Synthesis, spectroscopic and theoretical studies of new quaternary n,n-dimethyl-3-phthalimidopropylammonium conjugates of sterols and bile acids

Article abstract of DOI:10.3390/molecules19044212

New quaternary 3-phthalimidopropylammonium conjugates of steroids were obtained by reaction of sterols (ergosterol, cholesterol, cholestanol) and bile acids (lithocholic, deoxycholic, cholic) with bromoacetic acid bromide to give sterol 3β-bromoacetates and bile acid 3a-bromoacetates, respectively. These intermediates were subjected to nuclephilic substitution with N,N-dimethyl-3-phthalimidopropylamine to give the final quaternary ammonium salts. The structures of products were confirmed by spectral (¹H-NMR, ¹³C-NMR, and FT-IR) analysis, mass spectrometry (ESI-MS, MALDI) as well as PM5 semiempirical methods and B3LYP ab initio methods. Estimation of the pharmacotherapeutic potential has been accomplished for synthesized compounds on the basis of Prediction of Activity Spectra for Substances (PASS).

Full text of DOI:10.3390/molecules19044212

Molecules 2014, 19, 4212-4233; doi:10.3390/molecules19044212
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Synthesis, Spectroscopic and Theoretical Studies of New
Quaternary N,N-Dimethyl-3-phthalimidopropylammonium
Conjugates of Sterols and Bile Acids
Bogumil Brycki *, Hanna Koenig, Iwona Kowalczyk and Tomasz Pospieszny *
Laboratory of Microbiocide Chemistry, Faculty of Chemistry, Adam Mickiewicz University,
Grunwaldzka 6, Poznań 60-780, Poland; E-Mails: koenig@amu.edu.pl (H.K.);
iwkow@amu.edu.pl (I.K.).
*
Authors to whom correspondence should be addressed; E-Mails: brycki@amu.edu.pl (B.B.);
tposp@amu.edu.pl (T.P.); Tel.: +48-61-829-13-14 (B.B.); +48-61-829-13-07 (T.P.).
Received: 12 February 2014; in revised form: 19 March 2014 / Accepted: 21 March 2014 /
Published: 3 April 2014
Abstract: New quaternary 3-phthalimidopropylammonium conjugates of steroids were
obtained by reaction of sterols (ergosterol, cholesterol, cholestanol) and bile acids (lithocholic,
deoxycholic, cholic) with bromoacetic acid bromide to give sterol 3β-bromoacetates and bile
acid 3α-bromoacetates, respectively. These intermediates were subjected to nuclephilic
substitution with N,N-dimethyl-3-phthalimidopropylamine to give the final quaternary
1
13
ammonium salts. The structures of products were confirmed by spectral ( H-NMR, C-NMR,
and FT-IR) analysis, mass spectrometry (ESI-MS, MALDI) as well as PM5 semiempirical
methods and B3LYP ab initio methods. Estimation of the pharmacotherapeutic potential has
been accomplished for synthesized compounds on the basis of Prediction of Activity
Spectra for Substances (PASS).
Keywords: sterols; bile acids; quaternary ammonium salt; conjugates; N,N-dimethyl-3-
phthalimidopropylamine; PASS; PM5 calculations; B3LYP ab initio methods
1
. Introduction
Steroids are a large class of organic compounds. They play a very important role in animals, plants
and microorganisms. The best known steroid is certainly cholesterol. Cholesterol was isolated for the
first time from gall stones nearly two centuries ago by Chevreul [1,2]. This sterol is an important

Molecules 2014, 19
4213
component of mammalian cell membranes; it is also present in significant concentrations in the brain
and nervous tissue [3–6]. Cholesterol is the biosynthetic precursor of steroid hormones, bile acids,
vitamin D and lipoproteins [7–9]. Like the functions of cholesterol in mammals, ergosterol is
necessary to support the life of fungi. It serves two main purposes: a bulk membrane function and a
2
sparking function. Ergosterol is a biological precursor to vitamin D (ergocalciferol) [10–12].
All sterols are crystalline compounds with a secondary hydroxyl group in the position C(3) of the
steroid skeleton, one or two double bonds and differently modified side chains. Rings A/B of the
steroid skeleton may have trans geometry (the allo series) or cis (the normal series). Sterols have
the hydroxy group on the C(3) position forming a number of β-sterols with respect to the average
plane of the ring. By contrast bile acids have hydroxy groups on the C(3) position which prefer the
α orientation [13–17].
Bile acids are major metabolites of cholesterol, being end products of its metabolism in the liver [18,19].
They are isolated from the bile of higher animals, where they are found as sodium salts of peptide
conjugates with glycine and taurine. The most important are the primary bile acids, e.g.,
chenodeoxycholic acid and cholic acid, which are successively transformed into secondary bile acids
such as ursodeoxycholic, deoxycholic and lithocholic acids [20–22]. Bile acids (e.g., lithocholic,
deoxycholic and cholic) are very interesting because they display a large, rigid, and curved skeleton.
Moreover, they possess chemically different polar hydroxy groups (3α, 3α,7α and 3α,7α,12α) and
amphiphilic properties. Modifications of the functional groups of sterol molecules allow one to obtain
systems with high pharmacological activity [23].
Quaternary alkylammonium salts play an important role in the living organisms and many functions
of prokaryotic and eukaryotic cells have been shown to be alkylammonium salts dependent [24,25].
These compounds also exhibit excellent antimicrobial activity, and therefore they are used as antiseptics,
bactericides and fungicides, as well as therapeutic agents. In general, quaternary alkylammonium salts with
good antimicrobial activities contain one or two alkyl chains with lengths in the C –C range. For the
8
14
applications as softeners and hair conditioning agents hydrocarbon chain lengths between C16 and C18
are used [26–28]. Phthalimides, and N-substituted phthalimides are also an important class of
compounds because of their biological activities as antimicrobial agents [29,30]. It has recently been
shown that tetrachlorophthalimide derivatives are good α-glucosidase inhibitors [31]. The use of
microbiocides of the same type for a long time may cause an increase of resistance of microorganisms
to the chemicals used, which is a very serious and dangerous problem. Antimicrobial resistance of
bacteria comprises a wide variety of biochemical mechanisms and processes that allow microorganisms
to grow in the presence of microbiocides [32–34]. There are many ways to overcome the risk of an
increasing resistance of microorganisms, however the best one is a periodically application of new
microbiocides with modified structures [35,36]. Therefore, connections of sterols and bile acids with
various amines or polyamines appears to be an unusually interesting potential approach to such new
structures [37–40].
2
. Results and Discussion
In the present work, the synthesis and physicochemical properties of some new quaternary
N,N-dimethyl-3-phthalimidopropylammonium conjugates of sterols (ergosteryl 3β-bromoacetate (4),

