Synthesis of four cholic acid-based CSPs containing 2-naphthoyl carbamate and 3,5-dinitrophenylcarbamate moieties and their evaluation in the HPLC resolution of racemic compounds

Article abstract of DOI:10.1016/S0957-4166(02)00317-8

Four new chiral selectors, obtained by derivatising the hydroxy groups of cholic acid with 2-naphthylisocyanate and 3,5-dinitrophenylisocyanate have been prepared and linked to silica gel to obtain new chiral stationary phases (CSPs) for the HPLC separation of enantiomers. The CSP containing only 2-naphthylcarbamate groups is able to separate the enantiomers of π-acidic substrates, whereas the CSPs containing one 3,5-dinitrophenylcarbamate group and two 2-naphthyl carbamate moieties resolve π-acidic racemic compounds as well as π-basic substrates, with the observed enantiodiscriminating capabilities depending on the arrangement of the different carbamoyl units on the cholestanic backbone.

Full text of DOI:10.1016/S0957-4166(02)00317-8

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 13 (2002) 1265–1275
Synthesis of four cholic acid-based CSPs containing 2-naphthyl
carbamate and 3,5-dinitrophenylcarbamate moieties and their
evaluation in the HPLC resolution of racemic compounds
A. Iuliano,a,* I. Pieraccini,a G. Fe´lixb and P. Salvadoria
aDipartimento di Chimica e Chimica Industriale, via Risorgimento 35, 56126 Pisa, Italy
bLaboratoire d’Analyse Chimique par Reconnaissance Mole´culaire, ENSCPB 16, Avenue Pey-Berland, 33607 Pessac, France
Received 8 May 2002; accepted 12 June 2002
Abstract—Four new chiral selectors, obtained by derivatising the hydroxy groups of cholic acid with 2-naphthylisocyanate and
3,5-dinitrophenylisocyanate have been prepared and linked to silica gel to obtain new chiral stationary phases (CSPs) for the
HPLC separation of enantiomers. The CSP containing only 2-naphthylcarbamate groups is able to separate the enantiomers of
p-acidic substrates, whereas the CSPs containing one 3,5-dinitrophenylcarbamate group and two 2-naphthyl carbamate moieties
resolve p-acidic racemic compounds as well as p-basic substrates, with the observed enantiodiscriminating capabilities depending
on the arrangement of the different carbamoyl units on the cholestanic backbone. © 2002 Elsevier Science Ltd. All rights
reserved.
1. Introduction
phases (CSPs), we previously described the synthesis of
CSPs obtained by derivatising the hydroxyl groups of
deoxycholic acid with 3,5-dichlorophenylisocyanate
(whose aromatic ring has p-basic character) and 3,5-
dimethylphenylisocyanate (having a p-acidic aromatic
group) and using its carboxylic group for linking the
chiral selectors to silica gel.7 In this way, four CSPs
have been obtained which have proven to be effective in
the resolution of various racemic compounds. The
enantiodiscrimination capabilities of these CSPs
depended not only on the nature of the derivatising
aromatic groups but also on their arrangement on the
cholestanic skeleton.7 In particular, CSP 1 (Fig. 1),
which possesses a 3,5-dimethylphenylcarbamate group
Bile acids play an important role in the field of molecu-
lar recognition. They have been successfully used as
molecular tweezers,1 organic gelators,2 optically active
hosts in the formation of inclusion complexes3 and
chiral auxiliaries for asymmetric synthesis.4 The recent
use of bile acids as chiral selectors for the HPLC
resolution of racemic compounds has opened new per-
spectives about the potential of these natural products.
They have proven to be effective either as salts, which
form micelles on the silica gel surface,5 or as simple
mono arylcarbamate derivatives.6 In
approach aimed at achieving biselector chiral stationary
a
different
Figure 1. Structure of CSP 1.
* Corresponding author. Tel.: +39-050-918232; fax: +39-050-918260; e-mail: iuliano@dcci.unipi.it
0957-4166/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(02)00317-8

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A. Iuliano et al. / Tetrahedron: Asymmetry 13 (2002) 1265–1275
at the 12-position of the cholestanic skeleton and a
3,5-dichlorophenylcarbamate moiety at the 3-position,
is able to resolve both p-acidic and p-basic racemates,
so behaving as a biselector CSP.7
a terminal double bond which can be used for linking
the chiral selectors to silica gel, was introduced. N-
Methylallylamine was chosen instead of allylamine, in
order to avoid the formation, during the derivatisation
of the hydroxy group at the 12-position of the
cholestanic backbone, of a side product from the reac-
tion of the amide nitrogen with the aryl isocyanate.7
The reaction of 7 with a four-fold excess of 2-naph-
thylisocyanate in refluxing toluene afforded 8 in good
yield. Since the hydroxy group at the 3-position of the
cholestanic skeleton, which is equatorial, is more reac-
tive than the other two, which are axial, the mixed
selector 10 can be obtained simply by adjusting the
reaction temperature: at room temperature only the
3-OH group should react, whereas higher temperatures
are required in order to derivatise the other hydroxy
groups. Therefore, 7 was treated with a slight excess of
3,5-dinitrophenylisocyanate in THF at room tempera-
ture. However, under these mild reaction conditions, a
small amount of the product derivatised at both the 3-
and 12-positions was obtained, probably due to the
highly electrophilic character of the 3,5-dinitrophenyl
isocyanate, and hence, after chromatographic purifica-
tion, pure 9 was obtained in only 65% yield. The
reaction of 9 with an excess (2.5 equiv.) of 2-naph-
thylisocyanate in refluxing toluene afforded 10 in 70%
yield after chromatographic purification.
In an attempt to improve the enantiodiscrimination
capabilities of these systems we addressed our attention
toward the synthesis of bile acid derivatives possessing
aromatic groups having stronger p-acid and p-basic
character than 3,5-dichlorophenyl isocyanate and 3,5-
dimethylphenyl isocyanate, respectively, in order to
obtain chiral selectors capable, in principle, to establish
stronger p–p interactions with the racemic compounds
and, consequently, to afford better chromatographic
separations. In addition, the enantiodiscriminating
capability could also take advantage from the presence
of
a further aromatic carbamoyl group on the
cholestanic backbone. Taking into account these con-
siderations, we decided to use cholic acid as a chiral
scaffold to which aromatic carbamoyl units could be
linked, since this bile acid possesses three hydroxy
groups which can be reacted selectively.8 2-Naphthyl
isocyanate having stronger p-basic character than 3,5-
dimethylphenyl isocyanate and 3,5-dinitrophenyl iso-
cyanate, with greater p-acid character than 3,5-
dichlorophenyl isocyanate, were chosen as derivatising
groups of cholic acid. In this article we describe the
synthesis of four cholic acid-derived CSPs, the first,
containing only 2-naphthylcarbamoyl groups, and the
others possessing two 2-naphthylcarbamoyl groups and
one 3,5-dinitrophenyl carbamoyl moiety at different
positions of the cholestanic skeleton (Fig. 2), and their
use in the chromatographic resolution of racemic
compounds.
