Divergent and stereoselective synthesis of dafachronic acids

Article abstract of DOI:10.1016/j.tet.2011.01.022

A new divergent synthesis of DAF-12 ligands, namely Δ⁴-and Δ⁷-dafachronic acid, is described starting from the natural bile acid hyodeoxycholic acid. Homologation of the side chain followed by stereoselective reduction of the Δ²

Full text of DOI:10.1016/j.tet.2011.01.022

Tetrahedron 67 (2011) 1924e1929
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Divergent and stereoselective synthesis of dafachronic acids
*
Antimo Gioiello, Paola Sabbatini, Emiliano Rosatelli, Antonio Macchiarulo, Roberto Pellicciari
ꢀ
Dipartimento di Chimica e Tecnologia del Farmaco, Universita di Perugia, Via del Liceo 1, 06123 Perugia, Italy
a r t i c l e i n f o
a b s t r a c t
A new divergent synthesis of DAF-12 ligands, namely
D D
4- and 7-dafachronic acid, is described starting
Article history:
Received 6 September 2010
Received in revised form 30 November 2010
Accepted 6 January 2011
from the natural bile acid hyodeoxycholic acid. Homologation of the side chain followed by stereo-
selective reduction of the D24 olefinic linkage, 6
a
-dehydroxylation and C3-oxidation affords dafachronic
acids in good yields and high diastereoselectivity making this approach easily accessible and scalable.
Available online 13 January 2011
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
D
D
4-Dafachronic acid
7-Dafachronic acid
DAF-12
Stereoselective hydrogenation
1. Introduction
(S)
CO2H
(S)
CO2H
Upon unfavorable conditions and difficult environmental
plights, many organisms from worms to mammals respond by ar-
resting their development and initiating programs of reversible
states of dormancy.1 Several strategies of diapause have evolved
even within the same species, allowing them to survive until con-
ditions improve and they can return to normal reproductive life.
Recent studies on the nematode Caenorhabditis elegans are begin-
ning to provide crucial insights into the diversity and complexity of
these alternate life strategies, as well as into the molecular mech-
anisms governing these responses.2 It has been reported, in par-
ticular, that upon environmental cues both G protein-coupled
receptors (GPCRs) and nuclear hormone receptors (NHRs) are in-
volved in modulating diapause programs in the adult reproductive
and larval stage, respectively.1a,2a,3
O
O
H
25(S)-Δ7-Dafachronic Acid (2)
25(S)-Δ4-Dafachronic Acid (1)
(R)
(R)
CO2H
CO2H
O
O
H
25(R)-Δ7-Dafachronic Acid (4)
25(R)-Δ4-Dafachronic Acid (3)
Fig. 1. Structure of dafachronic acids.
more potent toward DAF-12 than the corresponding 25-R-epimers
3 and 4, with 2 being the most potent ligand so far reported.4a,6b
In addition, while the dauer diapause represents a survival
strategy, it was reported to help dispersal of the C. elegans, a phe-
nomenon, which has suggested an important evolutionary link
with parasitism.7 Indeed, it has been recently demonstrated that
the DA/DAF-12 signal is crucial during infection caused by parasitic
nematodes. As in free-living C. elegans, DAs activate parasitic DAF-
12 orthologs and promote the recovery of the third stage of in-
fective larvae (iL3) in Strongyloides stercoralis and hookworm.7a,b In
The most investigated among these arrests are the larval stage
one (L1) and the third dauer diapause (L3). In both these cases,
a key hormonal role is played by dafachronic acids (DAs, 1e4)
(Fig. 1),4 3-keto-steroids derived from cholesterol.5 Upon the
binding to the NHR DAF-12 (‘DAuer larva Formation-12’),6a DAs
activate daf-12 genes and prevent the entry of C. elegans into the
dauer recovery, while the absence of the ligands induces the qui-
escent L3 stage, in which the nematode exhibits more stress re-
sistance, an extended larval survival, and, interestingly, an
increased life span.2,3,6 At this regard, it has been reported that
particular, administration of S-D
7-DA (2) causes a concomitant and
among the four DA isomers (Fig. 1), S-D D
4-DA (1) and S- 7-DA (2) are
significant reduction in the infection progression and in the path-
ogenic dauer-like iL3 population of the S. stercoralis. These impor-
tant results, which indicate a conserved NHR signaling pathway
governing the stage 3 larvae, suggest a potential therapeutic utility
* Corresponding author. Tel.: þ39 075 5855120; fax: þ39 075 5855124; e-mail
address: rp@unipg.it (R. Pellicciari).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.01.022

A. Gioiello et al. / Tetrahedron 67 (2011) 1924e1929
1925
of DAs and DA derivatives in the treatment of disseminated
strongyloidiasis.7a,b,8
CO2Me
CO2Me
On the basis of these findings, the readily availability of DAs be-
came of primary importance not only to fully define the biological
relevance of DAF-12 but also to grasp the endocrine circuitry and
molecular mechanism that govern its actions. To this end, in the last
few years a significant effort has been directed toward the de-
velopment of facile and scalable procedures for the synthesis of the
a
b
10
AcO
AcO
O
13
14
16
H
CO2Me
d
CO2Me
c
DAs 1e4.9e13 The first synthesis of
D
4-DA (1) was reported in 2005 as
-acetoxy-pregn-5-en-20-car-
a multistep elaboration of 20(S)-3
b
AcO
O
AcO
OH
H
H
boxylic acid side chain to give 1 in 11 steps with an overall yield of
15
4%.9 The first diastereoselective synthesis of the biologically active
25(S)-D
7-DA (2) was published by Corey in 2007, starting from the
CO2H
g
CO2H
plant sterol
both 25(S)-
b
D
-stigmasterol (16 steps,13%).10 A divergent synthesis of
7-DAs (1, 2) has been reported from 3
b-
e, f
4- and 25(S)-
D
hydroxychol-5-en-24-oic acid.11 In this case, the stereogenic center
at C25 was achieved by stereoselective Evans aldol reaction and gave
the desired derivatives 1 and 2 in 12 (19%) and 15 steps (18%), re-
spectively. Moreover, while diosgenin has been largely employed as
starting material for the preparation of the R-epimers 3 and 4, as it
provides the 25(R)-configuration,12 a stereocontrolled synthesis of
2
HO
H
O
17
Scheme 3. Synthesis of 25(S)-D
7-dafachronic acid (2). Reagent and conditions: (a)
AcOK, AcOH, reflux, 60%. (b) CrO3, 3,5-dimethylpyrazole, CH2Cl2, 83%. (c) H2, Pd/C,
EtOAc, 93%. (d) L-Selectride, THF, 88%. (e) SOCl2, pyridine. (f) NaOH, MeOH, 86% from
16. (g) Jones oxidation, 87%.
the 25(R)-
D b-ergosterol in
7-DA (4) was successfully achieved from
10 steps with an overall yield of 13%.13
2. Results and discussion
With the aim to provide a new and efficient synthetic route for
the preparation of DA isomers 1e4, we report here an alternate and
a divergent synthesis of DAs using the naturally occurring bile acid
hyodeoxycholic acid (5) as starting material (Schemes 1e3).
