Synthesis and evaluation of a C-glycosyl nucleoside as an inhibitor of chitin synthase

Article abstract of DOI:10.1016/S0008-6215(01)00191-4

As part of our ongoing program devoted to inhibit chitin synthases, we have prepared a novel C-glycosyl nucleoside as metabolically stable substrate analog of UDP-GlcNAc. The synthetic strategy relies on the consecutive coupling of nucleoside and amino C-

Full text of DOI:10.1016/S0008-6215(01)00191-4

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Carbohydrate Research 334 (2001) 177–182
Synthesis and evaluation of a C-glycosyl nucleoside as
an inhibitor of chitin synthase
Juan Xie,a,* Annie Thellend,b Hubert Becker,b Anne Vidal-Crosb
aLaboratoire de Chimie des Glucides, Uni6ersite´ Pierre et Marie Curie, CNRS UMR 7613, 4 Place Jussieu,
F-75005 Paris, France
bLaboratoire de Chimie Organique Biologique, Uni6ersite´ Pierre et Marie Curie, CNRS UMR 7613,
4 Place Jussieu, F-75005 Paris, France
Received 30 May 2001; accepted 5 July 2001
Abstract
As part of our ongoing program devoted to inhibit chitin synthases, we have prepared a novel C-glycosyl
nucleoside as metabolically stable substrate analog of UDP-GlcNAc. The synthetic strategy relies on the consecutive
coupling of nucleoside and amino C-glycosyl moieties with L-tartaric acid. However, this compound inhibited only
weakly chitin synthase I, with an IC50 value of 20 mM. © 2001 Elsevier Science Ltd. All rights reserved.
Keywords: C-Glycosyl nucleoside; Amino C-glycosyl compound; Substrate analog; Chitin synthase inhibitor
1. Introduction
attractive target for novel fungicides lacking
host toxicity. Chitin synthases (EC 2.4.1.16)
are inverting, processive b-(1“4)-N-acety-
laminoglucosaminyltransferases which cata-
lyze the synthesis of chitin by transferring an
Complex oligosaccharides are involved in a
wide variety of biological function and conse-
quently show enormous potential as therapeu-
tic agents for a number of cases ranging from
infectious diseases to cancer therapies.1–5 Inhi-
bition of glycosyltransferases, which are re-
sponsible for the biosynthesis of oligo-
saccharides, represents a valuable target.6–12
Chitin, the b-(1“4)-linked homopolymer
N-acetyl- -glucosamine (GlcNAc) residue
D
from uridine-5%-diphosphoGlcNAc (UDP-Glc-
NAc) to a growing chain of b-(1“4)-linked
GlcNAc residues.14 The efficiency of chitin
biosynthesis inhibition approach for antifun-
gal therapeutics was exemplified by peptidyl
nucleosides polyoxin D and nikkomycin Z.
These natural nucleoside antibiotics have been
demonstrated to be competitive inhibitors of
chitin synthases and exhibit antifungal, insec-
ticidal and acaricidal activities.15,16
As part of an ongoing program directed
towards the design of potential chitin syn-
thases inhibitors,17 we have synthesized a
novel C-glycosyl nucleoside 1 (Scheme 1) as a
metabolically stable donor substrate analog.
Since no data is still available concerning the
of N-acetyl- -glucosamine (GlcNAc), is the
D
second most abundant biological polymer af-
ter cellulose and is found in a wide diversity of
invertebrates and fungi. Since chitin is an
essential structural component of the cell wall
of most fungi and is absent in plants and
mammals,13 its biosynthesis seems to be an
* Corresponding author. Tel.: +33-1-44275893; fax: +33-
1-44275513.
E-mail address: xie@ccr.jussieu.fr (J. Xie).
0008-6215/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(01)00191-4

178
J. Xie et al. / Carbohydrate Research 334 (2001) 177–182
L
-tartaric acid 3 with the nucleoside 4 and the
amino C-glycosyl compound 9 (Scheme 2).