Molecules 2014, 19
4214
cholesteryl 3β-bromoacetate (5), dihydrocholesteryl 3β-bromoacetate (6)) and derivatives of bile acids
methyl litocholate 3α-bromoacetate (13), methyl deoxycholate 3α-bromoacetate (14) and methyl
(
cholate 3α-bromoacetate (15)) with N,N-dimethyl-3-phthalimidopropylamine in acetonitrile are investigated.
New quaternary 3-phthalimidopropylammonium conjugates of steroids were obtained by reaction of
ergosterol (1), cholesterol (2), cholestanol (5α-cholestan-3β-ol, 3), and bile acids 10–12 with bromoacetic
acid bromide to give 4–6 and 13–15. The 3β-bromoacetates of sterols and 3α-bromoacetates of bile acids,
as well as N,N-dimethyl-3-phthalimidopropylamine were prepared according to the literature
1
13
procedures [41,42]. The structure of products was confirmed by H-NMR, C-NMR, and FT-IR
analysis, as well as ESI-MS and MALDI. The syntheses of conjugates 7–9 and 16–18 are shown
in Scheme 1.
Scheme 1. Synthesis of quaternary phthalimidopropylammonium conjugates of sterols 7–9
(
a) and bile acids 16–18 (b).
a)
21
10'
18
22
19
28
9'
8
'
2
3
24
3
8
HO
O
27
5
7
25
7'
6
N
O
26
5'
3'
6'
Br
(1)
O
3'
Br
4'
N
O
O
N
2'
1'
BrCH
2
COBr, TEBA,
O
N(CH )
3 2
O
O
HO
HO
CN, 81 o
C
CaH2, PhCH
3
CH
3
H
(
(
(
4)
5)
6)
(7)
(8)
(9)
(2)
(3)
Potential pharmacological activities of the synthesized compounds have been determined on the
basis of computer-aided drug discovery approach with in silico Prediction of Activity Spectra for
Substances (PASSs) program. It is based on a robust analysis of the structure-activity relationship in a
heterogeneous training set currently including about 60,000 biologically active compounds from

Molecules 2014, 19
4215
different chemical series with about 4,500 types of biological activities. Since only the structural
formula of the chemical compound is necessary to obtain a PASS prediction, this approach can be used
at the earliest stages of investigation. There are many examples of the successful use of the PASS
approach leading to new pharmacological agents [43–47]. The PASS software is useful for the study of
biological activity of secondary metabolites. We have selected the types of activities that were
predicted for a potential compound with the highest probability (focal activities). If predicted activity
is higher than 0.7 (PA > 0.7), the substance is very likely to exhibit the activity in experiment and the
chance of the substance being the analogue of a known pharmaceutical agent is also high. If predicted
activity is between 0.5 and 0.7 (0.5 < PA < 0.7), the substance is unlikely to exhibit the activity in
experiment and the similarity to known pharmaceutical substance is very limited.
1
13
The structures of all synthesized compounds were determined from their H- and C-NMR, FT-IR
and ESI-MS spectra. Moreover, PM5 calculations and B3LYP ab initio methods were performed for
all compounds. Additionally, analyses of the biological prediction activity spectra for the new esters
prepared herein are good examples of in silico studies of chemical compounds. We also selected the
types of activity that were predicted for a potential compound with the highest probability (focal
activities) (Table 1). According to these data the most frequently predicted types of biological activity
are: inhibitors glyceryl-ether monooxygenase, acylcarnitine hydrolase, alkylacetylglycerophosphatase,
plasmanylethanolamine desaturase, N-(acyl)ethanolamine deacylase and protein-disulfide reductase.
Table 1. “Probability to be Active” (PA) values for the predicted biological activity of
7
–9 and 16–18.
Compounds
16
0.87 0.91 0.93 0.93 0.94 0.95
Focal Predicted Activity (PA > 0.80)
7
8
9
17
18
Glyceryl-ether mono-oxygenase inhibitor
Acylcarnitine hydrolase inhibitor
-
-
-
-
-
-
-
-
-
-
-
-
-
-
0.81 0.83 0.91 0.94
Alkylacetylglycerophosphatase inhibitor
Plasmanylethanolamine desaturase inhibitor
CYP3A4 substrate
-
0.82 0.90 0.86
-
-
0.71 0.78
0.70 0.73
0.73 0.76
-
-
N-(acyl)ethanolamine-deacylase inhibitor
Protein-disulfide reductase inhibitor
-
-
0.72
-
0.75
-
Alkenylglycerophosphocholine hydrolase inhibitor
Oxidoreductase inhibitor
-
-
0.80
-
0.87 0.77
-
-
-
-
Alcohol O-acetyl-transferase inhibitor
DELTA14-sterol reductase inhibitor
Alkylacetylglycerophosphatase inhibitor
Antieczematic
0.88
-
-
-
-
-
-
-
-
-
-
0.73
-
-
-
-
-
-
-
-
0.84
-
-
-
-
-
-
0.72
-
0.73
-
-
-
Glucan endo-1,3-β-D-glucosidase inhibitor
D-lactaldehyde dehydrogenase inhibitor
-
-
0.74
1
The H-NMR spectra of compounds 7–9 show characteristic multiplets in the range 4.96–4.48 ppm
assigned to the C3α–H protons of the sterol skeleton. Similarly, compounds 16–18 exhibit multiplets in
the range 4.92–4.55 ppm which are assigned to the C3β–H protons of the bile acid skeleton (Figure 1).
A proton singlet at 0.83 ppm for 7 and singlets in the range of 0.68–0.64 ppm for other conjugates are

Molecules 2014, 19
4216
assigned to CH –18. The other singlets ranging from 1.04–0.79 ppm, 0.91 ppm and 0.89 ppm are
3
assigned to CH
3
–19 for 7–9, 17 and 18, respectively. In the case of compound 16 signal of the CH
3
–19
group and CH –21 group form the multiplet. The characteristic doublets of CH
3
3
–21, with the exception
of conjugate 16, are observed at 0.98–0.90 ppm and are assigned to conjugates 7–10, 17 and 18.
1
Figure 1. H-NMR spectra in the region (8.0–3.5 ppm) of the most characteristic signals of
conjugates 8 (a) and 18 (b).
+
N (CH
3
)
2
C9'-H,
C10'-H
PhthNCH
2
+
2
COCH N
+
H–6
CH
2
N
3
-H
(
a)
2 3
CO CH
+
N (CH
3
)
2
PhthNCH
2
,
7
-H
C9'-H,
C10'-H
+
12–H,
COCH N
2
+
2
CH –N
3
-H
(
b)
The characteristic doublets of the ergosterol-substituted derivatives are observed at 1.01 ppm for
1
CH
3
–28 group and 0.84 ppm for CH
3
–27 and CH
3
–26 groups, respectively. The H-NMR spectra of
conjugates 8 and 9 show doublets at 0.87 and doublet of doublets at 0.86 ppm of the C(26) and C(27)

