A convenient synthesis of 5β-cholestan-26-oic and 5β-cholestan-26,27-dioic acids

Article abstract of DOI:10.1016/S0039-128X(99)00099-9

A new method for the preparation of 5β-cholestan-26-oic acids 7 and their analogs is described. The key steps in the synthesis are: iodination of bis- and tris-formyloxy-5β-cholan-24-ols 3; nucleophilic substitution of iodides 4 with diethyl sodiomalonate; complete alkaline hydrolysis of esters 5; and subsequent decarboxylation of geminal diacids 6 in DMSO. Copyright (C) 2000 Elsevier Science Inc.

Full text of DOI:10.1016/S0039-128X(99)00099-9

Steroids 65 (2000) 143–147
A convenient synthesis of 5␤-cholestan-26-oic and
5
␤-cholestan-26,27-dioic acids
a
a
a
b
a,
I. Starchenkov , P. Trapencieris , V. Kauss , G. Jas , I. Kalvinsh *
a
Latvian Institute of Organic Synthesis, Aizkraukles iela 21, Riga, LV-1006, Latvia
b
AnalytiCon AG, Potsdam, Germany
Received 10 December 1998; received in revised form 21 September 1999; accepted 24 September 1999
Abstract
A new method for the preparation of 5␤-cholestan-26-oic acids 7 and their analogs is described. The key steps in the synthesis are: iodination
of bis- and tris-formyloxy-5␤-cholan-24-ols 3; nucleophilic substitution of iodides 4 with diethyl sodiomalonate; complete alkaline hydrolysis of
esters 5; and subsequent decarboxylation of geminal diacids 6 in DMSO. © 2000 Elsevier Science Inc. All rights reserved.
Keywords: Cholic acid; Chenodeoxycholic acid; 5␤-Cholestan-26-oic acids; 5␤-Cholestan-26; 27-Dioic acids
1
. Introduction
diformyloxy-5␤-cholestan-24-oic- or 3␣,7␣,12␣-triformy-
loxy-5␤-cholestan-24-oic acid chloride. The use of diazo-
ethane decreases a value of method in a large-scale
synthesis of bile acid derivatives. More recently, Fujimoto
et al. [5] enlarged the side chain by Wittig reaction of cholic
aldehyde with phosphonium ylide. Japanese researchers
have used some unstable intermediates in their way to target
compounds. To our knowledge, cholestan-26,27-dioic acids
6a–c are not synthesized yet. However, Une and co-workers
[6] have prepared unprotected 3␣,7␣,12␣-trihydroxy-5␤-
cholestan-26,27-dioic acid diethylester and hydrolyzed it by
usual procedures only to monocarboxylic acid. Researchers
have also used crude 24-mono tosylate. Haslewood group
[7] had used diethyl sodiomalonate for the synthesis of
3␣,7␣,12␣-trihydroxy-5␤-cholestan-26,27-dioic acid dieth-
ylester no attempts to prepare free acids were made. Par-
mentier et al. have exploited malonic ester synthesis [8], but
have used more complicated 2-carbethoxy-␥-butyrolactone
for new C-C bond formation.
Side chain degradation of 3␣,7␣,12␣-trihydroxy-5␤-
cholestan-26-oic acid (7b) in liver proceeds via a mecha-
nism similar to ␤-oxidation of fatty acids to give the pri-
mary bile acid-cholic acid (1b) [1]. 3␣,7␣-Dihydroxy-5␤-
cholestan-26-oic acid (7a) has been postulated [2] as an
intermediate in the biosynthetic pathway from cholesterol to
chenodeoxycholic acid (1a). To investigate biosynthetic
pathways of bile acid formation, it is important to obtain
different mono (7a, 7b) and dicarboxylic (6a–c) acids.
