Novel glucocorticoid antedrugs possessing a 21-(γ-lactone) ring

Article abstract of DOI:10.1039/b200190j

Pregnane derivatives bearing γ-butyrolactones at C21 were prepared and tested as glucocorticoid agonists. The compounds were also tested for their liability in human plasmas. The compounds were found to be rapidly hydrolyzed by the enzyme paraoxonase to the respective hydroxyacids.

Full text of DOI:10.1039/b200190j

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Novel glucocorticoid antedrugs possessing a 21-(ꢀ-lactone) ring
Richard M. Angell, Keith Biggadike, Rosanne M. Farrell, Stephen S. Flack,
Ashley P. Hancock, Wendy R. Irving, Sean M. Lynn and Panayiotis A. Procopiou*
1
GlaxoSmithKline Medicines Research Centre, Gunnels Wood Road, Stevenage, Hertfordshire,
UK SG1 2NY
Received (in Cambridge, UK) 4th January 2002, Accepted 11th February 2002
First published as an Advance Article on the web 26th February 2002
A series of novel pregnane derivatives bearing γ-butyrolactones at C21 were prepared and tested as glucocorticoid
agonists. The compounds were also tested for their lability in human plasma, and found to be rapidly hydrolysed by
the enzyme paraoxonase to the respective hydroxyacids.
Introduction
The incidence of asthma in developed countries is increasing
and is responsible for an increasing proportion of healthcare
costs. Inhaled glucocorticoids are currently used for the treat-
ment of all types of asthma, including mild forms of the dis-
ease, and for this reason the search for new and even safer
glucocorticoids is continuing.
The terms ‘antedrug’1 and ‘soft drug’2 were introduced to
describe drugs designed to act topically at the side of applica-
tion but that are transformed into inactive metabolites upon
entry into the systemic circulation. Recently our group has
discovered that the incorporation of a γ-lactone moiety
provides derivatives which are extremely rapidly inactivated in
plasma but which show remarkable stability in human lung
S9 fraction.3,4 These ideal properties make such derivatives
excellent lung selective antedrug candidates for use in asthma.
The enzyme responsible for the plasma hydrolysis of these
lactones was identified by our group3 as human serum para-
oxonase (EC 3.1.8.1), an organophosphate-detoxifying enzyme
whose natural substrates have recently been shown to include
homocysteine thiolactone.5
As part of our medicinal chemistry programme we have
investigated the scope for paraoxonase-mediated hydrolysis of
a variety of glucocorticoid lactone derivatives and have recently
reported on some 16,17-fused γ-lactones,6 and on 17β-sulfur
linked butyrolactones.4
Substitution of the 21-hydroxy group of fluocinolone aceto-
Results and discussion
nide (1a) by a small alkylthio group such as methylthio was
reported by Mitsukuchi et al. to enhance topical antiinflamma-
tory activity measured by vasoconstrictive activity in humans.7
In addition butixocort propionate, a C21 thiopropionate ester,8
was progressed by Jouveinal to phase II clinical studies as an
inhaled antiinflammatory agent for the treatment of asthma.
Furthermore, butixocort 21-propionate was found to undergo
ester hydrolysis in rat lung to the corresponding 21-thiol, and
subsequently methylation of the resulting thiol to the S-methyl
derivative. Both metabolites were found to be active with
topical activity similar to that of the parent compound.9 We
envisaged that incorporation of a γ-lactone linked via sulfur at
C21 would retain glucocorticoid activity, however, the meta-
bolism of such analogues was not easily predicted. In our
preliminary communication3 we have reported that the lactone
2a was stable in human lung S9 fraction, but rapidly hydrolysed
Lactone 2a (1 : 1 mixture of diastereoisomers) was pre-
pared by displacement of the 21-methanesulfonate 4a7 with
α-mercapto-γ-butyrolactone 510 or alternatively from the 21-
mercaptopregnane 6a7 and commercially available α-bromo-
γ-butyrolactone 7. The resulting diastereoisomers 2aS and
2aR were readily separated by reverse phase preparative HPLC
(Scheme 1). The absolute configuration of the individual
diastereoisomers was assigned following diastereoselective
synthesis of 2aS starting from the commercially available
(R)-(ϩ)-α-hydroxy-γ-butyrolactone 8R as shown in Scheme 2.
Hydroxylactone 8R, which can also be conveniently prepared
from (R)-malic acid,11 was converted to the corresponding
crystalline methanesulfonate 9R with methanesulfonyl chloride
in the presence of triethylamine. The absolute configuration
of 2aS was confirmed by an X-ray diffraction study (Fig. 1).
Similarly the (R)-diastereoisomer 2aR was obtained from the
(S)-(Ϫ)-α-hydroxy-γ-butyrolactone 8S via the corresponding
methanesulfonate 9S.
in human plasma (t < 1 min) to the corresponding hydroxy-
½
acid 3a. In this paper we report the synthesis and structure–
activity relationships of a series of pregnanes possessing a
γ-lactone at C21.
The β-linked lactone 11a was prepared from the thiol 6a and
furan-2(5H )-one (10) in the presence of potassium carbonate
DOI: 10.1039/b200190j
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This journal is © The Royal Society of Chemistry 2002
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Scheme 1 Reagents and conditions: i) NaH, THF, 0 ЊC; ii) Et3N,
CH2Cl2, 0 ЊC.
Scheme 3 Reagents and conditions: i) K2CO3, 6, DMF, 20 ЊC; ii) Et3N,
6, THF, 20 ЊC.
in DMF, and was obtained as an inseparable mixture of
diastereoisomers in 79% yield (Scheme 3). The analogous γ-
linked lactones 13a were prepared from thiol 6a and γ-chloro-
γ-butyrolactone 12.12 The individual diastereoisomers were
separable by silica gel chromatography (26 and 13% respec-
tively), but their configuration at the lactone asymmetric centre
was not established. Addition of 6a to α-methylene-γ-butyro-
lactone (14) in the presence of triethylamine provided the
homologous lactone 15a as a 3 : 1 mixture of diastereoisomers
(55%).
Scheme 2 Reagents and conditions: CH3SO2Cl, Et3N, CH2Cl2, 0 ЊC;
ii) 6a, NaH, DMF, 0 ЊC; iii) 6a, K2CO3, DMF, 20 ЊC.
The dihydro α-linked lactones 2bS and 2bR were prepared
from dihydro methanesulfonate 4b7 and thiol 5. The diastereo-
isomers were separated by preparative HPLC (34 and 28%
respectively). Glucocorticoids with the 16,17-butylidene moiety
are generally more potent than the corresponding 16,17-
isopropylidenes and it was thus important to synthesise such
analogues. The lactones in the butylidene series were prepared
in a similar way to the acetonide series starting from 1a. The
acetonide group was replaced by the (R)-butylidene group by
the Astra method13 of transacetalisation to form 16a, then
converted to the methanesulfonate 17a (97%), followed by
displacement of the methanesulfonate with thiol 5 to give a
mixture of diastereoisomers 18aR and 18aS (Scheme 4). The
diastereoisomers were separated by HPLC and their con-
figuration was established following diastereoselective synthesis
of 18aR from 2aR using the Astra procedure.13
The dihydro analogues in the butylidene series were prepared
from dihydro alcohol 16b.14 Thus reaction with methane-
sulfonyl chloride in pyridine gave the methanesulfonate 17b
(63%) which was reacted with thiol 5 to give the dihydro α-linked
lactones 18bR and 18bS after preparative HPLC (18 and 45%
respectively). The absolute configuration of 18bR and 18bS
was established by diastereoselective synthesis (Scheme 5).
Thus reaction of 16b with thioacetic acid under Mitsunobu
Fig. 1 X-Ray crystal structure of 2aS.
832
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Table 1 Human plasma stability and in vitro glucocorticoid agonist
activity
Compound number
Plasma stabilitya
Relative potency
2aS
0
0
29
NTb
0
36
49
22
0
44
57
NTb
0
4.5
6.9
11.7
29
2aR
2bS
2bR
11a
7.9
1.6
1.2
2.5
1.0
0.9
3.2
1.3
2.4
1.4
2.7
1.0
13a isomer A
13a isomer B
15a
18aS
18aR
18bS
18bR
21b
26a
23
76
—
26b
Dexamethasone
a % remaining at 60 min. b NT = not tested.
of a catalytic amount of toluene-p-sulfonic acid gave the cyclic
orthoester 23a which was hydrolysed by aqueous acetic acid
to give selectively the 17α-propionate 24a (Scheme 6).15,16
Scheme 4 Reagents and conditions: i) n-PrCHO, sand, 70% HCIO4,
heptane; ii) CH3SO2Cl, pyridine; iii) 5, NaH, THF, 0 ЊC.
Scheme 6 Reagents and conditions: i) (EtO)3CEt, TsOH, DMF, PhMe;
ii) AcOH, H2O, MeOH; iii) CH3SO2Cl, pyridine; iv) 5, NaH, THF;
v) H2, (Ph3P)3RhCl, EtOH.
Scheme
5
Reagents and conditions: i) Ph3P, diisopropyl
azodicarboxylate, AcSH, THF, 0 ЊC; ii) H2NNH2, THF, Ϫ15 to 20 ЊC;
iii) 9R, K2CO3, DMF, or NaH, THF; iv) 10, Et3N, THF.
