Synthesis of Spacered Cyclopropanoid Muramyldipeptide Analogues as Potential Immunostimulants

Article abstract of DOI:10.1515/znb-2003-1216

A novel class of cyclopropanoic muramyldipeptide analogues containing an additional methylene spacer between the cyclopropane ring and the lactyl residue has been prepared by a straightforward synthesis starting from isopropyl (R)-lactate.

Full text of DOI:10.1515/znb-2003-1216

Synthesis of Spacered Cyclopropanoid Muramyldipeptide Analogues as
Potential Immunostimulants
Rene´ Csuk and Gunnar Go¨the
Institut fu¨r Organische Chemie, Martin-Luther-Universita¨t Halle-Wittenberg, Kurt-Mothes-Straße 2,
D-06120 Halle (Saale), Germany
Reprint requests to Prof. Dr. R. Csuk. E-mail: csuk@chemie.uni-halle.de
Z. Naturforsch. 58b, 1247 – 1254 (2003); received September 29, 2003
A novel class of cyclopropanoic muramyldipeptide analogues containing an additional methylene
spacer between the cyclopropane ring and the lactyl residue has been prepared by a straightforward
synthesis starting from isopropyl (R)-lactate.
Key words: Muramyldipeptide Analogues, Cyclopropanes, Immunostimulants
Introduction
Interest in immunostimulation [1] has been fu-
elled by the advances in bacterial cell wall chemistry
and by the rapidly expanding knowledge of endoge-
nous mediators of cell-differentiation and cooperation.
Thus, over the past two decades muramyldipeptide (N-
acetyl-muramyl-L-alanyl-D-isoglutamine, MDP) and
its derivatives have been investigated in detail and
many of these compounds revealed adjuvant activ-
ity and showed stimulation of nonspecific resistance
against bacterial, viral and parasite infections [2 – 4]
as well as anticancer activities. Albeit this progress,
many of the compounds exhibited undesired side ef-
fects, among them pyrogenicity, induction of arthrithis,
transient leucopenia as well as sensitivization to endo-
toxin [5 – 7].
Fig. 1. MDP and its spacered cyclopropanoid analogues.
interest for several years and the synthesis of highly
functionalized cyclopropanes has become a viable
discipline in its own right [18]. In our own approach to
novel and unprecedented MDP analogues we decided
to prepare target compounds possessing a spacered
cyclopropane moiety instead of the carbohydrate
portion.
Thus, allylation of commercially available isobutyl
(R)-lactate with allyl bromide in the presence of
Ag2O [19] gave 78% of isobutyl (2R)-(allyloxy)pro-
panoate (1) (Scheme 1) whose rhodium acetate cat-
alyzed reaction [20] with tert-butyl diazoacetate fur-
nished a 1:1:2:2 mixture of the corresponding cis- and
trans-configurated cyclopropanes 2 that could not be
separated even by exhaustive chromatography under a
variety of different conditions.
Structure activity relationships for these MDP ana-
logues have been established [8, 9] and as a result it
has been assumed that an intact carbohydrate part is
not essential for establishing immunostimulant activ-
ity. Several carbocyclic [10– 12] as well as acyclic ana-
logues [13] have been synthesized and tested. Even
more recently, the synthesis of lipophilic phospho-
nate [14], phosphonamidate [14], adamantyl [15] or
acridine substituted analogues [16, 17] has been re-
ported.
Selective cleavage of the tert-butyl ester leaving the
isopropyl ester intact was performed by treatment of
2 with trifluoroacetic acid [21, 22]. The acid 3 was
then subjected to a modified Curtius-degradation us-
ing diphenylphosphoryl azide (DPPA) [23] in the pres-
Results and Discussion
Cyclopropanes and cyclopropanoid modified ence of tert-butanol and triethylamine. Thus, the N-
biomolecules have been in the focus of synthetic Boc-protected cyclopropylamine 4 could be obtained
c
0932–0776 / 03 / 1200–1247 $ 06.00 ꢀ 2003 Verlag der Zeitschrift fu¨r Naturforschung, Tu¨bingen · http://znaturforsch.com
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R. Csuk – G. Go¨the · Synthesis of Spacered Cyclopropanoid Muramyldipeptide Analogues
The Boc group was cleaved by treatment of 6
with dry hydrochloric acid in ethyl acetate and
the resulting amine was acetylated by reaction with
acetyl chloride/triethylamine. Hydrogenolysis of the
N-acetyl-derivative 7 using Pd/C as the catalyst fi-
nally gave the target molecule 8. Similarly from 6
the octanoyl derivative 9 was obtained by deprotec-
tion of 6 followed by acylation using octanoyl chlo-
ride/triethylamine. Tedious chromatography of the re-
sulting mixture of products allowed the separation
of cis-configurated 9a as well as of trans-9b. Hy-
drogenolysis of 9a/9b finally gave 10a and 10b, re-
spectively.
The determination of the different biological activi-
ties of these novel carbocyclic MDP analogues is still
in progress.
Scheme 1. Reagents: a) MgSO4/Ag2O; b) N2CHCO2
tBu/[(Rh(OAc)2)2]; c) CF3COOH; d) DPPA, tBuOH, NEt3;
e) KOH in EtOH; f) ClCO2iBu/NMM, then H2N-L-Ala-D-
iGln-OBn.