In order to obtain 13, the amide derivative 7 was
reacted with a slight excess of 2-naphthylisocyanate in
the presence of a catalytic amount of DMAP in THF as
a solvent at room temperature. The mono-arylcarba-
mate derivative 11 was obtained as sole product, under
these reaction conditions, so confirming that, using an
arylisocyanate less reactive than 3,5-dinitrophenyliso-
cyanate, the regioselectivity is guaranteed, simply by
changing the reaction temperature. Although the reac-
tivity of the two hydroxy groups at the 7- and 12-posi-
tions of the cholestanic backbone is similar and, hence,
the use of protecting groups is required in order for
selective derivatisation to be accomplished,1a much to
our surprise the reaction of 11 with an excess of 3,5-
dinitrophenylisocyanate in refluxing toluene afforded
12 as the sole product, which was obtained in 85% yield
2. Results and discussion
2.1. Synthesis of CSPs 2–5
The synthesis of selectors 8, 10 and 13 is summarised in
Scheme 1. The common starting point was the prepara-
tion of the N-methylallylamide derivative 7, obtained
by means of the mixed anhydride method:9 in this way,
Figure 2. Structures of CSPs 2–5.

A. Iuliano et al. / Tetrahedron: Asymmetry 13 (2002) 1265–1275
1267
Scheme 1. Reagents and conditions: (a) i. Bu3N, dioxane, 10°C, ii. EtOCOCl, iii. N-methylallylamine; (b) 2-naphthylisocyanate,
DMAP, toluene, reflux; (c) 3,5-dinitrophenylisocyanate, THF, rt; (d) 2-naphthylisocyanate, DMAP, rt; (e) 3,5-dinitrophenyliso-
cyanate, toluene, reflux.
after chromatographic purification. This probably hap-
pens because the crowding generated by the presence of
a 3,5-dinitrophenylcarbamate at the 12-position pre-
vents the approach of another 3,5-dinitrophenylcarba-
mate group to the 7-position. Additionally, using a
four-fold excess of 3,5-dinitrophenyl isocyanate and
prolonging the reaction time, no trace of the product
having a 3,5-dinitrophenylcarbamate group at the 7-
position can be detected. By reacting 12 with an excess
of 2-naphthylisocyanate in refluxing toluene 13 was
obtained in 60% yield, after chromatographic purifica-
tion. The moderate yield is due to incomplete conver-
sion of 12, again probably because of the steric
hindrance exerted by the 3,5-dinitrophenylcarbamate
moiety at the 12-position.
The preparation of the last chiral selector 18 required a
different synthetic approach, which is summarised in
Scheme 2. Since 18 possesses two 2-naphthylcarbamoyl
groups at the 3- and 12-positions and a 3,5-dinitro-
phenylcarbamoyl group at the 7-position, and the pres-
ence of
a
2-naphthylcarbamate moiety at the
12-position does not prevent the derivatisation of the
hydroxy group at the 7-position, protection of this

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A. Iuliano et al. / Tetrahedron: Asymmetry 13 (2002) 1265–1275
Scheme 2. Reagents and conditions: (a) NBS, 0.37 M NaHCO3, rt to 85°C; (b) i. Bu3N, dioxane, 10°C, ii. EtOCOCl, iii.
N-methylallylamine, 10°C to rt; (c) 2-naphthylisocyanate, DMAP, toluene, reflux; (d) NABH4, THF/MeOH 0°C to rt; (e)
3,5-dinitrophenylisocyanate, toluene, reflux.
cm (internal diameter 4.6 mm). The amount of selector
bonded to the silica gel was determined in each case by
means of elemental analysis and resulted in comparable
loading values for all of the CSPs prepared.
group is mandatory. This protection can be accom-
plished by means of regioselective oxidation of the 7
hydroxy group of the cholic acid with NBS in alkaline
solution, because it is well known that NaBH4 reduc-
tion of the carbonyl function takes place with complete
stereoselectivity and that the stereogenic centre is
restored to the same absolute configuration as in 6.1a
Therefore, 6 was reacted with NBS in bicarbonate
solution and the ketoacid 14 was converted into the
corresponding N-methylallylamide 15, using the mixed
anhydride method. The reaction of 15 with a 2.5-fold
excess of 2-naphthylisocyanate in refluxing toluene, fol-
lowed by reduction with NaBH4 afforded the disubsti-
tuted derivative 17 with complete stereoselectivity. The
selector 18 was then obtained by treating 17 with an
excess of 3,5-dinitrophenylisocyanate in refluxing
toluene.
2.2. Use of CSPs 2–5 in the chromatographic separa-
tion of racemic compounds
The racemic compounds reported in Chart 1 were used
to test the enantiodiscriminating capability of CSPs
2–5. The chromatographic results obtained in the sepa-
ration of the p-acidic derivatives are reported in Table
1. CSP 2, which possesses only 2-naphthyl carbamate
moieties is able to separate the enantiomers of all the
selected p-acceptor racemates, with low to moderate
enantioselectivity values. The best results are obtained
in the case of the amino alcohol derivatives (runs 3 and
4), suggesting that the hydroxy group of the racemic
substrate represents a further enantioselective interac-
tion site with the chiral selector of the CSP. Further-
more, not only the 3,5-dinitrobenzoyl derivatives, but
also the less p-acidic 4-nitrobenzamides 21 (runs 5 and
6) are resolved using CSP 2. Perusal of Table 1 gives an
immediate idea of the different behaviour of the three
mixed CSPs with respect to the resolution of p-acidic
compounds. CSP 3, possessing a 3,5-dinitrophenylcar-
bamate group at the 3-position of the cholestanic back-
bone, is able to resolve only the phenylglycinol
derivative 20c (run 3), whereas CSP 4, which presents
the 3,5-dinitrophenylcarbamate moiety at the 12-posi-
Selectors 8, 10, 13 and 18 were covalently linked to
silica gel, as described in Scheme 3, by means of
reaction with a five-fold excess of 3-mercaptopropyl-
trimethoxysilane in the presence of AIBN in refluxing
CHCl3.7 Under these reaction conditions the selectors
were fully converted into the corresponding silane
derivatives, which were separated from the excess of
3-mercaptopropyltrimethoxysilane simply by washing
with pentane. The grafting to silica gel was carried out
in refluxing toluene over 24 h and, after being thor-
oughly washed and dried, the derivatised silica gels
were employed for packing stainless steel columns of 15

A. Iuliano et al. / Tetrahedron: Asymmetry 13 (2002) 1265–1275
1269
Scheme 3. Reagents and conditions: (a) 3-mercaptopropyltrimethoxysilane, AIBN, refluxing CHCl3; (b) silica gel, refluxing
toluene.
Chart 1.
tion, separates the enantiomers of all the derivatives
apart from N-3,5-dinitrobenzoyl valinol 20d (run 4).
An intermediate behaviour is detected in the case of
CSP 5, where the 3,5-dinitrophenylcarbamate group is
at the 7-position of the cholestanic system: this phase
resolves only four of the six p-acidic compounds, with
enantioselectivity values comparable to those observed
using CSP 4, the sole exception is represented by 20c
(run 3) which is resolved with a particularly high h
value, even higher than that observed upon CSP 2.
These chromatographic data indicate that the replace-
ment of one of the three p-basic 2-naphthylcarbamate
moieties with a p-acid 3,5-dinitrophenylcarbamate
group affords CSPs which can discriminate between the
enantiomers of p-acceptor racemic compounds, depend-
ing on the position where the substitution has taken
place.