The methyl hydrogen 2,3-O-benzylidene
L
-
tartrate (3) was selected as the key building
block so as to remove simultaneously all the
protecting groups. Partial hydrolysis of the
dimethyl 2,3-O-benzylidene -tartrate (2) with
L
potassium hydroxide at room temperature
produced 318, accompanied by some racemiza-
tion product that can be easily eliminated by
chromatography. The monoester 3 was ob-
tained in 54% yield after purification. The
asymmetry of the benzylidene group leads to
each compound existing as an inseparable
mixture of two diastereomers, complicating
Scheme 1.
active site structure of any processive glycosyl-
transferase, the suitable spacer to be intro-
duced between the C-linked N-acetyl- -
1
13
the H and C NMR spectra. For example, in
D
1
the H NMR spectrum of 3, two methyl pro-
glucosamine residue and the uridine moiety to
maximize interaction had to be found. A tar-
taric residue was introduced in the molecule to
mimic the diphosphate moiety in the substrate
for the chelating of divalent ion present at the
active site of enzyme. Recently, an 1-N-imi-
nosugar-based UDP-galactose analog bearing
a vicinal diol linker has been shown to be a
potent inhibitor of a-(1“3)-galactosyltrans-
ferase.12 We report herein the synthesis of
compound 1 and biological evaluation of this
C-glycosyl nucleoside as inhibitor of chitin
synthase.
tons (l 3.76, 3.82) and two benzylidene pro-
tons (l 6.07, 6.09) were observed in
quasi-equivalent proportions. Successful cou-
pling of the acid 3 with 5%-amino-2%,3%-di-O-
benzyl-5%-deoxyuridine (4)17 was carried out
with the DCC–HOBt method, affording 5 in
1
66% yield. The amide proton in the H NMR
spectrum of 5 resonated at l 6.74, 7.04 (t,
JNH,5% 6.0 Hz). Saponification of 5 with LiOH
in MeOH yielded 6 in 91% yield. The amino
C-glycosyl compound 9 was prepared from
the bromo C-glycosyl derivative 719 (Scheme
3). Treatment of 7 with an excess of NaN3 in
DMF afforded 8 in 88% yield. Selective reduc-
tion of the azido group is possible only with
PPh3–water, which gave 9 in 88% yield. Other
reducing systems such as Raney Ni, Lindlar
Pd or HS(CH2)3SH–NaBH4 were unsuccess-
2. Results and discussion
The synthesis of compound 1 can be accom-
plished by successive coupling of protected
Scheme 2. (a) KOH. MeOH, THF, rt, 54%; (b) DCC, HOBt, CH2Cl2, THF, 0 °C to rt, 66%; (c) LiOH, MeOH, rt, 91%; (d) DCC,
HOBt, CH2Cl2, THF, 0 °C to rt, 79%; (e) Pd(OH)2, cyclohexene, MeOH, 90 °C, 100%.

J. Xie et al. / Carbohydrate Research 334 (2001) 177–182
179
minum percolated plates of Silica Gel 60F-254
with detection by UV and by spraying with 6
N H2SO4 and heating about 2 min at 300 °C.
THF was distilled over Na and benzophenone
prior to use. Dichloromethane was distilled
over CaH2. Microanalyses were performed at
the Service de Microanalyse de l’Universite´
Pierre et Marie Curie. High-resolution mass
spectra (HRMS) were recorded using fast-
atom bombardement (FAB) method at the
Service de Spectrome`trie de Masse de l’Ecole
Normale Supe´rieure de Paris.
Scheme 3.
(4R,5R)-2-Phenyl-[1,3]dioxolane-4,5-dicar-
boxylic acid monomethyl ester (3)18.—To a
solution of KOH (231 mg, 4.135 mmol) in
MeOH (2 mL), was added dropwise a solution
ful; the starting material remained unchanged.
Condensation of the acid 6 with the amino
C-glycosyl compound 9 in the presence of
DCC–HOBt afforded 10 in 79% yield. Fi-
nally, hydrogenolysis of 10 with Pd(OH)2 in a
mixture of cyclohexene and MeOH at 90 °C
led to the target compound 1 in quantitative
yield (Scheme 2).
Chitin synthase inhibition studies were per-
formed using Saccharomyces cere6isiae micro-
somal preparations obtained as previously
described.20 Chitin synthase activity was as-
sayed by measuring the rate of formation of
14C-chitin from UDP-14C-GlcNAc in the pres-
ence of the Mg2+ cation and trypsin. Activa-
tion of enzyme present as zymogen was
performed by addition of trypsin in the assay.