Several methods are known for the synthesis of 5␤-choles-
tan-26-oic acids [2–4]. Thus, Bridgwater [3] used Kolbe
electrolytic cross-coupling reaction in conversion of cholic
acid into optically pure 3␣,7␣,12␣-trihydroxy-5␤-choles-
tanoic acids. This method used half-esters of methylsuccinic
acid and yielded complex mixtures of products. Difficult
chromatographic separation was required to isolate pure
acids. Cholestanoic acids isomeric at C-25 have been par-
tially synthesized by an improved [4] Kolbe reaction. Te-
dious synthesis of starting half-esters gave only 3 to 5% of
crystalline target products. A more efficient method used
Arndt–Eistert rearrangement of the diazoketone [2]. The
latter was obtained by the action of diazoethane on 3␣,7␣-
This paper describes a simple and general high-yield
procedure for the synthesis of title bile acid derivatives.
2. Experimental
Starting materials cholic and chenodeoxycholic acids
were obtained from Sigma. Other reagents and solvents
were obtained from Aldrich and Acros. Melting points were
*
Corresponding author. Tel.: ϩ371-755-3233; fax: ϩ371-754-1644.
E-mail address: kalvins@osi.lanet.lv (I. Kalvinsh)
0
039-128X/00/$ – see front matter © 2000 Elsevier Science Inc. All rights reserved.
PII: S0039-128X(99)00099-9

1
44
I. Starchenkov et al. / Steroids 65 (2000) 143–147
determined on a Fisher’s micro melting point apparatus and
are uncorrected. H NMR spectra were recorded on Varian
2.3. 3␣,7␣-Bis(formyloxy)-24-iodo-5␤-cholane (4a)
1
Mercury-200BB (200 MHz) or Bruker WH 90/DS (90
MHz) spectrometers with tetramethylsilane as an internal
standard. C NMR spectra were recorded on Varian Mer-
A flask fitted with a rubber septum, a magnetic stirring
bar, and an argon inlet/outlet was charged with 3a (3.29 g,
7.57 mmol), triphenylphosphine (2.62 g, 10 mmol), imida-
zole (0.68 g, 10 mmol), and the anhydrous THF (60 ml). To
the stirred, ice-cooled solution was added iodine (2.53 g, 10
mmol) solution in THF (15 ml) dropwise via a syringe over
50 min. The resulting mixture was stirred for 4 h at room
temperature. The reaction mixture was quenched with 10%
aqueous Na S O (20 ml) and THF was removed under
1
3
cury-200BB (50.5 MHz) spectrometer with CD OD as a
3
reference compound. Elemental analyses were performed
on Carlo Erba apparatus. Optical rotations were determined
on a Perkin Elmer 141 spectropolarimeter. HPTLC was
carried out on pre-coated silicagel 60 F254 plates (Merck)
with a 5% solution of phosphomolybdic acid in methanol as
the visualization reagent. Silica gel (Merck, 230–400 mesh)
was used for flash chromatography eluting on 2 to 6 bar
2
2 3
reduced pressure. Extractive work-up (diethyl ether) gave a
crude product, which was chromatographed on a silica gel
column (petroleum ether/ethyl acetate, 7:1) to give 4a as a
¨
BUCHI 681 pump. THF was freshly distilled from a purple
solution of sodium and benzophenone.
white solid (3.87 g, 94%). HPTLC (petroleum ether/ethyl
1
acetate; 6:1), Rf ϭ 0.42. H NMR (CDCl ): ␦ 0.64 (s, 3H,
3
2
.1. 3␣,7␣-Bis(formyloxy)-5␤-cholan-24-ol (3a)
18-Me), 0.90 (d, 3H, 21-Me, overlapped with 19-Me), 0.93
(
s, 3H, 19-Me), 3.13 (t, 2H, J ϭ 6.1 Hz, 24-CH ), 4.70 (m,
2
A three-necked, round-bottomed flask fitted with a rub-
1H, 3␤-H), 5.00 (s, 1H, 7␤-H), 8.00 (s, 1H, 3␣-CHO), 8.06
(s, 1H, 7␣-CHO)ppm. Analysis calculated for C H O I: C
57.35, H 7.59. Found: C 57.48; H 7.65.