Experimental Section
General
See ref. [23].
Isobutyl (2R)-2-(allyloxy)propanoate (1)
To a solution of isobutyl (R)-lactate (7.3 g, 0.05 mol)
in hexane (200 ml) a mixture of Ag2O (30.0 g, 0.13 mol)
and MgSO4 (1.2 g, 0.01 mol) was added. In the dark, al-
lyl bromide (9.1 g, 0.075 mol) was slowly added and stir-
ring at r.t. was continued for another 24 h. The suspension
was filtered, the residue washed with hexane and the com-
bined organic phases were evaporated. The remaining oil
(5.9 g, 78%) was used without further purification in the
next step. An analytical sample could be obtained by chro-
matography (silica gel, hexane/ethyl acetate 3:2). – RF (hex-
ane/ethyl acetate 3:2) 0.73. – [α]D 70.6 (c, 1.0 CHCl3). –
IR (film): ν = 3080w, 2965s, 2875m, 1750s, 1650w, 1470m,
1370m, 1275m, 1200s, 1140s, 1065m, 1025m cm−1. – 1H
NMR (400 MHz, CDCl3): δ = 5.90 (dddd, J = 17.2, 10.4,
6.1, 5.5 Hz, 1 H, HC=C), 5.27 (dd, J = 17.2, −1.7 Hz, 1 H,
H2C=Ctrans), 5.18 (dd, J = 10.4, −1.7 Hz, 1 H, H2C=Ccis),
4.14 (dd, J = 12.5, 5.5 Hz, 1 H, 1-HA,allyl), 4.01 (q, J =
6.9 Hz, 1 H, 2-H), 3.96 – 3.87 (m, 3 H, 1-HB,allyl and CH2 of
iBu), 1.95 (qqt, J = 6.7 Hz, CH of iBu), 1.41 (d, J = 6.9 Hz,
3 H, Me), 0.93 (d, J = 6.7 Hz, 6 H, 2 x Me of iBu). –
13C NMR (50 MHz, CDCl3): δ = 173.3 (s, C=O), 134.1 (d,
=CH), 117.6 (t, =CH2), 74.0 (d, 2-C), 71.0 (CH2O), 70.8 (t,
CH2O), 27.7 (d, CH), 19.0 (q, Me), 18.7 (q, Me). – MS (GC-
MS, EI, 70 eV): m/z (%) = 186 (1), 171 (1), 130 (7), 115 (1),
103 (1), 85 (75), 74 (14), 57 (35), 41 (100). – Analysis for
C10H18O3 (186.25): calcd. C 64.49, H 9.74; found C 64.13,
H 9.83.
Scheme 2. Reagents: a) HCl/EtOAc then AcCl/NEt3 (for 7)
or C7H15COCl/Et3N (for 9); b) Pd/C, H2, 3 bar.
in 51% yield. Hydrolysis of the isopropyl ester was
accomplished with potassium hydroxide in ethanol to
afford the free acid 5 which was subjected to a pep-
tide synthesis using the mixed-anhydrideprotocol [24].
Thus, treatment of 5 with isobutyl chloroformate/N-
methyl-morpholine (NMM) followed by the addition
of L-alanyl-D-i-glutamine-γ-benzyl ester (that was
freshly prepared from commercially available Boc-L-
Ala-D-iGln-OBn by acidic cleavage of the Boc group
using hydrochloric acid in ethyl acetate) gave 86% of
the protected derivative 6.
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R. Csuk – G. Go¨the · Synthesis of Spacered Cyclopropanoid Muramyldipeptide Analogues
1249
Isobutyl (2R)-2-{[2-(tert-butoxycarbonyl)cyclopropyl]meth- sure, toluene (twice 40 ml) added and evaporated and oily
oxy}propanoate (2)
3 (4.1 g, 100%) was obtained. It was used in the next step
without any purification. – IR (film): ν = 2965s, 2875m,
1735s, 1700s, 1470m, 1370m, 1275m, 1200s, 1170s, 1140s,
1070m, 1025m, 985m cm−1. – 1H NMR (400 MHz, CDCl3):
δ = 4.02 – 3.85 (m, 4 H, HA-CH2Ocis,A, 2-H, CH2 of
iBu), 3.72 – 3.65 (m, 2 H, CH2Ocis,B), 3.50 (dd, J = 10.2,
6.0 Hz, 1 H, HA-CH2Otrans,A), 3.47 – 3.39 (m, 3 H, HB-
CH2Ocis,A, CH2Otrans,B), 3.28 (dd, J = 10.2, 6.2 Hz, 1 H,
HB-CH2Otrans,A), 1.94 (qqt, J = 6.7 Hz, CH of iBu), 1.81 –
1.73 (m, 1 H, 2-H of cp), 1.72 – 1.65 (m, 1 H, 1-Hcis of cp),
1.62 – 1.55 (m, 1 H, 1-Htrans of cp), 1.391 (d, J = 6.8 Hz, 3
H, Me), 1.386 (d, J = 6.8 Hz, 3 H, Me), 1.35 (d, J = 6.8 Hz,
3 H, Me), 1.27 – 1.23 (m,1 H, 3-HA,trans of cp), 1.19 – 1.12
(m, 1 H, 3-HA,cis of cp), 1.10 – 1.06 (m, 1 H, 3-HB,cis of
cp), 0.98 – 0.93 (m, 3-HB,trans of cp), 0.92 (d, J = 6.9 Hz,
6 H, 2 x Me), 0.91 (d, J = 6.6 Hz, 6 H, 2 x Me). – 13C
NMR (100 MHz, CDCl3): δ = 179.72 (s, COOH), 179.65 (s,
COOH), 178.7 (s, COOH), 178.3 (s, COOH), 173.3 (s, C=O),
173.1 (s, C=O), 173.01 (s, C=O), 172.98 (s, C=O), 75.0 (d,
2-Ccis,A), 74.8 (d, 2-Ctrans,A), 74.7 (d, 2-Ctrans,B), 74.6 (d, 2-
Ccis,B), 71.1 (t, CH2), 70.93 (t, CH2), 70.92 (t, CH2), 70.90
(t, CH2), 70.87 (t, CH2), 70.85 (t. CH2), 68.1 (t, CH2Ocis,A),
67.6 (t, CH2Ocis,B), 27.78 (d, CH of iBu), 27.75 (d, CH of
iBu), 22.37 (d, 2-Ctrans,A of cp), 22.35 (d, 2-Ctrans,B of cp),
21.9 (d, 2-Ccis,A of cp), 21.5 (d, 2-Ccis,B of cp), 19.05 (q, Me
of iBu), 19.04 (q, Me of iBu), 18.7, 18.6, 18.4, 18.1, 17.40,
To a solution of 1 (4.70 g, 25.3 mmol) in abs.