Molecules 2014, 19
4217
1
methyl group. In the H-NMR spectra of sterol conjugates 7–9 and bile acid conjugates 16–18 a signal
+
of protons of the COCH
2
N group in the range 5.35–4.55 ppm is observed. The peaks of six methyl
+
+
protons of the N (CH
3
)
2
and two methylene protons of the N CH
2
appear as singlets and multiplets or
broad singlets in the range 3.69–3.61 ppm and 4.96–3.87 ppm, respectively. Two methylene protons of
attached to the phthalimide ring–N–CH group are seen as a broad singlets in the 3.83–3.82 ppm range.
2
1
3
The C-NMR spectra of conjugates 7–9 and 16–18 in CDCl
5.80 ppm (7), 12.66–11.79 ppm (8, 9, 16–18), and 19.19–17.25 ppm (7, 8, 16–18), 12.18 ppm (9)
which are assigned to CH –18 and CH –19, respectively. Carbon atoms of the CH –21 group for all
3
show characteristic signals at
1
3
3
3
conjugates give signals in the ranges 22.55–18.621 ppm. Characteristic shifts of methyl groups present
in the sterol side chain (CH –26 and CH –27) are positioned in the range 22.76–19.94 ppm and
3
3
2
1
2.52–19.61 ppm, respectively. The carbon atoms of the CO
2 3
CH unit resonated in the range of
74.77–174.72 ppm and 52.49–51.45 ppm, assigned to CO and CH , respectively.
2
3
Two important signals for C(1')=O and C(3)–O lie at 164.25–163.87 ppm and 77.97–74.87 ppm,
respectively. The spectra of all conjugates show two diagnostic signals associated with CH atoms in
N –C(2')H –CO and N –C(4')H groups. The carbon atoms of the first group are observed at
2
+
+
2
2
6
5
5
1
2.25–60.67 ppm and carbon atoms of the second group lie at 61.50–61.05 ppm for 8, 9 and 16–18 and
+
7.03 ppm for 7, respectively. The carbon atoms of N (CH
3
)
2
group appear in the range of
group resonate in the range of
68.34–168.09 ppm and 62.25–60.67 ppm assigned to C(7')=O and C(6')H , respectively.
The proton chemical shift assignments of N,N-dimethyl-(3β-acetate-cholest-5-ene)-3-phthal-
2 2
3.16–51.42 ppm. The carbon atoms of (C(7')=O) N–C(6')H
2
imidopropylammonium bromide (8) (Table 2) are based on 2D COSY experiments, in which the
proton-proton connectivity is observed through the off-diagonal peaks in the counter plot.
2
Table 2. Chemical shifts (δ, ppm) in D O and calculating GIAO nuclear magnetic
shielding tensors (σcal for N,N-dimethyl-(3β-acetate-cholest-5-ene)-3-phthalimido-
)
propylammonium bromide (8). The predicted GIAO chemical shifts were computed from
the linear equation δexp = a + b σcalc with a and b determined from the fit the experimental data.
δ
exp.
δ
calc
σ
calc
δ
exp.
δ
calc
σ
calc
C1'
C2'
C3'
C4'
C5'
C6'
C7'
C8'
C9'
163.90 160.96 98.55 H2'
62.05 66.51 168.03 H3'
52.38 44.94 183.90 H4'
61.05 58.56 173.88 H5'
23.76 20.94 201.56 H6'
37.63 44.15 184.48 H9'
168.12 154.39 105.71 H10'
4.80
3.66
3.95
-
5.94
3.58
4.94
-
26.538
28.992
27.566
30.748
28.389
25.346
25.430
28.987
27.472
32.113
31.924
32.112
31.924
-
3.83
7.83
7.77
3.66
5.35
0.68
0.99
0.92
0.87
-
4.16
7.08
7.00
3.58
5.04
131.72 134.68 117.88
123.49 128.37 122.52
H3
H6
C10' 134.22 137.31 115.95 H18
0.80
C3
C5
76.57 78.28 159.37 H19
138.76 138.26 115.25 H21
123.33 127.64 123.06 H26,27
0.82
0.58
0.76
-
C6
C18
C19
11.79
9.93 209.66
-
-
19.19 35.13 191.12
-
-
-

Molecules 2014, 19
4218
Table 2. Cont.
δ
exp.
δ
calc
σ
calc
δ
exp.
-
δ
calc
-
σ
calc
-
C21
18.65 25.79 197.99
22.76 14.29 206.45
22.50 11.67 208.38
-
-
-
-
-
-
C26
C27
-
-
-
-
-
-
a
a
-
-
-
-
-
-
294.9163
1.3593
0.9831
-
31.4274
0.9606
0.9443
-
b
b
-
-
2
c
r
-
-
a
b
c
intercept; slope; correlation coefficient.
1
13
The relations between the experimental H- and C-NMR chemical shifts (δexp) and the
Gauge-Independent Atomic Orbitals (GIAO) isotropic magnetic shielding tensors (σcalc) for 8 are shown in
Figure 2. Both correlations are linear, described by the equation: δ = a + bσ . The a and b parameters are
exp.
calc
1
2
2
13
given in Table 2. The very good correlation coefficients (r = 0.9379) for H and (r = 0.9984) for C
correlations of N,N-di-methyl-(3β-acetate-cholest-5-ene)-3-phthalimidopropyl-ammonium bromide confirm
the optimized geometry of 8.
Figure. 2. Experimental chemical shifts (δexp.) for N,N-dimethyl-(3β-acetate-cholest-5-
ene)-3-phthalimidopropylammonium bromide (8) vs. isotropic magnetic shielding constants
(σcalc) from the GIAO/B3LYP/6-31G(d,p) calculations; (a) carbons-13 and (b) protons.
The correlation between the experimental chemical shifts and calculated isotropic screening
constants are better for carbon atoms than for protons. The protons are located on the periphery of the
molecule and thus they are exposed to stronger interactions with solvent than carbon atoms, which are
more hidden inside of structure. The differences between the exact values of the calculated and
experimental shifts for protons are probably due to the fact that the shifts are calculated for single
molecules in gas phase, whereas experimental values are due to the condensed phase. For this reason
the agreement between the experimental and the calculated data for protons are worse than for carbons.
PM5 semiempirical calculations were performed using the WinMopac 2003 program and B3LYP
calculation are performed using the GAUSSIAN 03 program package with the 6-31G(d,p) basis set.
The final heat of formation (HOF) and energies for the sterols 1–3, bile acids 10–12 as well as their