ber septum, a magnetic stirring bar, and an argon inlet/outlet
was charged with 2a [9,10] (4.38 g, 9.76 mmol) and anhy-
drous THF (100 ml). To the stirred, ice-cooled solution was
2
6 41 4
added 1.0 M BH /THF complex in THF (17.5 ml) dropwise
2.4. 3␣,7␣,12␣-Tris(formyloxy)-24-iodo-5␤-cholane (4b)
3
via a syringe over a period of 20 min. The resulting mixture
was stirred for 20 h at room temperature. The reaction
mixture was quenched with 0.5 N HCl (30 ml), THF was
removed under reduced pressure and the residue was ex-
tracted with diethyl ether (3 ϫ 40 ml). The combined
organic layers were washed with aqueous solution of
NaHCO (3 ϫ 50 ml) and brine (50 ml) and dried (Na SO ).
Exploration of the above iodination procedure by the
treatment of 3b (6.47 g, 13.51 mmol) gave after work-up
and flash chromatography (petroleum ether/ethyl acetate;
6:1) iodide 4b (7.43 g, 93%) as a white solid. HPTLC
1
(petroleum ether/ethyl acetate; 4:1), Rf ϭ 0.40. H NMR
(CDCl ): ␦ 0.74 (s, 3H, 18-Me), 0.83 (d, 3H, J ϭ 5.7 Hz,
3
2
4
3
Evaporation under reduced pressure provided an oil. Puri-
fication of the crude product by flash chromatography (pe-
troleum ether/ethyl acetate, 3:1) afforded 3a (3.30 g, 77%)
21-Me), 0.93 (s, 3H, 19-Me), 3.14 (t, 2H, J ϭ 6.3 Hz,
24-CH ), 4.70 (m, 1H, 3␤-H), 5.07 (m, 1H, 7␤-H), 5.26 (m,
2
1H, 12␤-H), 8.01 (s, 1H, 3␣-CHO), 8.10 (s, 1H, 7␣-CHO),
8.16 (s, 1H, 12␣-CHO)ppm. Analysis calculated for
C H O I: C 55.11; H 7.02. Found: C 55.29; H 7.18.
as a white amorphous solid. HPTLC (petroleum ether/ethyl
1
acetate; 2:1), Rf ϭ 0.32. H NMR (CDCl ): ␦ 0.63 (s, 3H,
3
27 41 6
1
8-Me), 0.91 (d, 3H, 21-Me, overlapped with 19-Me), 0.93
(
5
7
s, 3H, 19-Me), 3.59 (m, 2H, 24-CH ), 4.71 (m, 1H, 3␤-H),
2.5. Ethyl 3␣,7␣-bis(formyloxy)-25-ethoxycarbonyl-5␤-
cholestan-26-oate (5a)
2
.00 (m, 1H, 7␤-H), 8.00 (s, 1H, 3␣-CHO), 8.06 (s, 1H,
␣-CHO)ppm. Analysis calculated for C H O : C 71.85;
2
6 42 5
H 9.74. Found: C 71.70; H 9.68. The combined alkaline
washings containing sodium salt of 2a were neutralized
with 2 N HCl and unreacted acid 2a (0.8 g) was collected by
filtration.
