N-Acetylmuramyl-L-Alanyl-D-Isoglutamine Glycosides: Effect of Glycoside Bond Configuration and Aglycone on Biological Activity

Article abstract of DOI:10.1023/A:1023944818406

Hexyl, octyl, and cyclohexyl β-glycosides and heptyl and cyclohexyl α-glycosides of muramyl dipeptide (MDP) were synthesized. Tests in vitro and in vivo revealed lower immunostimulating activities of MDP α-glycosides in comparison with the corresponding β-glycosides and MDP itself. In the case of alkyl β-glycosides, differences in hydrocarbon chain lengths (C₄-C₈) and in aglycone (aliphatic chain and aliphatic or aromatic ring) exerted no substantial effect on the immunostimulating activity.

Full text of DOI:10.1023/A:1023944818406

Russian Journal of Bioorganic Chemistry, Vol. 29, No. 3, 2003, pp. 286–292. Translated from Bioorganicheskaya Khimiya, Vol. 29, No. 3, 2003, pp. 316–322.
Original Russian Text Copyright © 2003 by Zemlyakov, Tsikalov, Kalyuzhin, Kur’yanov, Chirva.
N-Acetylmuramyl-L-Alanyl-D-Isoglutamine Glycosides:
Effect of Glycoside Bond Configuration and Aglycone
on Biological Activity
1
A. E. Zemlyakov*, V. V. Tsikalov*, O. V. Kalyuzhin**, V. O. Kur’yanov*, and V. Ya. Chirva*
*Vernadsky Tauriyan National University, ul. Yaltinskaya 4, Simferopol, 95007 Ukraine
**Research Institute of Human Morphology, Russian Academy of Medical Sciences,
ul. Tsuryupy 3, Moscow, 117418 Russia
Received March 22, 2002; in final form, July 10, 2002
Abstract—Hexyl, octyl, and cyclohexyl β-glycosides and heptyl and cyclohexyl α-glycosides of muramyl
dipeptide (MDP) were synthesized. Tests in vitro and in vivo revealed lower immunostimulating activities of
MDP α-glycosides in comparison with the corresponding β-glycosides and MDP itself. In the case of alkyl β-
glycosides, differences in hydrocarbon chain lengths (ë4–ë8) and in aglycone (aliphatic chain and aliphatic or
aromatic ring) exerted no substantial effect on the immunostimulating activity.
Key words: glycopeptides, muramyl dipeptide, muramyl dipeptide glycosides, immunostimulating activity, non-
specific infectious resistance
1
Methyl α- and β-glycosides of N-acetylmuramyl-L- moiety was protected by the treatment with 2,2-
alanyl-D-isoglutamine had been synthesized before the dimethoxypropane. Free hydroxy group at C3 was
beginning of our studies in order to use glycosylation alkylated with (S)-2-bromo- or (S)-2-chloropropionic
for fixing the configuration of the anomeric center [1] acid in dioxane in the presence of sodium hydride to
2
or the furanose form of MDP [2]. We used O-glycosy- give the derivatives of N-acetyl-D-muramic acid (IVa)–
lation of MDP as a method of chemical modification, (IVe), which were then coupled with L-alanyl-D-
which can affect the biological activity of this com- glutamine benzyl ester by the N-hydroxysuccinimide
pound. Various (alkyl [3, 4], 2,3-didodecyloxypropyl method. The two-step deprotection (acidic hydrolysis
[5], cholesteryl [6], and aryl [7]) β-glycosides of MDP of the acetal moiety and catalytic hydrogenolysis of the
possess high immunostimulating activities both in vitro benzyl ester in the glutamine residue) resulted in the
[8, 9] and in vivo [9–11]. With the goal to reveal struc- target glycosides (VII‡)–(VIIe).
tural factors that affect the biological activities of these
1
A comparison of H NMR spectra of deacetylated
MDP derivatives, we synthesized in this work hexyl,
glycosides (II‡)–(IIe) with those of glycosyl glycopep-
octyl, and cyclohexyl β-glycosides and heptyl and
tides (VI‡)–(VIe) confirmed the introduction of the lac-
cyclohexyl α-glycosides of MDP (VIIa)–(VIIe). Butyl
tylpeptide fragment. In particular, this was proven by
[3], heptyl [4], and phenyl [7] β-glycosides of MDP
synthesized earlier were also used in biological tests.
