Synthesis of N-Acetylmuramyl-L-Alanyl-D-Isoglutamine Aryl β-Glycosides

Article abstract of DOI:10.1023/A:1012940803366

Synthesis of N-acetylmuramyl-L-alanyl-D-isoglutamine phenyl and (2-naphthyl) β-glycosides, novel muramyl dipeptide derivatives with phenolic aglycons, was reported. The starting N-acetylglucosamine aryl glycosides were obtained by glycosylation of phenols with peracetylated α-glucosaminyl chloride under the conditions of phase-transfer catalysis and used for the synthesis of 4,6-O-isopropylidene-N-acetylmyramic acid aryl β-glycosides. Condensation of these derivatives with a dipeptide and subsequent deprotection resulted in the intended glycopeptides.

Full text of DOI:10.1023/A:1012940803366

Russian Journal of Bioorganic Chemistry, Vol. 27, No. 6, 2001, pp. 390–394. Translated from Bioorganicheskaya Khimiya, Vol. 27, No. 6, 2001, pp. 439–443.
Original Russian Text Copyright © 2001 by Zemlyakov, Tsikalov, Kur’yanov, Chirva, Bovin.
Synthesis of N-Acetylmuramyl-L-Alanyl-D-Isoglutamine
Aryl b-Glycosides
A. E. Zemlyakov*, V. V. Tsikalov*, V. O. Kur’yanov*, V. Ya. Chirva*, and N. V. Bovin**
* Vernadsky Tauric National University, ul. Yaltinskaya 4, Simferopol, 95007 Ukraine
** Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences,
ul. Miklukho-Maklaya 16/10, Moscow, 117997 Russia
Received January 15, 2001; in final form, April 19, 2001
Abstract—Synthesis of N-acetylmuramyl-L-alanyl-D-isoglutamine phenyl and (2-naphthyl) β-glycosides,
novel muramyl dipeptide derivatives with phenolic aglycons, was reported. The starting N-acetylglucosamine
aryl glycosides were obtained by glycosylation of phenols with peracetylated α-glucosaminyl chloride under
the conditions of phase-transfer catalysis and used for the synthesis of 4,6-O-isopropylidene-N-acetylmyramic
acid aryl β-glycosides. Condensation of these derivatives with a dipeptide and subsequent deprotection resulted
in the intended glycopeptides.
Key words: glycopeptides, muramyl dipeptide, N-acetylglucosamine aryl glycosides, glycosylation
1
INTRODUCTION
naphthol with α-chloride (I) at room temperature in
chloroform–1.25 N NaOH in the presence of triethyl-
benzylammonium chloride, a PTC catalyst, to prepare
peracetylated N-acetylglucosamine phenyl and naph-
thyl-2 β-glycosides (IIa, IIb) in yields, after crystalli-
zation, 66 and 69%, respectively (see the scheme). The
structures of aryl glycosides (IIa, IIb) were confirmed
Glycosides of N-acetylmuramyl-L-alanyl-D-iso-
glutamine exhibited the activity exceeding the effect of
MDP itself in a number of tests. For example, MDP
2
heptyl β-glycoside [1] is a potent stimulator of the
interleukin-1 and tumor necrosis factor production [2];
β-butyl [3] and β-cholesteryl MDP[4] displayed a
strong adjuvant effect upon immunization with HIV-1
rgp160 and rgp120 glycoproteins [5]. In previous stud-
ies we synthesized MDP phenyl and naphthyl-2 β-gly-
cosides, new MDP glycoside derivatives with phenolic
aglycons to investigate the correlation between the
structures of MDP glycosides and their biological
activity and to look for new promising immunomodula-
tors. Earlier, only synthesis of MDP β-p-aminophe-
nylglycoside was reported [6], whose condensation
with glutaric aldehyde resulted in the “macromolecu-
lar” MDP with a high activity [7]. Synthesis of phenyl
α- and β-glycosides of N-acetylmuramic acid, which
can be referred to as the carbohydrate moiety of the cor-
responding glycopeptides, has also been reported [8].
1
by the H NMR spectral data: in particular, signals of
five and seven aromatic protons, respectively, were
observed in a range of 6.96–7.80 ppm (see the Experi-
mental section). The doublets of anomeric protons in
these compounds (δ 5.28 and 5.40 ppm) are shifted
downfield relative to those of N-acetylglucosamine ali-
phatic glycosides (δ 4.6–4.8 ppm) [13]), and the cou-
pling constant of 8 Hz indicates the β-configuration of
the glycoside bond.