Reaction of 17β-hydroxymethyl ketone 24a with methane-
sulfonyl chloride gave methanesulfonate 25a, which was reacted
with thiol 5 to give an inseparable mixture of diastereoisomers
26a. Finally, dihydro analogue 26b was obtained from 24a
by selective hydrogenation using Wilkinson’s catalyst (85%),
followed by mesylation to 25b (100%) and displacement of
methanesulfonate with thiol 5 to give 26b (43%).
The compounds listed in Table 1 were tested in vitro for their
stability in human plasma and for their glucocorticoid agonist
activity. The chemical stability of the compounds in Krebs
buffer was examined by HPLC after incubating for 1 h and then
their stability in human plasma after incubating for 1 h at 37 ЊC.
The identity of the metabolites was obtained by LCMS and by
conditions gave the thioacetate 19b (100%), which was con-
verted to the thiol 20b by treatment with hydrazine (91%).
Reaction of 20b with the (R)-methanesulfonate lactone 9R
gave the lactone 18bS (37%). Reaction of thiol 20b with furan-
2(5H )-one (10) gave the β-linked lactone 21b (71%) as a
mixture of diastereoisomers (Scheme 5).
In addition to 16,17-acetonides and butylidenes, 16α-methyl-
17α-propionate derivatives were synthesised, as these analogues
are generally more potent glucocorticoids. Reaction of
flumethasone 22a with triethyl orthopropionate in the presence
J. Chem. Soc., Perkin Trans. 1, 2002, 831–839
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chemical synthesis in some cases (2a, 11a). The results are
expressed as a percentage (%) of compound remaining. All the
compounds were found to be essentially stable in Krebs buffer
after 1 h incubation, and to hydrolyse to the corresponding
hydroxy carboxylic acids in plasma. The metabolite of the γ-
linked lactones 13a is a hemiacetal, which then collapses to
the 21-mercapto derivative 6a. As this metabolite is a potent
glucocorticoid these analogues were not of any further interest.
In addition the β-linked lactones 11a and 21b were found to
undergo to a small extent retro-Michael reaction on prolonged
storage to again produce the corresponding 21-mercapto
derivatives. The C-linked lactone 15a was found unexpectedly
to hydrolyse in plasma, albeit more slowly than the S-linked
lactones (22% lactone remaining after 1 h incubation) in con-
trast to our earlier findings in the 17β-sulfur linked butyro-
lactone series.4
The pharmacological activity was assessed in a functional in
vitro assay of glucocorticoid agonist activity, which is generally
predictive of antiinflammatory or anti-allergic activity in vivo.
The functional assay was based on that described by Farrow
et al.17 A549 cells stably transfected with a reporter gene con-
taining the NF-κB responsive elements from the ELAM gene
promoter coupled to sPAP (secreted alkaline phosphatase) were
treated with test compounds at appropriate doses for 1 h at
37 ЊC. The cells were then stimulated with tumour necrosis
factor (TNF, 10 ng mlϪ1) for 16 h, after which time the amount
of alkaline phosphatase produced was measured by a standard
colorimetric assay. Dose response curves were constructed from
which EC50 values were estimated. The relative potencies of
the compounds in Table 1 are expressed as the ratio of the EC50
value of the test compound to that of dexamethasone which
was used as a standard.
The potencies of the individual diastereoisomers at the lac-
tone asymmetric centre were found to be similar. Butyro-
lactones linked to the steroidal nucleus at the γ-position were
generally more potent than those linked at the α-and β-
positions based on the acetonide series where a complete set of
α-, β- and γ-linked analogues were examined. However, because
of the active metabolite associated with the β- and γ-linked
analogues, the latter were of less interest. The 1,4-dien-3-one
analogues (a series) were found to be more potent than the 4-
en-3-one analogues (b series) e.g. 2a > 2b, 18a > 18b, 26a > 26b,
confirming our findings in the 17β-lactone series.4 Similarly, the
potency across the series was found to be in the order of 17α-
propionates ≈ 16α,17α-butylidenes > 16α,17α-isopropylidenes.
block and are uncorrected. Optical rotations were measured
with an Optical Activity AA100 digital polarimeter at 20 ЊC
and are given in units of 10Ϫ1 deg cm2 gϪ1. IR spectra were
recorded by reflectance from KBr on a Bio-Rad FTS-7 FT-IR
1
spectrometer. H NMR spectra were recorded at 250 MHz,
and the chemical shifts are expressed in ppm relative to tetra-
methylsilane. All J values are in Hz. MS (TSP ϩve) and MS
(ES ϩve) refer to mass spectra run in positive mode using
thermospray or electrospray techniques, respectively. Residual
solvents reported in microanalytical data were observed in the
NMR spectra of such samples.
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-16ꢁ,17ꢁ-isopropylidenedioxy-21-
(2-oxotetrahydrofuran-3-ylsulfanyl)pregna-1,4-diene-3,20-dione
(2a)
Method A using ꢁ-mercapto-ꢀ-butyrolactone 5. A solution of
5 (80 mg, 0.68 mmol) in anhydrous tetrahydrofuran (2 ml) was
added dropwise to a stirring suspension of sodium hydride
(60% oil dispersion; 27 mg, 0.68 mmol) in anhydrous tetra-
hydrofuran (1 ml) at 0 ЊC under a nitrogen atmosphere. The
resulting solution was stirred at 0 ЊC for 30 min by which time
effervescence had ceased. A solution of 6α,9α-difluoro-11β-
hydroxy-16α,17α-isopropylidenedioxy-21-methylsulfonyloxy-
pregna-1,4-diene-3,20-dione (4a) (300 mg, 0.57 mmol) in
anhydrous tetrahydrofuran (10 ml) was added and the reaction
mixture was stirred for a further 1 h at 0–21 ЊC. The reaction
mixture was poured into water (30 ml) and extracted with
ethyl acetate (10 ml × 3). The combined organic extracts were
washed with saturated brine (20 ml) and dried. Removal of
the solvent under reduced pressure yielded a white solid, which
was separated by HPLC (50% MeCN–H2O) to give 6α,9α-
difluoro-11β-hydroxy-16α,17α-isopropylidenedioxy-21-[(3S)-2-
oxotetrahydrofuran-3-ylsulfanyl]pregna-1,4-diene-3,20-dione
(2aS) (88 mg, 28%) as a white solid: analytical HPLC tr 8.11
min; mp 226–229 ЊC; νmax (KBr)/cmϪ1 3391, 1766, 1716 and
1668; δH (DMSO-d6) includes 7.30 (1H, d, J 10, 1-H), 6.30 (1H,
d, J 10, 2-H), 6.11 (1H, s, 4-H), 5.74 and 5.54 (1H, 2 m, 6-H),
5.60 (1H, d, J 4.5, 16-H), 4.91 (1H, br s), 4.39–4.15 (3H, m),
4.22 (1H, d, J 17.5, 21-H), 3.93 (1H, dd, J 8 and 6, SCHCO),
3.83 (1H, d, J 17.5, 21-H), 1.48 (3H, s), 1.35 (3H, s), 1.08 (3H, s)
and 0.82 (3H, s); MS (TSP ϩve) m/z 553 (M ϩ H)ϩ (Found:
C, 60.0; H, 6.1; S, 5.6. C28H34F2O7Sؒ0.5H2O requires C, 59.9;
H, 6.3; S 5.7%) and 6α,9α-difluoro-11β-hydroxy-16α,17α-iso-
propylidenedioxy-21-[(3R)-2-oxotetrahydrofuran-3-ylsulfanyl]-
pregna-1,4-diene-3,20-dione (2aR) (72 mg, 23%): analytical
HPLC tr 8.34 min; mp 204–205 ЊC; νmax (KBr)/cmϪ1 3474, 1762,
1719, 1668 and 1633; δH (DMSO-d6) includes 7.27 (1H, d, J 10,
1-H), 6.30 (1H, d, J 10, 2-H), 6.11 (1H, s, 4-H), 5.69 and 5.54
(1H, 2 m, 6-H), 5.58 (1H, m), 4.90 (1H, br s), 4.36–4.15 (4H, m),
3.90 (1H, dd, J 8 and 6.5, SCHCO), 3.82 (1H, d, J 18, 21-H),
1.48 (3H, s), 1.35 (3H, s), 1.10 (3H, s) and 0.79 (3H, s); MS
(TSP ϩve) m/z 553 (M ϩ H)ϩ (Found: C, 57.3; H, 6.4; S, 5.4.
C28H34F2O7Sؒ2H2O requires C, 57.1; H, 6.5; S, 5.45%).
Conclusions
In conclusion, a series of novel lactone-containing pregnanes
were synthesised and tested as glucocorticoid agonists. The
1,4-dien-3-one analogues possessing a 17α-propionate ester or
the 16α,17α-butylidene were found to be the most potent gluco-
corticoids in this series. In addition, the butyrolactones were
found to hydrolyse in human plasma to the respective hydroxy
carboxylic acids.