the presence of resonances of benzyl ester protons (sin-
glets of methylene groups at δ 5.02–5.08 ppm and mul-
The MDP glycosides were synthesized according to
the known scheme (see scheme). The starting α- and β-
glycosides of N-acetylglucosamine (Ia)–(Ie) were
obtained by glycosylation of the corresponding alco-
hols with 2-acetamido-3,4,6-tri-O-acetyl-α-D-glu-
copyranosyl chloride by a modified Koenigs–Knorr
method using mercury(II) iodide as catalyst [12]. Then
they were deacetylated to (II‡)–(IIe), in which 4,6-diol
tiplets of phenyl protons at δ 7.35–7.36 ppm), triplets of
the γ-methylene group at δ 2.20–2.36 ppm, and two sin-
glets of amide protons of isoglutamine residue in a
range of 7.06–7.13 and 7.29–7.34 ppm (see table for
details).
Activation of the production of such important for
antitumor and antibacterial immunity mono- and lym-
phokines as TNF and ILs is the most characteristic indi-
cator of the immunostimulating activity of MDP and its
derivatives in vitro. The effect of MDP glycosides on
the production of IL-1, IL-2, and TNF by murine peri-
toneal macrophages are given in Fig. 1. The total effect
of muramyl dipeptides on immune system can be easily
estimated in the test of stimulation of the nonspecific
1
Corresponding author; phone: +7 (065) 223-3885; fax: +7 (065)
223-2310; e-mail: vladimir@tnu.crimea.ua
2
Abbreviations: ConA, concanavalin A; IL, interleukin; LPS,
lipopolysaccharide; MDP, muramyl dipeptide, N-acetylmuramyl-
L-alanyl-D-isoglutamine; TNF, tumor necrosis factor. Aglycone
designations and other abbreviations correspond to IUPAC–IUB
recommendations.
1068-1620/03/29032-0286$25.00 © 2003 MAIK “Nauka /Interperiodica”

N-ACETYLMURAMYL-L-ALANYL-D-ISOGLUTAMINE GLYCOSIDES
287
Me
OAc
OH
O
Me
O
O
O
H
AcO
AcO
HO
HO
Me2C(OMe)2
O
MeOH
MeONa
R
R
R
TosOH
HO
AcN
AcN
AcN
H
H
R'
O
R'
R'
(Ia)–(Ie)
(IIa)–(IIe)
(IIIa)–(IIIe)
Me
Me
O
Me
Me
NaH
CH3CHClCOOH
O
H
O
R
O
O
HOSu, DCC
R
O
O
L-Ala-D-Glu(OBzl)-NH2
AcN
AcNH
Me
Me
R'
R'
COOH
(IVa)–(IVe)
CO-L-Ala-D-Glu(OBzl)-NH2
(Va)–(Ve)
OH
O
HO
1. H2O, H+
2. H2/Pd
R
O
AcNH
Me
R'
CO-L-Ala-D-Glu(OR'')-NH2
(VIa)–(VIe) R'' = Bzl
(VIIa)–(VIIe) R'' = H
a: R = O(CH ) CH , R' = H; b: R = O(CH ) CH , R' = H; c: R =
, R' = H;
O
2 5
3
2 7
3
d: R = H, R' = O(CH ) CH ; e: R = H, R' =
O
2 6
3
Scheme 1.
antiinfectious resistance in mice using the model of solution as a mixture of α- and β-anomers, than that of
peritonitis caused by the intraperitoneal administration MDP β-glycosides. A low adjuvant capacity of α-1-O-
3
of Salmonella typhi at a dose of 100 LD50 (Fig. 2).
acyl MDP [15] compared to that of the mixture of α-
and β-1-O-acyl-MDP [16] also becomes clear.