Compounds (IIa, IIb) were deacetylated according
to Zemplen, and the β-diol moiety of the resulting triols
(IIIa, IIIb) was protected by treatment with 2,2-
dimethoxypropane. Alkylation of the free 3-hydroxyl
group in (IVa, IVb) with (2S)-bromopropionic acid in
anhydrous dioxane in the presence of NaH gave 4,6-O-
isopropylidene-N-acetyl-D-muramic acid aryl β-glyco-
sides (Va, Vb). Condensation of the muramic acid acti-
vated esters (Va, Vb) with L-alanyl-D-isoglutamine
benzyl ester yielded protected glycopeptides (VIa,
VIb). The acetal protecting group was removed by acid
hydrolysis.
RESULTS AND DISCUSSION
In recent years, the traditional methods of synthesis
of N-acetylglucosamine aryl glycosides (oxazoline
synthesis [9] and interaction of phenolates with per-
acetylated α-glucosaminyl chloride (I) in polar sol-
vents [10]) have been enriched with facile and mild
PTC syntheses [11, 12]. We glycosylated phenol and β-
1
Comparison of the H NMR spectra of glycopep-
tides (VIa, VIb) with the spectra of glycosides of acids
(Va, Vb) and glycosides (IIIa, IIIb) proves the pres-
ence of lactyl dipeptide fragments in (VII), which can
be inferred from the proton signals of the lactic acid,
1
To whom correspondence should be addressed; phone: +38
(0652) 23-3885; fax: +38 (0652) 23-2310.
2
Abbreviations: MDP, muramyl dipeptide, N-acetylmuramyl-L-
alanyl-D-isoglutamine; PTC, phase-transfer catalysis.
1068-1620/01/2706-0390$25.00 © 2001 MAIK “Nauka /Interperiodica”

SYNTHESIS OF N-ACETYLMURAMYL-L-ALANYL-D-ISOGLUTAMINE ARYL
391
CH2OAc
CH2OR'
OR'
CH2OH
O
H3C
OCH2
OR'
O
O
O
O
OR
OR
OR
OAc
Cl
NHAc
R'O
R'O
AcOAcO
HO
H3C
O
NHAc
NHAc
NHAc
CH3CHCO-L-Ala-D-iGln-OR'
(I)
(II‡, b) R' = Ac
(III‡, b) R' = H
(IV‡, b) R' = H
(V‡, b) R' = CH(CH3)COOH
(VII‡, b) R' = Bn
(VIII‡, b) R' = H
(VI‡, b) R' = CH(CH3)CO-L-Ala-D-iGln-OBn
R =
(a)
(b)
alanine, isoglutamine, and benzyl ester residues (see
The study of MDP aryl β-glycosides in the nonspe-
Table 1). The final catalytic hydrogenolysis of benzyl cific anti-infection resistance stimulation test in mice
esters (VIIa, VIIb) led to the target MDP aryl glyco- with model peritonitis induced by intraperitoneal
sides (VIIIa, VIIIb).
administration of Salmonella typhi in a dose of
Table 1. Characteristic signals in the 1H NMR spectra of (IIIa, IIIb), (Va, Vb), and (VIIa, VIIb) (DMSO-d6)
Compound
Resonances
from fragments
(IIIa)
(Va)
(VIIa)
(IIIb)
(Vb)
(VIIb)
C1-OAr
6.97 m
7.29 m
6.97 m
7.29 m
6.98 m
7.30 m
7.17 m (1H)
7.42 m (3H)
7.83 m (3H)
5.14 d (8)
1.82 s
7.18 m (1H)
7.45 m (3H)
7.86 m (3H)
5.42 d (7)
1.81 s
7.17 m (1H)
7.45 m (3H)
7.86 m (3H)
5.12 d (8)
1.79 s
H1 (J1, 2, Hz)
4.96 d (8)
1.81 s
5.25 d (6)
1.80 s
4.95 d (8)
1.78 s
NAc, NH
7.80 d
7.84 d
7.47 d
7.85 d
7.90 d
7.81 d
7.91 d
7.96 d
8.14 d
8.15 d
>CMe2
1.33 s
1.48 s
1.35 s
1.50 s
C4-OH, C6-OH
CH3CH
5.09 d
4.59 t
5.40 br. s
4.69 br. s
1.25 d
5.11 d
5.43 d
4.72 t
4.62 br. s
1.24 d
4.19 q
1.27 d
4.22 q
1.26 d
4.25 q
1.28 d
4.21 dq
2.36 t
4.26 q
CH3 (Ala)
CH (Ala)
1.27 d
4.18 dq
2.36 t
γ-CH2 (Glu)
β-CH2 (Glu)
1.80 m
2.02 m
3.90 ddd
7.13 s
1.82 m
2.01 m
3.96 ddd
7.14 s
7.32 s
5.08 s
7.36 m
CH (Glu)
CONH2 (Glu)
7.32 s
CO2CH2Ph
5.08 s
7.36 m
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 27 No. 6 2001

392
ZEMLYAKOV et al.