Molecules 2014, 19
4219
conjugates 7–9 and 16–18 is presented in Table 3. Representative conjugates of sterol 7 and bile acid
1
8 are shown in Figure 3.
Table 3. Heat of formation (HOF) [kcal/mol] and energy [a.u.] of sterols (1–3), bile acids
(
10–12) and their conjugates (7–9, 16–18).
Heat of Formation
Compound
ΔHOF
Energy
[a.u.]
ΔEnergy
[
kcal/mol]
[kcal/mol]
[a.u.]
1
2
3
7
8
9
97.1208
140.1058
162.7945
177.1668
220.6382
243.3231
236.1585
278.4616
318.1685
306.6215
348.9986
388.2588
-
-
-
1113.175477
1118.205536
1119.450757
-
-
-
80.0460 4569.562486 3456.387009
80.5324 4570.807880 3452.602344
80.5286 4605.917678 3486.466921
1
0
1
2
6
7
8
-
-
-
1204.997432
1263.040016
1337.190617
-
-
-
1
1
1
1
1
70.4630 4640.248926 3435.251494
70.5370 −4714.391510 3451.351494
−70.0903 4788.548913 3451.358296
ΔHOF = HOFconjugates (7–9) – HOFsterols (1–3); ΔHOF = HOFconjugates (16-18) – HOFbile acids (10–12); ΔEnergy =
Energyconjugates (7–9) – Energysterols (1–3); ΔEnergy = Energyconjugates (16–18) – Energybile acids (10–12)
.
Figure 3. Molecular models of representative compounds 7 and 18 calculated by the PM5 method.
(
7)
(18)
The lowest values of HOF for sterols are observed for cholestanol 3 and its conjugate 9, where there
are no double bonds which stabilize the molecule and hinder its reactivity, in contrast to conjugates of
ergosterol 7 and cholesterol 8 where the double bonds increase the reactivity of the molecule, thereby
increasing values of HOF. The HOF relationship for methyl esters of bile acids 10–12 and their
corresponding conjugates 16–18 can be explained in a similar manner. In this case, the number of
hydroxyl groups in the steroid skeleton lowers the value of the determinant of HOF. This spatial
arrangement of bile acids can facilitate the formation of stable host-guest complexes. These complexes
may be stabilized by hydrogen bonding or electrostatic interactions that arise from the number of
hydroxyl groups in the bile acid molecule. Similar correlations have been observed using the
B3LYP method.
The spatial arrangement and interaction of the conjugates 7 and 18 are shown in Figure 4.
The final heat of formation is –1249.429 kcal/mol for 7 and –1358.893 kcal/mol for 18 and the
distances between the quaternary nitrogen and the anion bromide are 4.34 Å and 4.33 Å, respectively.

Molecules 2014, 19
4220
Compensation charges occurs only through intermolecular electrostatic interaction. This is a very good
confirmation of the conclusion that interactions reduce HOF. The dipole moments and selected
geometry parameters were calculated at the PM5 and B3LYP /6-31G(d,p) level of theory are presented
in Table 4.
Figure 4. Molecular models of conjugates 7 and 18 calculated by the PM5 method.
Table 4. Calculated structural parameters (B3LYP\6-31G(d,p), PM5) for sterol conjugates
–9 as well as bile acid conjugates 16–18.
7
Parameters
Dipole moments (Debye)
Bond lengths [Å]
7
8
9
16
17
18
9.0817 8.9725 8.8533 8.9578 8.4897 7.7646
1
1
1
1
1
1
1
1
1
1
1
1
.451 1.451 1.451 1.459 1.459 1.459
.428 1.427 1.428 1.431 1.432 1.430
.495 1.494 1.494 1.492 1.492 1.451
.471 1.471 1.471 1.469 1.469 1.469
.261 1.260 1.260 1.262 1.263 1.262
.219 1.220 1.219 1.220 1.220 1.220
.573 1.570 1.573 1.572 1.572 1.571
.546 1.546 1.546 1.543 1.544 1.543
.570 1.574 1.570 1.571 1.572 1.571
.527 1.527 1.527 1.525 1.525 1.525
.260 1.261 1.260 1.255 1.255 1.255
.210 1.210 1.210 1.208 1.208 1.208
N(1)-C(7')
N(1)-C(3')
C(1')-O(3)
N(2)-C(4')
N(2)-C(2')
C(7')-O(1)

Molecules 2014, 19
4221
Table 4. Cont.
Parameters
7
8
9
16
17
18
Bond angles [°]
1
1
1
1
1
1
1
1
1
1
11.5
10.8
12.2
10.4
05.3
05.6
11.6
14.2
06.7
09.2
112.0
110.7
112.1
110.5
105.4
105.5
111.6
114.0
106.8
109.4
112.2
110.9
112.1
110.4
105.5
111.5
111.5
114.0
106.9
109.4
108.8
108.0
111.5
110.4
105.6
105.6
111.3
113.9
107.6
109.6
109.1
108.1
111.3
110.5
105.8
105.6
111.1
113.9
102.1
109.1
108.8
107.7
111.5
110.8
105.6
105.4
111.4
114.0
107.6
109.5
C(6')-C(5')-C(4')
N(1)-C(6')-C(5')
C(4')-N(2)-C(2')
N(2)-C(2')-C(1')
C(2')-C(1')-O(3)
Torsion angles [°]
−
58.1 −60.0 −60.8
82.2 −80.3 −79.4
58.3
86.8
57.3
85.5
58.5
77.6
C(7')-N(1)-C(6')-C(5')
−
−
177.9 −178.5 −178.8 178.2
178.9
178.1
C(8')-C(7')-N(1)-C(6')
C(5')-C(4')-N(2)-C(2')
C(3')-N(2)-C(2')-C(1')
C(6')-C(5')-C(4')-N(2)
1
79.9 −176.9 −178.0 −177.8 −178.1 178.1
1
1
70.0
72.9
171.4
172.1
56.3
172.1
178.3
178.0
178.2
172.4 −169.2 −168.5 −170.6
5
3.6
1.7
56.1
52.7
56.3
55.6
56.4
56.2
56.5
55.1
6
53.1
−
99.3 −98.4 −98.0 −179.8 179.1
179.8
−104.8 −103.8 −103.2 −167.7 −167.3 −172.0
Hydrogen bonds and short contacts lengths
Distances [Å]
3
3
3
3
3
3
.149
.283
.077
.075
.370
.459
3.147
3.288
3.076
3.080
3.372
3.464
3.147
3.288
3.075
3.075
3.373
3.463
3.157
3.434
3.067
3.051
3.369
3.458
3.159
3.291
3.064
3.045
3.368
3.463
3.159
3.303
3.068
3.303
3.370
3.459
C(4')-H···Br
C(2')-H···Br
N(2)···Br
Angles [deg]
C(4')-H···Br
1
1
1
1
53.0
44.1
57.7
49.6
153.6
143.8
158.0
150.5
153.9
143.9
158.0
150.1
153.5
139.1
158.4
152.0
153.3
138.2
158.5
153.1
153.4
139.4
158.4
152.5
C(2')-H···Br
The calculated bond lengths and bond angles for 7–9 and 16–18 optimized by the PM5 and B3LYP
methods are quite similar, however the bond lengths N(2)-C(2') and N(2)-C(4') are different. Also the
torsion angles calculated by the PM5 and B3LYP methods are slightly different, especially the
C(5')-C(4')-N(2)-C(2') angle for fatty acid conjugates 16–18. This shows a crucial role of electrostatic
interaction between oppositely charged groups in the structure of the investigated compounds (Table 4).
Hydrogen bonds and short contact lengths distances are shorter for compounds calculated by B3LYP
method. These data prove that in the gas phase the type of quantum chemical methods used play an