Method B using ꢁ-bromo-ꢀ-butyrolactone 7. Triethylamine
(45 µl, 0.32 mmol) was added to a stirring suspension of 6α,9α-
difluoro-11β-hydroxy-21-mercapto-16α,17α-isopropylidenedi-
oxypregna-1,4-diene-3,20-dione7 (6a) (50 mg, 0.11 mmol) in
dichloromethane (1 ml) under a nitrogen atmosphere. The sus-
pension was then cooled to 0 ЊC and α-bromo-γ-butyrolactone
(7) (27 µl, 0.32 mmol) was added. The resulting reaction
mixture was then stirred at 0–21 ЊC for 4 h. The solvent was
evaporated under reduced pressure and the residue was par-
titioned between ethyl acetate (25 ml) and 0.5 M hydrochloric
acid (25 ml). The organic layer was washed with water (25 ml ×
2) and saturated brine (25 ml) and dried. Removal of the
solvent under reduced pressure yielded a colourless residue
which was purified by HPLC (50–95% MeCN–H2O) to give 2aS
(27 mg, 46%): mp 224–228 ЊC; δH (CDCl3) includes 7.12 (1H, d,
Experimental
Organic solutions were dried over anhydrous magnesium
sulfate. TLC was performed on Merck Kieselgel 60 F254 plates,
and column chromatography was performed on Merck
Kieselgel 60 (art. 7734 or 9385). Analytical HPLC was con-
ducted on a Phenomenex Prodigy ODS-2 column (15 cm ×
0.46 cm) eluting with 15–95% MeCN–H2O over 16 min. Pre-
parative HPLC was performed on a Gilson Medical Electronics
system using a reversed-phase Dynamax 60Å C18 column
(25 cm × 5 cm) flow rate 45 ml minϪ1, detecting at 230 nm.
Appropriate fractions were combined and evaporated under
reduced pressure. Melting points were determined on a Kofler
834
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J 10, 1-H), 6.44 (1H, s, 4-H), 6.37 (1H, d, J 10, 2-H), 5.48 and
5.29 (1H, 2 m, 6-H), 5.06 (1H, d, J 4.5, 16-H), 4.55–4.33 (3H,
m), 4.04 (1H, d, J 19, 21-H), 3.88 (1H, d, J 19, 21-H), 3.83 (1H,
dd, J 8.5 and 3.5, SCHCO), 1.53 (3H, s), 1.43 (3H, s), 1.16 (3H,
s) and 0.94 (3H, s) and 2aR (29 mg, 49%): mp 203–206 ЊC;
δH (CDCl3) includes 7.12 (1H, d, J 10, 1-H), 6.44 (1H, s, 4-H),
6.38 (1H, d, J 10, 2-H), 5.48 and 5.29 (1H, 2 m, 6-H), 5.05 (1H,
d, J 4.5, 16-H), 4.55–4.30 (3H, m), 4.27 (1H, d, J 17.5, 21-H),
3.93 (1H, d, J 17.5, 21-H), 3.68 (1H, dd, J 8 and 4.5, SCHCO),
1.53 (3H, s), 1.43 (3H, s) 1.19 (3H, s) and 0.90 (3H, s).
a stirring solution of (S)-3-hydroxy-2-oxotetrahydrofuran
(500 mg, 4.90 mmol) and triethylamine (0.88 ml, 6.37 mmol) in
anhydrous dichloromethane (20 ml) at 0 ЊC under a nitrogen
atmosphere. The resulting mixture was stirred at 0 ЊC for 0.5 h
and at 21 ЊC for a further 5 h. The solvent was removed under
reduced pressure and the residue was purified by flash column
chromatography eluting with ethyl acetate–cyclohexane (3 : 2)
to give 9S as a white crystalline solid (341 mg, 39%): mp 74–76
ЊC; [α]2D0 Ϫ57 (c 1.1 in CHCl3); νmax (KBr)/cmϪ1 1787 and 1363;
δH (CDCl3) 5.34 (1H, t, J 9, 3-H), 4.53 (1H, dt, J 3 and 9, 5-H),
4.35 (1H, dt, J 6 and 9, 5-H), 3.29 (3H, s, MeSO3), 2.86–2.71
(1H, m, 4-H) and 2.66–2.47 (1H, m, 4-H); MS (TSP ϩve)
m/z 198 (M ϩ NH4)ϩ (Found: C, 33.5; H, 4.9; S, 17.8. C5H8O5S
requires C, 33.3; H, 4.5; S, 17.8%).
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-16ꢁ,17ꢁ-isopropylidenedioxy-21-
[(3S)-2-oxotetrahydrofuran-3-ylsulfanyl]pregna-1,4-diene-3,20-
dione (2aS)
A solution of 6α,9α-difluoro-11β-hydroxy-21-mercapto-16α,
Methanesulfonic acid (3R)-2-oxotetrahydrofuran-3-yl ester (9R)
17α-isopropylidenedioxypregna-1,4-diene-3,20-dione
(6a)
White crystalline solid (214 mg, 30%): mp 73–74 ЊC; [α]2D0 ϩ58
(c 0.96 in CHCl3); νmax (KBr)/cmϪ1 1774 and 1363; δH (CDCl3)
5.33 (1H, t, J 9, 3-H), 4.53 (1H, dt, J 3 and 9, 5-H), 4.35 (1H, dt,
J 6 and 9, 5-H), 3.30 (3H, s, MeSO3), 2.88–2.72 (1H, m, 4-H)
and 2.66–2.47 (1H, m, 4-H); MS (TSP ϩve) m/z 198 (M ϩ
NH4)ϩ (Found: C, 33.5; H, 4.2; S, 17.55. C5H8O5S requires C,
33.3; H, 4.5; S, 17.8%).
(100 mg, 0.21 mmol) in anhydrous DMF (2 ml) was added to
a stirring suspension of sodium hydride (60% oil dispersion;
9 mg, 0.21 mmol) in anhydrous DMF (1 ml) at 0 ЊC under a
nitrogen atmosphere. The resulting mixture was stirred at 0 ЊC
for 0.5 h at which point a solution of 9R (38 mg, 0.21 mmol) in
anhydrous DMF (3 ml) was added. The reaction mixture was
stirred at 0 ЊC for 0.5 h and at 21 ЊC for a further 1 h. The
mixture was partitioned between water (20 ml) and ethyl acetate
(20 ml). The aqueous layer was extracted with ethyl acetate
(20 ml) and the combined organic extracts were washed with
saturated brine (20 ml), dried and evaporated under reduced
pressure to yield a yellow oily residue. This material was puri-
fied by flash column chromatography eluting with ethyl acetate
to give 2aS as a white solid (38 mg, 32%): mp 220–222 ЊC;
chromatographic and spectroscopic data were identical to those
obtained above.
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-16ꢁ,17ꢁ-isopropylidenedioxy-21-
(2-oxotetrahydrofuran-4-ylsulfanyl)pregna-1,4-diene-3,20-dione
(11a)
A
suspension of 6α,9α-difluoro-11β-hydroxy-21-mercapto-
16α,17α-isopropylidenedioxypregna-1,4-diene-3,20-dione (6a)
(100 mg, 0.23 mmol) and anhydrous potassium carbonate
(32 mg, 0.23 mmol) in dry DMF (2 ml) was treated with furan-
2(5H )-one (10) (0.035 ml, 0.5 mmol) and the mixture was
stirred at 20 ЊC under a nitrogen atmosphere for 4 h. The
reaction mixture was poured into 0.5 M hydrochloric acid
(20 ml) and extracted with ethyl acetate (40 ml). The organic
phase was washed with water (10 ml), aqueous sodium
bicarbonate solution, water, saturated brine (20 ml each)
and dried. Removal of the solvent under reduced pressure and
trituration in diethyl ether (3 × 2 ml) yielded 11a (100 mg, 79%):
analytical HPLC tr 7.77 min; νmax (KBr)/cmϪ1 3480, 1780, 1715
1668 and 1631; δH (DMSO-d6) includes 7.30 (1H, d, J 9, 1-H),
6.31 (1H, d, J 9, 2-H), 6.13 (1H, s, 4-H), 5.70 and 5.58 (1H, 2 m,
6-H), 5.51 (1H, d, J 4, 16-H), 4.93 (1H, d, J 4, 16-H), 4.58 (1H,
dd, J 9 and 8), 4.23 (2H, m), 4.03 and 4.01 (1H, 2 d, J 17, 21-H),
3.68 and 3.66 (1H, 2 d, J 17, 21-H), 3.90 (1H, m), 3.83 (1H, d,
J 17), 3.02 (1H, dd, J 8 and 2 ), 1.51 (3H, s), 1.37 (3H, s), 1.11
(3H, s) and 0.83 (3H, s); δH (CDCl3) includes 7.13 (1H, d, J 10,
1-H), 6.44 (1H, s, 4-H), 6.38 (1H, d, J 10, 2-H), 5.50 and 5.30
(1H, 2 m, 6-H), 5.03 (1H, d, J 5, 16-H), 4.64 (1H, m), 4.42 (1H,
m), 4.24 (1H, m), 3.87 (1H, m), 3.71 and 3.68 (1H, 2 d, J 16,
21-H), 3.57 and 3.53 (1H, 2 d, J 16, 21-H), 2.96 (1H, m), 1.53
(3H, s), 1.43 (3H, s), 1.15 (3H, s) and 0.93 (3H, s); δC (DMSO-
Crystal structure analysis of 2aS. Suitable crystals were
obtained from methyl isobutyl ketone. Crystal data† for
C28H34F2O7SؒnC6H12O (where n ≈ 1, disordered solvent present
in crystal): M = 552.64, orthorhombic, a = 7.939(2), b =
14.627(3), c = 29.719(6) Å, U = 3451.0(12) Å3, T = 293 K, space
group P212121 (no. 19), Z = 4, µ(Cu-Kα) = 1.316 mmϪ1; 2624
unique reflections measured, of which 1781 were observed
[>2σ(I )], (Rσ = 0.0694). The final wR(F 2) was 0.1620 (observed
reflections) and Robs was 0.0684.