The strategy employed to access DAs was based on the prepa-
ration of a common intermediate 8 obtained from the homologa-
tion of hyodeoxycholic acid (5) side chain by Wittig reaction
(Scheme 1).
Thus, 5 was protected at the C3a- and C6a-hydroxy groups by
using 3,4-dihydro-2H-pyran in the presence of catalytic amount of
p-TSA at room temperature to furnish the corresponding dihy-
dropyranyl derivative in quantitative yield (Scheme 1). The termi-
nal carboxylic group was then reduced to alcohol by treatment with
ClCO2Et and Et3N in THF at 0 ꢀC, followed by the addition of a sus-
pension of NaBH4 in H2O at room temperature. The alcoholic in-
termediate 6 was converted into the corresponding aldehyde 7 by
Swern oxidation (92% yield). The following Wittig reaction was
performed with [(1-carboethoxy)ethyl]triphenylphosphonium
bromide14 in THF using t-BuOK as a base. The resulting adduct was
submitted to acidic (HCl/MeOH) and basic hydrolysis (NaOH/
CO2H
a, b
OH
c
THPO
HO
H
H
OTHP
OH
6
Hyodeoxycholic acid (5)
O
CO2H
d, e, f
THPO
HO
MeOH) to give (E)-3a,6a-dihydroxy-25-methyl-24-bishomo-5b-
H
H
OTHP
OH
chol-24-en-26-oic acid (8) (E/Z>20/1), in excellent yield (89%)
(Scheme 1). The stereochemistry of 8 was assigned based on NMR
COSY and NOE analysis (Fig. 2).
7
8
Scheme 1. Synthesis of
3a,6a-dihydroxy-25-methyl-24-bishomo-5b-chol-24-en-26-
oic acid (8). Reagents and conditions: (a) 3,4-DHP, p-TSA, dioxane, quantitative. (b) 1.
ClCO2Et, Et3N, THF; 2. NaBH4, H2O, 95%. (c) (COCl)2, DMSO, Et3N, CH2Cl2, 92%. (d) (Ph3P)
CH3CHCO2EtBr, t-BuOK, THF. (e) HCl, MeOH. (f) NaOH, MeOH, 89% from 7.
COSY
H
COSY
CO2H
H
CO2H
CH3
NOE
H
H
H
H
CH3
COSY
CO2H
a, b
CO2Me
c
Fig. 2. Diagnostic 1H NMR COSY and NOE for 8.
HO
TsO
H
H
OH
9
OTs
10
Stereoselective reduction of the C24eC25 double bond was
attempted according to diverse reaction conditions (Table 1). For
CO2Me
d, e
the preparation of 3a,6a-dihydroxy-25(S)-methyl-24-bishomo-5b-
CO2H
cholan-26-oic acid (9), the best result was obtained by using (S)-Ru
(OAc)2(BINAP) as a catalyst (90% yield, de: 100%, Table 1, entry 3),
which although retains the selectivity and efficiency of the parent
(S)-Ru(OAc)2(H8-BINAP), is consistently cheaper. Next, in order to
provide a procedure to synthesize the corresponding 25(R)-epimer
12, the key intermediate for the synthesis of the 25(R)-DA 3 and 4,
we sought to use (R)-Ru(OAc)2(BINAP). While in this case the
1
HO
O
11
Scheme 2. Synthesis of 25(S)-
D
4-dafachronic acid (1). Reagents and conditions:
(a) p-TSA, MeOH. (b) TsCl, pyridine, 96%. (c) AcOK, DMF, H2O, 62%. (d) Al(OiPr)3,
cyclohexanone, toluene. (e) NaOH, MeOH, 83% from 11.

1926
A. Gioiello et al. / Tetrahedron 67 (2011) 1924e1929
Table 1
Stereoselective reduction of 8
CO2H
CO2H
+
H2
8
Catalyst,
Solvent
HO
H
HO
H
OH
12
OH
9
Entry
Catalyst
PtO2
Solv.
T,
Press.
Yielda (S/R Ratio)b
1
2
3
4
5
AcOH
MeOH
MeOH
MeOH
rt,
98% (55/45)
90% (100/0)
90% (100/0)
85% (40/60)
97% (3/97)
3 atm
50 ꢀC,
2 atm
50 ꢀC,
2 atm
50 ꢀC,
2 atm
50 ꢀC,
5 atm
(S)-Ru(OAc)2(H8-BINAP)
(S)-Ru(OAc)2(BINAP)
(R)-Ru(OAc)2(BINAP)
(R)-RuCl[(p-cymene)(BINAP)]Cl
MeOH/Et3N (1 equiv)
a
Calculated after purification by flash chromatography on silica gel.
S/R ratio was calculated by HPLC analysis of the crude reaction mixture.
b
reaction proceeded with low levels of selectivity (S/R ratio: 40/60),
hydrogenation conducted with (R)-RuCl[(p-cymene)(BINAP)]Cl in
the presence of Et3N in MeOH at 50 ꢀC afforded 12 with high di-
astereoisomeric ratio (Table 1, entry 5). The absolute configuration
assignment to epimers 9 and 12 was based upon 13C NMR
comparison.15
4. Experimental section
4.1. General methods
All reagents were commercially available unless otherwise
noted. All reactions were carried out in dried glassware under a dry
nitrogen atmosphere. The final products were purified by chro-
matography on silica gel (70e230 mesh). TLC was performed on
aluminium backed silica plates (silica gel 60 F254). Spots on TLC
were visualized by using UV and by staining and warming with
phosphomolybdate reagent (5% solution in EtOH). All the reactions
were performed using distilled solvent. 1H NMR spectra were
recorded at 200 and 400 MHz, 13C NMR spectra were recorded at
50.3 and 100.6 MHz, respectively, using the solvents indicated be-
low. Chemical shifts are reported in parts per million. The abbre-
viations used are as follows: s, singlet; d, doublet; t, triplet; q,
quartet; br s, broad signal. Melting points were determined with an
electrothermal apparatus and are uncorrected. For HRMS a Micro-
mass spectrometer was used. Purity of the DAs was >95% according
to NMR and HPLC analysis. The HPLC analyses were carried out on
apparatus with a chromatography data software, a pump, a system
controller, a low pressure gradient formation unit, an on-line
degasser and an injector with a 20 mL stainless steel loop. An
evaporative light scattering detector (ELSD) was used as detector.
An interface allowed the analog-to-digital conversion of the
output signal from the ELSD. The column temperature was con-
Reaction of the 3
cholan-26-oic acid (9) with tosyl chloride in pyridine at room
temperature afforded the corresponding ,6 -ditosylate 10
(quantitative yield), which was then transformed into 3 -hydroxy-
5-methyl ester 11 by 6
-tosylate elimination and Walden in-
a,6a-dihydroxy-25(S)-methyl-24-bishomo-5b-
3
a a
b
D
a
version achieved by refluxing 10 in a H2O/DMF solution of AcOK
(Scheme 2).16 Finally, Oppenauer oxidation and subsequent ester
hydrolysis provided 25(S)-
For the preparation of 25(S)-
the reaction condition for detosylation (Scheme 3). Thus, when 10
was treated with AcOK in boiling AcOH, methyl 3 -acetoxy-25(S)-
methyl-24-bishomochol-5-en-26-oate (13) was isolated in 60%
D
4-DA (1), in 35% overall yield (12 steps).
