Solid-phase synthesis of muramyl dipeptide (MDP) derivatives using a multipin method

Article abstract of DOI:10.1016/S0960-894X(00)00241-9

Solid-phase synthetic method of muramyl dipeptide derivatives is reported. A diverse library of muramyl dipeptides could be potentially synthesized by acylation, reductive alkylation, sulfonamide formation, urea formation, N-alkylation, amine addition, or component Ugi reactions based on this method for drug screening. (C) 2000 Elsevier Science Ltd. All rights reserved.

Full text of DOI:10.1016/S0960-894X(00)00241-9

Bioorganic & Medicinal Chemistry Letters 10 (2000) 1361±1363
Solid-Phase Synthesis of Muramyl Dipeptide (MDP) Derivatives
Using a Multipin Method
Gang Liu,* Shuo-De Zhang, Shu-Quan Xia and Zhen-Kai Ding
Institute of Pharmacology and Toxicology, Academy of Military Medical Science, Beijing 100850, China
Received 18 February 2000; accepted 17 April 2000
AbstractÐSolid-phase synthetic method of muramyl dipeptide derivatives is reported. A diverse library of muramyl dipeptides
could be potentially synthesized by acylation, reductive alkylation, sulfonamide formation, urea formation, N-alkylation, amine
addition, or component Ugi reactions based on this method for drug screening. # 2000 Elsevier Science Ltd. All rights reserved.
Muramyl dipeptide (MDP) is the minimum structure of
the cell wall of Gram-positive bacteria that can be recog-
nized by human immunological response. Since it can
3. Compound 3 was further activated by DCC and
HOSu to form Boc-d-Glu(OBzl)-OSu 4 active ester in
anhydrous THF. Compound 4 was reacted by 25%
1
stimulate non-speci®cally human macrophage to become
active against virus, bacteria, and tumors, it represents a
potential therapeutic agent. Drawbacks to its clinical use,
NH .OH to give Boc-d-isoGln(Bzl) 5. The benzyl group
4
was removed by a 5% Pd/C in HOAc for 3 days to yield
Boc-d-isoGln-OH 6. After removal of Boc by 50% TFA
in DCM, Fmoc-OSu was reacted with 6 for an additional
2
however, include poor penetration of macrophages, pyr-
3
ogenicity, nonspeci®c induction of autoimmune respon-
4
3 days at rt in the presence of 20% NaHCO to yield
3
ꢀ
ses and in¯ammatory reaction. Many derivatives of
MDP have been synthesized by solution-phase methods
and these compounds have been further studied by in
Fmoc-d-isoGln 7 (76.7% totally, mp. 204±205 C).
The peptide assembly was performed by a standard
16
5
vitro and in vivo assays. A few of them, including
6
Fmoc peptide synthetic strategy as shown in Scheme
7,8
9,10
11
GMDP, threonyl-MDP, MTP-PE,
1
Murabutide,
Romurtide, and B30-MDP are now in clinical trials. In
this paper, we are the ®rst to report a solid-phase Multi-
2. Fmoc protected crowns were treated by 20% piper-
idine in DMF twice, each for 5 min and 15 min respec-
tively. After thoroughly washing by DMF and
methanol separately, the crowns were suspended in a 3-
fold-time excess of Fmoc-Lys(Dde)-OH, BOP, HOBt
and NMM stock solution for 4 h. These peptide cou-
pling steps were repeated until the protected muramic
acid was coupled onto the peptide. The Dde protected
group of lysine was then removed by a treatment of 2%
NH NH in DMF twice, each for 3 min. After repeated
2
13
1
4
pin parallel synthesis of MDP derivatives method that
can potentially be used to make a diverse MDP derivative
library with potential application for lead drug screening.
The macro crowns with a loading capacity of 5±8 mmol/
pin from Chiron Mimotopes were used for the synthesis
of MDP derivatives. In order to explore the solid-phase
synthesis on pins, two critical building blocks were syn-
2
2
washing steps, the exposed free amino group was further
acylated with various organic acid building blocks using
a BOP as coupling reagent, and HOBt plus NMM as
additives at rt overnight. The ®nal products were cleaved
o€ from solid support by a reaction of crowns with 95%
1
5
thesized (protected muramic acid and Fmoc-d-isoGln
as Scheme 1).
7
Benzyl ester protected d-glutamic acid 2 was made from
d-glutamic acid 1 and benzyl-alcohol in the presence of
H SO (58.9%). The crude Boc-N that was synthesized
TFA/H O for 2 h at rt. After removal of TFA by lyo-
2
philization, all products were analyzed by HPLC at 214
nm wavelength with a gradient: B from 0±100% over 20
min. A: 0.1% TFA in water, B: 70% ACN in 0.1%
TFA water. Sixty compounds were synthesized, all of
them have a purity over 75% and correct molecular
weight by electrospray ionization (ESI) mass spectro-
metry without further puri®cation. Table 1 shows
2
4
3
from NaNO , Boc-N H in HOAc and H O was used to
2
2
3
2
protect amino group of 2 to yield Boc-d-Glu(OBzl)-OH
*
4
9
Corresponding author at current address UC Davis Cancer Center,
645 2nd Ave., Suite 1300, Sacramento, CA 95817, USA. Tel.: +1-
16-734-6414; fax: +1-916-734-6415; e-mail: gangliu27@yahoo.com
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(00)00241-9