The solution prepared from diethyl methyl malonate
(1.72 ml, 10 mmol) and NaH (0.48g, 10 mmol) (60% in oil)
in anhydrous THF (5 ml) was evaporated to dryness. The
residue was added to a vigorously stirred solution of 4a
(3.85 g, 7.07 mmol) in anhydrous DMSO (10 ml). The
2
.2. 3␣,7␣,12␣-Tris(formyloxy)-5␤-cholan-24-ol (3b)
mixture was stirred for 3 h at room temperature, then diluted
with water (80 ml). Extractive work-up (methylene chlo-
ride) gave a crude product, which was chromatographed on
a silica gel column (petroleum ether/ethyl acetate, 6:1) to
Exploration of the above reduction procedure by the
treatment of 2b (2.16 g, 4.38 mmol) gave after work-up and
flash chromatography (petroleum ether/ethyl acetate; 3:1)
alcohol 3b (0.91 g, 43%) as a white solid. HPTLC (petro-
give 5a as a white solid (3.13 g, 75%). HPTLC (petroleum
1
ether/ethyl acetate; 4:1), Rf ϭ 0.47. H NMR (CDCl ): ␦
3
1
leum ether/ethyl acetate; 1:1), Rf ϭ 0.55. H NMR
0.63 (s, 3H, 18-Me), 0.87 (d, 3H, J ϭ 6.0 Hz, 21-Me), 0.93
(s, 3H, 19-Me), 1.22 (t, 6H, J ϭ 7.0 Hz, OCH CH ), 1.38 (s,
(CDCl ): ␦ 0.75 (s, 3H, 18-Me), 0.85 (d, J ϭ 7.0 Hz, 21-H),
3
2
3
0
.88 (s, 3H, 19-Me), 3.60 (t, 2H, J ϭ 7.1 Hz, 24-CH ), 4.72
3H, 25-Me), 4.17 (q, 4H, J ϭ 7.0 Hz, OCH CH ), 4.73 (m,
2
2 3
(
8
1
m, 1H, 3␤-H), 5.09 (s, 1H, 7␤-H), 5.29 (s, 1H, 12␤-H),
.02 (s, 1H, 3␣-CHO), 8.11 (s, 1H, 7␣-CHO), 8.16 (s, 1H,
2␣-CHO)ppm.
1H, 3␤-H), 5.02 (s, 1H, 7␤-H), 8.00 (s, 1H, 3␣-CHO), 8.06
(s, 1H, 7␣-CHO)ppm. Analysis calculated for C H O : C
69.12; H 9.21. Found: C 69.21; H 9.28.
3
4 54 8

I. Starchenkov et al. / Steroids 65 (2000) 143–147
145
2
2
.6. Diethyl 3␣,7␣,12␣-tris(formyloxy)-5␤-cholestan-
6,27-dioate (5b)
ml). Mixture was further stirred for 7 h, then pH ϭ 1 was
adjusted with 1 N HCl. The precipitate was washed with
water and chromatographed on a silica gel column (ethyl
acetate/ethanol/acetic acid, 4:1:0.1) to give after crystalliza-
tion from ethyl acetate 6b (1.57 g, 78%) as a white solid
with m.p. 187–188°C. HPTLC (ethyl acetate/ethanol/acetic
Diethyl malonate was converted to 5b by the method
described for the preparation of 5a. Thus, iodide 4b (3.22
g, 5.47 mmol) gave after column chromatography on
silica gel (petroleum ether/ethyl acetate; 3:1) diester 5b
acid, 5:1:0.1), Rf ϭ 0.18; (chloroform/methanol, 2:1), Rf ϭ
1
(
2.70 g, 83%) as a white solid. HPTLC (petroleum ether/
0.14. H NMR (DMSO-D ): ␦ 0.65 (s, 3H, 18-Me), 0.87 (s,
6
1
ethyl acetate; 2:1), Rf ϭ 0.38. H NMR (CDCl ): ␦ 0.67
3H, 19-Me), 0.95 (d, 3H, J ϭ 5.6 Hz, 21-Me), 3.24 (t, 1H,
J ϭ 7.2 Hz, 25-H), 3.36 (m, 1H, 3␤-H), 3.64 (m, 1H, 7␤-H),
3
(
s, 3H, 18-Me), 0.74 (d, 3H, J ϭ 5.6 Hz, 21-Me), 0.86 (s,
1
3
3
1
H, 19-Me), 1.20 (t, 6H, J ϭ 7.0 Hz, OCH CH ), 3.34 (t,
3.83 (m, 1H, 12␤-H)ppm. C NMR (CDCl ): ␦ 174.3, 74.9,
2
3
3
H, J ϭ 7.0 Hz, 25-H), 4.16 (q, 4H, J ϭ 7.0 Hz,
73.7, 70.0, 53.9, 49.1, 48.3, 44.0, 43.8, 41.8, 41.3, 37.9,
OCH CH ), 4.71 (m, 1H, 3␤-H), 5.06 (m, 1H, 7␤-H),
37.6, 37.4, 36.8, 36.7, 32.0, 31.4, 30.4, 29.7, 28.7, 25.9,
2
3
0
5
7
.28 (s, 1H, 12␤-H), 8.01 (s, 1H, 3␣-CHO), 8.10 (s, 1H,
␣-CHO), 8.15 (s, 1H, 12␣-CHO). Analysis calculated
25.1, 24.1, 18.9, 13.9ppm. [␣] : ϩ34.4 (c ϭ 1, MeOH).