D
7-DA (2) we envisaged to change
b
yield along with the corresponding
D
3,5-diene derivative obtained
as by-product of the reaction.17 Allylic oxidation of 13 with CrO3
and 3,5-dimethylpyrazole in CH2Cl2 at room temperature furnished
the enone 14, in 83% yield (Scheme 3).18
Palladium-catalyzed hydrogenation of the C5eC6 double bond
allowed to obtain the 5a-steroid 15, in high yields. Stereoselective
reduction of the 7-keto group with L-Selectride in THF at ꢁ78 ꢀC
followed by the treatment of the 7a-hydroxy intermediate 16 with
thionyl chloride in pyridine at room temperature and alkali hy-
drolysis (NaOH/MeOH) furnished 3 -hydroxy-25-methyl-24-bish-
omo-5
-chol-7-en-26-oic acid (16), in 71% yield.12c Finally, Jones
trolled through a heater/chiller thermostat. Column: RP-18
b
(250ꢂ4.6 mm, 5 m). Eluent: H2O/MeCN/MeOH, 50/45/5 (v/v/v)þ
m
a
NH4HCO2¼40 mM pH 3.5. Tcol: 25 ꢀC. Flow-rate: 0.700 mL/min.
Detector: ELSD (Tvap¼50 ꢀC, Tneb¼30 ꢀC, Gas Flow-rate¼1.50 L/
min, Gain¼2.00).
oxidation gave the desired 25(S)-D
7-DA (2) in 22% overall yield (16
steps).
3. Conclusions
4.2. Synthesis of 3
a,6a-dihydroxy-25-methyl-24-bishomo-5b-
chol-24-en-26-oic acid (8)
In summary, we have developed a new efficient diaster-
eoselective synthesis of DAs starting from the readily available
hyodeoxycholic acid (5). The method, which includes a Wittig re-
action and a stereoselective hydrogenation, furnishes 25(S)-DAs
(1e2) in good yield and high isomeric purity. Our approach results
to be flexible and a valuable alternative to the previous reported
methodology as it can easily provide DA isomers 1e4 via a common
intermediate, obtained in high overall yield also on a large scale
synthesis.
4.2.1. 3a,6a-Ditetrahydropyranyloxy-24-hydroxy-5b-cholane
(6)19. To a solution of hyodeoxycholic acid (5) (15.00 g, 38.20 mmol)
andp-toluensulfonic acid (0.7 g, 3.64 mmol)in 1,4-dioxane(100 mL),
3,4-dihydro-2H-pyran (48.20 g, 570 mmol) was added dropwise in
5 h. At the end of the addition the reaction mixture was diluted with
water (120 mL)and extractedwith EtOAc(3ꢂ100 mL). The combined
organic layers were dried over Na2SO4 and evaporated under re-
duced pressure. The resulting yellow oil was dissolved in a solution

A. Gioiello et al. / Tetrahedron 67 (2011) 1924e1929
1927
of MeOH (100 mL) and 5% aqueous NaOH, and stirred at room
temperature for 2 h. The solvent was evaporated under reduced
pressure, the resulted residue was dissolved in H2O (150 mL) and
washed with Et2O (2ꢂ100 mL). The aqueous phase was neutralized
by addition of 3N HCl and then extracted with EtOAc (3ꢂ100 mL).
The combined organic layers were dried over Na2SO4 and evapo-
(150 mL, 1:1, v/v), and the resulting solution was extracted with
EtOAc (2ꢂ100 mL). The combined organic layers were washed with
brine (100 mL), dried over Na2SO4 and evaporated under reduced
pressure. The residual brown oil was dissolved in 5% HCl in MeOH
(150 mL) and stirred at room temperature for 2 h. The solvent was
removed under reduced pressure, the residue was dissolved in H2O
(120 mL) and extracted with CHCl3 (3ꢂ60 mL). The combined or-
ganic layers were washed with H2O (80 mL), brine (80 mL), dried
over Na2SO4 and evaporated under reduced pressure. The crude was
rated under reduced pressure to furnish 3
a,6a-ditetrahydropyr-
aloxy-5 -cholan-24-oic acid (21.40 g, 38.10 mmol) as white solid
b
that was used for the next step without further purifications. The
3,6-diprotected acid thus obtained was dissolved in dry THF
(200 mL) and Et3N (13.25 g, 131.18 mmol) at 0 ꢀC, and a solution of
EtCO2Cl (13.40 g, 123.50 mmol) in dry THF (10 mL) was added
dropwise. The resulting mixturewas stirredat roomtemperature for
3 h. A suspension of NaBH4 (15.70 g, 415.34 mmol) in H2O (50 mL)
was added dropwise. The resulting mixture was stirred at room
temperature overnight and then diluted with H2O (500 mL) and
extracted with EtOAc (3ꢂ100 mL). The combined organic layers
were dried over Na2SO4 and evaporated under reduced pressure to
furnish a yellow oil that was purified by flash chromatography
eluting with CHCl3 to obtain 6 as mixture of diastereoisomers
(19.84 g, 36.10 mmol, 95%). Mp: 102e103 ꢀC; Rf (30% EtOAc/PET)
0.38; dH (200 MHz, CDCl3) 0.61 (3H, s,18-CH3), 0.88e0.91 (6H, m,19-
CH3þ21-CH3), 0.99e2.03 (41H, m), 3.45e3.48 (2H, m, OCH2-THP),
3.57e3.60 (2H, m, 24-CH2), 3.69e3.72 (1H, m, 3-CH), 3.83e3.93 (2,
m, OCH2-THP), 3.95e34.00 (1H, m, 6-CH), 4.59e4.66 (1H, m, OCHO-
THP), 4.72e4.76 (1H, m, OCHO-THP); dC (100.6 MHz, CDCl3) 11.9,
18.6, 19.8, 20.0, 20.1, 20.2, 20.7, 23.5, 24.2, 25.5, 25.8, 26.3, 26.4, 27.6,
27.9, 28.2, 28.4, 28.5, 29.4, 31.1, 31.2, 31.3, 31.8, 33.2, 34.7, 34.8, 35.4,
35.5, 35.6, 35.7, 35.9, 36.0, 39.8, 39.9, 42.8, 44.9, 45.1, 47.7, 47.9, 56.1,
56.2, 62.5, 62.8, 63.0, 63.1, 63.5, 72.0, 72.1, 72.3, 72.4, 75.1, 75.2, 75.5,
75.8, 95.9, 96.0, 96.2, 96.4, 96.5, 96.9, 97.1.