dichloromethane containing [(Rh(OAc)2)2] (100 mg) was
added a solution of tert-butyl diazoacetate (5.2 g, 36.6 mmol)
in abs. dichloromethane (20 ml) very slowly (approx. 20 h).
The solvents were removed under diminished pressure and
the residue was subjected to chromatography (silica gel, hex-
ane/ethyl acetate 16:1) to afford oily 2 (5.90 g, 78%) as a
mixture of isomers (cisA : cisB : transA : transB = 1:1:2:2
1
(by H NMR)). – RF (hexane/ethyl acetate 3:2) 0.69. – IR
(film) ν = 2970s, 2875s, 1725s, 1470s, 1395s, 1370s, 1325s,
1260s, 1210s, 1150s, 1070s, 1030s, 990m cm−1. – 1H NMR
(400 MHz, CDCl3): δ = 4.05 – 3.85 (m, 4 H, 2-H, HA-
CH2Ocis,A, CH2 of iBu), 3.70 (dd, J = 10.3, 7.2 Hz, 1 H, HA-
CH2Ocis,B), 3.61 (dd, J = 10.3, 7.0 Hz, 1 H, HB-CH2Ocis,B),
3.53 (dd, J = 10.2, 6.2 Hz, HA-CH2Otrans,A), 3.45 - 3.34 (m,
3 H, HB-CH2Ocis,A, CH2Otrans,B), 3.28 (dd, J = 10.2, 6.4 Hz,
1 H, HB-CH2Otrans,A), 1.94 (qqt, J = 6.7 Hz, 1 H, CH of
iBu), 1.74 – 1.54 (m, 1 H, 2-H of cp), 1.48 – 1.40 (m, 1 H,
1-H of cp), 1.46 (s, 9 H, tBu), 1.44 (s, 9 H, tBu), 1.43 (s, 9
H, tBu), 1.42 (s, 9 H, tBu), 1.394 (d, J = 6.8 Hz, 3 H, Me),
1.390 (d, J = 6.8 Hz, 3 H, Me), 1.36 (d, J = 6.8 Hz, 3 H,
Me), 1.14 – 1.09 (m, 1 H, 3-HA,trans of cp), 1.02 – 0.94 (m, 2
H, 3-Hcis of cp), 0.923 (d, J = 6.6 Hz, 6 H, 2 x Me), 0.915
(d, J = 6.6 Hz, 6 H, 2 x Me), 0.83 – 0.77 (m, 1 H, 3-HB,trans
of cp). – 13C NMR (100 MHz, CDCl3): δ = 173.1 (s, C=O),
172.9 (s, C=O), 172.88 (s, C=O), 172.85 (s, C=O), 172.55
(s, C=O), 172.49 (s, C=O), 171.4 (s, C=O), 171.2 (s, C=O),
80.4 (s, OC(CH3)3), 80.2 (s, OC(CH3)3), 74.9 (d, 2-Ccis,A),
74.7 (d, 2-Ctrans,A), 74.6 (d, 2-Ctrans,B), 74.4 (d, 2-Ccis,B),
71.6 (t, CH2Otrans,A), 71.4 (t, CH2Otrans,B), 70.8 (t, CH2 of
iBu), 70.7 (t, CH2 of iBu), 70.66 (t, CH2 of iBu), 68.1 (t,
CH2Ocis,A), 67.6 (t, CH2Ocis,B), 28.23 (q, OC(CH3)3), 28.20
(q, OC(CH3)3), 27.8 (d, CH of iBu), 21.0 (d, 2-Ctrans,A of
cp), 20.9 (d, 2-Ctrans,B of cp), 20.8 (d, 2-Ccis,A of cp), 20.2
(d, 2-Ccis,B of cp), 19.6 (q, Me), 19.3 (d, 1-C of cp), 19.1
(q, Me), 18.9, 18.8, 18.74, 18.69, 18.65, 18.57 (Me or 1-C
of cp), 13.0 (dd, 3-Ctrans,A of cp), 12.7 (dd, 3-Ctrans,B of cp),
11.9 3-Ccis,A of cp), 11.4 (dd, 3-Ccis,B of cp). – MS (GC-MS,
EI, 70 eV): m/z (%) = 301 (1), 245 (9), 227 (23), 216 (3), 198
(7), 188 (15), 170 (4), 155 (7), 143 (59), 117 (14), 99 (100).