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-16ꢁ,17ꢁ-isopropylidenedioxy-21-
[(3R)-2-oxotetrahydrofuran-3-ylsulfanyl]pregna-1,4-diene-3,20-
dione (2aR)
Potassium carbonate (15 mg, 0.11 mmol) was added in a single
portion to a stirring solution of 6α,9α-difluoro-11β-hydroxy-
21-mercapto-16α,17α-isopropylidenedioxypregna-1,4-diene-3,
20-dione (6a) (100 mg, 0.21 mmol) and 9S (38 mg, 0.21 mmol)
in anhydrous DMF (2 ml). The resulting reaction mixture was
stirred under a nitrogen atmosphere for 1.5 h at which point
another quantity of potassium carbonate (15 mg, 0.11 mmol)
was added. The mixture was stirred for a further 2.5 h. Ethyl
acetate (10 ml) and 2 M hydrochloric acid (10 ml) were added
and the organic phase was separated and washed with water
(10 ml), saturated brine (10 ml) and then dried. Removal of the
solvent under reduced pressure yielded a yellow residue, which
was purified by flash column chromatography eluting with
diethyl ether to give 2aR as a white solid (91 mg, 77%); chrom-
atographic and spectroscopic data were identical to those
reported above.
d ) includes 206.2, 184.2, 175.4 (3 × C᎐O); MS (ES ϩve)
᎐
6
m/z 553 (M ϩ H)ϩ (Found: C, 59.25; H, 6.1; S, 5.7.
C28H34F2O7Sؒ0.75H2O requires C, 59.4; H, 6.3; S 5.7%).
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-16ꢁ,17ꢁ-isopropylidenedioxy-21-
(2-oxotetrahydrofuran-5-ylsulfanyl)pregna-1,4-diene-3,20-dione
(13a)
A
solution of 6α,9α-difluoro-11β-hydroxy-21-mercapto-
16α,17α-isopropylidenedioxypregna-1,4-diene-3,20-dione (6a)
(400 mg, 0.85 mmol) and γ-chloro-γ-butyrolactone (12)10 (103
mg, 0.85 mmol) in anhydrous tetrahydrofuran (10 ml) was
treated with triethylamine (0.12 ml, 0.85 mmol) and the mixture
was stirred at 20 ЊC under a nitrogen atmosphere for 24 h.
Removal of the solvent under reduced pressure yielded a brown
foam. The crude product was purified by column chromato-
graphy eluting with dichloromethane–ethyl acetate (3 : 1) to
Methanesulfonic acid (3S)-2-oxotetrahydrofuran-3-yl ester (9S)
Methanesulfonyl chloride (0.49 ml, 6.37 mmol) was added to
† CCDC reference number 177055. See http://www.rsc.org/suppdata/
p1/b2/b200190j/ for crystallographic files in .cif or other electronic
format.
J. Chem. Soc., Perkin Trans. 1, 2002, 831–839
835

View Article Online
give 13a isomer A (124 mg, 26%): mp 238–239 ЊC; νmax (KBr)/
cmϪ1 1781, 1719 and 1669; δH (CDCl3) includes 7.19 (1H, d,
J 10, 1-H), 6.43 (1H, s, 4-H), 6.37 (1H, d, J 10, 2-H), 5.87 (1H,
m, SCHO), 5.49 and 5.29 (1H, 2 m, 6-H), 5.02 (1H, d, J 4,
16-H), 4.42 (1H, m, 11-H), 3.92 (1H, d, J 17, 21-H), 3.78 (1H, d,
J 17, 21-H), 1.53 (3H, s), 1.42 (3H, s), 1.17 (3H, s) and 0.90 (3H,
s); MS (TSP ϩve) m/z 553 (M ϩ H)ϩ (Found: C, 59.55; H, 6.2;
S, 5.6. C28H34F2O7Sؒ0.2CH2Cl2 requires C, 59.5; H, 6.1; S, 5.6%)
and 13a isomer B (62 mg, 13%): mp 244–246 ЊC; νmax (KBr)/
cmϪ1 1784, 1715 and 1688; δH (CDCl3) includes 7.14 (1H, d,
J 10, 1-H), 6.43 (1H, s, 4-H), 6.38 (1H, d, J 10, 2-H), 5.92
(1H, m, SCHO), 5.49 and 5.29 (1H, 2 m, 6-H), 5.06 (1H, d, J 4,
16-H), 4.42 (1H, m, 11-H), 3.91 (1H, d, J 18, 21-H), 3.72 (1H, d,
J 18, 21-H), 1.52 (3H, s), 1.42 (3H, s), 1.17 (3H, s) and 0.90 (3H,
s); MS (TSP ϩve) m/z 553 (M ϩ H)ϩ (Found: C, 61.0; H, 6.2; S,
5.6. C28H34F2O7S requires C, 60.9; H, 6.2; S, 5.8%).
was stirred for a further 1 h at 0 ЊC. The reaction mixture
was poured into water (20 ml) and extracted with ethyl acetate
(20 ml × 4). The combined organic extracts were then washed
with saturated brine (20 ml) and dried. Removal of the solvent
under reduced pressure yielded a residue which was purified by
HPLC (55% MeCN–H2O) to give 2b isomer A (282 mg, 34%):
analytical HPLC tr 7.82 min; mp 124–128 ЊC; νmax (KBr)/cmϪ1
3468, 1760, 1716 and 1669; δH (DMSO-d6) includes 5.80 (1H, s,
4-H), 5.60 and 5.41 (1H, 2 m, 6-H), 5.30 (1H, br s), 4.90 (1H, br
s), 4.40–4.10 (3H, m), 4.08–3.73 (3H, m), 1.47 (3H, s), 1.37 (3H,
s), 1.08 (3H, s), and 0.79 (3H, s); MS (TSP ϩve) m/z 555 (M ϩ
H)ϩ (Found: C, 59.7; H, 6.4; S, 5.6. C28H36F2O7Sؒ0.5H2O
requires C, 59.7; H, 6.6; S, 5.7%) and 2b isomer B (235 mg,
28%): analytical HPLC tr 7.54 min; mp 224–228 ЊC; νmax (KBr)/
cmϪ1 3482, 1762, 1714 and 1669; δH (DMSO-d6) includes 5.81
(1H, s, 4-H), 5.60 and 5.41 (1H, 2 m, 6-H), 5.28 (1H, br s), 4.91
(1H, br s), 4.40–4.10 (4H, m), 3.95–3.73 (2H, m), 1.47 (3H, s),
1.38 (3H, s), 1.11 (3H, s) and 0.77 (3H, s); MS (TSP ϩve)
m/z 555 (M ϩ H)ϩ (Found: C, 59.8; H, 6.6; S, 5.6. C28H36F2O7Sؒ
0.5H2O requires C, 59.7; H, 6.6; S, 5.7%).
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-16ꢁ,17ꢁ-isopropylidenedioxy-21-
(2-oxotetrahydrofuran-3-ylmethylsulfanyl)pregna-1,4-diene-
3,20-dione (15a)
Triethylamine (0.12 ml, 0.85 mmol) was added to a solution of
6 (400 mg, 0.85 mmol) and α-methylene-γ-butyrolactone (14)
(0.075 ml, 0.85 mmol) in tetrahydrofuran (10 ml) and the
mixture was stirred at 20 ЊC under nitrogen for 22 h. The
solvent was removed under reduced pressure and the residue
was purified by chromatography eluting with ethyl acetate–
cyclohexane (3 : 2) to give 15a (268 mg, 55%) as a white solid:
analytical HPLC indicated a 3 : 1 mixture of diastereoisomers;
δH (CDCl3) includes 7.16 (1H, d, J 10, 1-H), 6.44 (1H, s, 4-H),
6.38 (1H, d, J 10, 2-H), 5.49 and 5.30 (1H, 2 m, 6-H), 5.03 (1H,
d, J 4, 16-H), 4.52–4.37 (2H, m), 4.28 (1H, dt, J 7 and 9,
CH2OCO), 3.76 (0.5H, s, 21-H, minor isomer) and 3.68 (1.5H,
AB q, J 16, 21-H, major isomer), 1.54 (3H, s), 1.43 (3H, s), 1.15
(3H, s) and 0.98 (3H, s); MS (ES ϩve) m/z 567 (M ϩ H)ϩ
(Found: C, 61.1; H, 6.5; S, 5.5. C29H36F2O7S requires C, 61.5;
H, 6.4; S, 5.7%).