Using these conditions, ensuring a measure of
mainly chitin synthase I activity, the Km value
for UDP-GlcNAc was 0.3 mM and the IC50
value for the compound 1 was 20 mM.
In summary, a new C-glycosyl nucleoside
has been efficiently prepared, which appeared
to be a very poor inhibitor of chitin synthase
I.
of dimethyl 2,3-O-benzylidene- -tartrate (2, 1
L
g, 3.759 mmol) in THF (10 mL) during 1 h.
The solution was stirred at rt for 15 h. After
concentration, the residue was dissolved in a
mixture of 1:1 EtOAc–water (100 mL), neu-
tralized with 10% HCl. The organic layer was
washed with water (50 mL), dried (MgSO4)
and concentrated. The crude product was
chromatographed (1:3 EtOAc–hexane to pure
EtOAc) to give 3 as an oil (508 mg, 54%): Rf
1
0.41 (EtOAc); H NMR: l 7.51–7.34 (m, 5 H,
Ph), 6.09 and 6.07 (2s, 1 H, H-2), 6.00 (s, 1 H,
OH), 4.97 (d, 1 H, H-5), 4.84 (d, 1 H, J4,5 2.5
Hz, H-4), 3.82 and 3.76 (2s, 3 H, CH3). Anal.
Calcd for C12H12O6: C, 57.14; H, 4.80. Found:
C, 57.28; H, 4.71.
(4R,5R) - 5 - [(3%,4% - di - O - benzyl - 5 %- deoxy-
uridin-5%-yl)-carbamoyl]-2-phenyl-[1,3]dioxol-
ane-4-carboxylic acid methyl ester (5).—To a
solution of acid 3 (100 mg, 0.397 mmol) in
THF (1 mL) at 0 °C, were added successively
5%-amino-2%,3%-di-O-benzyl-5%-deoxy-uridine
(4)17 (168 mg, 0.397 mmol) in CH2Cl2 (1 mL),
HOBt (54 mg, 0.397 mmol) in THF (0.5 mL)
and DCC (82 mg, 0.397 mmol) in CH2Cl2 (0.5
mL). The mixture was stirred at 0 °C for 1 h
and at rt for 15 h. The precipitated DCU was
then filtered and the solution was diluted in
EtOAc (20 mL), washed with water (20 mL),
brine (20 mL), dried (MgSO4) and concen-
trated. The crude product was chro-
matographed with 3:2 EtOAc–hexane to give
5 as a white solid (172 mg, 66%): mp (dec)
3. Experimental
General procedures.—Melting points were
measured with a Thomas–Hoover apparatus.
13
1H and C NMR spectra were recorded on a
Bruker AGH-250 spectrometer unless noted in
CDCl3 solutions. Optical rotations were mea-
sured using a Perkin–Elmer 141 polarimeter
and a 10-cm cell. Column chromatography
was performed on E. Merck Silica Gel 60
(230–400 mesh). Analytical thin-layer chro-
matography was performed on E. Merck alu-
1
74-75 °C, Rf 0.31 (2:1 EtOAc–hexane); H
NMR: l 8.81 (s, 0.5 H, NH), 8.47 (s, 0.5 H,

180
J. Xie et al. / Carbohydrate Research 334 (2001) 177–182
centrated to give 8 as white solid (497 mg,
88%): mp 100 °C, [h]D +11.1 (c 1, CH2Cl2),
NH), 7.25–7.17 (m, 15 H, Ph), 7.04 (t, 0.5 H,
JNH,5% 6.0 Hz, NH), 7.01 (d, 0.5 H, J 8.0 Hz,
CHꢀ), 6.85 (d, 0.5 H, J 8.0 Hz, CHꢀ), 6.74 (t,
0.5 H, JNH,5% 6.0 Hz, NH), 6.04 (s, 0.5 H, H-2),
5.77 (s, 0.5 H, H-2), 5.56 (d, 0.5 H, J1%,2% 3.0