– Analysis for C16H28O5 (300.40): calcd. C 63.97, H 9.40;
found C 63.81, H 9.56.
17.36 (Me and 1-C of cp), 13.7 (dd, 3-C
of cp), 13.6
trans,A
(dd, 3-Ctrans,B of cp), 13.1 (dd, 3-Ccis,A of cp), 13.0 (dd,
3-Ccis,B of cp). – MS (EI, 70 eV): m/z (%) = 245 (5), 227
(37), 198 (5), 188 (5), 171 (3), 143 (39), 125 (4), 116 (14),
113 (41), 99 (100). – HRMS for C12H20O5: calcd. 244.1310;
found 244.1311.
Isobutyl (2R) 2-({2-[(tert-butoxycarbonyl)amino]cyclopro-
pyl}methoxy)propanoate (4)
To a solution of 3 (7.0 g, 28.7 mmol) containing triethy-
lamine (4.3 g, 42.6 mmol) and tert-butanol (8.5 g, 115 mmol)
under argon DPPA (9.5 g, 34.5 mmol) was carefully added
and the mixture heated for 40 h at 50 ◦C. The volatiles were
removed under reduced pressure and the residue was sub-
jected to chromatography (silica gel, hexane/ethyl acetate
5:1) to afford oily 4 (4.6 g, 51%). – RF (hexane/ethyl acetate
3:2) 0.62. – IR (film): ν = 3355m, 2970s, 2875m, 1720s,
1510s, 1470m, 1390m, 1365s, 1255s, 1170s, 1140s, 1065m,
1025m cm−1. – 1H NMR (400 MHz, CD3OD): δ = 5.85 (br,
1 H, NH, determined in CDCl3, cis), 4.70 (br, 1 H, NH, de-
2-({[(1R) 2-Isobutoxy-1-methyl-2-oxoethyl]oxy}methyl)-1-
cyclopropanecarboxylic acid (3)
To
a solution of 2 (5.0 g, 16.7 mmol) in dry termined in CDCl3, trans), 4.12 – 4.00 (m, 1 H, 2-H), 3.96 –
dichloromethane (100 ml) at 0 ◦C under argon a solution of 3.88 (m, 2 H, CH2 of iBu), 3.60 – 3.50 (m, 1 H, HA-CH2Ocis),
trifluoroacetic acid (11.4 g, 100 ml) in dry dichloromethane 3.43 (dd, J = 10.3, 6.5 Hz, 1 H, HA-CH2Otrans), 3.34 (dd,
(20 ml) was slowly added and stirring was continued for J = 10.3, 6.9 Hz, 1 H, HB-CH2Otrans), 3.29 – 3.22 (m, 1 H,
18 h. The solvents were removed under diminished pres- HB-CH2Ocis), 2.66 – 2.56 (m, 1 H, 2-Hcis of cp), 2.38 – 2.32
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R. Csuk – G. Go¨the · Synthesis of Spacered Cyclopropanoid Muramyldipeptide Analogues
(m, 1 H, 2-Htrans of cp), 1.94 (qqt, J = 6.6 Hz, 1 H, CH of Boc), 159.02 (s, C=O of Boc), 80.2 (s, OC(CH3)3), 75.5 (d,
iBu), 1.43 (s, 9 H, tBu), 1.364 (d, J = 6.9 Hz, 3 H, Me), 2-C), 75.3 (d, 2-C), 75.1 (d, 2-C), 72.8 (t, CH2Otrans,A), 72.7
1.359 (d, J = 6.8 Hz, 3 H, Me), 1.355 (d, J = 6.9 Hz, 3 (t, CH2Otrans,B), 70.4 (t, CH2Ocis,A), 69.9 (t, CH2Ocis,B),
H, Me), 1.29 – 1.19 (m, 1 H, 1-Hcis of cp), 1.18 – 1.10 (m, 28.74 (q, OC(CH3)3), 28.73 (q, OC(CH3)3), 28.1 (d, 2-C of
1 H, 1-Htrans of cp), 0.95 (d, J = 6.6 Hz, 6 H, 2 x Me of cp), 20.4 (d, 1-C of cp), 19.1 (q, Me), 19.0 (q, Me), 18.9 (q,
iBu), 0.95 – 0.88 (m, 1 H, 3-HA,cis of cp), 0.70 – 0.63 (m, 2 Me), 17.3 (d, 1-C of cp), 12.3 (dd, 3-C of cp), 12.1 (dd, 3-C
H, 3-Htrans of cp), 0.48 – 0.37 (m, 1 H, 3-HB,cis of cp). – of cp), 11.8 (dd, 3-C of cp). – MS (EI, 70 eV): m/z (%) =
13C NMR (100 MHz, CDCl3): δ = 174.3 (s, C=O), 173.0 260 (4), 244 (8), 232 (3), 203 (3), 186 (2), 170 (3), 143 (3),
(s, C=O), 172.9 (s, C=O), 157.8 (s, C=O of Boc), 157.0 (s, 128 (3), 113 (58), 100 (10), 70 (26), 57 (100). – HRMS for
C=O of Boc), 156.6 (s, C=O, C=O of Boc), 156.1 (s, C=O C12H21NO5: calcd. 259.1420; found 259.1419.