Table 2. The effect of MDP glycosides on the nonspecific resistance of mice to intraperitoneal infection with S. typhi
(103 cells/mouse)*
Survival, %
Doseofglycopeptide,
µg/mouse
Control
MDP
β-heptyl MDP
(VIIIa)
(VIIIb)
2
20
0
0
0
40
80
80
60
80
80
80
40
80
40
60
80
200
* The experiment was performed as described in [14].
100 LD50 [14] showed that the β-aryl aglycons in the [α]546 –13° (Ò 0.95, chloroform). Lit. [9]: [mp 203–
1
204°ë, [α]D –14.5° (chloroform); H NMR (C2çCl3):
1.95, 2.05, 2.06, and 2.08 (12 H, all s, NAc and 3 OAc);
3.88 (1 H, ddd, J5,6a = 5, J5,6b = 2.5, H5); 4.14 (1 H, ddd,
J2,3 = 10, H2); 4.16 and 4.29 (2 H, both dd, J6a,6b = 12,
H6a and H6b); 5.15 (1 H, dd, J4,5 = 9.5, H4); 5.28 (1 H,
d, J1,2 = 8, H1); 5.42 (1 H, dd, J3,4 = 9.5, H3); 5.75 (1 H,
d, J2,NH = 9, NH); and 7.01 and 7.28 (5 H, both m,
CHarom).
MPD molecule did not have marked effect on the
3
immunostimulating activity (Table 2). At the same
time, a high protective effect of small doses
(2 µg/mouse) of phenyl glycoside (VIIIa) should be
noted.
EXPERIMENTAL
Melting points were determined on a PTP instru-
ment. Optical rotation (λ546) was measured on a Pola-
2-Naphthyl
2-acetamido-2-deoxy-3,4,6-tri-O-
1
acetyl-b-D-glucopyranoside (IIb) was synthesized as
described for (IIa) from α-chloride (I) (1.0 g,
2.74 mmol) and naphthol-2 (0.79 g, 5.48 mmol). Yield
0.98 g (69%); mp 217–218°ë, [α]546 –8° (Ò 1.05, chloro-
mat-A polarimeter at 20–22°ë. H NMR spectra were
registered on a Varian VXR-300 (300 MHz) spectro-
meter using Me4Si as the internal standard. Chemical
shifts (δ, ppm) and coupling constants (J, Hz) are given.
TLC was performed on precoated Silufol UV-254 form). Lit. [11]: mp 220.1–220.5°ë, [α]D –65.8° (chlo-
roform). 1H NMR (C2çCl3): 1.95, 2.05, 2.06, and 2.08
(12 H, all s, NAc and 3 OAc); 3.94 (1 H, ddd, J5,6a = 5.5,
J5,6b = 2.5, H5); 4.19 (1 H, ddd, J2,3 = 10, H2); 4.20 and
4.30 (2 H, both dd, J6a,6b = 12, H6a and H6b); 5.16 (1 H,
dd, J4,5 = 9, H4); 5.40 (1 H, d, J1,2 = 8, H1); 5.45 (1 H,
dd, J3,4 = 9, H3); 5.82 (1 H, d, J2,NH = 8.5, NH); and 7.18
(1 H, m, CHarom); 7.41 (3 H, m, CHarom); and 7.77
(3 H, m, CHarom).
(Kavalier) and Kieselgel 60 F254 (Merck) plates. The
spots were visualized by carbonization at 300°ë (Silu-
fol) or by spraying with 5% H2SO4 and subsequent
heating to 200–300°ë (Kieselgel). The following
developing systems were used: (A) 15 : 1 chloroform–
ethanol, (B) 5 : 1 chloroform–ethanol, (C) 3 : 1 chloro-
form–ethanol, and (D) 10 : 1 benzene–ethanol. Chro-
matography was carried out on a silica gel (70–230
mesh, Aldrich or 240–400 mesh, Merck) column (1.8 ×
12 cm) The elemental analysis data for compounds syn-
thesized matched the calculated values.