Table
2 reports on the chromatographic results
obtained in the resolution of p-basic racemates upon
CSPs 3–5. As expected, CSP 2 did not give any resolu-
tion of these compounds, because of the lack of a
p-acid group which gives rise to p–p interactions with
the substrates.10 All three mixed CSPs are able to

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A. Iuliano et al. / Tetrahedron: Asymmetry 13 (2002) 1265–1275
Table 1. Chromatographic resolution of racemic p-acceptor compounds on CSPs 2–5a
Run
Compound
CSP 2
CSP 3
CSP 4
hc (o.e.)d
CSP 5
hc (o.e.)d
Eluente
k%b
hc (o.e.)d
k%b
hc
k%b
4.47
7.96
10.18
6.77
k%b
3.46
6.05
13.40f
10.75f
9.48h
13.10
1
2
3
4
5
6
20a
20b
20c
20d
21a
21b
4.32
7.35
8.85
7.50
3.55g
3.95
1.11
1.12
1.22
1.15
1.05 (+)
1.16 (+)
4.56
7.66
8.08
5.63
3.26
5.07
1
1
1.20
1
1
1
1.05
1.18
1.20
1
1.07 (+)
1.06 (+)
1.05
1
1.66
1
1.06 (+)
1.08 (+)
A
A
B
B
A
C
3.04
3.62
a Chromatographic conditions: UV detection (u=254 nm), flow 1 mL/min, T=25°C.
b Retention factor of the first eluted enantiomer.
c Enantioselectivity factor.
d Sign of the circular dichroism (at 254 nm) of the first eluted enantiomer.
e A=hexane/dichloromethane/2-propanol 70/30/5, B=hexane/dichloromethane/2-propanol 70/30/7, C=hexane/dichloromethane/2-propanol 70/
30/3.
f Eluent A.
g Eluent C.
h Eluent C.
Table 2. Chromatographic resolution of p-donor racemic compounds on CSPs 3–5a
Run
Compound
CSP 3
CSP 4
CSP 5
Eluente
k%b
hc (o.e.)d
k%b
hc (o.e.)d
k%b
hc (o.e.)d
1
2
3
4
5
6
7
8
9
22a
22b
23
24a
24b
24c
25a
25b
25c
3.76
5.11
3.79
1.53
1.22
2.66
3.82
2.17
3.69
1.09 (+)
1.05 (+)
1.08 (−)
1
1
1
1
1
1
3.06
1.98f
3.69
1.36
1.06
2.52
3.70
1.76
3.07
1.09 (+)
1.06 (+)
1.15 (−)
1.18 (+)
1.40 (+)
1.09 (+)
1.04
3.08
3.97
3.39
1.16
–
2.04
3.87
2.13
3.52
1.12 (+)
1.12 (+)
1.06 (−)
1
–
1
1
1
1
D
E
D
A
A
A
E
1.06
1.11
E
E
a Chromatographic conditions: UV detection (u=254 nm), flow 1 mL/min, T=25°C.
b Retention factor of the first eluted enantiomer.
c Enantioselectivity factor.
d Sign of the circular dichroism at 254 nm (240 nm for compounds 24) of the first eluted enantiomer.
e A=hexane/dichloromethane/2-propanol 70/30/5, D=hexane/dichloromethane/2-propanol 80/20/1, E=hexane/dichloromethane/2-propanol 90/
10/1.
f Eluent D.
resolve p-basic amide derivatives with the enantioselec-
tivity depending on the position of the 3,5-dinitro-
phenylcarbamate group on the cholestanic backbone.
CSPs 3 and 4 show the same behaviour toward the
chromatographic separation of the enantiomers of
amides 22, whereas CSP 5 affords slightly better resolu-
tion of these compounds, which is independent of the
structure of the substrates (runs 1 and 2). On the
contrary, the resolution of the anilide 23 is better using
CSP 4 than those seen with CSPs 3 and 5. As far as
underivatised compounds, i.e. binaphthol derivatives
and alkylarylcarbinols, are concerned, only CSP 4 has
proven effective (runs 4–9) affording resolution depen-
dent on the structure of the substrates. The chiral
recognition toward binaphthol derivatives is influenced
by the presence of substituents at the 6,6%- and 7,7%-posi-
tions of the binaphthyl system in an opposite mode: the
7,7%-diallyloxy-2,2%-dihydroxy-1,1%-binaphthyl 24b (run
5, Fig. 3) is better resolved than BINOL 24a (run 4),
whereas the enantiomers of 6,6%-dibromo-2,2%-dihy-
droxy-1,1%-binaphthyl 24c (run 6) are separated less well
with respect to BINOL.
Even the resolution of the alkylarylcarbinols depends
on the nature of the examined racemates. When the
aromatic ring of the substrate possesses an electron-
donating group, such as the dimethylamino moiety of
25c, the racemate is resolved with a higher h value (run
9). This suggests that the p–p interaction between the
electronically complementary aromatic moieties present
on the chiral selector of CSP 4 (3,5-dinitrophenyl) and
the substrate (4-dimethylaminophenyl) play an impor-
tant role in the enantiodiscrimination of these race-
mates. On the contrary, the presence of a tert-
butyl group on the stereogenic centre of the alcohol is
deleterious to the enantiodiscrimination and the separa-
tion of the enantiomers of a tert-butyl carbinol is poor
(run 8).

A. Iuliano et al. / Tetrahedron: Asymmetry 13 (2002) 1265–1275
1271
or in DMSO-d6, using TMS as internal standard. The
following abbreviations were used: s=singlet; d=dou-
blet; dd=double doublet; t=triplet; ddt=double dou-
ble triplet; m=multiplet.
TLC analyses were performed on silica gel plates
Macherey–Nagel 60 F254. Chromatographic purification
were performed using silica gel Macherey–Nagel, 70–
230 or 230–400 for flash-chromatography. Optical rota-
tions were measured at the sodium D-line on a digital
polarimeter JASCO-DIP 360: concentration, solvent
and temperature are those specified for every measure.
Melting points were taken using a Kofler Reichert–
Jung apparatus and are uncorrected. IR spectra were
recorded on a Perkin–Elmer 1710 spectrophotometer.
HPLC analyses were performed on a JASCO PU-980
chromatograph, equipped with a JASCO UV-975
detector and a circular dichroism JASCO J-600 detec-
tor. Elemental analyses were carried out at Laboratorio
di Microanalisi, Dipartimento di Farmacia, Universita`
di Pisa.
Figure 3. Chromatographic resolution of 24b upon CSP 4:
for chromatographic conditions see Table 2.
Toluene, THF and dioxane were heated under reflux
over sodium–benzophenone and distilled before use.
N-Methylallylamine, pyridine and tributylamine were
distilled over CaH2. Chloroform was distilled before
use. 2-Naphthoylchloride was distilled under reduced
pressure and 3,5-dinitrobenzoylchloride was recrys-
tallised from petroleum ether. Ethyl chloroformate was
distilled under nitrogen atmosphere just before use.
N-Bromosuccinimide was recrystallised from water. 3-
Mercaptopropyltrimethoxysilane was distilled under
reduced pressure before use. Unless otherwise specified
the reagents were used without any purification.