of Boc), 79.1 (s, OC(CH3)3), 78.8 (s, OC(CH3)3), 74.43
(d, 2-Ctrans,A), 74.37 (d, 2-Ctrans,B), 74.3 (d, 2-Ccis,A), 74.1
Benzyl N-[(2 R) 2-{[((tert-butoxycarbonyl)amino)cycloprop-
(d, 2-Ccis,B), 71.7 (t, CH2Otrans,A), 71.4 (t, CH2Otrans,B),
yl]methoxy}propio nyl]-L-alanyl-D-isoglutaminate (6)
70.7 (t, CH2 of iBu), 70.63 (t, CH2 of iBu), 70.57 (t, CH2
of iBu), 69.8 (t, CH2Ocis,A), 68.9 (t, CH2Ocis,B), 28.30 (q,
OC(CH3)3), 28.26 (q, OC(CH3)3), 28.1 (d, 2-C of cp), 27.6
(d, CH of iBu), 27.2 (d, 2-C of cp), 19.9 (d, 1-C of cp), 18.91
To a solution of Boc-L-alanyl-D-isoglutamine-γ-benzyl
ester (5.7 g, 14.0 mmol, Bachem) in abs. ethyl acetate (45 ml)
a solution of dry hydrochloric acid in abs. ethyl acetate (3.6 N
(q, Me), 18.86 (q, Me), 18.86 (q, Me), 18.81 (q, Me), 18.64
by titration, 23.6 ml, 85 mmol) was added and the mixture
(q, Me), 18.57 (q, Me), 18.5 (q, Me), 16.1 (d, 1-C of cp), 12.6
was stirred for 3 h at r.t. The volatiles were removed and
(dd, 3-C of cp), 12.04 (dd, 3-C of cp), 11.98 (dd, 3-C of cp),
the crude hydrochloride was used without any further purifi-
11.3 (dd, 3-C of cp). – MS (EI, 70 eV): m/z (%) = 316 (1),
cation. To a solution of 5 (3.2 g, 12.3 mmol) in dry ethyl
260 (12), 242 (1), 216 (6), 199 (1), 170 (10), 147 (6), 114
acetate (30 ml) and abs. dimethylformamide (30 ml) under
(51), 113 (50), 70 (99), 69 (100), 57 (100). – Analysis for
C16H29NO5 (315.41): calcd. C 60.93, H 9.27, N 4.44; found
C 60.81, H 9.42, N 4.51.
◦
argon NMM (1.42 g, 14.1 mmol) was added at 0 C, then
◦
the mixture was cooled to −15 C and isobutyl chlorofor-
mate (1.92 g, 14.1 mmol) was slowly added. After stirring
for 5 min at −15 ◦C a solution of the deprotected dipeptide
(vide supra, 4.8 g, 14.0 mmol) dissolved in a mixture con-
taining NMM (2.84 g, 28.2 mmol), ethyl acetate (40 ml) and
dimethylformamide (40 ml) was added. Stirring at r.t. was
(2R) 2-({2-[tert-Butoxycarbonyl)amino]cyclopropyl}meth-
oxy)propanoic acid (5)
To a solution of 4 (4.6 g, 14.6 mmol) in ethanol (40 ml) continued for 18 h, then the solvents were removed under
at 0 ◦C a solution of potassium hydroxide (2.5 g, 44.6 mmol) reduced pressure, the residue suspended in water (100 ml)
in ethanol (50 ml) was added. The reaction was stirred at r.t. and extracted with ethyl acetate (4×150 ml). The combined
for 2 h, then the solvents were removed under diminished organic phases were dried (Na2SO4), the solvents removed,
pressure and the residue was suspended in water (50 ml), and the residue was subjected to chromatography (silica gel,
the pH was adjusted to 3 by the addition of hydrochloric ethyl acetate/methanol 16:1 → 10:1) to afford 6 (5.8 g, 86%)
acid (10%) and the aq. phase was extracted with ethyl ac- as a white amorphous solid. – RF (ethyl acetate/methanol
etate (4×100 ml). The combined organic phases were dried 10:1) 0.43. – IR (KBr): ν = 3400m, 3335m, 3290m, 2980w,
(Na2SO4) and the solvents removed to afford oily 5 (3.8 g, 2935w, 1730s, 1670s, 1650s, 1530m, 1450w, 1390m, 1365m,
1
100%) that was used for the next step without any further pu- 1310w, 1250m, 1170m, 1100m, 1065w, 1025w cm−1. – H
rification. IR (film): ν = 3335m, 2980s, 2935s, 1715s, 1515s, NMR (400 MHz, CDCl3): δ = 7.77 (br, 1 H, NH), 7.36 –
1455m, 1395s, 1370s, 1255s, 1170s, 1065s, 1025m cm−1
–
.