D
Analysis calculated for C H O : C 67.47; H 9.23. Found:
2
7 44 7
for C H O : C 65.78; H 8.44. Found: C 65.92; H 8.49.
C 67.09; H 9.36.
3
4
52 10
2
.7. Ethyl 3␣,7␣,12␣-tris(formyloxy)-25-carboxy-5␤-
2
.10. 3␣,7␣,12␣-Trihydroxy-25-carboxy-5␤-cholestan-26-
cholestan-26-oate (5c)
oic acid (6c)
Under the above alkylation procedure, diethyl methyl
malonate was converted to 5c by the method described
for the preparation of 5a. Thus, iodide 4b (7.40 g, 12.57
mmol) gave after work-up and flash chromatography 5c
Exploration of the above hydrolysis procedure by refluxing
a solution of 5c (7.30 g, 11.50 mmol) gave after work-up, flash
chromatography, and crystallization from ethyl acetate 6c
(4.97 g, 87%) as a white solid with m.p. 198–199°C. HPTLC
(
7.43 g, 93%) as a white solid. HPTLC (petroleum ether/
(
ethyl acetate/ethanol/acetic acid, 5:1:0.1), Rf ϭ 0.26; (chlo-
1
ethyl acetate, 2:1), Rf ϭ 0.40. H NMR (CDCl ): ␦ 0.74
3
1
roform/methanol, 2:1), Rf ϭ 0.39. H NMR (DMSO-D ): ␦
6
(
1
s, 3H, 18-Me), 0.80 (d, 3H, 21-Me, overlapped with
8-Me), 0.93 (s, 3H, 19-Me), 1.22 (t, 6H, J ϭ 7.2 Hz,
OCH CH ), 1.37 (s, 3H, 25-Me), 4.16 (q, 4H, J ϭ 7.2 Hz,
0.65 (s, 3H, 18-Me); 0.86 (s, 3H, 19-Me); 0.95 (d, 3H, J ϭ 6.2
Hz, 21-Me), 1.36 (s, 3H, 28-Me), 3.61 (m, 1H, 3␤-H), 3.75 (s,
2
3
13
1
7
4
2
H, 7␤-H), 3.89 (s, 1H, 12␤-H). C NMR (CD OD): ␦ 174.4,
3
OCH CH ), 4.71 (m, 1H, 3␤-H), 5.07 (m, 1H, 7␤-H),
2
3
4.1, 72.9, 69.1, 50.3, 50.1, 49.9, 48.2, 47.7, 47.5, 43.2, 43.0,
1.0, 40.5, 37.5, 37.0, 36.5, 35.9, 31.2, 30.2, 29.5, 28.8, 27.9,
5
7
.26 (m, 1H, 12␤-H), 8.01 (s, 1H, 3␣-CHO), 8.09 (s, 1H,
␣-CHO), 8.14 (s, 1H, 12␣-CHO)ppm. Analysis calcu-
0
4.2, 23.2, 18.0, 13.0ppm. [␣] : ϩ32.5 (c ϭ 1, MeOH).