3. Conclusions
The chromatographic data concerning the resolution of
both p-acceptor and p-donor racemic compounds upon
CSPs 2–5 allow us to reach some conclusions about the
behaviour of these CSPs. The separation of the enan-
tiomers of p-acid compounds, and the resolution of
p-basic racemates depend not only on the electronic
nature of the aromatic carbamate moieties but also on
the relative position that these functions have on the
cholestanic backbone. CSP 2, possessing only 2-naph-
thyl carbamate moieties is able to separate the enan-
tiomers of all the examined p-acid substrates, whereas
no resolution of p-basic racemates is obtained. The
mixed CSPs 3–5, having a 3,5-dinitrophenylcarbamate
moiety in three different position of the cholestanic
skeleton, show enantiodiscrimination depending on the
positioning of the p-acceptor moiety. In particular,
CSP 4, which possesses a 3,5-dinitrophenylcarbamate
group at the 12-position of the cholestanic backbone
has proven to be the most versatile of these CSPs: as a
matter of fact it was able to resolve almost all of the
p-acid racemates and p-basic substrates examined,
including underivatized compounds, thus demonstrat-
ing that the use of adequately derivatised bile acids
represents a promising approach to the achievement of
broad-spectrum CSPs. In this case, and as we have
previously shown,7,11 the enantioselective behaviour of
the bile acid derivatives is strongly dependent on the
arrangement of the aromatic substituents on the
cholestanic backbone. Studies aimed at clarifying the
reasons for the different behaviour of the CSPs 3–5 are
now in progress and the results will be reported in due
course.
4.1. N-Allyl-N%-methylcholan-24-amide, 7
Dry tributylamine (8.7 mL, 36.70 mmol) was added to
a solution of cholic acid 6 (15.00 g, 36.70 mmol) in dry
dioxane (270 mL); the mixture was cooled to 10°C and
ethylchloroformate (3.5 mL, 36.70 mmol) in dry diox-
ane (12 mL) was added dropwise. After 10 min, N-
methylallylamine (8.8 mL, 91.80 mmol) in dry dioxane
(15 mL) was dropwise added. The resulting mixture was
stirred at 10°C for additional 30 min, and at room
temperature overnight. Then it was poured into water
(500 mL) and the crude product was extracted with
ethyl acetate (5×50 mL); the combined organic extracts
were washed with 10% HCl (2×50 mL), water, 10%
NaHCO3 and water, in that order, then dried over
anhydrous Na2SO4. After removing the solvent at
reduced pressure, 7 was obtained (10.80 g, 23.4 mmol,
1
64%): mp=76–80°C; [h]2D2=+2.6 (c 1.00; CH2Cl2); H
NMR (300 MHz, CDCl3, l): 0.65 (s, 3H, CH3), 0.90 (s,
3H, CH3), 1.00 (d, 3H, CH3 21), 1.10–2.70 (m, 27H,
steroidal CH and CH2, OH 3, 7, 12), 2.88–2.94 (s, 3H,
N-CH3), 3.40 (m, 1H, CH 3), 3.80–4.00 (m, 4H,
CH2CHꢀCH2, CH 7 and CH 12), 5.15 (m, 2H,
CH6 2ꢀCH), 5.75 (ddt, 1H, CH6
ꢀCH2); 13C NMR (50
4. Experimental
MHz, CDCl3, l): 12.5, 17.5, 22.4, 23.2, 26.3, 27.5, 28.1,
29.9, 30.4, 31.1, 31.4, 34.6, 34.7, 35.3, 35.6, 39.5, 41.4,
41.6, 46.4, 46.9, 52.2, 68.4 (C 7), 71.6 (C 3), 73.0 (C 12),
116.6 and 117.0 (ꢀCH2), 132.7 and 133.1 (-CHꢀ), 173.4
1H and 13C NMR spectra were recorded on a NMR
Varian Gemini 200 or on a Varian VXR-300 in CDCl3

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A. Iuliano et al. / Tetrahedron: Asymmetry 13 (2002) 1265–1275
and 174.0 (CꢀO). IR (KBr, cm−1): 3421, 2934, 1654,
1628, 1458, 1406, 1261, 1078, 1047, 914, 796.
4.4. N-Allyl-N%-methyl-3-(3,5-dinitrophenyl)carbamoyl-
oxy-7,12-bis(2-naphthyl)carbamoyloxy-cholan-24-amide,
10
2-Naphthylisocianate (0.93 g, 5.50 mmol) and DMAP
(0.015 g, 0.12 mmol) were added to a solution of 9 (1.47
g, 2.19 mmol) in dry toluene (40 mL) and the resulting
mixture was heated under reflux for 40 h; the solvent
was removed under reduced pressure and the crude
product was purified by flash chromatography (SiO2,
CH2Cl2/acetone=95:5), affording 10 (1.41 g, 1.40
mmol, 64%): mp=155–158°C; [h]2D1=+87.3 (c 0.99;
4.2. N-Allyl-N%-methyl-3,7,12-tris(2-naphthyl)carbamoyl-
oxycholan-24-amide, 8
2-Naphthylisocyanate (1.10 g, 6.50 mmol) and DMAP
(0.012 g, 0.1 mmol) was added to a solution of 7 (0.85
g, 1.85 mmol) in dry toluene (25 mL) and the resulting
mixture was heated under reflux for 40 h. The solvent
was removed under reduced pressure, and the crude
product was purified by flash chromatography (SiO2,
CH2Cl2/acetone=95:5), affording 8 (1.31 g, 1.35 mmol,
73%): mp=134–137°C; [h]2D0=+118.3 (c 1.01; CH2Cl2);
1H NMR (200 MHz, CDCl3, l): 0.80 (s, 3H, CH3), 0.90
(d, 3H, CH3), 0.95 (s, 3H, CH3), 1.00–2.40 (m, 24H,
steroidal CH and CH2), 2.80 (s, 3H, N-CH3), 3.65–4.00
1
CH2Cl2); H NMR (200 MHz, CDCl3, l): 0.80 (s, 3H,
CH3), 0.90 (d, 3H, CH3 21), 0.95 (s, 3H, CH3), 1.00–
2.50 (m, 24H, steroidal CH and CH2), 2.75 and 2.80 (s,
3H, N-CH3), 3.60–3.95 (m, 2H, CH2
1H, CH 3), 4.90–5.25 (m, 4H, CHꢀCH2
12), 5.50–5.70 (m, 1H, CHꢀCH2), 7.20–7.50 (m, 8H,
6
CHꢀCH2), 4.55 (m,
6
, CH 7 and CH
6
naphthylics and carbamate NH), 7.60–7.80 (m, 6H,
naphthylics), 7.90 (s, 2H, naphthylics), 8.30–8.60 (m,
4H, 3,5-dinitrophenylics and carbamate NH); 13C
NMR (50 MHz, CDCl3, l): 12.2, 17.7, 22.3, 22.4, 23.0,
25.6, 25.8, 26.8, 27.0, 27.2, 29.1, 29.2, 30.0, 30.5, 30.8,
31.3, 31.5, 33.6, 34.2, 34.4, 34.6, 35.0, 38.1, 40.7, 43.5,
45.5, 47.5, 48.0, 52.1, 72.7 (C 7), 76.0 (C 12), 77.6 (C 3),
111.9, 114.8, 115.2, 116.6, 117.1, 117.7, 119.1, 119.7,
124.7, 126.4, 126.5, 127.2, 127.3, 127.5, 128.6, 130.0,
132.3, 132.8, 133.8, 135.7, 140.7, 148.4, 152.2 (carba-
mate CꢀO), 152.5 (carbamate CꢀO), 153.3 (carbamate
CꢀO), 173.4 and 173.8 (amide CꢀO); IR (KBr, cm−1):
3392, 2937, 1734, 1636, 1544, 1430, 1343, 1222, 1069,
816, 728. Anal. calcd for C57H64N6O11: C, 67.84; H,
6.39; N, 8.33. Found: C, 68.02; H, 6.41; N, 8.19%.