7.25 (m, 6 H, NH and Ph), 6.88 (br, 1 H, NH), 6.83 (br, 1 H,
1H NMR (400 MHz, CD3OD): δ = 5.42 (br, 1 H, de- NH), 6.79 (br, 1 H, NH), 5.09 (AB system, J = 12.4 Hz, 2 H,
termined in CDCl3, cis), 4.82 (br, 1 H, NH, determined in CH2-Ph), 4.88 (br, 1 H, NH of Boc), 4.48 – 4.41 (m, 1 H, CH
CDCl3, trans), 4.05 – 3.96 (m, 1H, 2-H), 3.62 – 3.32 (m, 2 H, of iGln), 4.35 – 4.29 (m, 1 H, CH of Ala), 4.10 – 4.03 (m, 1 H,
CH2O), 2.66 – 2.58 (m, 1 H, 2-Hcis of cp), 2.38 – 2.32 (m, 1 CH of Lac), 3.86 – 3.80 (m, 1 H, CH of Lac), 3.70 – 2.95 (m,
H, 2-Htrans of cp), 1.43 (s, 9 H, tBu), 1.363 (d, J = 6.8 Hz, 2 H, CH2O), 2.94 – 2.64 (m, 1 H, 2-Hcis of cp), 2.59 – 2.51
3 H, Me), 1.360 (d, J = 6.9 Hz, 3 H, Me), 1.31 – 1.20 (m, 1 (m, 1 H, HA-4 of iGln), 2.47 – 2.40 (m, 1 H, HB-4 of iGln),
H, 1-Hcis of cp), 1.19 – 1.10 (m, 1 H, 1-Htrans of cp), 0.96 – 2.39 – 2.33 (m,1 H, 2-Htrans of cp), 2.24 – 2.17 (m, 1 H, HA-3
0.89 (m, 1 H, 3-HA,cis of cp), 0.72 – 0.64 (m, 2 H, 3-Htrans of iGln), 2.04 – 1.95 (m, 1 H, HB-3 of iGln), 1.411 (s, 9 H,
of cp), 0.46 – 0.41 (m, 1 H, HB-3cis,A of cp), 0.40 – 0.35 (m, tBu), 1.405 (s, 9 H, tBu), 1.400 (s, 9 H, tBu), 1.39 – 1.31 (m,
1 H, HB-3cis,B of cp). – 13C NMR (125 MHz, CD3OD): 6 H, Me of Ala and Me of Lac), 1.28 – 1.15 (m, 1 H, 1-H
δ = 177.06 (s, C=O), 176.99 (s, C=O), 176.89 (s, C=O), of cp), 1.00 – 0.94 (m, 1 H, HA-3cis of cp), 0.77 – 0.69 (m,
176.85 (s, C=O), 159.4 (s, C=O of Boc), 159.03 (s, C=O of 1 H, HA-3trans of cp), 0.67 – 0.61 (m, 1 H, HB-3trans of cp),
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R. Csuk – G. Go¨the · Synthesis of Spacered Cyclopropanoid Muramyldipeptide Analogues
1251
0.41 – 0.37 (m, 1 H, HB-3cis of cp). – 13C NMR (100 MHz, 3.59 (dd, J = 11.2, 4.8 Hz, 1 H, HA-CH2Otrans,B), 3.33 (dd,
CD3OD): δ = 176.2 (s, C=O), 175.94 (s, C=O), 175.87 (s, J = 11.0, 11.0 Hz, 1 H, HB-CH2Ocis,B), 3.11 (dd, J = 10.0,
C=O), 175.80 (s, C=O), 175.71 (s, C=O), 175.70 (s, C=O), 10.0 Hz, 1 H, HB-CH2Ocis,A), 3.06 (dd, J = 11.3, 9.0 Hz, 1
174.73 (s, C=O), 174.70 (s, C=O), 159.2 (s, C=O of Boc), H, HB-CH2O,trans,B), 2.79 – 2.70 (m, 1 H, 2-H of cp), 2.69
159.1 (s, C=O of Boc), 158.9 (s, C=O of Boc), 137.3 (s, Ph), (dd, J = 9.8, 9.8 Hz, 1 H, HB-CH2Otrans,A), 2.54 – 2.38 (m,
129.4 (d, Ph), 129.0 (d, Ph), 80.1 (s, OC(CH3)3), 77.5 (d, 2- 2 H, 4-H of iGln), 2.25 – 2.14 (m, 1 H, 3-HA of iGln), 2.05 –
Ccis,A of Lac), 77.0 (d, 2-Ctrans,A of Lac), 76.8 (d, 2-Ctrans,B 1.95 (m, 1 H, 3-HB of iGln), 1.94 (s, 3 H, Ac), 1.92 (s, 3
of Lac), 76.4 (d, 2-Ccis,B of Lac), 72.8 (t, CH2O), 72.3 (t, H, Ac), 1.90 (s, 3 H, Ac), 1.88 (s, 3 H, Ac), 1.40 – 1.31 (m,
