Synthesis of muramyl dipeptide isoflavone glycoside

Article abstract of DOI:10.1007/s10600-014-0812-4

The peracetate of 7-(2-acetamido-2-deoxy-β-D-glucopyranosyloxy)-2- methyl-6-propyl-3′,4′-trimethylenedioxyisoflavone was synthesized under phase-transfer catalysis conditions by quaternary ammonium salts at room temperature and with heating to 50 C in K₂CO₃ solution (0.18 M):CHCl₃. The corresponding glycoside of N-acetylmuramyl-L- alanyl-D-isoglutamine (MDP) was synthesized from the peracetate.

Full text of DOI:10.1007/s10600-014-0812-4

Chemistry of Natural Compounds, Vol. 49, No. 6, January, 2014 [Russian original No. 6, November–December, 2013]
SYNTHESIS OF MURAMYL DIPEPTIDE ISOFLAVONE GLYCOSIDE
1*
1
1
A. E. Zemlyakov, V. N. Tsikalova, S. G. Makarusꢀ,
UDC 547.963.057
1
2
V. Ya. Chirva, and V. P. Khilya
The peracetate of 7-(2-acetamido-2-deoxy-ꢁ-D-glucopyranosyloxy)-2-methyl-6-propyl-
3ꢀ,4ꢀ-trimethylenedioxyisoflavone was synthesized under phase-transfer catalysis conditions by quaternary
ammonium salts at room temperature and with heating to 50°C in K CO solution (0.18 M):CHCl . The
2
3
3
corresponding glycoside of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) was synthesized from the
peracetate.
Keywords: O-glycosides of isoflavone, glycosides of N-acetylglucosamine, phase-transfer catalysis, muramyl
dipeptide, muramyl dipeptide glycosides.
We reported earlier on the synthesis of ꢁ-(2-methylisoflavon-7-yl)- and ꢁ-(2-methyl-3ꢀ,4ꢀ-trimethylenedioxyisoflavon-
7-yl)glycosides of the methyl ester of N-acetylmuramyl-L-alanyl-D-isoglutamine (muramyl dipeptide, MDP) [1]. Interferon-
generating activity was found for MDP ꢁ-(2-methylisoflavon-7-yl)glycoside in in vivo tests [2]. In continuation of these
investigations, we synthesized a new chromone glycoside of MDP, i.e., ꢁ-(2-methyl-6-propyl-3ꢀ,4ꢀ-trimethylenedioxyisoflavon-
7-yl)-MDP.
A study of the glycosylation of 7-hydroxyisoflavone derivatives showed good yields of the 7-O-ꢁ-D-glucosaminides
in a phase-transfer (PT) system (solid K CO :CH CN) with crown-ether catalysis [3, 4] and in a system of K CO solution:CHCl
2
3
3
2
3
3
using quaternary ammonium salts (QAS) [4].
We studied the influence of the QAS structure using the reaction of 7-hydroxy-2-methyl-6-propyl-
3ꢀ,4ꢀ-trimethylenedioxyisoflavone (2) with a two-fold excess of 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-ꢂ-D-
glucopyranosylchloride (1) and PT catalysis in the system K CO (0.18 M):CHCl as an example. The reactions were carried
2
3
3
out at room temperature and with heating to 50°C. It was found (Fig. 1) that use of a weakly hydrophobic catalyst (Et NBr)
4
was ineffective whereas the best results for glycosylation of 7-hydroxyisoflavone (2) by highly hydrophobic QAS were obtained
for Bu NBr. In all instances, conducting the reaction at room temperature increased the conversion time of ꢂ-chloride 1. This
4
was accompanied by extensive decomposition of the glycosyl donor and reduction of the yield of target glycoside 3.
70
62
58
60
50
40
30
20
10
54
48
40
39
29
22
9
0
0
a
b
c
d
e
- room temp.
- heating
Fig. 1. Yields of glycoside 3 using various PT catalysts and temperatures
(a, Et NBr; b, Et BnNCl; c, C H Me NCl; d, Bu NI; e, Bu NBr).
4
3
18 37
3
4
4
1) V. I. Vernadskii Taurida National University, Prosp. Akad. Vernadskogo, 4, 95007, Simferopol, Ukraine, fax:
(0652) 23 23 10, e-mail: alex_z56@mail.ru; 2) Taras Shevchenko Kiev National University, Ul. Vladimirskaya, 62a, 01061,
Kiev, Ukraine, fax: (044) 235 12 73, e-mail: vkhilya@univ.kiev.ua. Translated from Khimiya Prirodnykh Soedinenii, No. 6,
November–December, 2013, pp. 871–873. Original article submitted July 1, 2013.
©
0009-3130/14/4906-1015 2014 Springer Science+Business Media New York
1015