Molecules 2014, 19
4222
important role in the molecular structure of ionic compounds. The solid-state IR spectra of sterols and
bile acids conjugates are shown in Figures 5 and 6, respectively.
−1
Figure 5. FT-IR spectra of sterol conjugates 7 (red) and 8 (blue) in the 3,100–400 cm region.
100
8
6
4
2
0
0
0
0
3000
2500
2000 1800 1600 1400 1200 1000
800
600
400
-1
Wavenumber [cm ]
Figure 6. FT-IR spectra of bile acid conjugates 16 (blue), 17 (red), 18 (black) in the
−1
3
100–400 cm region
100
8
6
4
2
0
0
0
0
0
3000
2500
2000 1800
1600
1400
1200
1000
800
600
400
-
1
Wavenumber [cm ]
−1
The FT-IR spectra of conjugates show characteristic bands at 1,775–1,772 cm which are due to the
asymmetric carbonyl group νasC=O stretching vibrations in a phthalimide moiety (Figures 5–8) [48,49].
The symmetric ν C=O stretching vibration appears in the FT-IR spectrum as an intense and broad
s
−1
nonsymmetrical band at 1,716–1,699 cm suggesting the small nonequivalence of carbonyl groups in
−1
the phthalimide moiety. Moreover strong characteristic bands in the region 1,251–1,240 cm are
present, which are assigned to the ν(C–O).

Molecules 2014, 19
4223
Figure 7. FT-IR spectra of bile acid conjugates in the carbonyl group region 16 (blue), 17
red), 18 (black).
(
1
00
8
6
4
2
0
0
0
0
0
1
773
1
773
1
775
1
740
1
712
1
747 1736
1712 1699
1
716
1
736
1
800
1750
1700
1650
-1
Wavenumbers/cm
Figure 8. Spectrum of N,N-dimethyl-(3β-acetate-5β-cholestan)-3-phthalimidopropyl-
ammonium bromide (9); (a) FT-IR (b) calculated scaled FT-IR spectrum.
100
a)
80
60
40
20
0
1
1
1
40 b)
20
00
80
60
40
20
0
3000 2500 2000
1800
1600
1400
1200
1000
800
600
400
-
1
Wavenumbers/cm

Molecules 2014, 19
4224
The FT-IR spectra of bile acid conjugates (Figure 7, blue line) shows characteristic vibration bands
−1
−1
of ν C=O and ν C=O in a phthalimide moiety at 1,773 cm and at 1,712 and 1,699 cm , respectively.
as
s
s
In this case the νasC=O and ν C=O bands are more nonsymmetrical in comparison to the carbonyl
bands of 17 and 18. The nonequivalence of ν C=O in the FT-IR spectrum is observed for N,N-bis-
as
(
phthalimidopropyl)-N-propylamine [50]. In contrast to the above examples, in N,N-dimethyl-3-
phthalimidopropylammonium hydrochloride monohydrate and N-n-butyltetrachlorophthalimide no
split of the carbonyl bands in FT-IR spectra were observed, in spite of the different interactions of each
carbonyl group in the supramolecular structure [51,52]. The ν(COO) stretching vibrations of carboxy
−1
groups are observed at 1,747–1,736 cm (Figure 7).
The room-temperature solid-state FT-IR and the calculated spectrum of 9 are shown in Figure 8.
−1
The band frequencies, relative intensities and their assignments in the 4,000–400 cm range are listed
in Table 5. For convenience of comparison, the band intensities for the calculated spectrum are scaled.
Table 5. Observed and calculated B3LYP/6-31G(d,p) vibrational frequencies and infrared
intensities for N,N-dimethyl-(3β-acetate-5β-cholestan)-3-phthalimidopropylammonium
bromide (9).
IR
IRcalc.
3,477
3,467
3,464
3,419
3,391
3,252
3,225
3,189
3,167
3,111
2,988
2,966
-
IRcalc
.
scaled
INT
3.34
17.8
5.26
18.2
381
10.9
6.74
8.81
16.7
485
515
994
-
Proposed Assignment
3
3
3
3
3
3
,462w
,459w
,380w
,304w
,243w
,060w
3,344
3,333
3,330
3,286
3,259
3,125
3,098
3,063
3,042
2,988
2,869
2,847
-
CH
CH
CH
CH2
CH
CH2
CH
2
3
,048s
,952s
,933s
,930s
,867s
,851s
2
2
CH3
CH3
CH2
2
2
2
2
CH
CH
2
2
2
2
2
,719w
,649w
,534w
CHBr
CHBr
CHBr
asCO
COO
sCO
CC
CC
CC
CC
CC
CC
CC, βCH2
βasCH3
βCH2
2,531
-
2,486
-
1982
-
1
,770m
1,845
1,811
1,800
1,728
1,706
1,679
1,671
1,636
1,608
1,581
1,577
1,529
1,432
1,761
1,728
1,718
1,650
1,627
1,600
1,593
1,558
1,532
1,505
1,502
1,455
1,361
16.9
55.6
190
2.38
2.13
4.59
29.7
17.7
14.2
2.76
14.1
17.2
175
1
,742s
,712s
1
1
,635vw
1
,614w
-
-
-
1
,467s
,454m
,445 m
1
1
1
,437m
,396s
1
βOH

