H-16); 5.36 (m, W ) 21, H-6). Anal. (C23H36O4) C, H.
Acknowledgment. This work was supported by Grant
Agency of the Czech Republic (Grant 203/06/1605). The authors
are indebted to Michaela Sedla´cˇkova´ for her skilled technical
assistance. F.J.D., A.S.V., and G.B. thank Agencia Nacional
de Promocio´n Cient´ıfica y Tecnolo´gica (PICT 10962). Univer-
sidad de Buenos Aires and CONICET (Argentina), PIP 5508,
are thanked for financial support.
3r-Hydroxy-16r-(2-hydroxyethoxy)-5r-pregnan-20-one (32).
(a) Using Alkaline Catalysis. Formate 30 (93 mg, 0.27 mmol)
and potassium tert-butoxide (177 mg, 1.58 mmol) were placed into
a test tube. tert-Butanol (2.0 mL) and ethylene glycol (1.0 mL)
were added, air was flushed out with argon, and the tube was sealed.
The tube was kept at 100 °C for 48 h. After cooling, the mixture
was transferred into a flask using 2-propanol (6.0 mL), neutralized
with citric acid (290 mg, 1.51 mmol), and concentrated on a rotary
evaporator. The mixture was diluted with brine (5.0 mL) and set
aside in a refrigerator. A steroid precipitate was filtered off, washed
with brine, dissolved in CHCl3, and purified using PLC (toluene/
ether/2-propanol, 5:8:0.2). The most polar zone yielded the title
compound 32 as white crystals (18 mg, 18%). Mp 171-172 °C
(acetone). [R]D +42 (c 0.2). CD: ∆ε287nm ) +4.1 (MeOH, c )
1.32 × 10-3 mol/L). IR (CHCl3): 3616, 3469, 1052, 1002 (OH);
Supporting Information Available: General experimental
methods, additional NMR data, and combustion analysis of
products. This material is available free of charge via the Internet
at http://pubs.acs.org.
References
(1) Lambert, J. J.; Peters, J. A.; Harney, S. C.; Belelli, D. Steroid
Modulation of GABAA Receptors. In Pharmacology of GABA and
Glycine Neurotransmission; Mo¨hler, H. Ed.; Handbook of Experi-
mental Pharmacology, Vol. 150; Springer: Berlin, 2001; pp 117-140.
(2) Lambert, J. J.; Belelli, D.; Peden, D. R.; Vardy, A. W.; Peters, J. A.
Neurosteroid modulation of GABAA receptors. Prog. Neurobiol. 2003,
71, 67–80.
1
1701, 1359, 589 (COCH3) cm-1. H NMR (CDCl3, 400 MHz): δ
0.61 (s, 3H, H-18); 0.78 (s, 3H, H-19); 1.96 (dt, J ) 12.2 and 3.4,
1H, H-12ꢀ); 2.17 (s, 3H, H-21); 2.57 (d, J ) 6.6, 1H, H-17); 3.38
(m, W ) 20, 1H), 3.48 (m, W ) 23, 1H), and 3.68 (m, W ) 38,
2H, -O-CH2-CH2OH); 4.05 (m, W ) 17, 1H, 3-H); 4.51 (bt, J )
7.2, 1H, H-16). Anal. (C23H38O4) C, H.
(3) Warner, M.; Gustafsson, J. Å. Nongenomic effects of estrogen. Why
all the uncertainty? Steroids 2006, 71, 91–95.
(4) Whiting, P. J. GABA-A receptor subtypes in the brain, a paradigm
for CNS drug discovery. Drug DiscoVery Today 2003, 8, 445–450.
(5) Hamilton, N. M. Interaction of steroids with GABAA receptor. Curr.
Top. Med. Chem. 2002, 2, 887–902.