TABLE 1. Characteristic PMR Resonances for 3, 7, and 8 (DMSO-d , ꢄ, ppm, J/Hz)
6
H atom
3
7
8
Me-2
H-5
H-8
2.26 s
7.77 s
7.31 s
2.28 s
7.74 s
7.31 s
2.27 s
7.74 s
7.21 s
Pr-6
0.87 t, 1.48 m, 2.13 t
6.89 (d, J = 2.0)
7.01 (d, J = 8.8)
6.84 (dd, J = 8.4; J = 2.0)
5.43 (d, J = 8.4)
1.80 s
0.87 t, 1.48 m, 2.13 t
6.88 br.d
7.01 (d, J = 8.8)
6.84 (dd, J = 8.0; J = 1.6)
5.29 (d, J = 8.0)
1.80 s
8.17 (d, JNH,2ꢀ = 9.2)
1.36 s, 1.51 s
1.25 d
0.87 t, 1.48 m, 2.12 t
6.87 br.d
7.00 (d, J = 7.6)
6.84 (dd, J = 8.4; J = 1.6)
5.10 (d, J = 8.0)
1.78 s
ꢀ
H-2
H-5ꢀ
H-6ꢀ
MurNAc:H-1
NAc
NH
8.18 (d, JNH,2ꢀ = 9.6)
8.22 (d, JNH,2ꢀ = 8.0)
–
Me2C
1.24 m
1.24 m
7.53 d
2.37 t
CH3CHÑÎ
Ala: CH3CH
NH
iGln: -CH2
ꢁ-CH2
CONH2
NH
COOCH2Ph
1.25 d
7.36 m
2.36 t
ꢅ
1.81 m, 2.01 m
7.14 s, 7.36 m
8.07 d
1.81 m, 2.01 m
7.13 s, 7.40 s
8.02 d
5.08 s, 7.36 m
5.08 s, 7.36 m
Me
OAc
OR
1
O
Me
O
O
O
a, b
c
d, e
O
OR
OR
AcO
R O
1
AcO
R O
HO
1
AcNH
AcNH
AcNH
Cl
1
3, 4
5
Me
OH
O
O
8
5
Me
O
f, g
HO
O
O
2 Me
R =
OR
O
OR
O
2'
O
Me
O
O
AcNH
Me
AcNH
Pr
CO-L-Ala-D-iGln-OR
1
COR
1
6, 7
9, 10
5'
3: R = Ac; 4, 10: R = H; 6: R = OH; 7: R = L-Ala-D-iGln-OBn; 9: R = Bn
1
1
1
1
1
a. ROH (2), K CO -H O/CHCl , (R ) NX; b. MeOH, MeONa; c. Me C(OMe) , TsOH; d. NaH, MeCHBrCOOH,
2
3
2
3
2 4
2
2
e. HOSu, DCC, L-Ala-D-iGln-OBn; f. H O, AcOH, tꢆC; g. H /Pd
2
2
The structure of 3 was confirmed by comparison with an authentic sample [4] and by PMR spectral data (Table 1).
The 4,6-diol sugar group was blocked by acetal protection through the reaction of deacetylated derivative 4 [4] with
2,2-dimethoxypropane. The C3-hydroxyl in 5 was treated with NaH and (S)-2-bromopropanoic acid under conditions facilitating
an S 2 mechanism. The catalyst for the alkylation reaction was 15-crown-5.
N
The resulting glycosylmuramic acid 6 was activated by N-hydroxysuccinimide and N,Nꢀ-dicyclohexylcarbodiimide
and condensed with the benzyl ester of L-alanyl-D-isoglutamine. Protected glycopeptide 7 was isolated in 94% yield by
column chromatography.
The PMR spectrum of 7 contained characteristic resonances corresponding to the isoflavone protons, the carbohydrate
residue, and the dipeptide (Table 1). Two-step deprotection of 7 included acid hydrolysis of the isopropylidene group and
removal of the benzyl ester in isoglutamine derivative 8 by catalytic hydrogenolysis. This gave the target glycoside of MDP 9.
EXPERIMENTAL
Melting points were determined on a PTP apparatus; optical rotation at 20–22°C, on a Polamat A polarimeter
(ꢃ 546 nm). PMR spectra were taken in DMSO-d with TMS internal standard on a Varian Mercury 400 spectrometer
6
1016