D
lated for C H O : C 66.22; H 8.57. Found: C 66.37; H 8.66.
35 54 10
Analysis calculated for C H O : C 67.71; H 9.74. Found: C
28 48 7
67.50; H 9.55.
2
.8. 3␣,7␣-Dihydroxy-25-carboxy-5␤-cholestan-26-oic
acid (6a)
2
.11. 3␣,7␣-Dihydroxy-5␤-cholestan-26-oic acid (7a)
A solution of 6a (1.60 g, 3.33 mmol) in DMSO (12 ml)
A solution of diester 5a (2.15 g, 3.64 mmol) in ethanol
20 ml) containing KOH (2.0 g) was stirred for 3 h at reflux
(
temperature. The solvent was removed under reduced pres-
sure, and the residue was stirred and acidified with 1 N HCl.
The precipitated solid was filtered, washed with water, and
chromatographed on a silica gel column (ethyl acetate/
ethanol/acetic acid, 7:1:0.1) to give after recrystallization
containing LiCl (0.50 g) and water (0.10 g) was stirred
for 1 h at 160°C. Main part of DMSO and water was
removed under reduced pressure and obtained semi-solid
was washed with water (2 ϫ 6 ml). The residue was
purified by flash chromatography on a silica gel column
(petroleum ether/ethyl acetate/acetic acid, 5:2:0.05) and
after recrystallization from ethyl acetate gave 7a (883
mg, 61%) as a white solid with m.p. 75–83°C. HPTLC
from ethyl acetate 6a (1.66 g, 95%) as a white solid. HPTLC
1
(
ethyl acetate/ethanol/acetic acid, 7:1:0.1): Rf ϭ 0.27. H
NMR (DMSO-D ): ␦ 0.68 (s, 3H, 18-Me), 0.88 (s, 3H, 19-
6
1
Me), 0.98 (d, 3H, J ϭ 6.2 Hz, 21-Me); 1.37 (s, 3H, 25-Me),
(hexane/ethyl acetate/acetic acid, 1:5:0.1), Rf ϭ 0.50. H
3.63 (m, 1H, 3␤-H); 3.78 (s, 1H, 7␤-H)ppm. Analysis calcu-
NMR (DMSO-D ): ␦ 0.65 (s, 3H, 18-Me), 0.90 (s and d,
6
lated for C H O : C 69.96; H 10.06. Found: C 69.81; H 9.89.
6H, 19-Me and 21-Me), 1.17 (d, 3H, J ϭ 7.2 Hz, 27-Me),
2
8 48 6
2
.45 (q, 1H, J ϭ 7.2 Hz, 25-H), 3.46 (m, 1H, 3␤-H), 3.84
1
3
2
.9. 3␣,7␣,12␣-Trihydroxy-5␤-cholestan-26,27-dioic acid
(m, 1H, 7␤-H)ppm. C NMR (CD OD): ␦ 180.5, 72.9,
3
(6b)
69.1, 51.5, 49.0, 48.2, 47.7, 43.7, 43.2, 41.1, 40.8, 40.5,
3
7.1, 36.6, 36.2, 35.9, 35.5, 34.1, 31.4, 29.4, 24.9, 24.7,
To a stirred solution of 5b (2.60 g, 4.19 mmol) in DMF
10 ml) was added a solution of NaOH (3.60 g) in water (20
23.4, 21.8, 19.2, 17.6, 12.2ppm. Analysis calculated for
C H O : C 74.60; H 10.67. Found: C 74.63; H 10.86.