Hz, H-1%), 5.48 (d, 0.5 H, CHꢀ), 5.47 (d, 0.5
H, CHꢀ), 5.34 (d, 0.5 H, J1%,2% 3.3 Hz, H-1%),
4.90 (d, 0.5 H, J4,5 4.6 Hz, H-4), 4.80 (d, 0.5
H, J4,5 3.8 Hz, H-4), 4.74 (d, 0.5 H, H-5), 4.64
(d, 0.5 H, H-5), 4.63–4.35 (m, 4 H, 2×
OCH2), 4.22–3.66 (m, 3 H, H-2%,3%,4%), 3.77
and 3.70 (2s, 3 H, CH3), 3.48–3.45 (m, 2 H,
1
Rf 0.47 (1:1 EtOAc–hexane); H NMR: l
7.47–7.35 (m, 15 H, Ph), 6.76 (d, 1 H, JNH,2%
9.5 Hz, NH), 4.77–4.53 (m, 6 H, 3×OCH2),
4.37 (m, 1 H, H-5%), 4.31–4.28 (m, 1 H, H-2%),
4.20–4.15 (m, 1 H, H-1%), 4.00 (dd, 1 H, J5%,6%a
7.3, Jgem 9.8 Hz, H-6%a), 3.87 (dd, 1 H, J5%,6%b
6.8 Hz, H-6%b), 3.82–3.80 (m, 1 H, H-4%),
3.71–3.70 (m, 1 H, H-3%), 3.51–3.49 (m, 2 H,
H-1), 2.01 (s, 3 H, CH3), 1.87–1.78 (m, 2 H,
H-2). 13C NMR: l 170.3 (CO), 138.5, 137.9,
137.7 (Cipso); 129.0, 128.9, 128.6, 128.4, 128.2,
128.1, 128.0 (CHꢁPh), 75.4, 74.6, 73.5 (C-
3%,4%,5%); 73.7, 72.5, 72.3 (OCH2); 68.1 (C-6%),
65.5 (C-1%), 48.3 (C-1), 48.0 (C-2%), 31.3 (C-2),
23.7 (CH3). Anal. Calcd for C31H36N4O5: C,
68.35; H, 6.66; N, 10.29. Found: C, 68.58; H,
6.72; N, 10.20.
13
H-5%). C NMR: l 169.3, 168.7, 168.6, 162.6,
162.5, 149.0 (CO); 141.0, 139.8 (Cꢀ); 136.2,
136.0, 134.4, 134.2 (Cipso); 129.2, 129.1, 127.5,
127.4, 127.3, 127.2, 127.1, 127.0, 126.1, 125.8
(CHꢁPh); 105.1, 105.0 (C-2); 101.4 (Cꢀ), 92.4,
90.5 (C-1%); 79.4, 79.3, 77.3, 77.2, 77.0, 76.9
(CH); 71.8, 71.6, 71.5, 71.4 (CH2), 51.8 (CH3),
39.9, 39.6 (C-5%). Anal. Calcd for
C35H35N3O10: C, 63.92; H, 5.36; N, 6.39.
Found: C, 63.78; H, 5.32; N, 6.47.
1-Amino-2-(2%-N-acetylamino-3%,4%,6%-tri-O-
benzyl-2%-deoxy-h-
D
-glucopyranosyl)
ethane
(9).—To a solution of 8 (370 mg, 0.680 mmol)
and PPh3 (196 mg, 0.748 mmol) in THF (3.4
mL), was added water (136 mL, 0.755 mmol).
The reaction was allowed to continue at rt for
4 days. After concentration, the crude product
was chromatographed (4:1 then 3:2 CH2Cl2–
MeOH) to give the title compound as a white
solid (310 mg, 88%): mp 139–140 °C, [h]D
+12.2 (c 1, CH2Cl2), Rf 0.40 (4:1 CH2Cl2–
MeOH); 1H NMR: l 7.45–7.30 (m, 15 H, Ph),
6.70 (d, 1 H, JNH,2% 9.8 Hz, NH), 4.73–4.31
(m, 6 H, 3×OCH2), 4.28 (m, 1 H, H-5%), 4.20
(m, 1 H, H-2%), 4.10 (m, 1 H, H-1%), 4.01 (dd,
1 H, J5%,6%a 8.0, Jgem 10.0 Hz, H-6%a), 3.76–3.67
(m, 2 H, H-4%,6%b), 3.57 (m, 1 H, H-3%), 2.85 (t,
2 H, J1,2 6.5 Hz, H-1), 2.15 (s, 3 H, CH3), 1.91
(s, 2 H, NH2), 1.80–1.48 (m, 2 H, H-2). 13C
NMR: l 170.4 (CO), 138.4, 138.0, 137.7 (C
ipso); 128.9, 128.8, 128.5, 128.3, 128.2, 128.0
(CHꢁPh); 75.1 (C-5%), 74.8 (C-4%), 73.7 (C-3%),
73.6, 72.6, 72.3 (OCH2); 67.8 (C-6%), 66.8 (C-
1%), 48.5 (C-2%), 39.3 (C-2); 34.8 (C-1), 23.7
(CH3). Anal. Calcd for C31H38N2O5: C, 71.79;
H, 7.38; N, 5.40. Found: C, 71.66; H, 7.42; N,
5.44.