purified by flash chromatography to obtain ethyl 3
a,6a-dihydroxy-
25-methyl-24-bishomo-5 -chol-24-en-26-oate as white solid. The
b
ester thus obtained was dissolved in 60 mL of 5% NaOH in MeOH and
the resulting mixture was stirred at 60 ꢀC overnight. The solvent was
evaporated under reduced pressure, the residue was dissolved into
H2O (100 mL), acidified with 3N HCl and extracted with EtOAc
(3ꢂ60 mL). The combined organic layers were washed with H2O
(100 mL), brine (100 mL), dried over Na2SO4 and evaporated under
reduced pressure to afford the desired acid 8 (5.70 g, 13.17 mmol,
89%, E/Z>20/1) as pure white solid. Mp: 203e205 ꢀC; Rf (10% MeOH/
CHCl3þ0.1% AcOH) 0.29; nmax (KBr) 3255, 2937, 2867, 1685, 1458,
1378,1261,1030, 751 cmꢁ1
;
dH (400 MHz, CDCl3þCD3OD) 0.55 (3H, s,
18-CH3), 0.81 (3H, s,19-CH3), 0.86 (3H, d, J 6.4 Hz, 21-CH3), 0.94e1.67
(22H, m), 1.73 (3H, s, 27-CH3), 1.88e2.11 (4H, m), 3.47 (1H, m, 3-CH),
3.68 (3H, br s, OH), 3.92 (1H, dt, J 4.7, 11.9 Hz, 6-CH), 6.70 (1H, t, J
7.4 Hz, 24-CH); dC (100.6 MHz, CDCl3) 11.7,11.9,18.2, 20.5, 23.2, 24.0,
25.3, 28.0, 28.6, 29.6, 34.3, 34.6, 35.3, 35.4, 35.7, 39.6, 39.8, 42.6, 48.2,
55.8, 55.9, 67.6, 71.0, 126.9, 143.7, 170.6.
4.3. General procedure for stereoselective reduction of 8
To a solution of 0.50 mmol of 8 in 10 mL of freshly distilled
solvent, 5 mol % of the catalyst was added. The resulting mixture
was reacted for 48 h according to the reaction conditions reported
in Table 1. The solution was then filtered through a Celite pad,
evaporated to dryness and purified by flash chromatography using
a solution of CHCl3/MeOH 95:5 (v/v).
4.2.2. 3a,6a-Ditetrahydropyranyloxy-5b
-cholan-24-al (7)20. To a so-
lution of(COCl)2 (4.49 g, 35.60mmol) in dryCH2Cl2 (30 mL)at ꢁ50ꢀC
a solution of DMSO (5.35 g, 68.55 mmol) in CH2Cl2 (10 mL) was
added dropwise in 30 min and then reacted at ꢁ50 ꢀC for 15 min. A
solution of the alcohol 6 (15.00 g, 27.42 mmol) in CH2Cl2 (30 mL) was
then added dropwise. After 2 h at ꢁ50 ꢀC Et3N (13.90 g,137.36 mmol)
was added and the reaction was allowed to warm at room temper-
ature overnight. The reaction mixture was poured into 2N KOH
(200 mL) and extracted with CH2Cl2 (3ꢂ60 mL). The combined or-
ganic layers were washed with H2O (100 mL), brine (100 mL), dried
over Na2SO4 and evaporated under reduced pressure. The crude was
purified by flash chromatography eluting with from 5 to 10% EtOAc
in petroleum ether to obtain the desired aldehyde 7 (13.70 g,
25.14 mmol, 92%) as mixture of diastereoisomers. Mp: 92e94 ꢀC; Rf
(20% EtOAc/PET) 0.62; dH (200 MHz, CDCl3) 0.62 (3H, s, 18-CH3),
0.89e0.91 (6H, m, 19-CH3þ21-CH3), 1.08e1.95 (36H, m), 2.36e2.38
(1H, m, 23-CHaHb), 2.41e2.45 (1H, m, 23-CHaHb), 3.46e3.49 (2H, m,
OCH2-THP), 3.58e3.63 (1H, m, 3-CH), 3.87e3.95 (2H, m, OCH2-THP),
3.96e4.02 (1H, m, 6-CH), 4.61e4.68 (1H, m, OCHO-THP), 4.72e4.76
(1H, m, OCHO-THP), 9.76 (1H, s, CHO); dC (100.6 MHz, CDCl3) 12.0,
18.3, 19.8, 20.0, 20.2, 20.7, 23.5, 24.1, 25.5, 25.8, 26.4, 27.6, 27.9, 28.2,
28.4, 28.5, 31.1, 31.2, 33.2, 34.7, 34.8, 35.3, 35.4, 35.6, 35.9, 36.0, 39.8,
39.9, 40.9, 42.8, 44.9, 45.1, 47.6, 47.9, 55.9, 56.2, 62.5, 62.9, 63.0, 63.1,
72.0, 72.1, 72.3, 75.1, 75.2, 75.4, 75.8, 95.9, 96.0, 96.2, 96.4, 96.5, 96.9,
97.1, 203.2.
4.3.1. 3a,6a-Dihydroxy-25(S)-methyl-24-bishomo-5b-cholan-26-oic
acid (9)22. Mp: 207e208 ꢀC; Rf (10% MeOH/CHCl3þ0.1% AcOH)
0.29; nmax (KBr) 3469, 3237, 2931, 1735, 1466, 1345, 1029, 731 cmꢁ1
;
dH (400 MHz, CDCl3) 0.58 (3H, s, 18-CH3), 0.83e0.85 (6H, m, 19-
CH3þ27-CH3), 0.96e1.00 (5H, m), 0.99 (3H, d, J 6.4 Hz, 21-CH3),
1.10e1.95 (26H, m), 2.34e2.37 (1H, m, 25-CH), 3.52 (1H, m, 3-CH),
3.97 (1H, dt, J1 4.7 Hz, J2 11.9 Hz, 6-CH); dC (100.6 MHz, CDCl3) 11.8,
16.9, 18.3, 20.6, 23.3, 23.6, 24.0, 28.0, 28.73, 29.72, 34.0, 34.4, 34.7,
35.4, 35.5, 35.6, 35.7, 39.2, 39.7, 39.8, 42.7, 48.2, 56.0, 56.1, 67.7, 71.1,
179.6.
4.3.2. 3a,6a-Dihydroxy-25(R)-methyl-24-bishomo-5b-cholan-26-oic
acid (12)22. Mp: 192e195 ꢀC; Rf (10% MeOH/CHCl3þ0.1% AcOH)
0.29; nmax (KBr) 3457, 3248, 2931, 1734, 1463, 1346, 1185, 1019,
720 cmꢁ1
; dH (400 MHz, CDCl3) 0.57 (3H, s, 18-CH3), 0.82e0.83 (6H,
m, 19-CH3þ27-CH3), 0.94e1.04 (5H, m), 1.09 (3H, d, J 7.0 Hz, 21-
CH3), 1.14e1.92 (26H, m), 2.34e2.35 (1H, m, 25-CH), 3.50 (1H, m, 3-
CH), 3.95 (1H, dt, J1 4.6 Hz, J2 11.9 Hz, 6-CH); dC (100.6 MHz, CDCl3)
11.8, 16.7, 18.4, 20.6, 23.3, 23.6, 24.0, 28.1, 28.73, 29.70, 33.9, 34.4,
34.7, 35.4, 35.5, 35.6, 35.8, 39.2, 39.7, 39.8, 42.6, 48.2, 2ꢂ 56.0, 67.7,
71.1, 179.8.