Molecules 2014, 19
4225
Table 5. Cont.
IR
IRcalc.
1,430
1,424
1,406
1,379
1,361
1,343
1,331
1,290
1,268
1,251
1,236
1,225
1,217
1,214
1,202
1,192
1,179
1,141
1,124
1,106
1,098
1,074
1,047
1,025
1,016
998
IRcalc
.
scaled
INT
15.7
178
Proposed Assignment
CH
1
,375 m
,364 m
,335 w
,313 w
,285 w
,272 w
,251 m
1,359
1,353
1,336
1,310
1,292
1,275
1,263
1,224
1,202
1,186
1,172
1,161
1,153
1,150
1,138
1,128
-
β
s
3
1
1
1
1
1
1
CO
CC
CN
3.82
18.5
10.4
34.6
82.7
17.7
232
CC
CC, βCH2
CO
1
228 m
,209 s
βCH2
CC
CC
CC
CN
1
1
1
1
1
1
1
1
1
1
1
1
1
1
,188 m
,176 m
,150 w
,142 w
,132 w
,108 w
,089 w
,074 w
,044 w
,037 w
,026 w
,017 m
,001 m
10.8
4.70
11.5
135
CN
βCH
141
25.0
169
CN
CN
γCH2
γCH2
10.6
14.3
3.42
3.28
5.41
32.5
13.0
3.87
13.6
3.96
43.5
25.0
6.08
2.12
2.04
5.89
3.62
13.5
11.0
1.86
8.70
3.00
0.13
28.5
3.71
6.76
15.1
7.31
14.9
1,116
1,079
1,063
1,045
1,037
1,014
988
γCH
δCH2
βCH
2
2
γCH2
βCCC
βCO
9
78 w
64 w
50 w
35 w
27 w
04 w
97 w
87 w
9
9
9
9
9
8
8
967
γCH2
958
βCH
2
966
941
γCH2
γCH2
βCCC
βCCC
ring
CC
βCCC
βCCC
βCCC
βCNC
βring
γCH
963
909
920
907
901
907
8
8
8
7
60 vw
42 vw
02 vw
87 vw
895
865
879
847
867
825
813
814
7
20 m
10 vw
92 vw
63 vw
36 vw
25 vw
05 vw
00 vw
45 vw
764
761
7
6
6
6
6
6
6
5
751
714
746
701
698
694
659
612
γCH
657
610
γCH
650
603
βring
βNCC
γCC
625
579
610
565
5
31 w
566
522
βCCC
ring
5
12 vw
551
508

Molecules 2014, 19
4226
Table 5. Cont.
IR
IRcalc.
540
515
469
434
409
386
345
329
282
257
205
177
102
56
IRcalc
.
scaled
INT
12.4
10.3
1.23
11.4
9.39
5.04
22.0
57.4
3.62
10.3
5.27
1.08
1.63
2.59
Proposed assignment
ring
4
98 vw
497
472
428
394
370
348
308
292
247
223
172
145
72
4
4
4
4
82 vw
γCCC
38 vw
Lattice mode
Lattice mode
Lattice mode
Lattice mode
Lattice mode
Lattice mode
Lattice mode
Lattice mode
Lattice mode
Lattice mode
Lattice mode
Lattice mode
19 vw
09 vw
-
-
-
-
-
-
-
-
-
28
The abbreviations are: s: strong; m: medium; w: weak; vw; very weak; ν: stretching; β: in plane bending;
δ: deformation; : wagging; γ: out of plane bending and τ: twisting.
The DFT harmonic vibrational wavenumbers are usually higher than the experimental values.
However, in this case the overall agreement between the experimental and calculated frequencies for
(
9) is very good (Figure 9).
−1
Figure 9. Correlation between the experimental and calculated wavenumbers (cm ) for
2
(
9); νscaled = 26.3525 + 0.9689νcalc., r = 0.9973.
500
1000
1500
2000
2500
3000
3500
3
500 3000 2500 2000 1500 1000 500
Calculated frequencies by B3LYP method
Any discrepancy noted between the observed and calculated frequency may be due to the fact
that the calculations have been done for a single molecule in the gaseous state contrary to the
experimental spectrum recorded in the presence of intermolecular interactions. The scaling procedure,
as recommended by Palafox was used [53,54]. The scaled IR spectrum is shown in Figure 8b and the

Molecules 2014, 19
4227
predicted frequencies are listed in Table 3 as νscaleq. Scaling of the harmonic vibrational frequencies
−1
reproduce the experimental solid-state FT-IR frequencies with the r.m.s. error of 38.1 cm . The
vibrational band assignments of 9 were made using Gauss-View molecular visualization program [55].
3. Experimental
3.1. General
The NMR spectra were measured with a Varian Mercury 300 MHz NMR spectrometer (Oxford,
1
13
UK), operating at 300.07 and 75.4614 for H and C, respectively. Typical conditions for the proton
spectra were: pulse width 32°, acquisition time 5 s, FT size 32 K and digital resolution 0.3 Hz per
point, and for the carbon spectra pulse width 60°, FT size 60 K and digital resolution 0.6 Hz per point,
1
3
1
the number of scans varied from 1200 to 10,000 per spectrum. The C and H chemical shifts were
measured in CDCl relative to an internal standard of TMS. Infrared spectra were recorded in the
3
KBr pellets using a FT-IR Bruker IFS 66 spectrometer (Karlsruhe, Germany). The ESI (electron
spray ionization) mass spectra were recorded on a Waters/Micromass (Manchester, UK) ZQ mass
spectrometer equipped with a Harvard Apparatus (Saint Laurent, QC, Canada), syringe pump. The
−5
sample solutions were prepared in methanol at the concentration of approximately 10 M. The
standard ESI-MS mass spectra were recorded at the cone voltage 110 V. The MALDI (matrix-assisted
laser desorption/ionization) mass spectra were recorded on a Waters Maldi Q-Tof Premiere. The
−5
sample solutions were prepared in methanol at the concentration of approximately 10 M. The matrix
was 2,5-dihydroxybenzoic acid (gentisic acid) and the standard was β-cyclodextrin (m/z 1157.3218).
PM5 semiempirical calculations were performed using the WinMopac 2003 program [56–58]. The
calculations were performed using the GAUSSIAN 03 program package [59] at the B3LYP [60–62]
levels of theory with the 6-31G(d,p) basis set [63]. The NMR isotropic shielding constants were
calculated using the standard Gauge-Independent Atomic Orbital (GIAO) approach of Gaussian 03 [64,65].
3.2. Synthesis
The appropriate 3β-bromoacetate of sterols or 3α-bromoacetate of bile acids (0.20 mmol) were
3
dissolved in CH CN (6 mL) under reflux. Then N,N-dimethyl-3-phthalimidopropylamine (0.24 mmol)
was added and the mixture heated under reflux for 3 h. The precipitate was filtered and crystallized from
CH CN-EtOH (90:1), to give white solids.
3
N,N-Dimethyl-(3β-acetate-ergosta-5,7,22-triene)-3-phthalimidopropylammonium bromide (7): white
1
solid (76%), m.p. 185–187 °C. H-NMR: δ
H
7.85 (bs, 2H, Ar–H), 7.75 (bs, 2H, Ar–H), 5.35 (s, 2H,
+
+
COCH N ), 5.31–5.12 (m, 4H, 6, 7, 22, 23–H), 4.96–4.58 (m, 3H, 3α–H, N CH ), 3.82 (bs, 2H,
2
2
+
CH
CH
2
–N–phthalimide ring), 3.69 (s, 6H, N (CH
–28), 0.93 (d, J = 6.7 Hz, 3H, CH
3
)
2
), 1.04 (s, 3H, CH
3
–19), 1.01 (d, J = 6,0 Hz, 3H,
3
3
–21), 0.84 (d, J = 6.7 Hz, 6H, CH
168.17 (C-7'), 163.98 (C-1'), 140.11 (C-8), 139.96 (C-5), 135.43 (C-22),
34.32, 132.08 (C-23), 131.81, 123.57, 118.11 (C-6), 118.03 (C-7), 74.87 (C-3), 62.40, 61.67, 60.67
3 3
–26 and CH –27), 0.83 (s,
1
3
3
1
3 C
H, CH –18). C-NMR: δ
(
C-2'), 57.03 (C-4'), 53.16 (C-3'), 44.76, 42.79, 40.80, 40.72, 38.86, 36.82, 36.65, 36.44, 36.40, 34.93,
3
1
4.03, 33.81, 33.05, 27.58, 27.45, 26.43, 25.10, 25.04, 22.81, 21.77 (C-21), 20.96 (C-19), 19.94, 19.61,
8.28, 18.20, 17.63, 15.80 (C-18). FT-IR (KBr) νmax: 2957, 2871, 1773, 1740, 1713, 1466, 1437, 1396,