1
362
G. Liu et al. / Bioorg. Med. Chem. Lett. 10 (2000) 1361±1363
Scheme 1. Synthesis of Fmoc-d-isoGln.
Scheme 2. Synthetic muramyl dipeptide derivatives on the crown.

G. Liu et al. / Bioorg. Med. Chem. Lett. 10 (2000) 1361±1363
Table 1. The synthetic muramyl dipeptide derivatices
1363
R
MWt (Calcd/found)
R
MWt (Calcd/found)
854.1/854.2
9
a
b
1049.7/1049.6
9h
9
922.2/922.4
9i
865.1/865.4
9
9
c
854.1/8554.4
862.1/862.2
9j
917.9/918.3
d
9k
1063.9/1064.1
�
9
e
f
CH
3
(CH
2
)
14
948.4/948.5
943.3/943.6
9l
Murml acyl
1075.4/1075.3
901.1/901.4
9
9m
9
g
942.2/942.2
9n
899.2/899.3
examples of 14 typical compounds with correct mole-
cular weight.
5. Baschang, G. Tetrahedron 1989, 45, 6331.
6. Palache, A. M.; Beyer, W. E.; Hendriksen, E.; Gerez, L.;
Aston, R.; Ledger, P. W.; de Regt, V.; Kerstens, R.; Roth-
barth, P. H.; Osterhaus, A. D. Vaccine 1996, 14, 1327.
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J.; Lerche, N. W.; Martin, M. E.; Scearce, R. M.; McDanal,
C.; Bolognesi, D. P.; Haynes, B. F. J. Immunol. 1990, 145,
In conclusion, we have developed a solid-phase syn-
thetic method of muramyl dipeptide derivatives using
the Multipin approach. Further more, a diversity library
synthesis is under way by acylation, reductive alkyla-
tion, sulfonamide formation, urea formation, N-alkyla-
tion, amine addition, or component Ugi reactions based
on this solid-phase synthetic method.
2
8
677.
. Ivins, B. E.; Welkos, S. L.; Little, S. F.; Crumrine, M. H.;
Nelson, G. O. Infect. Immun. 1992, 60, 662.
9. Kahn, J. O.; Sinangi, F.; Baenziger, J.; Murcar, N.; Wynne,
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Acknowledgements
1
0. Keefer, M. C.; Graham, B. S.; McElrath, M. J.; Matthews,
T. J.; Stablein, D. M.; Corey, L.; Wright, P. F.; Lawrence, D.;
Fast, P. E.; Weinhold, K.; Hsieh, R. H.; Cherno€, D.; Dekker,
C.; Dolin, R. AIDS Res. Hum. Retroviruses 1996, 12, 683.
This project was supported by the National Foundation
of Natural Sciences of China (NFNSC).
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