4.2.3. 3a,6a-Dihydroxy-25-methyl-24-bishomo-5b-chol-24-en-26-
oic acid (8)21. A suspension of (1-(ethoxycarbonyl)ethyl) triphe-
nylphosphonium bromide14 (21.40 g, 48.27 mmol) in dry THF
(100 mL) was reacted with potassium t-butoxide (44.0 ml, 1 M in
THF) at room temperature overnight. A solution of the aldehyde 7
(8.00 g, 14.68 mmol) in dry THF (100 mL) was then added and
refluxed for 4 h. The reaction mixture was allowed to cool at room
temperature, was diluted with hexane (100 mL) and H2O/MeOH
4.4. Synthesis of
4.4.1. Methyl 3 ,6
26-oate (10). To a solution of 9 (0.70 g, 1.61 mmol) in MeOH
(30 mL), p-toluensulfonic acid (30 mg, 0.16 mmol) was added and
the mixture was refluxed for 2 h. The solvent was evaporated under
reduce pressure, the residue was dissolved in CHCl3 (50 mL),
D
4-(S)-dafachronic acid (1)
a
a-ditosyloxy-25(S)-methyl-24-bishomo-5b-cholan-

1928
A. Gioiello et al. / Tetrahedron 67 (2011) 1924e1929
washed with aqueous NaHCO3 saturated solution (2ꢂ50 mL), H2O
(50 mL) and brine (50 mL). The organic layer was dried over Na2SO4
and evaporated under reduced pressure to afford the methyl ester
derivative as white solid. The residue was dissolved in dry pyridine
(4 mL) at 0 ꢀC and a solution of TsCl (0.67 g, 3.54 mmol) in dry
pyridine (4 mL) was added dropwise. The resulting solution was
stirred at room temperature for 48 h. The reaction mixture was
then poured into crushed ice and extracted with EtOAc (3ꢂ50 mL).
The combined organic layers were sequentially washed with 1N
HCl (3ꢂ100 mL), H2O (100 mL), brine (100 mL), dried over Na2SO4
and evaporated under reduced pressure to furnish the ditosylated
derivative 10 (1.20 g, 1.54 mmol, 96%) as off white solid. Mp:
146e148 ꢀC; Rf (20% EtOAc/PET) 0.77; nmax (KBr) 2946, 2873, 1732,
chromatography eluting with a solution of CHCl3/MeOH (92/8, v/v)
to obtain the desired compound 1 (0.22 g, 0.51 mmol, 83%) as off
white solid. Mp: 173e175 ꢀC; Rf (5% MeOH/CHCl3þ0.1% AcOH) 0.31;
a1D6 60.9 (c 1.9, CHCl3); dH (400 MHz, CDCl3) 0.70 (3H, s,18-CH3), 0.91
(3H, d, J 6.6 Hz, 21-CH3), 0.95e1.16 (6H, m), 1.18e1.19 (6H, m, 19-
CH3þ27-CH3), 1.25e2.04 (18H, m), 2.20e2.38 (1H, m, 25-CH),
2.35e2.39 (2H, m, 6-CH2), 2.42e2.47 (2H, m, 2-CH2), 5.73 (1H, s, 4-
CH); dC (100.6 MHz, CDCl3) 11.9, 17.0, 17.3, 18.5, 21.0, 23.7, 24.1, 28.1,
32.0, 32.9, 33.9, 34.0, 2ꢂ 35.5, 2ꢂ 35.6, 38.5, 39.3, 39.6, 42.3, 53.7,
55.8, 56.0, 123.7, 171.8, 182.4, 199.8. HRMS (ESIþ) m/z 415.3226
[(MþH)þ; calcd for C27H43O3 415.3212].
4.5. Synthesis of
D
7-(S)-dafachronic acid (2)
1456, 1358,1175, 923, 849, 669 cmꢁ1
; dH (400 MHz, CDCl3) 0.58 (3H,
s, 18-CH3), 0.80 (3H, s, 19-CH3), 0.85 (3H, d, J¼6.4 Hz, 21-CH3),
0.90e1.07 (7H, m), 1.14 (3H, d, J 6.9 Hz, 27-CH3), 1.19e1.94 (21H, m),
2.41e2.49 (7H, m, 25-CHþ2ꢂ Ar-CH3), 3.67 (3H, s, CO2CH3), 4.30
(1H, m, 3-CH), 4.78 (1H, dt, J 4.8, 12.0 Hz, 6-CH), 7.35 (4H, t, J 8.0 Hz,
ArH), 7.72 (2H, d, J 8.3 Hz, ArH), 7.79 (2H, d, J 8.3 Hz, ArH); dC
(100.6 MHz, CDCl3) 11.9, 17.2, 18.4, 20.4, 2ꢂ 21.6, 22.8, 23.7, 23.8,
26.4, 27.3, 28.0, 32.0, 34.2, 2ꢂ 34.7, 35.4, 35.5, 36.1, 39.4, 39.4, 39.5,
42.7, 46.2, 51.4, 55.7, 56.0, 79.6, 81.7, 4ꢂ 127.5, 4ꢂ 129.7, 2ꢂ 134.4,
2ꢂ 144.6, 177.3. HRMS (ESIþ) m/z 757.3810 [(MþH)þ; calcd for
C42H61O8S2 757.3808].
4.5.1. Methyl 3b-acetoxy-25(S)-methyl-24-bishomochol-5-en-26-
oate (13)10. To a solution of 10 (1.74 g, 2.30 mmol) in AcOH (80 mL),
anhydrous potassium acetate (6.81 g, 69.5 mmol) was added and the
resulting mixture was refluxed for 5 h. The reaction mixture was
then allowed to cool at room temperature and the solvent was re-
moved under vacuum. The crude was dissolved into H2O (150 mL)
and extracted with EtOAc (3ꢂ80 mL). The combined organic layers
were washed with 5% aqueous Na2CO3 solution (5ꢂ80 mL), brine
(150 mL), dried over Na2SO4 and evaporated under reduced pressure.
The crude was purified by flash chromatography eluting with from 5
to 30% EtOAc in petroleum ether to furnish the desired compound 13
(0.65 g, 1.38 mmol, 60%) as whitish solid. Mp: 112e114 ꢀC; Rf (10%
EtOAc/PET) 0.54; dH (400 MHz, CDCl3) 0.68 (3H, s, 18-CH3), 0.89 (3H,
d, J 6.4 Hz, 21-CH3), 1.03 (3H, s,19-CH3),1.03e1.10 (5H, m),1.14 (3H, d,
J 6.9 Hz, 27-CH3), 1.18e2.01 (21H, m), 2.02 (3H, s, COCH3), 2.31 (1H, d,
J 7.0 Hz, 4-CH), 2.40e2.45 (1H, m, 25-CH), 3.68 (3H, s, CO2CH3),
4.56e4.64 (1H, m, 3-CH), 5.36 (1H, bd, J 4.4 Hz, 6-CH); dC (100.6 MHz,
CDCl3) 11.8, 17.1, 18.5, 19.2, 20.9, 21.3, 23.7, 24.2, 27.7, 28.1, 2ꢂ 31.8,
34.2, 35.5, 35.7, 36.5, 36.9, 38.0, 39.4, 39.6, 42.2, 49.9, 51.4, 56.0, 56.6,
74.0, 122.5, 139.6, 170.6, 177.5.