A comparison of the immunostimulating activity of
MDP heptyl and cyclohexyl α- and β-glycosides dem-
onstrated using both in vitro and in vivo tests that α-gly-
cosides are less active than both the corresponding β-
glycosides and MDP itself. A similar effect was
observed in the case of MDP butyl α-glycoside in the
study of activation of T- and B-cell immune response to
HIV-1 proteins [9]. A higher adjuvant activity of MDP
methyl β-glycoside over that of the corresponding α-
glycoside in the test for the induction of experimental
allergic encephalomyelitis was reported in [13]; MDP
benzyl β-glycoside showed a stronger adjuvant action
than benzyl α-glycoside in the test for delayed hyper-
sensitivity [14]. It seems likely that the β-anomer of
MDP is the active form. This assumption helps explain
a lower stimulating effect of free MDP, which exists in
A comparison of stimulating effects of MDP alkyl
β-glycosides with various lengths of hydrocarbon chain
and also MDP glycosides with aglycones with the same
number of carbon atoms but different chemical struc-
tures (aliphatic chain, aliphatic ring, or aromatic ring)
showed that all of them possess comparable immuno-
stimulating activity.
EXPERIMENTAL
Melting points were taken on a PTP apparatus. The
values of optical rotation were measured on a Polamat-A)
polarimeter at λ 546 nm and 20–25°ë. 1H NMR spectra
were registered on a Varian VXR-300 (300 MHz)
instrument in DMSO-d6 using Me4Si as an internal
standard. Chemical shifts (δ, ppm) and coupling con-
stants (J, Hz) are given.
3
The studies were performed in cooperation with the researches
from the Mechnikov Research Institute of Vaccines and Sera,
Russian Academy of Medical Sciences, Moscow.
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 29 No. 3 2003

288
ZEMLYAKOV et al.
1H NMR spectra of compounds (IIa)–(IIe) and (VIa)–(VIe)*
Group or atom (IIa)
(VIa)
(IIb)
(VIb)
(IIc)
(VIc)
(IId)
(VId)
(IIe)
(VIe)
R
0.86t,
1.27m, 1.24m,
0.85t,
0.86t,
1.24m, 1.24m,
0.86t,
1.26m, 1.23m,
1.46m, 1.41m,
0.85t,
1.24m, 1.26m,
0.86t,
1.22m, 1.22m,
1.45m, 1.43m,
1.47m
1.43m
1.43m
1.44m
1.67m
1.60m
1.45m
1.51m
1.66m
1.66m
H1 (J1,2
)
4.28d
(8.0)
4.35d
(8.0)
4.25d
(8.0)
4.25d
(8.0)
4.43d
(8.5)
4.37d
(8.0)
4.72d
(3.0)
4.69d
(3.0)
4.79d
(3.0)
4.84d
(3.5)
NAc
1.79s
1.75s
1.78s
1.75s
1.82s
1.74s
1.80s
1.79s
1.82s
1.78s
C4-OH,
C6-OH
4.72d,
4.32bt
5.28d,
4.61t
4.85d,
4.47bt
4.25d,
4.57bt
4.89bt, 5.24d,
4.72d,
4.52t
5.27d,
4.53t
4.66d,
4.46t
5.28d,
4.53t
4.53bt
4.56t
CH3CH
–
1.24m
–
1.24m
–
1.23m
–
1.22d,
1.23d
–
1.22d,
1.25d
CHCH3
–
–
–
–
4.22q
–
–
–
–
4.22q
–
–
–
–
4.23q
–
–
–
–
4.29q
–
–
–
–
4.29m
4.29m
4.18ddd
CH(Ala)
4.18dq
4.10ddd
4.12dq
3.69ddd
4.17dq
4.09ddd
4.28dq
4.18ddd
CH(iGln)
β-CH2(iGln)
1.77m,
2.01m
1.71m,
1.94m
1.77m,
2.01m
1.76m,
2.02m
1.73m,
2.01m
γ-CH2(iGln)
–
–
2.35t
–
–
2.20t
–
–
2.35t
–
–
2.36t
–
–
2.36t
CONH2(iGln)
7.13s
7.29s
7.09s
7.33s
7.12s
7.32s
7.06s
7.32s
7.08s
7.34s
CH2Ph
NH
–
5.08s,
7.36m
–
5.02s,
7.36m
–
5.07s,
7.35m
–
5.08s,
7.36m
–
5.08s,
7.36m
7.50d
7.39d,
7.80d,
8.13d
7.63d
7.39d,
7.80d,
8.09d
7.54d
7.41d,
7.77d,
8.12d
7.56d
7.59d,
7.98d,
8.14d
7.62d
7.65d,
7.98d,
8.17d
* Abbreviations: bd, broadened doublet; bt, broadened triplet; dd, doublet of doublets; dq; doublet of quartets; and ddd, doublet of doublets
of doublets.