CH2O), 70.3 (t, CH2O), 69.7 (t, CH2O), 67.4 (t, CH2-Ph), 6 H, Me of Ala, Me of Lac), 1.28 – 1.10 (m, 1 H, 1-H of
53.5 (d, 2-C of iGln), 50.5 (d, 2-C of Ala), 31.43 (t, 4-C of cp), 1.03 – 0.95 (m, 1 H, 3-HAcis of cp), 0.85 – 0.79 (m, 1
iGln), 31.41 (t, 4-C of iGln), 29.4 (d, 2-C of cp), 29.3 (2-C H, 3-HBtrans,A of cp), 0.77 – 0.70 (m, 1 H, 3-HAtrans,B of cp),
of cp), 28.82 (q, OC(CH3)3), 28.80 (q, OC(CH3)3), 28.12 (t, 0.69 – 0.61 (m, 1 H, 3-HB,trans of cp), 0.41 – 0.35 (m, 1 H, 3-
3-C of iGln), 28.07 (t, 3-C of iGln), 21.0 (d, 1-C of cp), 20.7 HB,cis of cp). – 13C NMR (100 MHz, CDCl3): δ = 174.01 (s,
(d, 1-C of cp), 19.2 (q, Me), 18.92 (q, Me), 18.88 (q, Me), C=O), 173.99 (s, C=O), 173.99 (s, C=O), 173.90 (s, C=O),
18.0 (q, Me), 17.9 (q, Me), 11.9 (dd, 3-C of cp). – MS (EI, 173.8 (s, C=O), 173.7 (s, C=O), 173.03 (s, C=O), 172.99 (s,
70 eV): m/z (%) = 548 (1), 505 (1), 474 (3), 457 (2), 448 (2), C=O), 172.97 (s, C=O), 172.90 (s, C=O), 172.86 (s, C=O),
430 (5), 404 (5), 380 (11), 363 (8), 346 (3), 313 (12), 285 172.84 (s, C=O), 172.79 (s, C=O), 172.7 (s, C=O), 172.4 (s,
(21), 257 (21), 237 (13), 229 (56), 192 (100), 127 (24), 113 C=O), 172.1 (s, C=O), 135.55 (s, Ph), 135.52 (s, Ph), 128.37
(74), 91 (91). – Analysis for C27H40N4O8 (548.64): calcd. (d, Ph), 128.36 (d, Ph), 128.08 (d, Ph), 128.06 (d, Ph), 128.0
C 59.11, H 7.35, N 10.21; found C 59.01, H 7.49, N 10.30.
(d, Ph), 76.8 (d, 2-Ccis,A of Lac), 76.3 (d, 2-Ctrans,A of Lac),
75.4 (d, 2-Ccis,B of Lac), 75.0 (d, 2-Ctrans,B of Lac), 72.2 (t,
CH2Otrans,A), 71.0 (t, CH2Otrans,B), 69.4 (t, CH2Ocis,A), 68.9
(t, CH2Ocis,B), 66.54 (t, CH2-Ph), 66.51 (t, CH2-Ph), 66.47
(t, CH2-Ph), 53.0 (d, 2-Ccis,A of iGln), 52.9 (d, 2-Ctrans,A of
iGln), 52.6 (d, 2-Ctrans,B of iGln), 52.5 (d, 2-Ccis,B of iGln),
49.3 (d, 2-C of Ala), 49.2 (d, 2-C of Ala), 48.9 (d, 2-C of
Ala), 30.7 (t, 4-C of iGln), 30.6 (t, 4-C of iGln), 29.1 (d, 2-
Ctrans,A of cp), 28.6 (d, 2-Ctrans,B of cp), 27.4 (d, 2-Ccis,A of
cp), 27.03 (t, 3-C of iGln), 26.98 (d, 2-Ccis,B of cp), 26.7 (t, 3-
C of iGln), 26.5 (t, 3-C of iGln), 22.94 (q, Ac), 22.86 (q, Ac),
22.75 (q, Ac), 20.9, 20.0, 18.7, 18.4, 18.2, 17.9, 17.83, 17.77,
17.70, 17.0, 16.4 (Me or 1-C), 10.9 (dd, 3-Ccis,A of cp), 10.2
(dd, 3-Ctrans,A of cp), 10.0 (dd, 3-Ctrans,B of cp), 9.3 (3-Ccis,B
of cp). – MS (EI, 70 eV): m/z (%) = 490 (1), 472 (1), 446
(3), 380 (3), 363 (9), 297 (1), 272 (10), 255 (34), 237 (5),
227 (100), 192 (9), 144 (20), 112 (66), 91 (48). – Analysis
for C24H24N4O7 (490.56): calcd. C 58.76, H 6.99, N 11.42;
found C 58.60, H 7.11, N 11.52.