The least polar product was identified (TLC, IR) as 3R-hydroxy-
1
5R-pregn-16-en-20-one (31, 51 mg, 60%). H NMR (CDCl3, 400
MHz): δ 0.81 (s, 3H, H-18); 0.89 (s, 3H, H-19); 2.25 (s, 3H, H-21);
4.05 (m, W ) 18, 1H, H-3); 4.51(t, J ) 6.4, 1H, H-16).
(b) Using Acid Catalysis. Formate 30 (31 mg, 0.09 mmol) was
treated with sulfuric acid (5 drops) in ethylene glycol (10 drops),
THF (0.24 mL), and tert-butanol (0.4 mL) as in the preceding
paragraph. The polar product 32 (1 mg, 9%) had its NMR spectrum
identical with the above sample.
(6) Belelli, D.; Lambert, J. J. Neurosteroids, endogenous regulators of
the GABAA receptor. Nat. ReV. Neurosci. 2005, 6, 565–575.
(7) Akk, G.; Covey, D. F.; Evers, A. S.; Steinbach, J. H.; Zorumski, C. F.;
Mennerick, S. Mechanisms of neurosteroid interactions with GABAA
receptors. Pharmacol. Ther. 2007, 116, 35–57.
(8) Harrison, N. L.; Majewska, M. D.; Harrington, J. W.; Barker, J. L.
Structure-activity-relationships for steroid interaction with the gamma-
aminobutyric acidA receptor complex. J. Pharmacol. Exp. Ther. 1987,
241, 346–353.
(9) Akk, G.; Shu, H. J.; Wang, C.; Steinbach, J. H.; Zorumski, C. F.;
Covey, D. F.; Mennerick, S. Neurosteroid access to the GABAA
receptor. J. Neurosci. 2005, 25, 11605–11613.
(10) Reddy, D. S. Anticonvulsant activity of the testosterone-derived
neurosteroid 3R-androstanediol. NeuroReport 2004, 15, 515–518.
(11) Li, W. J.; Jin, X. C.; Covey, D. F.; Steinbach, J. H. Neuroactive steroids
and human recombinant rho 1 GABA(C) receptors. J. Pharmacol. Exp.
Ther. 2007, 323, 236–247.
3r-Hydroxy-16r-[2-hydroxy-(2-ethoxyethoxy)]-5r-pregnan-
20-one (33). Analogously, a solution of formate 30 (95 mg, 0.26
mmol) in tert-butanol (2.0 mL) was treated with diethylene glycol
(1.0 mL) in the presence of potassium tert-butoxide (200 mg). After
the usual workup, the target compound 33 was obtained as white
crystals (28 mg, 24%, or 50% when 40 mg of the unsaturated ketone
31 was accounted for). Mp 157-158 °C (acetone); [R]D +93 (c
0.08). IR (CHCl3): 3615, 3459, 1075, 1057, 1002 (OH); 1701, 1354,
596 (COCH3). 1H NMR (CDCl3, 400 MHz): δ 0.60 (s, 3H, H-18);
0.77 (s, 3H, H-19); 2.17 (s, 3H, H-21); 2.61 (d, J ) 6.6, 1H, H-17);
4.05 (m, W ) 18, 1H, H-3); 4.49 (bt, J ) 6.6, 1H, H-16). Anal.
(C25H42O5) C, H.
(12) Akk, G.; Bracamontes, J. R.; Covey, D. F.; Evers, A.; Dao, T.;
Steinbach, J. H. Neuroactive steroids have multiple actions to potentiate
GABAA receptors. J. Physiol. 2004, 558, 59–74.
(13) Hosie, A. M.; Wilkins, M. E.; da Silva, H. M. A.; Smart, T. G.
Endogenous neurosteroids regulate GABAA receptors via two discrete
transmembrane sites. Nature 2006, 444, 486–489.