(m, 2H, CH
(m, 4H, CHꢀCH
CHꢀCH2), 6.90 (s, 1H, NH), 7.10–7.50 (m, 11H, aro-
6
2CHꢀCH2), 4.55 (m, 1H, CH 3), 4.95–5.25
6
2, CH 7 and CH 12), 5.65 (m, 1H,
6
matics and NH), 7.60–8.10 (m, 12H, aromatics); 13C
NMR (50 MHz, CDCl3, l): 12.2, 17.9, 22.4, 23.0, 25.8,
26.8, 27.0, 27.2, 29.1, 29.8, 30.4, 30.7, 30.8, 31.1, 31.5,
33.5, 34.4, 34.6, 34.9, 38.0, 40.7, 43.6, 45.5, 47.5, 47.7,
49.9, 52.1, 72.4 (C 7), 75.0 (C 12), 76.8 (C 3), 114.7,
115.2, 116.5, 117.0, 117.7, 119.1, 119.2, 124.5, 124.7,
126.3, 126.6, 127.2, 127.4, 127.5, 128.5, 128.7, 129.9,
130.0, 132.4, 132.9, 133.8, 133.9, 135.3, 135.4, 135.5,
152.9 (carbamate CꢀO), 153.3 (carbamate CꢀO), 153.4,
(carbamate CꢀO), 173.2 and 173.6 (amide CꢀO); IR
(KBr, cm−1): 3402, 3297, 3052, 2939, 2068, 1718, 1633,
1605, 1534, 1506, 1432, 1396, 1358, 1215, 1045, 954,
853, 812, 746. Anal. calcd for C61H68N4O7: C, 75.59; H,
7.07; N, 5.78. Found: C, 75.69; H, 7.11; N, 5.67%.
4.5. N-Allyl-N%-methyl-3-(2-naphthyl)carbamoyl-
oxycholan-24-amide, 11
2-Naphthylisocyanate (1.44 g, 8.50 mmol) and DMAP
(0.052 g, 0.43 mmol) were added to a solution of 7 (3.57
g, 7.74 mmol) in dry THF (100 mL) and the resulting
mixture was stirred at room temperature for 16 h, then
filtered to remove 2-naphthylurea; the solvent was
evaporated under reduced pressure and the crude
product was purified by flash chromatography (SiO2;
CH2Cl2/acetone=80:20) to afford 11 (3.42 g, 5.42
mmol, 70%): mp=123–129°C; [h]2D9=+46.9 (c 1.07;
4.3. N-Allyl-N%-methyl-3-(3,5-dinitrophenyl)carbamoyl-
oxycholan-24-amide, 9
3,5-Dinitrophenylisocyanate (0.79 g, 3.76 mmol) was
added to a solution of 7 (1.58 g, 3.42 mmol) in dry
THF (40 mL) and the resulting mixture was stirred for
65 h at room temperature: the solvent was removed
under reduced pressure and the crude product was
purified by flash chromatography (SiO2; CH2Cl2/ace-
tone=80:20) affording 9 (1.49 g, 2.22 mmol, 65%):
1
CH2Cl2); H NMR (300 MHz, CDCl3, l): 0.68 (s, 3H,
CH3). 0.88 (s, 3H, CH3), 0.98 (d, 3H, CH3 21), 1.00–
2.48 (m, 26H, steroidal CH and CH2, OH 7 and 12),
2.88 and 2.92 (s, 3H, N-CH3), 3.82–4.02 (m, 4H,
1
mp=143°C; [h]2D3=+96.7 (c 1.00; CH2Cl2,); H NMR
(200 MHz, CDCl3, l): 0.70 (s, 3H, CH3), 0.90 (s, 3H,
CH3), 1.05 (d, 3H, CH3 21), 1.05–2.60 (m, 26 H,
steroidal CH and CH2, OH 7 and 12), 3.05 (s, 3H,
CH2
5.06–5.22 (m, 2H, CHꢀCH
CHꢀCH2), 7.19 (s, 1H, carbamate NH), 7.29–7.44 (m,
6
CHꢀCH2, CH 7 and CH 12), 4.58 (m, 1H, CH 3),
6
2), 5.64–5.82 (ddt, 1H,
N-CH3), 3.80–4.20 (m, 4H, CH2
CH 12), 4.60 (m, 1H, CH 3), 5.05–5.35 (m, 2H,
CHꢀCH2), 5.65–5.95 (ddt, 1H, CHꢀCH2), 8.65 (t, 1H,
6
CHꢀCH2, CH 7 and
6
3H, naphthylics), 7.68–7.75 (m, 3H, naphthylics), 7.98
(s, 1H, naphthylic); 13C NMR (50 MHz, CDCl3,
l):12.5, 17.6, 22.4, 23.2, 26.6, 27.5, 28.3, 30.4, 31.1,
31.4, 34.4, 34.7, 35.4, 35.6, 39.6, 41.2, 41.9, 46.5, 47.1,
52.2, 68.2 (C 7), 73.0 (C 12), 75.3 (C 3), 114.6, 116.6,
117.1 (ꢀCH2), 119.3, 124.4, 126.3, 127.4, 127.5, 128.6,
130.0, 132.7, 133.2 (CHꢀ), 134.0, 135.3, 153.5 (carba-
mate CꢀO), 173.5 and 173.9 (amide CꢀO); IR (KBr,
cm−1): 3435, 3056, 2938, 2869, 1706, 1629, 1550, 1506,
1466, 1433, 1400, 1359, 1233, 1047, 913, 854, 814, 746.
6
6
aromatic), 9.05 (s, 2H, aromatics), 9.65 (s, 1H, NH);
13C NMR (50 MHz, CDCl3, l): 12.6, 17.5, 22.3, 23.2,
26.4, 26.6, 27.8, 28.2, 29.6, 30.0, 31.6, 34.2, 34.7, 34.8,
35.3, 35.4, 39.6, 41.1, 41.9, 46.5, 47.6, 50.4, 52.5, 68.2,
73.1, 76.3, 111.5, 117.0, 118.0, 132.3, 142.4, 148.7, 153.4
(carbamate CꢀO), 174.2 and 174.5 (amide CꢀO); IR
(KBr, cm−1): 3446, 3110, 2940, 1734, 1617, 1544, 1466,
1420, 1345, 1245, 1221, 1071, 914, 820, 730.

A. Iuliano et al. / Tetrahedron: Asymmetry 13 (2002) 1265–1275
1273
4.6. N-Allyl-N%-methyl-3-(2-naphthyl)carbamoyloxy-12-
(3,5-dinitrophenyl)carbamoyloxycholan-24-amide, 12
1344, 1223, 1046, 955, 854, 809, 747. Anal. calcd for
C57H64N6O11: C, 67.84; H, 6.39; N, 8.33. Found: C,
67.98; H, 6.37; N, 8.21%.