(400 MHz). TLC was carried out on Sorbfil-AFV-UV plates (Sorbpolimer, Russia). Compounds were detected using H SO
2
4
(5%) in EtOH with heating to 200–300°C and UV (254 nm). We used solvent systems C H –propan-2-ol (10:1, 1), CHCl –
6
6
3
propan-2-ol (10:1, 2), CHCl –propan-2-ol–AcOH (5:5:1, 3); Et NBr, C H Me NCl, Bu NI, Bu NBr (Merck), and
3
4
18 37
3
4
4
benzyltriethylammonium chloride (Et BnNCl) [5].
3
(2-Methyl-6-propyl-3ꢀ,4ꢀ-trimethylenedioxyisoflavon-7-yl)-2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-ꢁ-D-
glucopyranoside (3). General Glycosylation Method. A mixture of CHCl (7.5 mL) and K CO solution (7.5 mL, 0.18 M)
3
2
3
was treated with 1 (250 mg, 0.68 mmol) [6], 2 (124 mg, 0.34 mmol), and Et NBr (71 mg, 0.34 mmol) and stirred at room
4
temperature (A) or at 50°C (B) until the glycosyl donor disappeared (TLC monitoring using systems 1 and 2). When the
reaction was finished, the mixture was treated with CHCl (15 mL). The organic layer was separated, washed with H O
3
2
(5 mL), dried over anhydrous Na SO , and evaporated. The residue was crystallized from MeOH (5 mL) to afford 3 (yields in
2
4
Fig. 1), mp 235–237°C, [ꢂ] +52° (c 1.0, CHCl ). Table 1 lists the PMR spectrum.
546
3
(2-Methyl-6-propyl-3ꢀ,4ꢀ-trimethylenedioxyisoflavon-7-yl)-2-acetamido-2-deoxy-4,6-O-isopropylidene-ꢁ-D-
glucopyranoside (5). A solution of 4 (130 mg, 0.23 mmol) [4] in THF (10 mL) was heated to 60°C and treated with
2,2-dimethoxypropane (0.12 mL, 0.92 mmol) and p-toluenesulfonic acid (15 mg). After 1 h (TLC monitoring using system 2),
the mixture was treated with Py (0.05 mL) and evaporated. Column chromatography (gradient elution with C H –propan-2-ol,
6
6
50:1ꢇ10:1) isolated 5 (50 mg, 36%), [ꢂ] +20° (c 1.0, CHCl ).
546
3
Benzyl Ester of O-[(2-Methyl-6-propyl-3ꢀ,4ꢀ-trimethylenedioxyisoflavon-7-yl)-2-acetamido-2-deoxy-4,6-O-
isopropylidene-ꢁ-D-glucopyranosid-3-yl]-D-lactoyl-L-alanyl-D-isoglutamine (7). A solution of 5 (50 mg, 0.08 mmol) in
anhydrous dioxane (10 mL) was stirred, treated in portions with NaH (8 mg, 0.32 mmol), heated (water bath ~95°C) for 1 h
(TLC monitoring using system 2), cooled to 65°C, treated with 15-crown-5 (0.05 mL, 0.25 mmol) and after 1 h with
(S)-2-bromopropanoic acid (11 ꢈL, 0.12 mmol), held at 65°C for another 1.5 h, and cooled. The excess of NaH was decomposed
with H O. The mixture was evaporated, dissolved in H O (20 mL), and acidified with H SO (0.1 N) until the pH was 3–4.
2
2
2
4