3r-Hydroxy-16r-(2,3-dihydroxypropoxy)-5r-pregnan-20-
one (6). Formate 30 (93 mg, 0.27 mmol) was treated with glycerol
(1.0 mL) in tert-butanol (2.0 mL) in the presence of potassium tert-
butoxide (175 mg, 1.56 mmol) as above. The product was not
precipitated but extracted with CHCl3. The extract was washed with
a solution of citric acid (295 mg, 1.53 mmol), dried by filtration
over sodium sulfate, and evaporated. PLC in the above solvent
system yielded compound 31 (76.9 mg, 90.0%) and the target
compound 6 (4.7 mg, 4.3%) as white crystals. Mp 174-175 °C
(acetone/heptane); [R]D +56 (c 0.11). IR (CHCl3): 3616, 3570,
(14) Nin, M. S.; Salles, F. B.; Azeredo, L. A.; Frazon, A. P. G.; Gomez,
R.; Barros, H. M. T. Antidepressant effect and changes of GABA(A)
receptor gamma 2 subunit mRNA after hippocampal administration
of allopregnanolone in rats. J. Psychopharmacol. 2008, 22, 477–485.
(15) Maguire, J.; Mody, I. Neurosteroid synthesis-mediated regulation of
GABAA receptors, relevance to the ovarian cycle and stress. J. Neu-
rosci. 2007, 2155–2162.
(16) Marx, C. E.; Stevens, R. D.; Shampine, L. J.; Uzunova, V.; Trost,
W. T.; Butterfield, M. I.; Massing, M. W.; Hamer, R. M.; Morrow,
A. L.; Lieberman, J. A. Neuroactive steroids are altered in schizo-
phrenia and bipolar disorder, relevance to pathophysiology and
therapeutics. Neuropsychopharmacology 2006, 31, 1249–1263.
(17) Bialer, M. The pharmacokinetics and interactions of new antiepileptic
drugs. An overview. Ther. Drug Monit. 2005, 27, 722–726.
(18) Death, A. K.; McGrath, K. C. Y.; Handelsman, D. H. Valproate is an
anti-androgen and anti-progestin. Steroids 2005, 70, 946–953.
(19) Alvarez, L. D.; Veleiro, A. S.; Baggio, R. F.; Garland, M. T.;
Edelsztein, V. C.; Coirini, H.; Burton, G. Synthesis and GABAA
receptor activity of oxygen-bridged neurosteroid analogues. Bioorg.
Med. Chem. 2008, 16, 3831–3838.
(20) Bian, X. Q.; Li, S. S.; Geng, X.; Liu, L. H.; Xie, Z. Y.; Wang, C.
Synthesis of the neuroactive steroid antagonist 17-phenyl-5alpha-
androst-16-en-3alpha-ol by a palladium-catalysed coupling reaction.
J. Chem. Res., Synop. 2008, 7, 422–424.
(21) Zeng, C. M.; Manion, B. D.; Benz, A.; Evers, A. S.; Zorumski, C. F.;
Mennerick, S.; Covey, D. F. Neurosteroid analogues. 10. The effect
of methyl group substitution at the C-6 and C-7 positions on the GABA
modulatory and anesthetic actions of (3alpha,5alpha)- and (3alpha,5beta)-
3-hydroxypregnan-20-one. J. Med. Chem. 2005, 48, 3051–3059.
1
3448, 1089, 1038, 1002 (OH); 1700, 1358 (COCH3). H NMR
(CDCl3, 400 MHz): δ 0.60 (s, 3H, H-18); 0.77 (s, 3H, H-19); 2.17
(s, 3H, H-21); 2.55 (d, J ) 6.6, 1H, H-17); 4.05 (m, W ) 16, 1H,
H-3); 4.49 (bt, J ) 6.6, 1H, H-16). Anal. (C24H40O5) C, H.