16ꢁ,17ꢁ-[(R)-Butylidenedioxy]-6ꢁ,9ꢁ-difluoro-11ꢂ-hydroxy-21-
methylsulfonyloxypregna-1,4-diene-3,20-dione (17a)
Methanesulfonyl chloride (0.41 ml, 5.35 mmol) was added to
a stirring solution of 16α,17α-[(R)-butylidenedioxy]-6α,9α-
difluoro-11β,21-dihydroxypregna-1,4-diene-3,20-dione (16a)
(500 mg, 1.07 mmol) in anhydrous pyridine (6 ml) under a
nitrogen atmosphere. The reaction mixture was stirred for 2 h
and was then poured into ice-cold 1 M hydrochloric acid
(30 ml). The resulting precipitate was collected by filtration
and dried at reduced pressure over phosphorus pentaoxide to
yield 17a as a pale yellow solid (566 mg, 97%): δH (DMSO-d6)
includes 7.27 (1H, d, J 10, 1-H), 6.30 (1H, d, J 10, 2-H), 6.10
(1H, s, 4-H), 5.73 and 5.53 (1H, 2 m, 6-H), 5.61 (1H, br s), 5.27
(1H, d, J 18, 21-H), 4.99 (1H, d, J 18, 21-H), 4.75 (2H, m),
4.20 (1H, m, 11-H), 3.29 (3H, s, MeSO3), 1.48 (3H, s), 0.87
(3H, t, J 7.5, CH2CH3) and 0.84 (3H, s); MS (TSP ϩve) m/z 545
(M ϩ H)ϩ (Found: C, 56.4; H, 6.2; S, 6.0. C26H34F2O8Sؒ0.4H2O
requires C, 56.6; H, 6.4; S, 5.8%).
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-16ꢁ,17ꢁ-isopropylidenedioxy-21-
methylsulfonyloxypregn-4-ene-3,20-dione (4b)
Methanesulfonyl chloride (0.85 ml, 11 mmol) was added to
a stirring solution of 6α,9α-difluoro-11β,21-dihydroxy-16α,
17α-isopropylidenedioxypregn-4-ene-3,20-dione (1b) (1 g, 2.2
mmol) in anhydrous pyridine (10 ml) at 0 ЊC under a nitrogen
atmosphere. The reaction mixture was stirred for 2 h and was
then poured into ice-cold 1 M hydrochloric acid (40 ml).
The resulting suspension was extracted with ethyl acetate
(20 ml × 4) and the combined organic extracts were washed
with saturated brine (20 ml) and dried. Removal of the solvent
under reduced pressure yielded a pale yellow residue which was
purified by HPLC (55% MeCN–H2O) to give 4b as a colourless
foam (843 mg, 72%): νmax (KBr)/cmϪ1 3453, 1732 and 1669;
δH (DMSO-d6) includes 5.82 (1H, s, 4-H), 5.61 and 5.42 (1H,
2 m, 6-H), 5.35 (1H, d, J 18, 21-H), 5.30 (1H, br s), 4.93 (1H, br
s), 4.90 (1H, d, J 18, 21-H), 4.19 (1H, m, 11-H), 3.32 (3H, s,
MeSO3), 1.48 (3H, s), 1.38 (3H, s), 1.15 (3H, s) and 0.80 (3H, s);
MS (ES ϩve) m/z 533 (M ϩ H)ϩ (Found: C, 55.7; H, 6.3; S, 5.9.
C25H34F2O8Sؒ0.4H2O requires C, 55.6; H, 6.5; S, 5.9%).
16ꢁ,17ꢁ-[(R)-Butylidenedioxy]-6ꢁ,9ꢁ-difluoro-11ꢂ-hydroxy-21-
[(3R)-2-oxotetrahydrofuran-3-ylsulfanyl]pregna-1,4-diene-3,20-
dione (18aR)
A mixture of sand (2 g), 2aR (100 mg, 0.018 mmol), n-butyr-
aldehyde (0.032 ml, 0.036 mmol) and perchloric acid (11.7 M;
0.062 ml) was stirred vigorously in heptane (10 ml) overnight.
The sand was collected by filtration and washed with heptane.
The sand was then stirred in a mixture of aqueous sodium
bicarbonate solution (50 ml) and ethyl acetate (50 ml). The
organic phase was separated, washed with brine, dried and fil-
tered. The filtrate was evaporated and the residue was triturated
in diethyl ether to give 18aR as a solid (92 mg, 90%): analytical
HPLC tr 11.40 min; mp 219–221 ЊC; νmax (KBr)/cmϪ1 3356,
1768, 1721, 1665, 1625 and 1609; δH (CDCl3) includes 7.12 (1H,
d, J 10, 1-H), 6.44 (1H, s, 4-H), 6.40 (1H, d, J 10, 2-H), 5.48 and
5.29 (1H, 2 m, 6-H), 4.92 (1H, d, J 5, 16-H), 4.67 (1H, t, J 4.5,
OCHO), 4.55–4.30 (3H, m), 4.19 (1H, d, J 18, 21-H), 3.81 (1H,
d, J 18, 21-H), 3.68 (1H, m), 1.53 (3H, s), 0.92 (6H, s and t,
J 7.5, CH2CH3); MS (TSP ϩve) m/z 567 (M ϩ H)ϩ (Found:
C, 61.35; H, 6.4; S, 5.6. C29H36F2O7S requires C, 61.5; H, 6.4; S,
5.7%).
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-16ꢁ,17ꢁ-isopropylidenedioxy-21-
(2-oxotetrahydrofuran-3-ylsulfanyl)pregn-4-ene-3,20-dione (2b)
A
solution of α-mercapto-γ-butyrolactone (5) (213 mg,
1.80 mmol) in anhydrous tetrahydrofuran (2 ml) was added,
dropwise, to a stirring suspension of sodium hydride (60% oil
dispersion; 72 mg, 1.80 mmol) in anhydrous tetrahydrofuran
(1 ml) at 0 ЊC under a nitrogen atmosphere. The resulting solu-
tion was stirred at 0 ЊC for 30 min by which time effervescence
had ceased. A solution of 4b (800 mg, 1.50 mmol) in anhydrous
tetrahydrofuran (10 ml) was added and the reaction mixture
16ꢁ,17ꢁ-[(R)-Butylidenedioxy]-6ꢁ,9ꢁ-difluoro-11ꢂ-hydroxy-21-
(2-oxotetrahydrofuran-3-ylsulfanyl)pregna-1,4-diene-3,20-dione
(18a)
A
solution of α-mercapto-γ-butyrolactone (5) (144 mg,
1.22 mmol) in anhydrous tetrahydrofuran (4 ml) was added
dropwise to a stirring suspension of sodium hydride (60% oil
836
J. Chem. Soc., Perkin Trans. 1, 2002, 831–839

View Article Online
dispersion; 49 mg, 1.22 mmol) in anhydrous tetrahydrofuran
(2 ml) at 0 ЊC under a nitrogen atmosphere. The resulting solu-
tion was stirred at 0 ЊC for 30 min by which time effervescence
had ceased. A solution of 17a (557 mg, 1.02 mmol) in
anhydrous tetrahydrofuran (15 ml) was added and the reaction
mixture was stirred for 18 h at 0–21 ЊC. Further quantities of
sodium hydride (24 mg, 0.61 mmol) and α-mercapto-γ-
butyrolactone (72 mg, 0.61 mmol) were added and the mixture
stirred for another 1 h. The reaction mixture was poured into
water (30 ml) and extracted with ethyl acetate (30 ml × 2). The
combined organic extracts were then washed with saturated
brine (30 ml) and dried. Removal of the solvent under reduced
pressure yielded a yellow residue which was purified by HPLC
(60% MeCN–H2O) to give 18aS (152 mg, 26%): analytical
HPLC tr 11.82 min; mp 221–223 ЊC; νmax (KBr)/cmϪ1 3356,
1766, 1715, 1665 and 1607; δH (CDCl3) includes 7.12 (1H, d,
J 10, 1-H), 6.44 (1H, s, 4-H), 6.38 (1H, d, J 10, 2-H), 5.48 and
5.28 (1H, 2 m, 6-H), 4.93 (1H, d, J 5.5, 16-H), 4.62 (1H, t, J 4.5,
OCHO), 4.55–4.32 (3H, m), 4.05 (1H, d, J 19, 21-H), 3.71 (1H,
d, J 19, 21-H), 3.78 (1H, m), 1.52 (3H, s), 0.95 (3H, s) and 0.92
(3H, t, J 7.5, CH2CH3); MS (TSP ϩve) m/z 567 (M ϩ H)ϩ
(Found: C, 61.0; H, 6.6; S, 5.3. C29H36F2O7Sؒ0.2H2O requires C,
61.1; H, 6.4; S, 5.6%) and 18aR (92 mg, 16%): analytical HPLC
tr 11.40 min, co-elutes with authentic 18aR; NMR spectrum
identical to 18aR prepared above.
18%): analytical HPLC tr 11.66 min; mp 99–102 ЊC; νmax (KBr)/
cmϪ1 1760, 1714 and 1668; δH (CDCl3) includes 6.14 (1H, s,
4-H), 5.37 and 5.18 (1H, 2 m, 6-H), 4.92 (1H, d, J 5, 16-H), 4.69
(1H, t, J 4.5, OCHO), 4.54–4.30 (3H, m), 4.22 (1H, d, J 18,
21-H), 3.80 (1H, d, J 18, 21-H), 3.70 (1H, t, J 4, SCHCO), 1.52
(3H, s), 0.95 (3H, t, J 7.5, CH2CH3) and 0.90 (3H, s); MS (TSP
ϩve) m/z 569 (M ϩ H)ϩ (Found: C, 59.5; H, 6.6; S, 5.4.