Phenyl 2-acetamido-2-deoxy-b-D-glucopyrano-
side (IIIa). Acetate (IIa) (0.76 g, 1.8 mmol) was dis-
solved in boiling anhydrous methanol, the solution was
cooled to ~40°ë, and 0.1 N sodium methylate in meth-
anol (0.5 ml) was added. The precipitate formed was
filtered off and washed with cold methanol to give
0.47 g (87%) of (IIIa); mp 232–232.5°ë, [α]546 –6° (Ò
Phenyl 2-acetamido-2-deoxy-3,4,6-tri-O-acetyl-
b-D-glucopyranoside (IIa). A mixture of 2-acet-
amido-2-deoxy-3,4,6-tri-O-acetyl-α-D-glucopyranosyl
chloride (I) [15] (1.0 g, 2.74 mmol), phenol (0.52 g,
5.48 mmol), triethylbenzylammonium chloride (0.52 g,
2.29 mmol), 1.25 N NaOH (3.5 ml, 4.38 mmol), and
chloroform (10 ml) was stirred vigorously at room tem-
perature until glycosyl donor disappeared (I) (TLC
monitoring in systems A and D). The mixture was
diluted with water (10 ml) and chloroform (10 ml); the
organic layer was separated and washed with 1 N
NaOH (2 × 5 ml) and water (10 ml). The chloroform
extract was dried over anhydrous Na2SO4 and evapo-
rated. The residue was crystallized from isopropanol to
give 0.76 g (66%) of glycoside (IIa): mp 205–206°ë,
1.0, methanol). For 1H NMR data, see Table 1. Lit. [16]:
mp 249°ë (decomp.).
2-Naphthyl 2-acetamido-2-deoxy-b-D-glucopyr-
anoside (IIIb) was synthesized as described for (IIIa)
by deacetylation of acetate (IIb) (0.95 g, 2.0 mmol) to
yield 0.46 g of the target compound. The mother liquor
was neutralized with KU-2 (ç+) cation exchanger, the
resin was washed with methanol, and the filtrate was
evaporated. The total yield of (IIIb) was 0.62 g (89%);
mp 236–237°ë, [α]546 +8° (Ò 1.0, methanol). For the 1H
NMR data, see Table 1. Lit. [11]: mp 239.8–240.3°ë,
[α]D +15.8° (DMSO).
3
The results of biological tests have been presented by O.V. Kalyu-
zhin (Institute of Human Morphology, Russian Academy of Sci-
ences, Moscow, Russia).
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 27 No. 6 2001

SYNTHESIS OF N-ACETYLMURAMYL-L-ALANYL-D-ISOGLUTAMINE ARYL
393
Phenyl
2-acetamido-2-deoxy-4,6-O-isopropyl- to yield 270 mg (59%) of glycopeptide (VIa) as amor-
idene-b-D-glucopyranoside (IVa). A suspension of phous powder, [α]546 +8° (Ò 1.0, chloroform).
compound (IIIa) (0.47 g, 1.57 mmol) in 10 ml of anhy-
O-(2-Naphthyl 2-acetamido-2-deoxy-4,6-O-iso-
drous dioxane was heated to 50–55°ë at stirring, and
propylidene-b-D-glucopyranosid-3-yl)-D-lactoyl-L-
2,2-dimethoxypropane (1.5 ml) and p-toluenesulfonic
alanyl-D-isoglutamine benzyl ester (VIb) was syn-
acid (10 mg) were added. After 1 h (TLC monitoring in
thesized as described above from acid (Vb) (210 mg,
system B), the reaction mixture was cooled, neutralized
0.46 mmol) and Boc-L-alanyl-D-isoglutamine benzyl
with pyridine, and precipitated by the addition of
ester (182 mg, 0.46 mmol).Yield 295 mg (86%); amor-
diethyl ether to yield 0.47 g (89%) of acetal (IV‡); mp
phous powder, [α]546 +21° (Ò 1.0, chloroform).
153–154°ë, [α]546 +55° (Ò 0.8, 3 : 1 chloroform–metha-
O-(Phenyl 2-acetamido-2-deoxy-b-D-glucopyra-
nosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine ben-
zyl ester (VIIa). Alkylidene derivative (VIa) (190 mg,
0.27 mmol) was dissolved in 80% acetic acid (3 ml) at
heating on boiling water bath and kept at this tempera-
ture for 5 min (TLC monitoring in system C). The solu-
tion was evaporated, the residue was co-evaporated
with toluene and triturated with diethyl ether to yield
179 mg (100%) of diol (VIIa); mp 212–213°ë
(decomp.), [α]546 +25° (Ò 0.67, ethanol). For the
nol).