Biological Evaluation. An in vitro test, based on binding [35S]-
tert-butyl bicyclo[2.2.2]phosphorothionate to receptor of γ-ami-
nobutyric acid (GABAA), was used. Membranes were isolated from
whole brains of adult male Wistar rats in accordance with our
previous study.37 The membranes were resuspended in a buffer
(20 mM KH2PO4, 200 mM KCl, pH 7.4). Aliquots were incubated
with 2 nM [35S]-tert-butyl bicyclo[2.2.2]phosphorothionate (TBPS,
Perkin-Elmer), 1 µM GABA, and 1 nM to 10 µM steroids for 60
min at 37 °C. The nonspecific binding was estimated using 200
µM picrotoxinin. The results were related to the control samples
containing DMSO and expressed in %.

Allopregnanolone DeriVatiVes with a Polar Chain
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7 2125
(22) Carter, R. B.; Wood, P. L.; Wieland, S.; Hawkinson, J. E.; Belelli,
D.; Lambert, J. J.; White, H. S.; Wolf, H. H.; Mirsadeghi, S.; Tahir,
S. H.; Bolger, M. B.; Lan, N. C.; Gee, K. W. Characterization of the
anticonvulsant properties of ganaxolone (CCD 1042; 3alpha-hydroxy-
3beta-methyl-5alpha-pregnan-20-one), a selective, high-affinity, steroid
modulator of the gamma-aminobutyric acid(A) receptor. J. Pharmacol.
Exp. Ther. 1997, 280, 1284–1295.
(23) Slav´ıkova´, B.; Kasal, A.; Uhl´ırˇova´, L.; Krsˇiak, M.; Chodounska´, H.;
Kohout, L. Suppressing aggressive behavior with analogs of allopreg-
nanolone (epalon). Steroids 2001, 66, 99–105.
(43) Fukushima, D. K.; Gallagher, T. F. The action of methanolic KOH
on a ∆16-20-ketosteroid, isolation of 3ꢀ-acetoxy-16-methoxy-∆5-
pregnen-20-one. J. Am. Chem. Soc. 1950, 72, 2306–2306.
(44) Nising, C. F.; Brase, S. The oxa-Michael reaction: from recent
developments to applications in natural product synthesis. Chem. Soc.
ReV. 2008, 37, 1218–1228.
(45) Ja´szay, Z. M.; Ne´meth, G.; Pham, T. S.; Petneha´zy, I.; Gru¨n, A.; To¨ke,
L. Catalytic enantioselective Michael addition in the synthesis of
R-aminophosphonates. Tetrahedron: Asymmetry 2005, 16, 3837–3840.
(46) Sharma, U.; Bora, U.; Boruah, R. C.; Sandhu, J. S. Alumina-promoted
fast solid-phase Michael addition of enamines with conjugated enones
under microwave irradiation. Tetrahedron Lett. 2002, 43, 143–145.
(47) Hajos, Z. G.; Parrish, D. R. Synthesis and conversion of 2-methyl-
2-(3-oxobutyl)-1,3-cyclopentanedione to isomeric racemic ketols of
[3.2.1]bicyclooctane of perhydroindan series. J. Org. Chem. 1974, 39,
1612–1615.
(48) Kisanga, P. B.; Ilankumaran, P.; Fetterly, B. M.; Verkade, J. G.
P(RNCH2CH2)3N, efficient 1,4-addition catalyst. J. Org. Chem. 2002,
67, 3555–3560.
(49) Murtagh, J. E.; McCooey, S. H.; Connon, S. J. Novel amine-catalysed
hydroalkoxylation reactions of activated alkenes and alkynes. Chem.
Commun. 2005, 227–229.
(50) Wabnitz, T. C.; Spencer, J. B. A general, Brønsted acid-catalyzed
hetero-Michael addition of nitrogen, oxygen, and sulfur nucleophiles.
Org. Lett. 2003, 5, 2141–2144.
(51) Farnworth, M. V.; Cross, M. J.; Louie, J. Rhodium-catalyzed addition
of alcohols to terminal enones. Tetrahedron Lett. 2004, 45, 7441–
7443.
(24) Huang, R. Q.; Dillon, G. H. Functional analysis of GABA receptors
in nucleus tractus solitarius A neurons from neonatal rats. Brain Res.