(
2
7
46
4

1
46
I. Starchenkov et al. / Steroids 65 (2000) 143–147
2
.12. 3␣,7␣,12␣-Trihydroxy-5␤-cholestan-26-oic acid (7b)
droxy-5␤-cholestan-26-oic acid (7a), 3␣,7␣,12␣-trihy-
droxy-5␤-cholestan-26-oic acid (7b); and dicarboxylic ac-
ids: 3␣,7␣,12␣-trihydroxy-5␤-cholestan-26,27-dioic acid
(6b), 3␣,7␣,12␣-trihydroxy-25-carboxy-5␤-cholestan-26-
oic acid (6c).
Exploration of the above decarboxylation procedure to
c (4.92 g, 9.91 mmol) gave after work-up, flash chro-
matography (petroleum ether/ethyl acetate/methanol/ace-
tic acid, 2:5:0.5:0.05) and recrystallization from ethyl
acetate 7b (2.68 g, 60%) as a white solid with m.p.
6
Formylated bile acids 2a and 2b were prepared [9,10] in
a high yield and converted into the corresponding alcohols
3a and 3b, by the selective reduction with borane/tetrahy-
drofuran complex [10]. To simplify the process, we pre-
ferred direct iodination to standard substitution of mesylates
or tosylates usually prepared from alcohols [11]. Direct
iodination of alcohol with iodotrimethylsilane [12] gener-
ated in situ failed. An alternative iodination of alcohols 3a,b
in the presence of triphenylphosphine and imidazole pro-
ceeds smoothly providing the corresponding iodo deriva-
tives 4a,b in excellent yields.
Nucleophilic substitution of iodo derivatives 4a,b with
diethyl sodiomalonate and diethyl sodiomethylmalonate
generated from the corresponding malonate by the action of
NaH afforded the diesters 5a–c. All attempts to use an
alternative method for the direct introduction of one car-
boxylic group, particularly, derivatives of propionic acid
failed. Thus, reactions of iodides 4a,b with methyl sodio-
propionate or trimethylsilylenolate [13], both generated
from methyl propionate, were not clean and gave the desired
product in low yield.
1
74–181°C. HPTLC (ethyl acetate/acetic acid, 50:1),
Rf ϭ 0.28; (chloroform/acetone/methanol, 7:5:1, devel-
1
oped twice), Rf ϭ 0.39. H-NMR (DMSO-D ): ␦ 0.62 (s,
6
3
H, 18-Me), 0.84 (s, 3H, 19-Me), 0.95 (d, 3H, J ϭ 6.2
Hz, 21-Me), 1.09 (d, 3H, J ϭ 7.0 Hz, 27-Me), 2.24 (m,
H, 25-H), 3.26 (m, 1H, 3␤-H), 3.68 (s, 1H, 7␤-H), 3.85
1
(
6
3
2
1
3
s, 1H, 12␤-H). C NMR (CD OD): ␦ 189.9, 74.1, 72.9,
3
9.1, 48.3, 47.4, 43.2, 42.9, 41.0, 40.8, 40.4, 37.1, 37.0,
6.5, 35.9, 35.8, 35.5, 31.2, 29.6, 28.8, 27.8, 24.9, 24.2,
0
3.2, 18.0, 17.8, 13.0ppm. [␣] : ϩ36.6 (c ϭ 1, MeOH).
D
Analysis calculated for C H O : C 71.95; H 10.29.
2
7
46
5
Found: C 71.86; H 10.17.
3
. Discussion
We attempted to find a convenient and a simple method
Scheme 1) for the synthesis of four modified bile acids.
Among the targets are mono carboxylic acids: 3␣,7␣-dihy-
(

I. Starchenkov et al. / Steroids 65 (2000) 143–147
147
Subsequent treatment of diesters 5a and 5c with potas-
sium hydroxide in boiling ethanol resulted in complete
deformylation together with both ester group hydrolysis in
side chain, providing free dicarboxylic acids 6 in good
yields.