Molecules 2014, 19
4228
+
1
365,1250, 1208, 1044, 926. ESI-MS (m/z): 670 (100%) [C H N O ] . MALDI-MS (m/z): 669.9.
4
3
61
2
4
61 2 4
HRMS: calcd 669.5678 for C43H N O ; found 669.5630.
N,N-Dimethyl-(3β-acetate-cholest-5-ene)-3-phthalimidopropylammonium bromide (8): white solid
1
(
82%), m.p. 199–200 °C. H-NMR: δ
J = 4.9 Hz, 1H, 6–H), 4.80 (bs, 2H, COCH
.83 (bs, 2H, CH –N–phthalimide ring), 3.66 (s, 6H, N (CH
–21), 0.87 (dd, J = 6.6, 1.4 Hz, 6H, CH –26 and CH
H
7.85–7.80 (m, 2H, Ar–H), 7.76–7.70 (m, 2H, Ar–H), 5.35 (d,
+
+
2
N ), 4.69–4.48 (m, 1H, 3α–H), 4.00–3.89 (m, 2H, N CH
2
),
+
3
2
3
)
2
), 0.99 (s, 3H, CH
3
–19), 0.92 (d,
J = 6.4 Hz, 3H, CH
3
3
3
3
–27), 0.68 (s, 1H, CH –18).
1
3
C-NMR: δ
C
168.12 (C-7'), 163.90 (C-1'), 138.76 (C-5), 134.22, 131.72, 123.49, 123.33 (C-6), 76.57
(C-3), 62.05 (C-2'), 61.05 (C-4'), 56.60, 56.06, 52.38 (C-3'), 49.93, 42.24, 39.62, 39.44, 37.63, 36.75,
3
1
1
6.44, 36.11, 35.71, 34.63, 31.84, 31.72, 29.64, 28.15, 27.95, 27.42, 24.21, 23.76, 22.76, 22.50, 20.95,
9.19 (C-19), 18.65 (C-21), 11.79 (C-18). FT-IR (KBr) νmax: 2943, 2868, 1774, 1737, 1713, 1467,
+
637, 1395, 1364, 1252, 1210, 1089, 925. ESI-MS (m/z): 660 (100%) [C42
H
63
N
2
O
4
] . MALDI-MS
(
m/z): 659.9. HRMS: calcd 659.5812 for C H N O ; found 659.5802.
42 63 2 4
N,N-Dimethyl-(3β-acetate-5β-cholestan)-3-phthalimidopropylammonium bromide (9): white solid
1
(
4
3
CH
H
83%), m.p. 191–192 °C. H-NMR: δ 7.83 (d, J = 3.90 Hz, 2H, Ar–H), 7.74 (m, 2H, Ar–H),
+
+
2 2 2
.88–4.55 (m, 3H, COCH N , 3α–H), 3.92 (bs, 2H, N CH ), 3.83 (bs, 2H, CH –N–phthalimide ring),
.61 (s, 6H, N (CH ) ), 0.90 (d, J = 6.5 Hz, 3H, CH -21), 0.86 (dd, J = 6.7, 1.9 Hz, 6H, CH –26 and
+
3
2
3
3
1
3
3
–27), 0.79 (s, 3H, CH
3
–19), 0.65 (s, 1H, CH
3
–18). C-NMR: δ
C
168.18 (C-7'), 163.89 (C-1'),
1
4
2
34.26, 131.74, 123.51, 76.68 (C-3), 62.25 (C-2'), 61.27 (C-4'), 56.34, 56.21, 54.10, 52.51 (C-3'),
4.62, 42.52, 39.90, 39.45, 36.56, 36.11, 35.74, 35.34, 34.65, 33.55, 31.90, 29.65, 28.44, 28.18, 27.96,
7.13, 24.14, 23.79, 22.78, 22.56, 22.52, 21.15, 18.62 (C-21), 12.18 (C-19), 12.02 (C-18). FT-IR
(
6
KBr) νmax: 2952, 2867, 1770, 1742, 1712, 1467, 1445, 1396, 1375, 1251, 1089, 927. ESI-MS (m/z):
+
61 (100%) [C42
65 2 4 65 2 4
H N O ] . MALDI-MS (m/z): 661.5. HRMS: calcd 661.5905 for C42H N O ;
found 661.5917.
N,N-Dimethyl-(methyl litocholate)-3-phthalimidopropylammonium bromide (16): white solid (96%),
1
H
m.p. 104–105 °C. H-NMR: δ 7.86–7.82 (m, 2H, Ar–H), 7.77–7.73 (m, 2H, Ar–H), 4.84–4.67 (m,
+
+
3
CO
H, 3β–H, COCH N ), 3.92 (bs, 2H, N CH ), 3.83 (bs, 2H, CH –N–phthalimide ring), 3.66 (s, 9H,
2
2
2
+
13
2
CH
3
and N (CH
3
)
2
), 0.91 (m, 6H, CH
3
–19 and CH
3
3 C
–21), 0.64 (s, 3H, CH –18). C-NMR: δ
1
74.72 (C-24), 168.09 (C-7'), 163.87 (C-1'), 134.24, 131.73, 123.45, 77.97 (C-3), 62.11 (C-2'), 61.14
(C-4'), 56.15, 55.79, 52.49 (C-3'), 51.42 (C-25), 43.04, 42.64, 41.89, 40.23, 39.89, 35.68, 35.28, 35.02,
3
1
1
4.81, 34.61, 34.45, 31.76, 31.00, 30.93, 28.10, 26.84, 26.23, 26.13, 24.09, 23.16, 22.53, 20.76 (C-21),
8.21 (C-19), 11.97 (C-18). FT-IR (KBr) νmax: 2937, 2867, 1773, 1746, 1737, 1712, 1698, 1466, 1438,
+
404, 1378, 1210, 1088, 930. ESI-MS (m/z): 664 (100%) [C40
; found 663.5396.
H
59
N
2
O
6
] . MALDI-MS (m/z): 663.5.
59 2 6
HRMS: calcd 663.5361 for C40H N O
N,N-Dimethyl-(methyl deoxycholate)-3-phthalimidopropylammonium bromide (17): white solid (90%),
1
m.p. 170–172 °C. H-NMR: δ 7.87–7.83 (m, 2H, Ar–H), 7.76–7.72 (m, 2H, Ar–H), 4.92–4.67 (m,
H
+
+
3H, 3β–H, COCH
2
N ), 3.98 (s, 1H, 12β–H), 3.96–3.87 (m, 2H, CH
2
–N ), 3.82 (bs, 2H, CH
2
–N–
+
phthalimide ring), 3.63 (s, 9H, CO CH and N (CH ) ), 0.98 (d, J = 5.7 Hz, 3H, CH –21), 0.91 (s, 3H,
CH –19), 0.66 (s, 3H, CH –18). C-NMR: δ 174.75 (C-24), 168.30 (C-7'), 164.00 (C-1'), 134.26,
3 3 C
2
3
3 2
3
1
3
131.76, 123.55, 77.66 (C-3), 72.81 (C-12), 62.07 (C-2'), 61.39 (C-4'), 52.55 (C-3'), 51.45 (C-25),
48.04, 47.08, 46.40, 41.81, 35.86, 35.13, 34.71, 34.03, 33.37, 31.62, 31.07, 30.90, 28.61, 27.41, 26.77,
26.09, 25.97, 23.62, 22.87, 22.55 (C-21), 17.26 (C-19), 12.66 (C-18). FT-IR (KBr) νmax: 2955, 2870,