2001, 921, 183–194.
ˇ
(25) S´ısˇa, M.; Hnilicˇkova´, J.; Swaczynova´, J.; Kohout, L. Syntheses of
new androstane brassinosteroids with 17ꢀ-ester groupssbutyrates,
heptafluorobutyrates, and laurates. Steroids 2005, 70, 755–762.
(26) Kasal, A. 6-Substituted derivatives of 7-norallopregnanolone. Tetra-
hedron 2000, 56, 3559–3565.
(27) Kasal, A.; Matya´sˇ, L.; Budeˇsˇ´ınsky´, M. Neurosteroid analogues,
synthesis of 6-aza-allopregnanolone. Tetrahedron 2005, 61, 2269–
2278.
(28) Sun˜ol, C.; Garc´ıa, D. A.; Bujons, J.; Krisˇtof´ıkova´, Z.; Matya´sˇ, L.;
Babot, Z.; Kasal, A. Activity of analogues of neurosteroids on the
GABAA receptor in primary neuronal cultures. J. Med. Chem. 2006,
49, 3225–3234.
(29) Lo¨scher, W.; Potschka, H. Drug resistance in brain diseases and the
role of drug efflux transporters. Nat. ReV. Neurosci. 2005, 6, 591–
602.
(52) Jenner, G. Effect of pressure on sterically congested cyanoalkylation
reactions of alcohols. Tetrahedron 2002, 58, 4311–4317.
(53) Bowers, A.; Denot, E.; Becerra, R. The abnormal addition of I-F to
∆5-steroids. J. Am. Chem. Soc. 1960, 82, 4007–4012.
(30) Wolka, A. M.; Huber, J. D.; Davis, T. Pain and the blood-brain barrier,
obstacles to obstacles to drug delivery. AdV. Drug DeliVery ReV. 2003,
55, 987–1006.
(54) Danilewicz, J. B.; Klyne, W. Side-chain-substituted 5R-pregnanes not
carrying substituents in the phenanthrene nucleus. J. Chem. Soc. 1962,
4950–4957.
(55) Kirk, D. N. The circular dichroism of strained, bridge-ring, and other
ketones. J. Chem. Soc., Perkin. Trans. 1 1977, 2122–2148.
(56) Wilkins, M. E.; Hosie, A. M.; Smart, T. G. Proton modulation of
recombinant GABA(A) receptors, influence of GABA concentration
and the beta subunit TM2-TM3 domain. J. Physiol. (London) 2005,
567, 365–377.
(57) Moreira, V. M. A.; Vasaitis, T. S.; Guo, Z.; Njar, V. C. O.; Salvador,
J. A. R. Synthesis of novel C17 steroidal carbamates. Studies on
CYP17 action, androgen receptor binding and function, and prostate
cancer cell growth. Steroids 2008, 73, 1217–1227.
(58) Dieckhaus, C. M.; Roller, S. G.; Santos, W. L.; Sofia, R. D.;
Macdonald, T. L. Role of glutathione S-transferases A1-1, M1-1, and
P1-1 in the detoxification of 2-phenylpropenal, a reactive felbamate
metabolite. Chem. Res. Toxicol. 2001, 14, 511–516.
(59) Kapetanovic, I. M.; Torchin, C. D.; Thompson, C. D.; Miller, T. A.;
McNeilly, P. J.; MacDonald, T. L.; Kupferberg, H. J.; Perhach, J. L.;
Sofia, R. D.; Strong, J. M. Potentially reactive cyclic carbamate
metabolite of the antiepileptic drug felbamate produced by human liver
tissue in vitro. Drug Metab. Dispos. 1998, 26, 1089–1095.
(60) Popovic, M.; Nierkens, S.; Pieters, R.; Uetrecht, J. Investigating the
role of 2-phenylpropenal in felbamate-induced idiosyncratic drug
reactions. Chem. Res. Toxicol. 2004, 17, 1568–1576.