Saponification of diester 5b with sodium hydroxide in an
aqueous dimethylformamide at the ambient temperature was
improved by the ultrasound sonification. Purification of bile
acids 6a–c was achieved by a flash chromatography on silica
gel by using ethyl acetate/ethanol/acetic acid as an eluent
followed by the crystallization from ethyl acetate. Decarboxy-
lation of geminal diacids 6a and 6c in wet DMSO containing
LiCl gave desired 5␤-cholestan–26(R,S)-oic acids 7a and 7b in
[2] Batta AK, Salen GS, Tint GS, Shefer S. Improved synthesis of
␤-cholestan-26-oic acids. Steroids 1979;33:589–94.
5
[
3] Bridgwater RJ. Partial synthesis of the two 3␣:7␣:12␣-trihydroxyco-
prostanic acids and of similar bile acids with extended side chains.
Biochem J 1956;64:593–9.
[
4] Briggs T. Partial synthesis of 25D- and 25L-cholestanoic acids from
some common bile acids. J Org Chem 1970;35:1431–4.
5] Yuri M, Tokumoto M, Hara N, Fujimoto Y, Kobayashi N, Morisaki
M. Identification of 27-nor-3␣,7␣,12␣-trihydroxycoprostan-24-one
apparently derived from 3␣,7␣,12␣-trihydroxy-24-oxocoprostanoic
acid, a postulated intermediate of bile acid biosynthesis. Chem Pharm
Bull 1993;41:1327–9.
[
[
6] Une M, Matsumoto N, Kihira K, Yasuhara M, Kuramoto T, Hoshita
T. Bile salts of frogs: a new higher bile acid, 3␣,7␣,12␣,26-tetrahy-
droxy-5␤-cholestanoic acid from the bile of Rana plancyi. J Lipid Res
1
980;21:269–76.
60 and 61% yield, respectively.
[
7] Haslewood GAD, Tammar AR. Bile salts of sturgeons (Acipenseri-
dae) and the paddlefish (Polyodon spathula): a new partial synthesis
of 5␤-cyprinol. Biochem J 1968;109:263–8.
An obvious advantage of the proposed method is a key
iodo derivatives 4. These electrophiles are slightly accessi-
ble with broad spectrum of carbon nucleophiles. Total yield
of the titles modified bile acids 6 and 7 obtained by this 4
and 5 step synthesis was 29 to 55%.
[
8] Parmentier GG, Busson RH, Janssen GA, Mannaerts GP, Eyssen HJ.
1
4
Synthesis and 29- C-labeling of 3␣,7␣,12␣-trihydroxy-27-carboxy-
methyl-5␤-cholestan-26-oic acid. A bile acid occuring in peroxisomal
diseases. Steroids 1993;58:351–6.
[9] Malik AA, Cormier RJ, Sharts CM. Selective protection of side chain
hydroxy group in bile alcohol derivatives. Org Prep Proced Int 1986;
Acknowledgments
1
8:345–52.
[
10] Malik AA, Sharts CM. Selective reduction of the formylated bile
acids to the corresponding formylated bile alcohols analogs. Org Prep
Proced Int 1987;19:1–7.
Financial support from AnalytiCon for investigations is
gratefully acknowledged. The authors thank Dr J. Popelis
for his technical assistance with NMR spectra.
[
11] Cho J-H, Djerassi C. Stereostructure and synthesis of new sponge
sterols jaspisterol and isojaspisterol. J Org Chem 1987;52:4517–21.
12] Olah GA, Narang SC, Gupta BGB, Malhotra R. Transformations with
chlorotrimethylsilane/sodium iodide, a convenient in situ iodotri-
methylsilane reagent. J Org Chem 1979;44:1247–51.
[
References
[
13] Reetz MT, Schwellnus K, H u¨ bner F, Massa W, Schmidt RE. Lewis
acid mediated ␣-tert-alkylation of carboxylic acids and carboxylic
esters. Chem Ber 1983;116:3708–24.
[1] Russell DW, Setchell KDR. Bile acid biosynthesis. Biochemistry
1
992;31:4737–49.