C29H38F2O7Sؒ0.8H2O requires C, 59.7; H, 6.85; S, 5.5%).
16ꢁ,17ꢁ-[(R)-Butylidenedioxy]-6ꢁ,9ꢁ-difluoro-11ꢂ-hydroxy-21-
[(3S)-2-oxotetrahydrofuran-3-ylsulfanyl]pregn-4-ene-3,20-dione
(18bS)
Potassium carbonate (238 mg, 1.72 mmol) was added to a solu-
tion of 20b (835 mg, 1.72 mmol) and 9R (310 mg, 1.72 mmol) in
anhydrous dimethylformamide (15 ml). The mixture was stirred
at 20 ЊC under nitrogen for 3 h. Ethyl acetate (100 ml) and 2 M
hydrochloric acid (100 ml) were added and the organic phase
was separated, washed with water (100 ml), brine (100 ml),
dried and evaporated to dryness. The residue was purified by
chromatography, eluting with ethyl acetate–dichloromethane
(1 : 3) and purified further by HPLC (60% MeCN–H2O) to give
the (S) isomer 18bS (358 mg, 37%) as a white crystalline solid:
analytical HPLC tr 11.88 min; spectroscopic data identical to
those reported earlier.
21-Acetylsulfanyl-16ꢁ,17ꢁ-[(R)-butylidenedioxy]-6ꢁ,9ꢁ-di-
fluoro-11ꢂ-hydroxypregn-4-ene-3,20-dione (19b)
16ꢁ,17ꢁ-[(R)-Butylidenedioxy]-6ꢁ,9ꢁ-difluoro-11ꢂ-hydroxy-21-
methylsulfonyloxypregn-4-ene-3,20-dione (17b)
Diisopropyl azodicarboxylate (0.91 ml, 4.62 mmol) was added
to a stirring solution of triphenylphosphine (1.21 g, 4.62 mmol)
in anhydrous tetrahydrofuran (20 ml) at 0 ЊC under a nitrogen
atmosphere. The resulting yellow suspension was stirred at
0–5 ЊC for 0.5 h after which time a solution of 16α,17α-[(R)-
butylidenedioxy]-6α,9α-difluoro-11β,21-dihydroxypregn-4-ene-
3,20-dione (16b) (1.40 g, 3.08 mmol) and thioacetic acid
(0.26 ml, 3.70 mmol) in anhydrous tetrahydrofuran (10 ml) was
added dropwise over 15 min. The reaction mixture was stirred
for a further 0.5 h at 0–5 ЊC and for 18 h at 20 ЊC. The reaction
mixture was poured into 2 M hydrochloric acid (100 ml) and
extracted with ethyl acetate (100 ml). The organic phase was
washed with aqueous sodium bicarbonate solution (100 ml),
water (100 ml), and saturated brine (100 ml) and dried.
Removal of the solvent under reduced pressure yielded a yellow
solid, which was purified by column chromatography eluting
with ethyl acetate–cyclohexane (2 : 3) to give 19b (1.63 g, 100%):
δH (CDCl3) includes 6.16 (1H, s, 4-H), 5.37 and 5.18 (1H, 2 m,
6-H), 4.90 (1H, d, J 5,16-H), 4.68 (1H, t, J 4, OCHO), 4.42 (1H,
m, 11-H), 3.94 (2H, s, 21-H), 2.40 (3H, s, AcS), 1.52 (3H, s),
0.95 (3H, t, J 7, CH2CH3) and 0.90 (3H, s); MS (TSP ϩve)
m/z 527 (M ϩ H)ϩ.
Methanesulfonyl chloride (0.82 ml, 10.65 mmol) was added to
a stirring solution of 16α,17α-[(R)-butylidenedioxy]-6α,9α-
difluoro-11β,21-dihydroxypregn-4-ene-3,20-dione (16b) (1 g,
2.13 mmol) in anhydrous pyridine (12 ml) at 0 ЊC under a nitro-
gen atmosphere. The reaction mixture was stirred for 0.5 h at
0 ЊC and 2.5 h at 21 ЊC and was then poured into ice-cold 1 M
hydrochloric acid (60 ml). The resulting precipitate was
collected by filtration and dried at reduced pressure over
phosphorus pentaoxide. The resulting pale yellow solid was
purified by HPLC (55% MeCN–H2O) to give 17b (730 mg,
63%): δH (CDCl3) includes 6.15 (1H, s, 4-H), 5.37 and 5.18 (1H,
2 m, 6-H), 5.04 (2H, s, 21-H), 4.89 (1H, d, J 5, 16-H), 4.65 (1H,
t, J 4.5, OCHO), 4.41 (1H, m, 11-H), 3.26 (3H, s, MeSO3), 1.52
(3H, s), 0.95 (3H, t, J 7.5, CH2CH3) and 0.94 (3H, s); MS (TSP
ϩve) m/z 547 (M ϩ H)ϩ (Found: C, 56.6; H, 6.4; S, 5.8.
C26H36F2O8Sؒ0.3H2O requires C, 56.6; H, 6.7; S, 5.8%).
16ꢁ,17ꢁ-[(R)-Butylidenedioxy]-6ꢁ,9ꢁ-difluoro-11ꢂ-hydroxy-21-
(2-oxotetrahydrofuran-3-ylsulfanyl)pregn-4-ene-3,20-dione (18b)
A
solution of α-mercapto-γ-butyrolactone (5) (187 mg,
1.58 mmol) in tetrahydrofuran (2 ml) was added dropwise to
a stirring suspension of sodium hydride (60% oil dispersion;
63 mg, 1.58 mmol) in anhydrous tetrahydrofuran (1 ml) at 0 ЊC
under an atmosphere of nitrogen. The resulting solution was
stirred at 0 ЊC for 45 min by which time effervescence had
ceased. A solution of 17b (722 mg, 1.32 mmol) in anhydrous
tetrahydrofuran (10 ml) was added and the reaction mixture
was stirred for a further 1.5 h at 0–21 ЊC. The reaction mixture
was poured into water (30 ml) and extracted with ethyl acetate
(30 ml × 2). The combined organic extracts were then washed
with saturated brine (30 ml) and dried. Removal of the solvent
under reduced pressure yielded a white solid which was purified
by HPLC (60% MeCN–H2O) to yield 18bS (335 mg, 45%):
analytical HPLC tr 11.92 min; mp 159–161 ЊC; νmax (KBr)/cmϪ1
1762, 1715 and 1669; δH (CDCl3) includes 6.14 (1H, s, 4-H),
5.37 and 5.17 (1H, 2 m, 6-H), 4.95 (1H, d, J 5, 16-H), 4.63 (1H,
t, J 4.5, OCHO), 4.55–4.29 (3H, m), 4.08 (1H, d, J 18, 21-H),
3.77 (1H, t, J 4, SCHCO), 3.72 (1H, d, J 18, 21-H), 1.52 (3H,
s), 0.95 (3H, t, J 7, CH2CH3) and 0.92 (3H, s); MS (TSP ϩve)
m/z 569 (M ϩ H)ϩ (Found: C, 60.3; H, 6.9; S, 5.5. C29H38F2O7Sؒ
0.4H2O requires C, 60.5; H, 6.8; S 5.6%) and 18bR (137 mg,
16ꢁ,17ꢁ-[(R)-Butylidenedioxy]-6ꢁ,9ꢁ-difluoro-11ꢂ-hydroxy-21-
mercaptopregn-4-ene-3,20-dione (20b)
Hydrazine hydrate (0.18 ml, 3.08 mmol) was added to a stirring
solution of 21-acetylsulfanyl-16α,17α-[(R)-butylidenedioxy]-
6α,9α-difluoro-11β-hydroxypregn-4-ene-3,20-dione
(19b)
(1.62 g, 3.08 mmol) in anhydrous tetrahydrofuran (25 ml) at
Ϫ15 ЊC under a nitrogen atmosphere. The reaction mixture was
stirred at Ϫ15 to Ϫ10 ЊC for 0.5 h and then at 20 ЊC for 5 h. The
reaction mixture was poured into 2 M hydrochloric acid (75 ml)
and extracted with ethyl acetate (75 ml). The organic phase was
washed with water (75 ml), saturated brine (75 ml) and dried.
Removal of the solvent under reduced pressure yielded 20b
(1.35 g, 91%): δH (CDCl3) includes 6.15 (1H, s, 4-H), 5.37 and
5.18 (1H, 2 m, 6-H), 4.94 (1H, d, J 5, 16-H), 4.65 (1H, t,
J 4, OCHO), 4.40 (1H, m, 11-H), 3.68 (1H, dd, J 16 and 7,
21-H), 3.42 (1H, dd, J 16 and 7, 21-H), 1.52 (3H, s), 0.94
(3H, t, J 7, CH2CH3) and 0.90 (3H, s); MS (TSP ϩve) m/z 485
(M ϩ H)ϩ.