TLC was performed on Silufol UV-254 (Kavalier)
and Kieselgel 60 F254 (Merck) precoated plates. Spots
were visualized by charring at 300°ë (Silufol) or treat-
ing with 2% H2SO4 in n-butanol and subsequent heat-
ing at 150°ë (Kieselgel). The following developing
systems were used: (A) 15 : 1 and (B) 5 : 1 chloroform–
ethanol, (C) 10 : 1 : 1 chloroform–benzene–ethanol,
(D) 100 : 10 : 10 : 10 : 3 ethanol–n-butanol–pyridine–
water–acetic acid; and (E) 3 : 1 : 1 n-butanol–acetic
acid–water. Column chromatography was carried out
on Silica gel 70–300 mesh (Aldrich) and 230–400 mesh
(Merck).
Isopropylidenation.
2,2-Dimethoxypropane
(3 equiv) and dry TosOH were added to a solution of
triol (II‡)–(IIe) in dioxane or THF (50 ml/g). After 1 h
(TLC monitoring in systems A and C), the reaction
mixture was neutralized with pyridine and evaporated
in a vacuum. The residue was dissolved in chloroform
(50 ml) and washed with water (3 × 25 ml). The organic
layer was dried over anhydrous Na2SO4 and evaporated
to dryness.
Synthesis of muramic acids. Sodium hydride
(4 equiv) was added in portions to a stirred solution of
acetal (III‡)–(IIIe) in anhydrous dioxane (20 ml/g).
Elemental analysis data for key compounds corre-
spond to calculated values. Biological activity was The reaction mixture was heated to 95°ë, kept for 1 h
studied by the techniques reported in [8, 10].
A number of general synthetic procedures were
used in this study.
Zemplen deacetylation. Sodium methylate (0.1 N
solution in methanol, 0.01–0.05 equiv) was added to a
solution of acetate (Ia)–(Ie) in anhydrous methanol
(10 ml/g). The reaction mixture was kept for 12–24 h
and neutralized with KU-2 (H+) cation exchanger. The
resin was filtered off and washed with methanol. The
combined filtrate was concentrated in a vacuum.
at this temperature, and cooled to 65°ë. (S)-2-Bro-
mopropionic acid (1.5 equiv) or (S)-2-chloropropionic
acid (2 equiv) was added, and the mixture was kept at
65°ë for another 1 h. The reaction mixture was cooled,
the excess of sodium hydride was decomposed with
ethanol, and the mixture was concentrated and poured
in cold water. The solution was acidified with 1 N
hydrochloric acid to pH 2–3, and muramic acid was
extracted with chloroform. The extract was dried over
anhydrous Na2SO4 and concentrated in a vacuum.
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 29 No. 3 2003

N-ACETYLMURAMYL-L-ALANYL-D-ISOGLUTAMINE GLYCOSIDES
289
PI
1 µg/ml
10 µg/ml
100 µg/ml
20
(‡)
16
12
8
4
0
LPS MDP Bu
Hx
Hp
Oc
cHx
Ph α-Hp α-cHx
CTA, %
60
(b)
50
40
30
20
10
0
LPS MDP Bu
Hx
Hp
Oc
cHx
Ph α-Hp α-cHx
PI
30
(c)
25
20
15
10
5
0
ConA MDP Bu
Hx
Hp
Oc
cHx
Ph α-Hp α-cHx
Fig. 1. The effect of MDP glycosides (in doses of 1, 10, and 100 µg/ml; the corresponding aglycone is given under the abscissa axis)
in combination with suboptimal dose of (a, b) LPS (20 ng/ml) and (c) concanavalin A (1 µg/ml) on the production of (a) IL-1,
(b) TNF by peritoneal macrophages, and (c) IL-2 by murine splenocytes C57BL/6. The experiment was carried out as described
earlier [8]. PI, proliferation index; CTA, cytotoxic activity. All glycosides belong to β-series except for heptyl (α-Hp) and cyclo-
hexyl (α-cHx) glycosides.