(4R,5R) - 5 - [(3%,4% - di - O - benzyl - 5% - deoxy-
uridin-5%-yl)-carbamoyl]-2-phenyl-[1,3]dioxol-
ane-4-carboxylic acid (6).—To a solution of
ester 5 (100 mg, 0.152 mmol) in MeOH (1
mL), was added LiOH·H2O (10 mg, 0.228
mmol). The reaction was allowed to continue
15 h at rt. After concentration, EtOAc (20
mL) and water (10 mL) were added. The
mixture was neutralized with HCl 10%. The
resulting organic layer was washed with water
(20 mL), dried (MgSO4) and concentrated to
give the title compound as white solid (89 mg,
91%): mp (dec) 86–88 °C, Rf 0.22 (9:1
1
CH2Cl2–MeOH); H NMR: l 9.60 and 9.48
(2s, 1 H, NH), 7.46–7.15 (m, 15 H, Ph), 6.97
and 6.84 (2d, 1 H, J 8.0 Hz, CHꢀ), 6.00 and
5.85 (2s, 1 H, H-2), 5.50 (d, 1 H, CHꢀ), 5.42
and 5.25 (2d, 1 H, J1%,2% 3.0 Hz, H-1%), 4.83–
4.31 (m, 6 H, H-4,5, 2×OCH2), 4.13–3.44
(m, 5 H, H-2%,3%,4%,5%).
1-Azido-2-(2%-N-acetylamino-3%,4%,6%-tri-O-
benzyl-2%-deoxy-h-
D
-glucopyranosyl)
ethane
(8).—A mixture of bromide 719 (600 mg,
1.033 mmol) and NaN3 (1.342 g, 20.654
mmol) in anhyd DMF (5 mL) was heated at
70 °C for 15 h. Water (50 mL) was then added
before extraction with EtOAc (3×50 mL).
The combined organic layers were washed
with water, dried (MgSO4), filtered and con-
(4R,5R)-2-Phenyl-[1,3]dioxolane-4,5-dicar-
boxylic acid 4-{[2-(2%-N-acetylamino-4%,5%,6%-
tri-O-benzyl-2%-deoxy-h- -glucopyranosyl)-
D
ethyl]-amide}-5-[(3%,4%-di-O-benzyl-5%-deoxy-
uridin-5%-yl)-amide] (10).—To a solution of

J. Xie et al. / Carbohydrate Research 334 (2001) 177–182
181
ethylene), 1.83 (s, 3 H, CH3), 1.82–1.50 (m, 2
H, CH2 ethylene). 13C NMR (CD3OD): l
175.5, 175.0, 174.0, 166.6, 152.8 (CO); 143.8,
103.7 (Cꢀ uridine); 92.2 (C-1% uridine), 84.3,
75.6, 75.1, 74.6, 73.3, 73.0, 72.7, 72.3 (CH),
63.7 (C-6%), 55.2, 50.2 (CH), 41.6, 37.6, 26.8
(CH2); 23.1 (CH3). FAB-HRMS Calcd for
C23H35N5O14Na [M+Na]+ 628.2078. Found
628.2092.