J. Chem. Soc., Perkin Trans. 1, 2002, 831–839
837

View Article Online
16ꢁ,17ꢁ-[(R)-Butylidenedioxy]-6ꢁ,9ꢁ-difluoro-11ꢂ-hydroxy-21-
(2-oxotetrahydrofuran-4-ylsulfanyl)pregn-4-ene-3,20-dione (21b)
washed with water (30 ml × 3) and dried at reduced pressure
over phosphorus pentaoxide to yield 25a (2.658 g, 100%):
mp 185–187 ЊC; νmax (KBr)/cmϪ1 3544, 1731, 1667 and 1633;
δH (DMSO-d6) includes 7.25 (1H, d, J 10, 1-H), 6.30 (1H, d,
J 10, 2-H), 6.11 (1H, s, 4-H), 5.73 and 5.53 (1H, 2 m, 6-H), 5.54
(1H, br s), 5.07 (1H, d, J 16, 21-H ), 4.83 (1H, d, J 16, 21-H),
4.18 (1H, m, 11-H), 3.26 (3H, s, MeSO3), 3.23 (1H, m), 2.40
(2H, q, J 7.5, COCH2CH3), 1.48 (3H, s), 1.00 (3H, t, J 7.5,
COCH2CH3), 0.96 (3H, s) and 0.85 (3H, d, J 7, 16-Me); MS
(TSP ϩve) m/z 545 (M ϩ H)ϩ (Found: C, 57.0; H, 6.3; S, 5.4.
C26H34F2O8Sؒ0.3H2O requires C, 56.8; H, 6.3; S, 5.8%).
A solution of 16α,17α-[(R)-butylidenedioxy]-6α,9α-difluoro-
11β-hydroxy-21-mercaptopregn-4-ene-3,20-dione (20b) (500
mg, 1.03 mmol) and furan-2(5H )-one (10) (0.073 ml, 1.03
mmol) in anhydrous tetrahydrofuran (10 ml) was treated with
triethylamine (0.14 ml, 1.03 mmol) and the mixture was stirred
at 20 ЊC under a nitrogen atmosphere for 48 h. Removal of
the solvent under reduced pressure yielded a cream foam,
which was purified by column chromatography eluting with
ethyl acetate–cyclohexane (3 : 2) to give 21b (413 mg, 71%):
νmax (KBr)/cmϪ1 1779, 1712 and 1668; δH (CDCl3) includes 6.16
(1H, s, 4-H), 5.37 and 5.18 (1H, 2 m, 6-H), 4.91 (1H, d, J 5,
16-H), 4.70 (1H, t, J 4, OCHO), 4.62 (1H, dd, J 9 and 7), 4.40
(1H, m, 11-H), 4.22 (1H, m), 3.82 (1H, m), 3.63 and 3.60 (1H,
2 d, J 15), 3.43 and 3.39 (1H, 2 d, J 16, 21-H), 2.95 (1H, dd, J 18
and 8), 1.52 (3H, s), 0.94 (3H, t, J 7, CH2CH3) and 0.91 (3H, s);
MS (TSP ϩve) m/z 569 (M ϩ H)ϩ (Found: C, 62.4; H, 7.4; S,
5.0. C29H38F2O7Sؒ0.3C6H12 requires C, 62.3; H, 7.1; S 5.4%).
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-16ꢁ-methyl-21-(2-oxotetrahydro-
furan-3-ylsulfanyl)-17ꢁ-propionyloxypregna-1,4-diene-3,20-
dione (26a)
A solution of α-mercapto-γ-butyrolactone (5) (220 mg, 1.84
mmol) in anhydrous tetrahydrofuran (10 ml) was added to
a stirring suspension of sodium hydride (60% oil dispersion;
74 mg, 1.84 mmol) in anhydrous tetrahydrofuran (2 ml) at 0 ЊC
under a nitrogen atmosphere. The resulting solution was stirred
at 0 ЊC for 30 min by which time effervescence had ceased. A
solution of 25a (1 g, 1.84 mmol) in anhydrous tetrahydrofuran
(20 ml) was added and the reaction mixture was stirred for
16 h at 0–21 ЊC. Further quantities of sodium hydride (37 mg,
0.92 mmol) and α-mercapto-γ-butyrolactone (110 mg, 0.92
mmol) were added and the mixture stirred for another 6 h. The
reaction mixture was poured into water (30 ml) and extracted
with ethyl acetate (30 ml × 4). The combined organic extracts
were then washed with saturated brine (20 ml) and dried.
Removal of the solvent under reduced pressure yielded a pale
yellow residue which was purified by HPLC (50% MeCN–H2O)
to give 26a (177 mg, 17%): νmax (KBr)/cmϪ1 3484, 1761, 1731,
1669 and 1629; δH (CDCl3) includes 7.14 (1H, d, J 10, 1-H), 6.44
(1H, s, 4-H), 6.38 (1H, d, J 10, 2-H), 5.49 and 5.30 (1H, 2 m,
6-H), 4.53–4.28 (3H, m), 4.00–3.75 (3H, m), 3.60–3.30 (2H,
m), 2.43 (1H, q, J 7.5, COCH2CH3), 2.40 (1H, q, J 7.5, COCH2-
CH3), 1.53 (3H, s), 1.14 (3H, t, J 7.5, COCH2CH3), 1.06 and
1.05 (3H, 2 s), 0.94 (3H, d, J 7.5, 16-Me); MS (ES ϩve) m/z 567
(M ϩ H)ϩ (Found: C, 61.6; H, 6.3; S, 5.75. C29H36F2O7S
requires C, 61.5; H, 6.4; S, 5.7%).
6ꢁ,9ꢁ-Difluoro-11ꢂ,17,21-trihydroxy-16ꢁ-methylpregna-1,4-
diene-3,20-dione, cyclic 17,21-(ethyl orthopropionate) (23a)
Toluene (140 ml) was added to a solution of flumethasone (22a)
(10.26 g, 25 mmol) in dry dimethylformamide (14 ml) where-
upon some precipitation occurred to give a cream suspension.
Toluene-p-sulfonic acid (50 mg) was then added followed by
triethyl orthopropionate (10 ml, 50 mmol) and the mixture was
stirred at 20 ЊC. After 2 h the suspension was partitioned
between water (250 ml) and ethyl acetate (350 ml) and the solid
was collected by filtration and washed with water (20 ml)
and ethyl acetate (20 ml). The solid was dried over phosphorus
pentaoxide under reduced pressure to give the orthoester
23a15,16 (9.41 g, 76%) as a white solid: δH (DMSO-d6) 7.28 (1H,
d, J 10, 1-H), 6.29 (1H, dd, J 10, 2-H), 6.10 (1H, s, 4-H), 5.55
and 5.75 (1H, 2 d, 6-H), 5.40 (1H, d, J 4, OH), 4.20 (1H, m,
11-H), 4.09 (1H, d, J 16, 21-H), 3.95 (1H, d, J 16, 21-H), 3.45
(2H, q, J 7, OCH2CH3), 1.48 (3H, s), 1.03 (3H, t, J 7), 0.90 (3H,
t, J 7), 0.87 (3H, s), 0.86 (3H, d, J 7, 16-H); MS (TSP ϩve)
m/z 495 (M ϩ H)ϩ. Additional 23a (1.73 g, 14%) was obtained
by evaporation of the filtrate and trituration with ethyl acetate.
6ꢁ,9ꢁ-Difluoro-11ꢂ,21-dihydroxy-16ꢁ-methyl-17ꢁ-propionyl-
oxypregn-4-ene-3,20-dione (24b)
6ꢁ,9ꢁ-Difluoro-11ꢂ,21-dihydroxy-16ꢁ-methyl-17ꢁ-propionyl-
oxypregna-1,4-diene-4,20-dione (24a)
A stirring solution of 6α,9α-difluoro-11β,21-dihydroxy-16α-
A suspension of 23a (11.1 g, 22.4 mmol) in methanol (400 ml)
was diluted with 5% aqueous acetic acid (80 ml) and the
mixture was heated to reflux for 30 min. The solution was con-
centrated under reduced pressure to a volume of about 100 ml
by which time the product started to crystallise. Water was
added (100 ml) and the solid was collected by filtration, washed
well with water (50 × 3 ml) and dried in vacuo over phosphorus
pentaoxide to give 24a15,16 (10.09 g, 96%) as a white solid: νmax
(KBr)/cmϪ1 3424, 1729, 1715, 1668 and 1631; δH (DMSO-d6)
7.25 (1H, d, J 10, 1-H), 6.28 (1H, d, J 10, 2-H), 6.10 (1H, s,
4-H), 5.70 and 5.50 (1H, 2 m, 6-H), 5.47 (1H, m), 5.07 (1H, t,
J 5.5, 21-OH), 4.20 (1H, m), 4.10 (2H, m), 3.20 (1H, m, 16-H),
2.36 (2H, q, J 7, COCH2CH3), 1.50 (3H, s), 1.00 (3H, t, J 7,
COCH2CH3), 0.91 (3H, s) and 0.83 (3H, d, J 7,16-Me); MS
(TSP ϩve) m/z 467 (M ϩ H)ϩ.
methyl-17α-propionyloxypregna-1,4-diene-3,20-dione
(24a)
(3 g, 6.43 mmol) was hydrogenated over tris(triphenylphos-
phine)rhodium() chloride (0.6 g, 0.64 mmol) in ethanol
(100 ml) at 1 atmosphere for 60 h. The solvent was removed
under reduced pressure and the residue was purified by chrom-
atography eluting with ethyl acetate–cyclohexane (3 : 1) to give
24b as a pale yellow solid (2.57 g, 85%): analytical HPLC tr 7.06
min; νmax (KBr)/cmϪ1 3428, 1730, 1717 and 1669; δH (DMSO-d6)
includes 5.82 (1H, s, 4-H), 5.60 and 5.42 (1H, 2 m, 6-H), 5.20
(1H, br s), 5.07 (1H, t, J 6), 4.25–3.95 (3H, m), 3.24 (1H, m),
2.39 (2H, q, J 7.5, COCH2CH3), 1.48 (3H, s), 1.03 (3H, t, J 7.5
COCH2CH3), 0.90 (3H, s) and 0.84 (3H, d, J 7, 16-Me); MS
(TSP ϩve) m/z 469 (M ϩ H)ϩ; HRMS (ESI ϩve) found
469.2401 (M ϩ H)ϩ. C25H35F2O6 requires 469.2417.