2-Naphthyl 2-acetamido-2-deoxy-4,6-O-isopro-
pylidene-b-D-glucopyranoside (IVb) was obtained as
described above from 0.44 g (1.27 mmol) of triol
(IIIb). Yield 0.47 g (96%); amorphous powder, [α]546
−48° (Ò 1.0, chloroform).
Phenyl
2-acetamido-2-deoxy-4,6-O-isopropy-
lidene-3-O-(D-1-carboxyethyl)-b-D-glucopyranoside
(Va). Sodium hydride (4 eq) was added portionwise at
stirring to a suspension of (IVa) (0.45 g, 1.36 mmol) in
anhydrous dioxane (10 ml). The mixture was heated to
95°ë, kept for 1 h, and cooled to 65°ë. (2S)-Bromopro-
pionic acid (180 µl, 2 mmol) was added, and the mix-
ture was kept at 65°ë for further 3 h. The mixture was
cooled, the excess sodium hydride was quenched with
ethanol, and the mixture was concentrated and poured
into 50 ml of cold water. The solution was acidified
with 2 N HCl to pH 3–4, and the muramic acid glyco-
side was extracted with chloroform (3 × 20 ml). The
extract was dried over anhydrous Na2SO4 and evapo-
rated. The residue was crystallized by the addition of
diethyl ether to give 0.42 g (76%) of acid (V‡); mp
194–196°ë (decomp.), [α]546 –4° (Ò 1.0, chloroform).
1H NMR data, see Table 1.
O-(2-Naphthyl 2-acetamido-2-deoxy-b-D-glucopy-
ranosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine ben-
zyl ester (VIIb) was obtained as described for com-
pound (VIIa) by treatment (VIb) (275 mg, 0.37 mmol)
with acetic acid. Yield 260 mg (100%); mp 218–219°ë
(decomp.), [α]546 +56° (Ò 0.67, ethanol). For the
1H NMR data, see Table 1.
O-(Phenyl 2-acetamido-2-deoxy-b-D-glucopyra-
nosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine (VIIIa).
Benzyl ester (VIIa) (180 mg, 0.27 mmol) was dis-
solved in ethanol (10 ml) and hydrogenated over 10%
Pd/C (100 mg) at room temperature for 4 h. The cata-
lyst was filtered off and washed with ethanol (5 ml), he
filtrate was concentrated, and the residue was triturated
with diethyl ether to give 130 mg (84%) of glycopep-
tide (VIIIa) as amorphous powder.
For the 1H NMR data, see Table 1.
2-Naphthyl 2-acetamido-2-deoxy-4,6-O-isopro-
pylidene-3-O-(D-1-carboxyethyl)-b-D-glucopyrano-
side (Vb) was obtained as described for (V‡) by treat-
ing acetal (IVb) (0.47 g, 1.12 mmol) with NaH (4 eq.)
O-(2-Naphthyl
2-acetamido-2-deoxy-b-D-glu-
and (2S)-bromopropionic acid (160 µl, 1.82 mmol). copyranosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine
Yield 0.49 g (88%); mp 115–117°C, [α]546 +8° (Ò 1.0, (VIIIb) was obtained as described for compound
chloroform). For the 1H NMR data, see Table 1.
(VIIIa) by hydrogenolysis of benzyl ester (VIIb)
(136 mg, 0.19 mmol) in 92% yield (110 mg) as amor-
phous powder.
O-(Phenyl 2-acetamido-2-deoxy-4,6-O-isopropyl-
idene-b-D-glucopyranosid-3-yl)-D-lactoyl-L-alanyl-D-
isoglutamine benzyl ester (VIa). N-Hydroxysuccin-
imide (84 mg, 0.73 mmol) and DCC (150 mg,
0.73 mmol) were added to a solution of acid (Va)
(270 mg, 0.66 mmol) in anhydrous dioxane (10 ml) at
stirring.After 3–5 h, the precipitate of dicyclohexylurea
was filtered off and washed with dioxane. L-Alanyl-D-
isoglutamine benzyl ester trifluoroacetate (obtained by
treatment of the corresponding Boc-derivative (270 mg,
0.66 mmol) with trifluoroacetic acid and subsequent
evaporation to dryness) and triethylamine to pH 8 were
added to the filtrate. After the reaction was over (TLC
monitoring in system B), the reaction mixture was con-
centrated, and diethyl ether (30 ml) was added. The
product was filtered off and chromatographed on silica
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