3,5-Dinitrophenylisocyanate (0.76 g, 3.64 mmol) was
added to a solution of 11 (1.48 g, 2.35 mmol) in dry
toluene (30 mL) and the resulting mixture was heated
under reflux for 16 h, then allowed to cool to room
temperature. The solvent was removed under reduced
pressure and the solid obtained was purified by flash
chromatography (SiO2, CH2Cl2/acetone=88:12) to
afford 12 (1.64 g, 1.95 mmol, 83%): mp=145–149°C,
[h]2D2=+96.6 (c 0.90; CH2Cl2); 1H NMR (200 MHz,
CDCl3, l): 0.75 (s, 3H, CH3), 0.90 (s, 3H, CH3), 0.95
(d, 3H, CH3 21), 1.00–2.45 (m, 25H, steroidal CH and
CH2, OH 7), 2.90 (s, 3H, N-CH3), 3.80–4.05 (m, 3H,
4.8. N-Allyl-N%-methyl-3,12-dihydroxy-7-oxocholan-24-
amide, 15
Cholic acid 6 (3.00 g, 7.34 mmol) was added to a
solution of NaHCO3 (120 mL, 0.372 M) warmed at
about 60°C, until the solid was completely dissolved.
After cooling to room temperature, NBS (3.27 g, 18.37
mmol) was added and the resulting mixture was stirred
for 17 h at room temperature and for 2 h at 80–85°C,
then allowed to cool to room temperature. The mixture
was acidified with aqueous HCl (6 M, 100 mL): the
yellow precipitate was isolated by filtration and washed
with water, vigorously scratching. The product was
dissolved in acetone and dried over anhydrous Na2SO4;
the solvent was removed under reduced pressure afford-
ing the crude product 14 (3.27 g), which was then
dissolved in dry dioxane (60 mL) and cooled to 10°C;
dry tributylamine (1.9 mL, 8.00 mmol) was added; then
ethyl chloroformate (0.8 mL, 8.00 mmol) in dry diox-
ane (5 mL) was dropwise added, and, after 10 min,
N-methylallylamine (1.9 mL, 20.11 mmol) in dry diox-
ane (5.0 mL) was added dropwise. The resulting mix-
ture was stirred at 10°C for 30 min and at room
temperature overnight, then poured into water (100
mL), and the crude product was extracted with ethyl
acetate (5×10 mL); the combined organic extracts were
washed with a 10% aqueous HCl solution (2×10 mL),
water, 10% NaHCO3 solution and water, in that order,
then dried over anhydrous Na2SO4. After removing the
solvent at reduced pressure, pure 15 (2.80 g, 0.9 mmol,
83%) was obtained: mp=71–75°C; [h]2D3=−7.0 (c 0.88;
CH
(m, 3H, CHꢀCH2
CHꢀCH2), 6.91 (s, 1H, carbamate NH), 7.27–7.50 (m,
6
2CHꢀCH2, CH 7), 4.55 (m, 1H, CH 3), 5.05–5.25
6
, CH 12), 5.60–5.85 (ddt, 1H,
6
3H, naphthylics), 7.65–7.80 (m, 3H, naphthylics), 7.90
(s, 1H, naphthylic), 8.60 (d, 1H, 3,5-dinitrophenylic),
8.65 (t, 2H, 3,5-dinitrophenylics), 8.80 (s, 1H, carba-
mate NH); 13C NMR (50 MHz, CDCl3, l): 12.1, 17.8,
22.4, 22.9, 25.5, 27.1, 27.4, 27.5, 29.9, 30.6, 31.0, 31.3,
33.7, 34.6, 34.7, 34.8, 35.1, 35.7, 39.1, 41.1, 41.4, 45.2,
47.7, 47.9, 50.1, 52.2, 68.0 (C 7), 75.5 (C 12), 76.0 (C 3),
112.2, 114.6, 116.7 and 117.2 (ꢀCH2), 118.3, 119.1,
124.6, 126.5, 127.3, 127.4, 128.8, 130.0, 132.4, 132.8,
133.6, 135.6, 141.3, 141.4, 148.7, 152.9, 153.0 (carba-
mate CꢀO), 153.4 (carbamate CꢀO), 173.5 and 173.6
(amide CꢀO); IR (KBr, cm−1): 3403, 2939, 1734, 1628,
1544, 1432, 1344, 1224, 1047, 910, 854, 807, 731.
4.7. N-Allyl-N%-methyl-3,7-bis(2-naphthyl)carbamoyl-
oxy-12-(3,5-dinitrophenyl)carbamoyloxychol-an-
24-amide, 13
1
CH2Cl2); H NMR (200 MHz, CDCl3, l): 0.65 (s, 3H,
CH3), 0.95 (d, 3H, CH3 21), 1.15 (s, 3H, CH3), 0.90–
2.50 (m, 25H, steroidal CH and CH2, OH 3 and 12),
2.75–2.90 (m, 1H, CH 8), 2.95 (s, 3H, N-CH3), 3.50–
2-Naphthylisocyanate (0.52 g, 3.08 mmol) and DMAP
(13 mg, 0.10 mmol) were added to a solution of 12
(1.62 g, 1.93 mmol) in dry toluene (25 mL) and the
resulting mixture was heated under reflux for 16 h, then
allowed to cool to room temperature; the solvent was
removed at reduced pressure, and the obtained solid
was purified by flash chromatography (SiO2, CH2Cl2/
acetone=95:5) affording 13 (1.11 g of 1.1 mmol, yield
57%): mp=135–140°C, [h]2D2=+63.1 (c 0.91; CH2Cl2);
1H NMR (200 MHz, CDCl3, l): 0.77 (s, 3H, CH3), 0.90
(d, 3H, CH3 21), 0.95 (s, 3H, CH3), 1.05–2.50 (m, 24H,
steroidal CH and CH2), 2.85 (s, 3H, N-CH3), 3.70–4.05
3.68 (m, 1H, CH 3), 3.90–4.05 (m, 3H, CH2
and CH 12), 5.08–5.29 (m, 2H, CH2ꢀCH), 5.65–5.90
(ddt, 1H, CH
ꢀCH2); 13C NMR (50 MHz, CDCl3, l):
6 CHꢀCH2
6
6
12.7, 17.6, 22.8, 24.3, 27.6, 29.2, 29.7, 31.3, 34.1, 34.6,
35.2, 35.9, 37.3, 40.9, 45.3, 45.5, 46.0, 46.4, 46.5, 49.5,
70.9 (C 12), 72.0 (C 3), 116.9 and 117.0 (ꢀCH2), 132.8
and 133.0 (-CHꢀ), 173.7 and 173.9 (amide CꢀO), 211.5
(carbonil CꢀO); IR (KBr, cm−1): 3422, 2936, 1706,
1628, 1458, 1400, 1290, 1067, 923.