4.4.2. Methyl
3b-hydroxy-25(S)-methyl-24-bishomochol-5-en-26-
oate (11). To a solution of 10 (0.80 g, 1.04 mmol) in DMF (12 mL)
potassium acetate (82 mg, 0.84 mmol) dissolved in H2O (1.8 mL) was
added and the resulting mixture was refluxed overnight. The reaction
mixture was then cooled to room temperature and poured into
crushed ice. The aqueous phase was extracted with EtOAc (3ꢂ60 mL)
and the combined organic layers were stirred with a 2 M aqueous
solution of K2CO3 for 30 min. The phases were separated, the organic
phase was washed with H2O (100 mL), brine (100 mL), dried over
Na2SO4 and evaporated under reduced pressure. The resulting solid
was purified by flash chromatography eluting with from 5 to 40%
EtOAc in petroleum ether to obtain the desired compound 11 (0.28 g,
0.64 mmol, 62%) as off white solid. Mp: 102e104 ꢀC; Rf (40% EtOAc/
PET) 0.28; nmax (KBr) 3450, 2935, 2867, 2356, 1735, 1461, 1378, 1364,
4.5.2. Methyl
3b-acetoxy-7-keto-25(S)-methyl-24-bishomochol-5-
en-26-oate (14)10. To a suspension of CrO3 (1.50 g, 15.20 mmol) in
CH2Cl2 (20 mL) at ꢁ20 ꢀC, 3,5-dimethylpyrazole (1.46 g,
15.20 mmol) was added and the resulting mixture was stirred at
ꢁ20 ꢀC for 20 min. A solution of 13 (0.40 g, 0.88 mmol) in CH2Cl2
(10 mL) was then added and the mixture was allowed to warm at
room temperature and reacted for 2 h. The reaction mixture was
then filtered through a Celite pad, washing the filter with CH2Cl2,
and evaporated to dryness. The crude was purified by flash chro-
matography eluting with from 5 to 10% EtOAc in petroleum ether to
furnish the desired compound 14 (0.34 g, 0.70 mmol, 83%) as off
white solid. Mp: 110e112 ꢀC; Rf (10% EtOAc/PET) 0.37; dH (400 MHz,
CDCl3) 0.67 (3H, s, 18-CH3), 0.91 (3H, d, J 6.4 Hz, 21-CH3), 1.02e1.10
(3H, m), 1.15 (3H, d, J 6.9 Hz, 27-CH3), 1.21 (3H, s, 19-CH3), 1.24e2.01
(19H, m), 2.05 (3H, s, COCH3), 2.20e2.25 (1H, m, 25-CH), 2.39e2.54
(3H, m, 4-CH2þ8-CH), 3.67 (3H, s, CO2CH3), 4.70 (1H, m, 3-CH), 5.70
(1H, br s, 6-CH); dC (100.6 MHz, CDCl3) 11.9, 2ꢂ 17.2, 18.7, 21.1, 21.2,
23.7, 26.2, 27.3, 28.4, 34.2, 35.5, 35.7, 35.9, 37.7, 38.2, 38.6, 39.4, 43.0,
45.3, 49.7, 49.9, 51.4, 54.6, 72.1, 126.6, 163.8, 170.2, 177.3, 201.8.
1193,1165 cmꢁ1
; dH (400 MHz, CDCl3) 0.62 (3H, s,18-CH3), 0.85 (3H, d,
J 6.4 Hz, 21-CH3), 0.95 (3H, s,19-CH3), 0.99e1.04 (5H, m),1.08 (3H, d, J
6.6 Hz, 27-CH3), 1.20e1.99 (23H, m), 2.37 (1H, q, J 6.9 Hz, 25-CH),
3.40e3.48 (1H, m, 3-CH), 3.61 (3H, s, CO2CH3), 5.28(1H, bd, J 4.7 Hz, 6-
CH); dC (100.6 MHz, CDCl3) 11.7, 16.82, 18.4, 19.2, 23.6, 24.1, 28.0, 31.4,
2ꢂ 31.7, 34.0, 34.18, 35.5, 35.6, 36.36, 37.1, 39.3, 39.6, 2ꢂ 42.1, 49.9,
51.3, 55.9, 56.6, 71.4, 121.4, 140.7, 177.3. HRMS (ESIþ) m/z 431.3526
[(MþH)þ; calcd for C28H47O3 431.3525].
4.4.3. 25(S)-D
4-Dafachronic acid (1). To a solution of 11 (0.27 g,
0.63 mmol) in dry toluene (15 mL), cyclohexanone (0.26 g,
2.63 mmol) and aluminium isopropoxide (0.20 g, 0.96 mmol) were
added and the resulting mixture was refluxed overnight. The re-
action mixture was then diluted with EtOAc (50 mL) and 1%
aqueous H2SO4 (50 mL), and stirred at room temperature for
30 min. The phases were separated and the aqueous phase was
extracted with EtOAc (3ꢂ50 mL). The combined organic layers were
washed with H2O (100 mL), brine (100 mL), dried over Na2SO4 and
evaporated under reduced pressure. The crude was dissolved in 5%
NaOH in MeOH (12 mL) and was treated with MW (T¼70 ꢀC,
P¼200 psi, power 100 W) for 10 min. The brown reaction mixture
was evaporated to dryness, dissolved into water (100 mL) and
extracted with diisopropyl ether (2ꢂ50 mL). The organic phase was
separated and acidified to pH¼4 with 3N HCl and extracted with
EtOAc (3ꢂ50 mL). The combined organic layers were washed with
H2O (100 mL), brine (100 mL), dried over Na2SO4 and evaporated
under reduced pressure. The crude was purified by flash
4.5.3. Methyl
7-keto-3b-acetoxy-25(S)-methyl-24-bishomo-5a-
cholan-26-oate (15)10. To a solution of 14 (0.30 g, 0.62 mmol) in
EtOAc (30 mL) Pd/C 10% w/w (20 mg, 0.04 mmol) was added and
the resulting mixture was hydrogenated at 1 atm for 5 h. The re-
action mixture was then filtered through a Celite pad, washing the
filter with EtOAc. The filtrate was evaporated under reduced pres-
sure to give the desired 5a-derivative 15 (0.28 g, 0.56 mmol, 93%) as
white solid that was used for the next step without further puri-
fication. Mp: 116e118 ꢀC; Rf (10% EtOAc/PET) 0.41; dH (400 MHz,
CDCl3) 0.64 (3H, s, 18-CH3), 0.88 (3H, d, J 6.4 Hz, 21-CH3), 0.93e1.07
(4H, m), 1.09 (3H, s, 19-CH3), 1.13 (3H, d, J 6.9 Hz, 27-CH3), 1.18e1.99

A. Gioiello et al. / Tetrahedron 67 (2011) 1924e1929
1929
(19H, m), 2.02 (3H, s, COCH3), 2.15e2.25 (1H, m, 25-CH), 2.30 (2H,
bt, J 12.0 Hz, 6-CH2), 2.42 (1H, q, J 6.8 Hz, 8-CH), 3.67 (3H, s,
CO2CH3), 4.67 (1H, m, 3-CH); dC (100.6 MHz, CDCl3) 11.6, 12.0, 17.2,
18.6, 21.3, 21.7, 23.7, 24.9, 27.0, 28.3, 33.8, 34.2, 35.4, 35.6, 35.7, 35.9,
38.6, 39.4, 42.4, 45.8, 46.4, 48.8, 49.9, 51.4, 54.9, 54.9, 72.7, 170.4,
177.3, 211.5.