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-21-methylsulfonyloxy-16ꢁ-methyl-
17ꢁ-propionyloxypregna-1,4-diene-3,20-dione (25a)
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-21-methylsulfonyloxy-16ꢁ-methyl-
17ꢁ-propionyloxypregn-4-ene-3,20-dione (25b)
Methanesulfonyl chloride (1.66 ml, 21 mmol) was added
dropwise to a stirring solution of 6α,9α-difluoro-11β,21-di-
hydroxy-16α-methyl-17α-propionyloxypregna-1,4-diene-3,20-
dione (24a) (2 g, 4.29 mmol) in anhydrous pyridine (20 ml)
under a nitrogen atmosphere. The reaction mixture was stirred
for 2 h and was then poured into ice-cold 2 M hydrochloric acid
(40 ml). The resulting precipitate was collected by filtration,
Methanesulfonyl chloride (1.66 ml, 21 mmol) was added drop-
wise over 2 min to a stirring solution of 24b (2g, 4.27 mmol) in
anhydrous pyridine (20 ml) under a nitrogen atmosphere. The
reaction mixture was stirred for 2 h and was then poured into
ice-cold 2 M hydrochloric acid (40 ml). The resulting precipitate
was collected by filtration, washed with water (30 ml × 3) and
dried at reduced pressure over phosphorus pentaoxide to yield
838
J. Chem. Soc., Perkin Trans. 1, 2002, 831–839

View Article Online
25b (2.390 g, 100%): mp 157–159 ЊC (decomp.); νmax (KBr)/cmϪ1
3532, 1731 and 1668; δH (DMSO-d6) includes 5.81 (1H, s, 4-H),
5.60 and 5.41 (1H, 2 m, 6-H), 5.24 (1H, br s), 5.05 (1H, d, J 16,
21-H), 4.82 (1H, d, J 16, 21-H), 4.16 (1H, m, 11-H), 3.26 (3H, s,
MeSO3), 2.43 (2H, q, J 7.5, COCH2CH3), 1.48 (3H, s), 1.02
(3H, t, J 7.5, COCH2CH3), 0.94 (3H, s) and 0.85 (3H, d, J 7, 16-
Me); MS (TSP ϩve) m/z 547 (M ϩ H)ϩ (Found: C, 56.1; H, 6.5;
S, 5.7. C26H36F2O8Sؒ0.5H2O requires C, 56.4; H, 6.7; S, 5.8%).
dione sodium salt (3aR) as a white solid after trituration with
ethyl acetate and then with diethyl ether: δH (DMSO-d6)
includes 7.34 (1H, d, J 10, 1-H), 6.27 (1H, dd, J 10 and 2, 2-H),
6.18 (1H, s), 6.10 (1H, s), 5.73 and 5.53 (1H, 2 m, 6-H), 4.89
(1H, br s), 4.21 (1H, br), 4.03 (1H, d, J 18, 21-H), 3.67 (1H, dd,
J 18, 21-H), 1.50 (3H, s), 1.30 (3H, s), 1.07 (3H, s), and 0.80
(3H, s); MS (ES ϩve) m/z 571 (M ϩ H)ϩ (Found: C, 53.25;
H, 6.3; S, 4.9. C28H35F2NaO8Sؒ2H2O requires C, 53.5; H, 6.25;
S, 5.1%) and 21-[(1S)-1-carboxy-3-hydroxypropyl)sulfanyl]-6α,
9α-difluoro-11β-hydroxy-16α,17α-isopropylidenedioxypregna-
1,4-diene-3,20-dione sodium salt (3aS): δH (DMSO-d6) includes
7.36 (1H, d, J 10, 1-H), 6.37 (1H, br), 6.26 (1H, d, J 10, 2-H),
6.10 (1H, s, 4-H), 5.73 and 5.53 (1H, 2 m, 6-H), 4.89 (1H, br s),
4.21 (1H, br), 3.94 (1H, d, J 18, 21-H), 3.75 (1H, d, J 18, 21-H),
1.50 (3H, s), 1.30 (3H, s), 1.03 (3H, s), and 0.82 (3H, s); MS
(ES ϩve) m/z 571 (M ϩ H)ϩ (Found: C, 53.9; H, 6.2; S, 4.8.
C28H35F2NaO8Sؒ1.6H2O requires C, 54.1; H, 6.2; S, 5.15%).
The configurations of 3aR and 3aS were established by re-
lactonisation of the sodium salts to 2aR and 2aS respectively
under acid conditions.
6ꢁ,9ꢁ-Difluoro-11ꢂ-hydroxy-16ꢁ-methyl-21-(2-oxotetrahydro-
furan-3-ylsulfanyl)-17ꢁ-propionyloxypregn-4-ene-3,20-dione
(26b)
A solution of α-mercapto-γ-butyrolactone (5) (220 mg, 1.84
mmol) in anhydrous tetrahydrofuran (10 ml) was added drop-
wise to a stirring suspension of sodium hydride (60% oil dis-
persion; 74 mg, 1.84 mmol) in anhydrous tetrahydrofuran
(2 ml) at 0 ЊC under a nitrogen atmosphere. The resulting solu-
tion was stirred at 0 ЊC for 30 min by which time effervescence
had ceased. A solution of 25b (1 g, 1.84 mmol) in anhydrous
tetrahydrofuran (20 ml) was added and the reaction mixture
was stirred for 16 h at 0–21 ЊC. Further quantities of sodium
hydride (37 mg, 0.92 mmol) and 5 (110 mg, 0.92 mmol) were
added and the mixture stirred for another 6 h. The reaction
mixture was poured into water (30 ml) and extracted with ethyl
acetate (30 ml × 4). The combined organic extracts were then
washed with saturated brine (20 ml) and dried. Removal of the
solvent under reduced pressure yielded a yellow residue which
was purified by HPLC (55% MeCN–H2O) to give 26b (455 mg,
43%): mp 171–175 ЊC; νmax (KBr)/cmϪ1 3505, 1757, 1732 and
1669; δH (CDCl3) includes 6.14 (1H, s, 4-H), 5.37 and 5.18 (1H,
2 m, 6-H), 4.52–4.26 (3H, m), 4.03–3.74 (2H, m), 3.59–3.32
(2H, m), 1.52 (3H, s), 1.17 (3H, t, J 7.5, COCH2CH3), 1.03
and 1.02 (3H, 2 s) and 0.94 (3H, d, J 7, 16-Me); MS (ES ϩve)
m/z 569 (M ϩ H)ϩ (Found: C, 61.2; H, 7.0; S, 5.5. C29H38F2O7S
requires C, 61.25; H, 6.7; S, 5.6%).
Acknowledgements
We thank Mrs Y. E. Solanke, Mrs S. E. Walton and Mr
D. R. Mobbs for conducting the biological assays.
References
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Sodium hydroxide solution (0.1 M, 4.52 ml) was added to
a solution of 11a (250 mg, 0.452 mmol) in methanol (15 ml)
and the mixture was stirred overnight. The solvent was removed
under reduced pressure and the residue was dissolved in
tetrahydrofuran (10 ml) and water (2 ml) and purified by
HPLC (80% MeCN–H2O) to give the corresponding hydroxy
carboxylic acid sodium salt (115 mg, 43%) as a beige solid:
analytical HPLC tr 8.22 min; νmax (KBr)/cmϪ1 1715, 1669, 1634,
1576 and 1383; δH (DMSO-d6) includes 7.27 (1H, d, J 10, 1-H),
6.28 (1H, dd, J 10 and 1, 2-H), 6.10 (1H, s), 5.74 and 5.55 (1H,
2 m, 6-H), 4.89 (1H, br s), 4.19 (1H, d, J 10), 1.50 and 1.49 (3H,
2 s), 1.34 (3H, s), 1.09 and 1.07 (3H, 2 s), 0.88 and 0.82 (3H, 2 s);
MS (ES ϩve) m/z 571 (M ϩ H)ϩ (Found: C, 51.4; H, 6.2; N, 1.1.
C28H35F2NaO8Sؒ3.4H2Oؒ0.6C2H3N requires C, 51.7; H, 6.5;
N, 1.2%).
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Metabolite of 2a
A diastereoisomeric mixture of 3a3 was separated by HPLC
(35% MeCN–H2O containing 0.1% formic acid) to give 21-
[(1R)-1-carboxy-3-hydroxypropyl)sulfanyl]-6α,9α-difluoro-11β-
hydroxy-16α,17α-isopropylidenedioxypregna-1,4-diene-3,20-
J. Chem. Soc., Perkin Trans. 1, 2002, 831–839
839