Chitin synthase assay.—Chitin synthase as-
says were performed in a standard 50 mL
volume containing 50 mM Tris–HCl pH 7.4,
1 mM UDP-GlcNAc, 0.01 mCi UDP[U-14C]-
GlcNAc, 40 mM GlcNAc, 0.2% digitonine, 5
mM Mg(OAc)2, 1 mg trypsin and 200 mg
protein. Incubations were performed at 30 °C
for 20 min and terminated by adding 1 mL of
10% trichloroacetic acid. After filtration
through a glass fiber filter (GF/C Whatman)
and washing with 3:7 AcOH–EtOH, discs
were dried and radioactivity measured in a
liquid scintillation counter.
acid 6 (84 mg, 0.131 mmol) in THF (1 mL) at
0 °C, were added successively amine 9 (68 mg,
0.131 mmol) in CH2Cl2 (1 mL), HOBt (18 mg,
0.131 mmol) in THF (0.5 mL) and DCC (27
mg, 0.131 mmol) in CH2Cl2 (0.5 mL). The
mixture was stirred at 0 °C for 1 h and at rt
for 15 h. The precipitated DCU was then
filtered and the crude product was purified by
preparative TLC with 15:1 CH2Cl2 –MeOH as
eluent to give 10 as a white solid (117 mg,
79%): mp 90–92 °C; Rf 0.51 (9:1 CH2Cl2–
1
MeOH); H NMR: l 9.15 (s, 1 H, NH),
7.98–7.91 (m, 1 H, NH), 7.76–7.31 (m, 31 H,
NH and 6×Ph), 7.21 and 7.16 (2d, 1 H, J 7.3
Hz, CHꢀ), 6.86 and 6.84 (2d, 1 H, JNH,2% 9.6
Hz, NHAc), 6.18 and 6.08 (2s, 1 H, H-2), 5.74
and 5.71 (2d, 1 H, J 7.3 Hz, CHꢀ), 5.67 and
5.59 (2d, 1 H, J1%,2% 3.8 Hz, H-1% uridine),
4.93–4.31 (m, 14 H), 4.20–3.25 (m, 10 H),
2.15 (s, 3 H, CH3), 2.03–1.92 (m, 2 H, CH2
ethylene). 13C NMR: l 170.6, 170.5, 169.7,
169.4, 163.7, 150.3 (CO); 142.2, 141.6 (Cꢀ
uridine), 138.3, 138.0, 137.7, 136.0 (Cipso);
130.4, 129.0, 128.7, 128.6, 128.4, 128.2, 128.0,
127.3 (CHꢁPh); 106.1, 105.5 (C-2); 102.9 (Cꢀ
uridine), 93.3, 92.4 (C-1% uridine); 81.3, 80.9,
78.7, 78.5, 75.0, 74.4 (CH); 73.4, 73.2, 72.9,
72.6, 72.2 (OCH2); 68.1, 67.9 (CH); 67.5, 66.8
(OCH2); 48.5 (CHꢁN), 40.6, 38.0, 37.7, 30.9
(CH2); 23.7 (CH3). Anal. Calcd for
C65H69N5O14: C, 68.23; H, 6.08; N, 6.12.
Found: C, 68.01; H, 6.17; N, 6.23. FAB-
HRMS Calcd for C65H70N5O14 [M+H]+
1144.4919. Found 1144.4908.
Acknowledgements
The authors thank the undergraduate stu-
dents Se´bastian Bareyt, Franc¸ois Durrat and
Claire Ferret-Courtel for the assistance in the
synthetic work. We are grateful to CNRS
(Centre National de Recherche Scientifique)
for financial support (PCV program).
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h- -glucopyranosyl)-ethyl]-N%-(5%-deoxyuridin-
D
5%-yl)-2,3-dihydroxysuccinamide (1).—To a
solution of 10 (50 mg, 0.044 mmol) in MeOH
(3 mL), were added cyclohexene (7 mL) and
20% Pd(OH)2 (48 mg). The suspension was
heated at 90 °C for 17 h. After filtration and
concentration, the title compound was ob-
tained as a white solid (27 mg, 100%): mp
200–203 °C, [h]D +78 (c 0.5, water), Rf 0.28
1
(3:2 CH2Cl2–MeOH); H NMR (CD3OD): l
7.62 (d, 1 H, J 8.0 Hz, CHꢀ), 5.71 (d, 1 H,
J1%,2% 5.0 Hz, H-1% uridine), 5.67 (d, 1 H, CHꢀ),
4.49 (m, 2 H), 4.23 (t, 1 H, J1%,2%=J2%,3%=5.0
Hz, H-2% uridine), 4.20–3.90 (m, 4 H), 3.85
(dd, 1 H, J5%,6% 2.0, Jgem 11.5 Hz, H-6%), 3.76–
3.49 (m, 6 H), 3.32–3.25 (m, 2 H, CH2N

182
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