under reduced pressure The residue was purified by flash chro-
matography using 5e40% EtOAc in petroleum ether to afford the
desired compound 2 (68 mg, 0.17 mmol, 87%) as off white solid. Mp:
139e141 ꢀC; Rf (5% MeOH/CHCl3þ0.1% AcOH) 0.42; a1D6 42.6 (c 0.8,
CHCl3); dH (400 MHz, CDCl3) 0.56 (3H, s, 18-CH3), 0.95 (3H, d, J
6.4 Hz, 21-CH3), 1.01 (3H, s, 19-CH3), 1.21 (3H, d, J 6.9 Hz, 27-CH3),
1.25e2.18 (1H, m, CH24), 2.15e2.25 (2H, m, 2-CH2), 2.30e2.35 (1H,
m, 25-CH), 2.42e2.47 (2H, m, 4-CH2), 5.19 (1H, br s, 7-CH); dC
(100.6 MHz, CDCl3) 11.8, 12.4, 17.0, 18.7, 21.6, 22.9, 23.7, 27.9, 30.0,
34.0, 34.3, 35.6, 36.0, 38.1, 38.7, 39.3, 39.4, 42.8, 43.3, 44.2, 48.8,
54.9, 56.0, 117.0, 139.4, 182.1, 212.0. HRMS (ESIþ) m/z 415.3215
[(MþH)þ; calcd for C27H43O3 415.3212].
4.5.4. Methyl 7a-hydroxy-3b-acetoxy-25(S)-methyl-24-bishomo-5a-
cholan-26-oate (16). To a solution of the 7-keto derivative 15
(0.26 g, 0.52 mmol) in dry THF (10 mL) at ꢁ78 ꢀC L-selectrideÒ
(0.8 mL) was added dropwise. The resulting mixture was stirred at
ꢁ78 ꢀC for 2 h, and at ꢁ30 ꢀC for 12 h. A mixture of H2O/EtOH (1:4,
v/v, 20 mL) was added and the reaction mixture was allowed to
warm at 0 ꢀC. At this temperature the reaction was poured into an
aqueous saturated solution of NH4Cl (60 mL), warmed at room
temperature and extracted with EtOAc (3ꢂ40 mL). The combined
organic layers were washed with H2O (50 mL), brine (2ꢂ50 mL),
dried over Na2SO4 and evaporated under reduced pressure. The
crude was purified by flash chromatography eluting with from 5 to
Supplementary data
Supplementary data related to this article can be found online at
doi:10.1016/j.tet.2011.01.022. These data include MOL file and
InChIKey of the most important compounds described in this
article.
20% EtOAc in petroleum ether to furnish the corresponding 7a-OH
derivative 16 (0.22 g, 0.46 mmol, 88%) as off white solid. Mp:
References and notes
107e109 ꢀC; Rf (15% EtOAc/PET) 0.26; nmax (KBr) 3523, 2944, 2865,
2357, 2138, 1734, 1457, 1375, 1261, 751 cmꢁ1
; dH (400 MHz, CDCl3)
1. (a) Ogawa, A.; Sommer, R. J. Science 2009, 326, 944; (b) Fielembach, N.; Antebi,
A. Genes Dev. 2009, 22, 2149; (c) Baumeister, R.; Schaffitzel, E.; Hertweck, M. J.
Endocrinol. 2006, 190, 191; (d) Beckstead, R. B.; Thummel, C. S. Cell 2006, 124,
1137; (e) Riddle, D. L.; Albert, P. S. In C. elegans II, 2nd Edition; Riddle, D. L.,
Blumenthal, T., Meyer, B. J., Priess, J. R., Ed.; Cold Spring Harbor, NY, 1997; pp.
739e768.
2. (a) Angelo, G.; Van Gilst, M. R. Science 2009, 326, 954; (b) Shostak, Y.; Van Gilst,
M. R.; Antebi, A.; Yamamoto, K. R. Genes Dev. 2007, 18, 2529.
3. Kim, K.; Sato, K.; Shibuya, M.; Zeiger, D. M.; Butcher, R. A.; Ragains, J. R.; Clardy,
J.; Touhara, K.; Sengupta, P. Science 2009, 326, 994.
4. (a) Gerish, B.; Rottier, V.; Li, D.; Motola, D. L.; Cummins, C. L.; Lehrach, H.;
Mangelsdorf, D. J.; Antebi, A. Proc. Nat. Acad. Science 2007, 104, 5014; (b)
Schroeder, F. C. ACS Chem Biol. 2006, 1, 198.
5. Dumas, K. J.; Guo, C.; Wang, X.; Burkhart, K. B.; Adams, E. J.; Alam, E.; Hu, P. J.
Dev. Biol. 2010, 340, 605.
6. (a) Riddle, D. L.; Swanson, M. M.; Albert, P. S. Nature 1981, 290, 668; (b) Motola, D.
L.; Cummins, C. L.; Rottiers, V.; Sharma, K. K.; Li, T.; Li, Y.; Suino-Powell, K.; Xu, H.
E.; Auchus, R. J.; Antebi, A.; Mangelsdorf, D. J. Cell 2006, 124, 1209; (c) Antebi, A.;
Yeh, W. H.; Tait, D.; Hedgecock, E. M.; Riddle, D. L. Genes Dev. 2000, 14, 1512; (d)
Antebi, A.; Culotti, J. G.; Hedgecock, E. M. Development 1998, 125, 1191.
7. (a) Ogawa, A.; Streit, A.; Antebi, A.; Sommer, R. J. Curr. Biol. 2009, 19, 67; (b)
Wang, Z.; Zhou, X. E.; Motola, D. L.; Gao, X.; Suino-Powell, K.; Conneely, A.;
Ogata, C.; Sharma, K. K.; Auchus, R. J.; Lok, J. B.; Hawdon, J. M.; Kliewer, S. A.; Xu,
H. E.; Mangelsdorf, D. J. Proc. Nat. Acad. Science 2009, 106, 9138; (c) Viney, M. E.
Bioassays 2009, 31, 496.