Synthesis of glycopeptides by the N-hydroxysuc- monitoring in systems Ä and C), the solvent was evap-
orated.
cinimide method. N-Hydroxysuccinimide (1.1 equiv)
and DCC (1.1 equiv) were added to a solution of
muramic acid (IV‡)–(IVe) in anhydrous dioxane or
THF (10 ml/g) under stirring. After 3–5 h (TLC moni-
toring in systems Ä and C), the precipitate of dicyclo-
hexylurea was filtered off and washed with the solvent.
L-Alanyl-D-isoglutamine benzyl ester trifluoroacetate
[17] (1 equiv) and triethylamine (to pH 8) were added
Hydrolysis of isopropylidene groups. Alkylidene
derivatives (V‡)–(Ve) were dissolved in 80% acetic
acid (10 ml/g) under heating in boiling water bath, kept
for 5–15 min at this temperature (TLC monitoring in
systems A and C), and evaporated to dryness.
Hydrogenolysis of benzyl protecting groups.
Benzyl esters (VIa)–(VIe) were dissolved in ethanol
to the filtrate. After the reaction was finished (TLC (50–100 ml/g) and hydrogenated over 10% Pd/C (cata-
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 29 No. 3 2003

290
ZEMLYAKOV et al.
2 µg/mouse 20 µg/mouse
200 µg/mouse
100
80
60
40
20
0
Control
MDP
Bu
Hp
cHx
Ph
α-Hp α-cHx
Fig. 2. The effect of MDP glycosides (in doses of 2, 20, and 200 µg/mouse) on the protective effect upon the i.p. administration of
3
S. typhi (10 cell/mouse) to mice. The experiment was carried out as described earlier [10]. The same abbreviations as in Fig. 1 are
used.
lyst–substance ratio of 1 : 5) at room temperature for 3–
O-Octyl 2-acetamido-2,3-dideoxy-b-D-glucopyra-
6 h. After the reaction was finished (TLC monitoring in nosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine (VIIb).
systems D and E), the catalyst was filtered off and O-Octyl 2-acetamido-2-deoxy-β-D-glucopyranoside
washed with the solvent. The filtrate was evaporated in (IIb) was obtained by deacetylation of acetate (Ib)
a vacuum.
(2.5 g, 5.45 mmol); yield 1.80 g (99%); mp 185–
188°ë, [α]546 –42° (Ò 1.0, DMF). For 1H NMR data, see
table.
Octyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-
β-D-glucopyranoside (IIIb) was synthesized by iso-
propylidenation of triol (IIb) (1.65 g, 4.95 mmol);
yield after column chromatography (elution with chlo-
O-(Hexyl 2-acetamido-2,3-dideoxy-b-D-glucopyra-
nosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine (VIIa).
Hexyl-2-acetamido-2-deoxy-β-D-glucopyranoside (IIa)
was obtained by deacetylation of acetate (Ia) (1.54 g,
3.57 mmol); yield 1.0 g (92%); mp 160–162°ë; [α]546
–29° (Ò 1.0, ethanol). For 1H NMR data, see table.
roform
25 : 1 chloroform–ethanol) 1.55 g (84%);
Hexyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-
β-D-glucopyranoside (IIIa) was synthesized by isopro-
pylidenation of triol (IIa) (1.0 g, 3.28 mmol); yield after
column chromatography (elution with chloroform
20 : 1 chloroform–ethanol) 0.61 g (54%); glassy sub-
stance, [α]546 –88° (c 1.0, chloroform).
amorphous substance; [α]546 –71° (c 1.0, chloroform).
Octyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-
3-O-(D-1-carboxyethyl)-β-D-glucopyranoside (IVb)
was obtained by alkylation of acetal (IIIb) (2.2 g,
5.9 mmol) with (S)-bromopropionic acid; yield after
column chromatography (elution with chloroform
25 : 1 chloroform–ethanol) 2.4 g (92%); glassy sub-
stance, [α]546 –12° (c 1.0, chloroform).
O-(Octyl 2-acetamido-2,3-dideoxy-b-D-glucopyr-
anosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine ben-
zyl ester (VIb). Condensation of muramic acid (IVb)
(2.0 g, 4.49 mmol) with dipeptide resulted in glycopep-
tide (Vb) (2.0 g, 61%). The resulting compound (Vb)
(1.0 g, 1.36 mmol) was deprotected by acidic hydroly-
sis, and the target (VIb) was isolated by column chro-
Hexyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-
3-O-(D-1-carboxyethyl)-β-D-glucopyranoside (IVa)
was obtained by alkylation of acetal (IIIa) (485 mg,
1.41 mmol) with (S)-bromopropionic acid; yield 0.57 g
(97%); amorphous substance; [α]546 –15° (Ò 1.0, chlo-
roform).
O-Hexyl 2-acetamido-2,3-dideoxy-β-D-glucopyra-
nosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine benzyl
ester (VIa). Muramic acid (IVa) (0.55 g, 1.32 mmol)
was condensed with dipeptide. The isopropylidene pro-
tecting group of the resulting (Va) was removed by
hydrolysis. The target compound (VIa) was isolated by
column chromatography (elution with chloroform
10 : 1 chloroform–ethanol); yield 0.48 g (55%); amor-
phous powder; [α]546 +2° (Ò 1.0, ethanol). For 1H NMR
data, see table.
matography (elution with chloroform
5 : 1 chloro-
form–ethanol); yield 0.72 g (76%); amorphous powder;
[α]546 +9° (Ò 1.0, ethanol). For 1H NMR data, see table.
O-(Octyl 2-acetamido-2,3-dideoxy-β-D-glucopyra-
nosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine (VIIb)
was obtained by catalytic hydrogenolysis of benzyl
ester (VIb) (350 mg, 0.51 mmol); yield 290 mg (95%);
amorphous powder; [α]546 +12° (Ò 0.93, ethanol).
O-(Cyclohexyl 2-acetamido-2,3-dideoxy-b-D-glu-
copyranosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine
(VIIc). Cyclohexyl 2-acetamido-2-deoxy-β-D-glu-
copyranoside (IIc) was obtained by deacetylation of
O-(Hexyl 2-acetamido-2,3-dideoxy-β-D-glucopyra-
nosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine (VIIa)
was obtained by catalytic hydrogenolysis of benzyl
ester (VIa) (250 mg, 0.38 mmol); yield 170 mg (78%);
amorphous powder; [α]546 +5° (Ò 0.83, ethanol).
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N-ACETYLMURAMYL-L-ALANYL-D-ISOGLUTAMINE GLYCOSIDES
291
acetate (Ic) (2.8 g, 6.5 mmol); yield 1.9 g (96%). An protecting group of the resulting glycopeptide (Vd)
analytical sample was crystallized from methanol; mp was removed by hydrolysis. The target compound
1
(VId) was isolated by precipitation with diethyl ether;
yield 290 mg (78%); amorphous substance; [α]546 +95°
(c 0.83, ethanol). For 1H NMR data, see table.
167–169°ë, [α]546 –37° (c 0.67, methanol). For H
NMR data, see table.
Cyclohexyl 2-acetamido-2-deoxy-4,6-O-isopropy-
lidene-β-D-glucopyranoside (IIIc) was synthesized by
isopropylidenation of triol (IIc) (830 mg, 2.74 mmol);
yield after column chromatography (elution with 75 : 1
O-(Heptyl 2-acetamido-2,3-dideoxy-α-D-glucopyr-
anosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine (VIId)
was obtained by catalytic hydrogenolysis of benzyl
ester (VId) (190 mg, 0.29 mmol); yield 150 mg (90%);
amorphous powder; [α]546 +96° (c 0.67, ethanol).
benzene–ethanol
25 : 1 benzene–ethanol) 765 mg
(81%); glassy substance; [α]546 –69° (c 1.0, chloro-
form).