(m, 2H, CH2
(m, 4H, CHꢀCH2
CHꢀCH2), 7.00–8.10 (m, 16H, naphthylics and carba-
6
CHꢀCH2), 4.55 (m, 1H, CH 3), 5.05–5.25
4.9. N-Allyl-N%-methyl-3,12-bis(2-naphthyl)carbamoyl-
6
, CH 7 and 12), 5.65 (ddt, 1H,
oxy-7-oxocholan-24-amide, 16
6
mate NH), 8.20–8.70 (m, 3H, 3,5-dinitrophenyilics); 13C
NMR (50 MHz, DMSO-d6, l): 11.4, 17.1, 21.8, 22.2,
24.9, 26.3, 26.6, 28.2 29.1, 30.4, 31.1, 33.4, 34.1, 34.5,
37.3, 38.7, 39.1, 39.6, 40.0, 40.1, 40.3, 40.4, 42.5, 45.0,
46.6 and 46.9, 70.9 (C 7), 74.7 (C 12), 77.3 (C 3), 110.8,
113.8, 113.9, 114.3, 115.5, 117.1 and 117.4 (ꢀCH2),
119.3, 119.4, 119.5, 123.6, 125.6, 125.7, 126.4, 126.5,
126.6, 127.5, 127.7, 128.0, 128.1, 133.1, 133.2, 133.3,
136.3, 141.4, 148.1, 148.2, 152.8 (carbamate CꢀO),
152.9 (carbamate CꢀO), 171.7 (amide CꢀO); IR (KBr,
cm−1): 3290, 2937, 1733, 1635, 1606, 1544, 1506, 1432,
2-Naphthylisocyanate (2.01 g, 11.87 mmol) and DMAP
(0.032 g, 0.25 mmol) were added to a solution of the
amide 15 (2.18 g, 4.75 mmol) in dry toluene (65 mL)
and the resulting mixture was heated under reflux for
23 h, then allowed to cool to room temperature; the
solvent was removed under reduced pressure and the
crude product was purified by flash chromatography
(SiO2, CH2Cl2/acetone=92:8) affording 37 (1.82 g, 2.28
mmol, 48%): mp=137°C, [h]2D6=+120.3 (c 0.86;
1
CH2Cl2); H NMR (300 MHz, CDCl3, l): 0.78 (s, 3H,
CH3), 0.90 (d, 3H, CH3 21), 1.20 (s, 3H, CH3), 1.00–

1274
A. Iuliano et al. / Tetrahedron: Asymmetry 13 (2002) 1265–1275
2.40 (m, 23H, steroidal CH and CH2), 2.90–2.94 (m,
4H, N-CH3 and CH 8), 3.80–4.00 (m, 2H,
(s, 3H, CH3), 0.88 (d, 3H, CH3 21), 0.95 (s, 3H, CH3),
1.00–2.50 (m, 24H, steroidal CH and CH2), 2.85 (s,
CH2
CHꢀCH2
6
CHꢀCH2), 4.65 (m, 1H, CH 3), 5.00–5.25 (m, 3H,
3H, N-CH3), 3.70–4.00 (m, 2H, CH2
4.75 (m, 1H, CH 3), 4.95–5.30 (m, 4H, CHꢀCH2
7 and 12), 5.52–5.68 (ddt, 1H, CHꢀCH2), 7.10–8.70
6
CHꢀCH2), 4.50–
6
, CH 12), 5.6–5.8 (ddt, 1H, CHꢀCH2), 6.70
6
6
, CH
(s, 1H, carbamate NH), 7.06 (s, 1H, carbamate NH),
7.24–7.48 (m, 6H, naphthylics), 7.68–7.80 (m, 6H,
naphthylics), 7.87 (s, 1H, naphthylic), 8.01 (s, 1H,
naphthylic); 13C NMR (50 MHz, CDCl3, l): 12.6,
17.9, 22.7, 24.1, 26.3, 26.6, 27.5, 29.6, 30.0, 31.1, 33.5,
33.6, 34.7, 34.8, 37.0, 42.1, 45.0, 45.2, 45.3, 45.6, 45.7,
45.8, 46.9, 48.9, 49.2, 73.9 (C 12), 75.8 (C 3), 114.8,
114.9, 116.8, 116.9 119.2, 124.6, 124.7, 126..4, 126.6,
127.3, 127.4, 127.5, 128.7, 128.9, 130.2, 133.9, 135.3,
135.5, 152.9 (carbamate CꢀO), 153.0 (carbamate CꢀO),
173.3 (amide CꢀO), 211.1 (carbonil CꢀO); IR (KBr,
cm−1): 3284, 2942, 1718, 1630, 1607, 1585, 1543, 1507,
1473, 1432, 1358, 1232, 1052, 954, 854, 813, 746.
6
(m, 20H, naphthylics and 3,5-dinitrophenylics, carba-
mate NH); 13C NMR (50 MHz, CDCl3, l): 12.4, 17.8,
22.4, 23.0, 26.1, 27.1, 27.2, 27.5, 29.3, 29.4, 29.7, 30.3,
30.8, 31.0, 31.5, 33.7, 34.6, 34.7, 34.8 35.0, 37.9, 40.7,
44.0, 45.6, 47.2, 47.4, 50.1, 52.3, 73.8 (C 7), 75.8 (C
12), 76.4 (C 3), 111.8, 115.0, 116.8, 117.2 (ꢀCH2),
118.1, 119.1, 119.4, 124.7, 126.6, 127.2, 127.4, 127.6,
128.7, 128.8, 129.9, 130.0, 132.3, 132.7, 133.7, 133.9,
135.3, 135.9, 140.8, 148.2, 152.5 (carbamate CꢀO),
153.6 (carbamate CꢀO), 173.7 and 174.1 (amide CꢀO);
IR (KBr, cm−1): 3392, 3056, 2938, 1733, 1633, 1605,
1547, 1506, 1432, 1344, 1220, 1126, 1045, 955, 894,
853, 810, 730. Anal. calcd for C57H64N6O11: C, 67.84;
H, 6.39; N, 8.33. Found: C, 67.76; H, 6.41; N, 8.25%.
4.10. N-Allyl-N%-methyl-3,12-bis(2-naphthyl)carbamoyl-
oxycholan-24-amide, 17
Compound 16 (1.79 g, 2.24 mmol) was dissolved in a
mixture of dry THF (4 mL) and methanol (20 mL)
cooled to 0°C, and NaBH4 (0.13 g, 3.45 mmol) was
added slowly; when gas evolution ceased, the mixture
was allowed to warm to room temperature and stirred
overnight. The solvent was removed at reduced pres-
sure, and the remaining solid was dissolved in ethyl
acetate; the solution was washed with 10% NaHCO3
(2×30 mL) and brine (2×30 mL), then dried over
anhydrous Na2SO4. After removing the solvent, 17
was obtained (1.54 g, 1.93 mmol, 86%): mp=133–
4.12. Preparation of silane derivatives 19: representa-
tive procedure
3-Mercaptopropyltrimethoxysilane (0.8 mL, 4.25
mmol) was added to a solution of the selector (0.85
mmol) in CHCl3 (10 mL) and the resulting mixture
was heated under reflux until TLC analysis showed
complete conversion of the substrate. After cooling,
the solvent was removed at reduced pressure, and the
remaining oil was dispersed in pentane (30 mL); the
precipitate was filtered and washed again with pentane
(5×30 mL) to afford the pure product.
1
135°C, [h]2D4=+125.1 (c 1.47; CH2Cl2); H NMR (200
MHz, CDCl3, l): 0.80 (s, 3H, CH3), 0.95 (s, 6H, CH3
and CH3 21), 1.00–2.50 (m, 25H, steroidal CH and
CH2, OH 7), 2.88 (s, 3H, N-CH3), 3.75–4.00 (m, 3H,
4.12.1. N-Methyl-N%-[(trimethoxysylylpropylthio)propyl]-
3,7,12-tris(2-naphthyl)carbamoyloxycholan-24-amide,19a.