Molecules 2014, 19
4229
1
774, 1736, 1716, 1485, 1466, 1405, 1393, 1201, 1091, 967. ESI-MS (m/z): 680 (100%)
+
[C H N O ] . MALDI-MS (m/z): 679.5. HRMS: calcd 679.5358 for C H N O ; found 679.5341.
40 59 2 7 40 59 2 7
N,N-Dimethyl-(methyl cholate)-3-phthalimidopropylammonium bromide (18): white solid (85%), m.p.
1
2
H
04–205 °C. H-NMR: δ 7.86–7.83 (m, 2H, Ar–H), 7.76–7.69 (m, 2H, Ar–H), 4.95 (s, 2H,
+
+
COCH
2
0
2
N ), 4.66–4.55 (m, 1H, 3β–H), 3.97 (bs, 1H, 12β–H), 3.92–3.89 (m, 2H, CH
H, CH –N–phthalimide ring), 3.80 (bs, 1H, 7β–H), 3.63 (s, 3H, CO CH ,), 3.62 (s, 6H, N (CH
.97 (d, J = 5.8 Hz, 3H, CH –21), 0.89 (s, 3H, CH –19), 0.66 (s, 3H, CH
2
–N ), 3.82 (bs,
+
2
2
3
3
)
2
),
3 C
–18). C-NMR: δ 174.77
1
3
3
3
(
C-24), 168.34 (C-7'), 164.25 (C-1'), 134.19, 131.78, 123.49, 76.57 (C-3), 72.62 (C-12), 67.75 (C-7),
6
3
1.86 (C-2'), 61.50 (C-4'), 52.50 (C-3'), 51.41 (C-25), 46.95, 46.35, 41.89, 41.22, 39.54, 35.26, 34.86,
4.66, 34.37, 31.13, 30.91, 28.37, 27.45, 26.68, 26.30, 23.13, 22.55, 22.32 (C-21), 17.25 (C-19), 12.47
(
C-18). FT-IR (KBr) νmax: 2938, 2870, 1772, 1739, 1711, 1468, 1437, 1399, 1370, 1208, 1073, 953.
+
59 2 8
ESI-MS (m/z): 696 (100%) [C40H N O ] . MALDI-MS (m/z): 695.5. HRMS: calcd 695.5192 for
C H N O ; found 695.5242.
4
0
59
2
8
4
. Conclusions
In conclusion, six new quaternary N,N-dimethyl-3-phthalimidopropylammonium conjugates of
sterols (compounds 7–9) and bile acids (compounds 16–18) were prepared by the reactions of
ergosteryl 3β-bromoacetate, cholesteryl 3β-bromoacetate, dihydrocholesteryl 3β-bromoacetate as well
as methyl litocholate 3α-bromoacetate, methyl deoxycholate 3α-bromoacetate and methyl cholate
3
α-bromoacetate, with N,N-dimethyl-3-phthalimidopropylamine in acetonitrile. These new compounds
were characterized by spectroscopic and molecular structure methods. The obtained conjugates may
find applications in molecular recognition and in pharmacology, especially as compounds with a high
antimicrobial activity.
Acknowledgments
This work was supported by the funds from Adam Mickiewicz University, Faculty of Chemistry.
Author Contributions
The listed authors contributed to this work as described in the following. Bogumił Brycki gave the
concepts of work, interpreted the results and prepared the manuscript. Hanna Koenig carried out of the
synthetic work, interpreted the results and cooperated in the preparation of the manuscript. Tomasz
Pospieszny performed semiempirical calculations and Prediction of Activity Spectra for Substances
(
PASS). Iwona Kowalczyk performed quantum chemical calculations. All authors contributed with
valuable discussions and scientific input and approved the final version.
Conflicts of Interest
The authors declare no conflict of interest.

Molecules 2014, 19
4230
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(