(61) Anderson, R. A.; Baillie, T. A.; Axelson, M.; Cronholm, T.; Sjoevall,
K.; Sjoevall, J. Steroids 1990, 55, 443–457.
(62) Bladon, P. The Michael reaction of 3ꢀ-acetoxypregna-5,16-dien-20-
one. J. Chem. Soc. 1958, 372, 3–26.
(31) Reddy, D. S.; Castaneda, D. C.; O’Malley, B. W.; Rogawski, M. A.
Anticonvulsant activity of progesterone and neurosteroids in proges-
terone receptor knockout mice. J. Pharmacol. Exp. Ther. 2004, 310,
230–239.
(32) Park, K. K.; Ko, D. H.; You, Z.; Heiman, A. S.; Lee, H. J. Synthesis
and pharmacological evaluations of new steroidal anti-inflammatory
antedrugs, 9R-fluoro-11ꢀ,17R,21-trihydroxy-3,20-dioxo-pregna-1,4-
diene-16R-carboxylate (FP16CM) and its derivatives. Steroids 2006,
71, 83–89.
(33) Mitsukuchi, M.; Ikemoto, T.; Taguchi, M.; Higuchi, S.; Abe, S.; Yasui,
H.; Hatayama, K.; Sota, K. Synthesis of 17R-acyloxy-9R-fluoro-11ꢀ-
hydroxy-16ꢀ-methyl-1,4-pregnadiene-3,20-dione 21-thio derivatives
and related compounds. Chem. Pharm. Bull. 1989, 37, 3286–3293.
(34) Alexander, N. J.; Kim, H. K.; Blye, R. R.; Blackmore, P. F. Steroid
specificity of the human sperm membrane progesterone receptor.
Steroids 1996, 61, 116–125.
(35) Selye, H. Pharmaco-chemical interrelations among catatoxic steroids.
ReV. Can. Biol. 1970, 29, 49–102.
(36) Slav´ıkova´, B.; Kasal, A. Epalons, synthesis of new 16R-carboxymethyl
derivatives. Collect. Czech. Chem. Commun. 1999, 64, 1479–1486.
(37) Slav´ıkova´, B.; Kasal, A.; Chodounska´, H.; Krisˇtof´ıkova´, Z. 3R-Fluoro
analogues of “allopregnanolone” and their binding to GABAA recep-
tors. Collect. Czech. Chem. Commun. 2002, 67, 30–46.
(38) Maresˇ, P.; Haugvicova´, R.; Kasal, A. Action of two neuroactive
steroids against motor seizures induced by pentetrazol in rats during
ontogeny. Physiol. Res. 2006, 55, 437–444.
(39) Maresˇ, P.; Mikulecka´, A.; Haugvicova´, R.; Kasal, A. Anticonvulsant
action of allopregnanolone in immature rats. Epilepsy Res. 2006, 70,
110–117.
(40) Mazu, R. H.; Cella, J. A. 16-Substituted steroids. Tetrahedron 1959,
7, 130–137.
(63) Bandyopadhyay, P.; Janout, V.; Zhang, L.; Regen, S. L. Ion conductors
derived from cholic acid and spermine. Importance of facial hydro-
philicity on Na+ transport and membrane selectivity. J. Am. Chem.
Soc. 2001, 123, 7691–7696.
(64) Wall, M. E.; Kenney, H. E.; Rothman, E. S. Conversion of steroidal
sapogenin to ∆16-20-ketopregnanes. J. Am. Chem. Soc. 1955, 77,
5665–5668.
(41) Kano, T.; Tanaka, Y.; Maruoka, K. Organocatalytic oxy-Michael
addition of alcohols to R,ꢀ-unsaturated aldehydes. Tetrahedron Lett.
2006, 47, 3039–3041.
(42) Marker, R. E. 17-Hydroxy-20-ketopregnanes from steroidal sapogenins.
J. Am. Chem. Soc. 1949, 71, 4149–4151.
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