O-(Cyclohexyl 2-acetamido-2,3-dideoxy-a-D-glu-
copyranosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine
(VIIe). Cyclohexyl 2-acetamido-2-deoxy-α-D-glucopy-
ranoside (IIe) was obtained by deacetylation of (Ic)
(3.43 g, 3.22 mmol); yield 2.42 g (100%). An analytical
sample was crystallized from methanol; mp 206–
207°ë, [α]546 +192° (c 1.0, ethanol). For 1H NMR data,
see table.
Cyclohexyl 2-acetamido-2-deoxy-4,6-O-isopropyl-
idene-α-D-glucopyranoside (IIIe) was synthesized by
isopropylidenation of triol (IIe) (1.0 g, 3.30 mmol); after
column chromatography (elution with benzene
20 : 1 benzene–ethanol), yield 925 mg (82%); amor-
phous powder; [α]546 +100° (c 1.0, chloroform).
Cyclohexyl-2-acetamido-2-deoxy-4,6-O-isopropyl-
idene-3-O-(D-1-carboxyethyl)-β-D-glucopyranoside
(IVc) was obtained by alkylation of acetal (IIIc)
(750 mg, 2.19 mmol) with (S)-bromopropionic acid;
yield 850 mg (94%); amorphous powder, [α]546 –6°
(c 1.0, chloroform).
O-Cyclohexyl 2-acetamido-2,3-dideoxy-β-D-glu-
copyranosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine
benzyl ester (VIc). Muramic acid (IVc) (835 g,
2.01 mmol) was condensed with the dipeptide. The iso-
propylidene protecting group was removed from the
resulting compound (Vc) by hydrolysis. The target
compound (VIc) was isolated by column chromatogra-
phy (elution with chloroform
10 : 1 chloroform–
O-(Cyclohexyl 2-acetamido-2,3-dideoxy-α-D-glu-
copyranosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine
benzyl ester (VIe). Acetal (IIIe) (910 mg, 2.65 mmol)
was alkylated with (S)-2-chloropropionic acid, and the
resulting muramic acid (IVe) was condensed with the
dipeptide. The isopropylidene protecting group of the
resulting compound (Ve) was removed by hydrolysis.
The target compound (VIe) was isolated by column
ethanol); yield 635 mg (48%); amorphous powder;
[α]546 +6° (Ò 1.0, ethanol). For 1H NMR data, see table.
O-(Cyclohexyl 2-acetamido-2,3-dideoxy-β-D-glu-
copyranosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine
(VIIc) was obtained by catalytic hydrogenolysis of
benzyl ester (VIc) (325 mg, 0.49 mmol); yield 265 mg
(92%); amorphous powder; [α]546 +6° (Ò 0.67, ethanol).
O-(Heptyl
2-acetamido-2,3-dideoxy-a-D-glu-
chromatography (elution with chloroform
20 : 1
copyranosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine
(VIId). Heptyl 2-acetamido-2-deoxy-α-D-glucopyra-
noside (IId) was obtained by deacetylation of acetate
(Id) (800 mg, 1.80 mmol); yield 500 mg (87%). An
analytical sample was crystallized from methanol; mp
163–165°ë, [α]546 +131° (Ò 1.0, methanol). For 1H NMR
data, see table.
chloroform–ethanol); yield 0.78 g (44%); amorphous
powder; [α]546 +98° (c 1.0, ethanol). For 1H NMR data,
see table.
O-(Cyclohexyl 2-acetamido-2,3-dideoxy-α-D-glu-
copyranosid-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine
(VIIe) was obtained by catalytic hydrogenolysis of
benzyl ester (VIe) (380 mg, 0.57 mmol); yield 330 mg
(98%); amorphous powder; [α]546 +93° (c 1.0, ethanol).
Heptyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-
α-D-glucopyranoside (IIId) was synthesized by iso-
propylidenation of triol (IId) (1.0 g, 3.30 mmol); after
column chromatography (elution with 75 : 1 benzene–
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