Muramic acid was extracted with CHCl (3 ꢉ 10 mL). The CHCl layer was washed once with H O (5 mL), dried over
3
3
2
anhydrous Na SO , and evaporated. The residue was co-evaporated with benzene.
2
4
Acid 6 (56 mg, 0.08 mmol) in THF (10 mL) was stirred and treated with N-hydroxysuccinimide (18 mg, 0.16 mmol)
and N,Nꢀ-dicyclohexylcarbodiimide (33 mg, 0.16 mmol). After 27 h (TLC monitoring using system 2), the precipitate of
N,Nꢀ-dicyclohexylurea was filtered off and washed with solvent (3 mL). The filtrate was treated with N-deprotected dipeptide
[obtained by treatment of the benzyl ester of Boc-L-alanyl-D-isoglutamine (34 mg, 0.08 mmol) with trifluoroacetic acid
(100 ꢈL) with subsequent evaporation to dryness] and Et N until the pH was 7–8. When the reaction was finished (TLC
3
monitoring using system 2), the precipitate was filtered off. The filtrate was evaporated. The residue was dissolved in CHCl
3
(20 mL) and washed once with HCl solution (5 mL, 0.01 N), saturated NaHCO solution (5 mL), and H O (5 mL). The CHCl
3
2
3
layer was dried over anhydrous Na SO and evaporated. The residue was co-evaporated with benzene to afford 7 (75 mg,
2
4
94%), mp 175–180°C, [ꢂ] +21° (c 1.0, CHCl ). Table 1 lists the PMR spectrum.
546
3
Benzyl Ester of O-[(2-Methyl-6-propyl-3ꢀ,4ꢀ-trimethylenedioxyisoflavon-7-yl)-2-acetamido-2-deoxy-ꢁ-D-
glucopyranosid-3-yl]-D-lactoyl-L-alanyl-D-isoglutamine (8). Protected glycopeptide 7 (65 mg, 0.067 mmol) was dissolved
in AcOH (5 mL, 60%) with heating on a boiling-water bath and held for 20 min (TLC monitoring using systems 2 and 3). The
reaction mixture was evaporated. The residue was co-evaporated with benzene and crystallized from Et O to afford 8 (50 mg,
2
81%), mp 167–171°C, [ꢂ] +8° (c 1.0, CHCl ). Table 1 lists the PMR spectrum.
546
3
O-[(2-Methyl-6-propyl-3ꢀ,4ꢀ-trimethylenedioxyisoflavon-7-yl)-2-acetamido-2-deoxy-ꢁ-D-glucopyranosid-3-yl]-
D-lactoyl-L-alanyl-D-isoglutamine (9). Benzyl ester 8 (40 mg, 0.04 mmol) was dissolved in THF–H O (5 mL, 9:1) and
2
subjected to hydrogenolysis over Pd/C (20 mg, 10%) at room temperature for 2 h. When the reaction was finished (TLC
monitoring using system 3), the catalyst was filtered off and washed with the solvent mixture (3 mL). The filtrate was
evaporated. The residue was co-evaporated with benzene. The resulting product was ground with Et O to afford 9 (15 mg,
2
42%), [ꢂ] –10° (c 1.0, EtOH).
546
1017

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4.
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