The mixture was heated under reflux for 20 h and 0.99
g of product 19a was obtained: mp=90–95°C; [h]2D6=+
94.6 (c 0.91; CH2Cl2); 1H NMR (200 MHz, CDCl3,
l): 0.70 (d, 2H, CH2), 0.80 (s, 3H, CH3), 0.90 (d, 3H,
CH3 21), 0.95 (s, 3H, CH3), 1.05–2.60 (m, 34H,
steroidal CH and CH2, chain CH2), 2.80 and 2.87 (s,
3H, N-CH3), 3.30 (m, 2H, N-CH2), 3.55 (s, 9H,
Si(OCH3)3), 4.55 (m, 1H, CH 3), 5.00–5.25 (m, 2H,
CH 7 and CH 12), 7.00–8.10 (m, 24H, naphthylics and
NH); IR (KBr, cm−1): 3299, 2939, 1726, 1635, 1605,
1542, 1506, 1432, 1359, 1228, 1072, 955, 854, 813, 747.
CH2
5.25 (m, 3H, CHꢀCH
CHꢀCH2), 6.65 (s, 1H, carbamate NH), 7.05 (s, 1H,
6
CHꢀCH2, CH 7), 4.50–4.65 (m, 1H, CH 3), 5.00–
6
2, CH 12), 5.60–5.80 (ddt, 1H,
6
carbamate NH), 7.25–7.50 (m, 6H, naphthylics), 7.65–
7.80 (m, 6H, naphthylics), 7.90 (s, 1H, naphthylic),
8.05 (s, 1H, naphthylic); 13C NMR (50 MHz, CDCl3,
l): 12.3, 17.9, 22.5, 23.1, 25.8, 27.0, 27.3, 27.8, 31.1,
34.7, 34.8, 35.0, 35.7, 124.5, 124.6, 126.4, 126.5, 127.3,
127.4, 128.7, 128.8, 130.1, 130.2, 132.7, 133.9, 134.0,
135.6, 153.2 (carbamate CꢀO), 173.4 (amide CꢀO); IR
(KBr, cm−1): 3399, 3298, 3054, 2938, 2868, 1716, 1633,
1537, 1505, 1471, 1433, 1397, 1358, 1232, 1126, 1047,
954, 909, 853, 813, 745.
4.11. N-Allyl-N%-methyl-3,12-bis(2-naphthyl)carbamoyl-
oxy-7-(3,5-dinitrophenyl)carbamoyloxy-cholan-24-amide,
18
4.12.2. N-Methyl-N%-[(trimethoxysylylpropylthio)propyl]-
3-(3,5-dinitrophenyl)carbamoyloxy-7,12-bis(2-naphthyl)-
carbamoyloxylcholan-24-amide, 19b. The mixture was
heated under reflux for 48 h and 0.96 g of product 19b
was obtained: mp=110°C; 1H NMR (200 MHz,
CDCl3, l): 0.75 (d, 2H, CH2), 0.85 (s, 3H, CH3), 0.90
(d, 3H, CH3 21), 0.95 (s, 3H, CH3), 1.00–2.60 (m,
34H, steroidal CH and CH2, chain CH2), 2.80 and
2.85 (s, 3H, N-CH3), 3.10–3.40 (m, 2H, N-CH2), 3.50
(s, 9H, Si(OCH3)3), 4.55 (m, 1H, CH 3), 4.95–5.25 (m,
2H, CH 7 and CH 12), 7.10–8.10 (m, 16H, naphthylics
and NH), 8.20–8.60 (m, 4H, 3,5-dinitrophenylics and
NH).
3,5-Dinitrophenylisocyanate (1.03 g, 4.94 mmol) was
added to a solution of 17 (1.52 g, 1.90 mmol) in dry
toluene (25 mL), and the resulting mixture was heated
under reflux for 22 h. After cooling to room tempera-
ture, the solvent was removed under reduced pressure
and the crude product was purified by flash chro-
matography (SiO2, CHCl3/acetone=90:10) to give 18
(1.57 g, 1.56 mmol, 82%): mp=156°C, [h]3D3=+95.2 (c
1
0.93; CH2Cl2); H NMR (200 MHz, CDCl3, l): 0.75

A. Iuliano et al. / Tetrahedron: Asymmetry 13 (2002) 1265–1275
1275
4.12.3.
N-Methyl-N%-[(trimethoxysylylpropylthio)-
CSP 4: C, 13.97; H, 1.91; N, 1.72% corresponding to
0.205 mmol/g.
CSP 5: C, 12.55; H, 1.84; N, 1.51% corresponding to
0.180 mmol/g.
propyl]-3,7-bis(2-naphthyl)carbamoyloxy-12-(3,5-dinitro-
phenyl)carbamoyloxycholan-24-amide, 19c. The mixture
was heated under reflux for 20 h and 1.02 g of product
19c was obtained: mp=94°C; [h]2D5=+42.3 (c 0.87;
1
CH2Cl2); H NMR (200 MHz, CDCl3, l): 0.70 (d, 2H,
Four 15 cm stainless steel columns were slurry packed
with each of these materials, using conventional high
pressure packing techniques.
CH2), 0.75 (s, 3H, CH3), 0.85 (d, 3H, CH3 21), 0.95 (s,
3H, CH3), 1.00–2.60 (m, 34H, steroidal CH and CH2,
aliphatic chain CH2), 2.75 and 2.95 (s, 3H, N-CH3),
3.10–3.40 (m, 2H, N-CH2), 3.50 (s, 9H, Si(OCH3)3),
4.55 (m, 1H, CH 3), 4.90–5.25 (m, 2H, CH 7 and CH
12), 7.10–8.10 (m, 16H, naphthylics and NH 3 and 7),
8.50–8.80 (m, 4H, 3,5-dinitrophenylics and NH); IR
(KBr, cm−1): 3392, 2941, 1728, 1636, 1606, 1545, 1507,
1432, 1344, 1233, 1073, 955, 809, 748.
Acknowledgements
This work was supported by MURST (Progetto
Nazionale Stereoselezione in Sintesi Organica:
Metodologie e Applicazioni).
4.12.4.
N-Methyl-N%-[(trimethoxysylylpropylthio)-
propyl]-3,12-bis(2-naphthyl)carbamoyloxy-7-(3,5-dinitro-
phenyl)carbamoyloxycholan-24-amide, 19d. The mixture
was heated under reflux for 48 h and 0.96 g of product
19d was obtained: mp=128–130°C; 1H NMR (200
MHz, CDCl3, l): 0.80 (s, 3H, CH3), 0.94 (d, 3H, CH3
21), 0.98 (s, 3H, CH3), 1.00–2.60 (m, 34H, steroidal CH
and CH2, chain CH2), 2.60–2.95 (s, 3H, N-CH3), 3.50
(s, 9H, Si(OCH3)3), 4.50–4.70 (m, 1H, CH 3), 5.00–5.25
(m, 2H, CH 7 and CH 12), 7.10–8.70 (m, 20H, aromat-
ics and NH); IR (KBr, cm−1): 3299, 2941, 1730, 1606,
1546, 1508, 1433, 1345, 1221, 1073, 956, 896, 854, 812,
730.
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A solution of the 3-mercaptopropyltrimethoxysilanic
derivative in dry toluene (20 mL) was added dropwise
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CSP 2: C, 18.07; H, 2.26; N, 1.37%; corresponding to
0.245 mmol/g.
CSP 3: C, 14.50; H, 1.93; N, 1.80% corresponding to
0.214 mmol/g.