0.65 (3H, s, 18-CH3), 0.82 (3H, s, 19-CH3), 0.89 (3H, d, J 6.5 Hz, 21-
CH3), 1.01e1.13 (4H, m), 1.16 (3H, d, J 6.5 Hz, 27-CH3), 1.25e1.97
(22H, m), 2.02 (3H, s, COCH3), 2.41e2.46 (1H, m, 25-CH), 3.67 (3H, s,
CO2CH3), 3.82 (1H, bd, J 2.6 Hz, 7-CH), 4.71 (1H, m, 3-CH); dC
(100.6 MHz, CDCl3) 11.1, 11.7, 17.1, 18.5, 20.9, 21.4, 23.6, 23.7, 27.3,
28.1, 33.5, 34.2, 35.5, 35.6, 35.7, 36.2, 36.4, 36.9, 39.4, 39.4, 42.6,
45.7, 50.5, 51.4, 56.0, 67.8, 73.5, 170.5, 177.3. HRMS (ESIþ) m/z
491.3734 [(MþH)þ; calcd for C30H51O5 491.3737].
4.5.5. 3
acid (17)10. Methyl 7
omo-5 -cholan-26-oate (16) (0.16 g, 0.32 mmol) was dissolved in
dry pyridine (6 mL) and SOCl2 (95 mg, 0.80 mmol) was added at
ꢀC. The resulting solution was stirred at room temperature for
b
-Hydroxy-25(S)-methyl-24-bishomo-5
a-chol-7-en-26-oic
a
-hydroxy-3 -acetoxy-25(S)-methyl-24-bish-
b
a
0
48 h, and then cautiously poured into crushed ice (40 mL) and
extracted with Et2O (3ꢂ50 mL). The combined organic phases were
washed with NaHCO3 saturated solution (40 mL), 1
N HCl
(2ꢂ40 mL), H2O (40 mL), brine (40 mL), dried over Na2SO4 and
evaporated under reduced pressure to furnish the corresponding
8. (a) Hotez, P. J.; Bethony, J.; Bottazzi, M. E.; Brooker, S.; Diemert, D.; Loukas, A.
Trends Parasitol. 2006, 22, 327; (b) Jasmer, D. P.; Goverse, A.; Smant, G. Annu.
Rev. Phytopathol. 2003, 41, 245.
D
7-derivative (0.14 g, 0.28 mmol, 90%) that was submitted to hy-
drolysis without further purification. The thus obtained crude was
dissolved into 5% NaOH in MeOH (4 mL) and reacted at room
temperature overnight. The solvent was evaporated under reduced
pressure, the residue was dissolved into H2O (40 mL), washed with
iPr2O (2ꢂ20 mL), acidified with 2 N HCl and extracted with EtOAc
(3ꢂ40 mL). The combined organic layers were washed with H2O
(50 mL), brine (50 mL), dried over Na2SO4 and evaporated under
reduced pressure to yield the desired product 17 (0.11 mg,
0.27 mmol, 96%) as white solid. Mp: 94e96 ꢀC; Rf (5% MeOH/
CHCl3þ0.1% AcOH) 0.28; dH (400 MHz, CDCl3) 0.52 (3H, s, 18-CH3),
0.78 (3H, s, 19-CH3), 0.90 (3H, d, J 6.4 Hz, 21-CH3), 0.92e1.06 (4H,
m), 1.15 (3H, d, J 6.9 Hz, 27-CH3), 1.21e1.97 (23H, m), 2.42e2.51 (1H,
m, 25-CH), 2.50e2.75 (2H, br s, OHþCO2H), 3.64 (1H, m, 3-CH), 5.17
(1H, br s, 7-CH); dC (100.6 MHz, CDCl3) 11.7, 12.9, 17.0, 18.7, 21.4,
22.9, 23.7, 27.8, 29.6, 31.2, 34.10, 34.15, 35.6, 36.0, 37.0, 37.74, 39.2,
39.5, 40.1, 43.3, 49.3, 54.9, 56.0, 70.9, 117.4, 139.5, 180.0.
9. Khripach, V. A.; Zhabinskii, V. N.; Konstantinova, O. V.; Khripach, N. B.; An-
tonchick, A. V.; Antonchick, A. P.; Schneider, B. Steroids 2005, 70, 551.
10. Giroux, S.; Corey, E. J. J. Am. Chem. Soc. 2007, 129, 9866.
11. Martin, R.; Cabritz, F.; Entchev, E. V.; Kurzchalia, T. V.; Knolker, H.-J. Org. Biomol.
Chem. 2008, 6, 4293.
12. (a) Sharma, K. K.; Wang, Z.; Motola, D. L.; Cummins, C. L.; Mangelsdorf, D. J.;
Auchus, R. J. Mol. Endocrinol. 2009, 23, 640; (b) Martin, R.; Schmidt, A. W.;
Treumer, G.; Krause, T.; Entchev, E. V.; Kurzchzlia, T. V.; Knolker, H.-J. Org. Bi-
omol. Chem. 2009, 7, 909; (c) Martin, R.; Schmidt, A. W.; Treumer, G.; Kurzchzlia,
T. V.; Knoelker, H.-J. Synlett 2008, 1965; (d) Martin, R.; Entchev, E. V.; Dabrtiz, F.;
Kurzchalia, T. V.; Knolker, H.-J. Eur. J. Org. Chem. 2009, 22, 3703.
13. Giroux, S.; Corey, E. J. Org. Lett. 2008, 10, 801.
14. Dauben, W. G.; Gerdes, J. M.; Bunce, R. A. J. Org. Chem. 1984, 49, 4293 [(1-
Carboethoxy)ethyl]triphenylphosphonium bromide was prepared according to
the literature by refluxing ethyl 2-bromo propionate and 1 equiv of PPh3 in
benzene for 12 h.
15. Pellicciari, R.; Sato, H.; Gioiello, A.; Costantino, G.; Macchiarulo, A.; Sadeghpour,
B. M.; Giorgi, G.; Schoonjans, K.; Auwerx, J. J. Med. Chem. 2007, 50, 4265.
16. Corbellini, A.; Nathansohn, G. Gazz. Chim. Ital. 1956, 86, 1240.
17. Iida, T.; Kokiyama, G.; Hibiya, Y.; Miyata, S.; Inoue, T.; Ohno, K.; Goto, T.; Mano,
N.; Nambara, T.; Hofmann, A. F. Steroids 2006, 71, 18.
4.5.6. 25(S)-D
7-dafachronic acid (2). A fresh made Jones reagent
18. Salmond, W. G.; Barta, M. A.; Havens, J. L. J. Org. Chem. 1978, 43, 2057.
19. Kaiser, E.T. G.B. Patent 2,038,833A, 1979.
20. Kaiser, E.T. U.S. Patent 4,354,972A, 1982.
21. Kurosawa, T.; Sato, M.; Kikuchi, F.; Watanabe, T.; Suga, T.; Tohma, M. Steroids
1997, 62, 474.
22. (a) Kurosawa, T.; Sato, M.; Kikuchi, F.; Watanabe, T.; Tazawa, Y.; Tohma, M. Anal.
Sci. 1996, 12, 839; (b) Kurosawa, T.; Nakano, H.; Sato, M.; Tohma, M. Steroids
1995, 60, 439.
(1.0 mL) was added dropwise to a stirred solution of 17 (80 mg,
0.19 mmol) in acetone (15 mL) at 0 ꢀC and the mixture was stirred at
room temperature for 2 h. Methanol (15 mL) was then added and
the oxidized product was extracted with EtOAc (2ꢂ30 mL). The
combined organic layers were dried over Na2SO4 and evaporated