Benzyl N-[(2R) 2-{[(2-acetylamino)cyclopropyl]meth-
oxy}propionyl]-L-alanyl-D-isoglutaminate (7)
To a solution of 6 (1.0 g, 1.8 mmol) in ethyl acetate (8 ml)
a solution of dry hydrochloric acid in ethyl acetate (3.6 N
by titration, 3.3 ml, 11.8 mmol) was added and the reac-
tion was stirred for 3 h at r.t., then the volatiles were re-
moved and the residue was dissolved in dichloromethane
(30 ml) containing triethylamine (1.8 g, 18 mmol). Af-
◦
ter cooling to 0 C a solution of acetyl chloride (200 mg,
2.5 mmol) in dichloromethane (5 ml) was added dropwise
and stirring at r.t. was continued for another 18 h. The sol-
vents were removed under reduced pressure, water (50 ml)
was added and the solution was extracted with ethyl ac-
etate (4 × 50 ml). The combined organic phases were dried
(Na2SO4), the solvent was evaporated and the residue sub-
jected to chromatography (silica gel, ethyl acetate/methanol
13:1 → 10:1) to afford 7 (594 mg, 67%) as a white amor-
phous solid. RF (ethyl acetate/methanol 10:1) 0.12. – IR
(KBr): ν = 3280s, 3070m, 2930m, 1730s, 1650s, 1540s,
1455m, 1370m, 1245m, 1170m, 1110m cm−1. – 1H NMR
(2R) 2-{[2-(Acetylamino)cyclopropyl]methoxy}propionyl-L-
alanyl-D-isoglutamine (8)
Hydrogenolysis of 7 (350 mg, 0.7 mmol) in ethanol
(400 MHz, CDCl3): δ = 8.32 (d, J = 8.3 Hz, 1 H, NH), 8.12 (50 ml) in the presence of Pd/C (10%, 50 mg) for 8 h at
(d, J = 7.1 Hz, 1 H, NH), 7.56 – 7.47 (m, 2 H, NH), 7.39 (br, 3 bar followed by filtration and chromatography (chloro-
1 H, NH), 7.34 – 7.26 (m, 5 H, Ph), 7.14 (br, 1 H, NH), 6.97 form/ethanol/acetic acid 70:25:5) gave 8 (280 mg, 100%) as
(br, 1 H, NH), 6.47 (br, 1 H, NH), 6.43 (br, 1 H, NH), 6.32 a white amorphous solid. RF (chloroform/ethanol/acetic acid
(br, 1 H, NH), 6.10 (br, 1 H, NH), 6.06 (br, 1 H, NH), 6.01 70:25:5) 0.38. – IR (KBr): ν = 3415s, 1655s, 1540s, 1450m,
1
(br, 1 H, NH), 5.07 (AB system, J = 12.5 Hz, 2 H, CH2-Ph), 1375m, 1300w, 1255w, 1175w, 1110w, 1060w cm−1. – H
4.59 – 4.53 (m, 1 H, CH of Ala), 4.43 – 4.35 (m, 2 H, CH of NMR (400 MHz, DMSO-d6): δ = 8.20 – 8.14 (m, 1 H, NH),
iGln and CH of Ala), 4.14 (q, J = 6.7 Hz, 1 H, CH of Lac), 7.98 – 7.88 (m, 2 H, NH), 7.34 (br, 1 H, NH), 7.06 (br, 1 H,
3.89 (dd, J = 9.8, 4.4 Hz, 1 H, HA-CH2Otrans,A), 3.82 (q, NH), 4.27 – 4.22 (m, 1 H, CH of iGln), 4.18 – 4.11 (m, 1 H,
J = 6.9 Hz, 1 H, CH of Lac), 3.74 (dd, J = 10.0, 5.2 Hz, HA- CH of Ala), 3.97 (q, J = 6.8 Hz, 1 H, CH of Lac), 3.85 (q,
CH2Ocis,A), 3.69 (dd, J = 11.8, 4.6 Hz, 1 H, HA-CH2Ocis,B), J = 6.7 Hz, 1 H, CH of Lac), 3.79 (q, J = 6.9 Hz, 1 H, CH
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1252
R. Csuk – G. Go¨the · Synthesis of Spacered Cyclopropanoid Muramyldipeptide Analogues
of Lac), 3.48 – 3.20 (m, 2 H, CH2O), 2.75 – 2.65 (m, 1 H, 2- 1 H, 3-HA of iGln), 2.10 (t, J = 7.6 Hz, 2 H, 2-H of oct),
Htrans of cp), 2.62 – 2.56 (m, 1 H, 2-Hcis of cp), 2.17 – 2.13 2.07 – 1.97 (m, 1 H, 3-HB of iGln), 1.61 – 1.53 (m, 2 H, 3-H
(m, 2 H, 4-H of iGln), 1.99 – 1.88 (m, 1 H, 3-HA of iGln), of oct), 1.36 (d, J = 7.0 Hz, 3 H, Me), 1.33 (d, J = 6.8 Hz,
1.79 (s, 3 H, Ac), 1.78 (s, 3 H, Ac), 1.74 (s, 3 H, Ac), 1.73 – 3 H, Me), 1.30 – 1.20 (m, 8 H, oct), 1.15 – 1.08 (m, 1 H, 1-
1.67 (m, 1 H, 3-HB of iGln), 1.26 – 1.18 (m, 6 H, Me of Ala H of cp), 0.85 (t, J = 6.9 Hz, 3 H, Me of oct), 0.76 – 0.69
and Me of Lac), 1.16 – 1.02 (m, 1 H, 1-H of cp), 0.87 – 0.81 (m, 1 H, 3-HA of cp), 0.68 – 0.61 (m, 1 H, 3-HB of cp). –
(m, 1 H, 3-HA,cis of cp), 0.62 – 0.52 (m, 2 H, 3-Htrans of cp), 13C NMR (100 MHz, CDCl3): δ = 175.2 (s, C=O), 174.1 (s,
0.42 – 0.38 (m, 1 H, 3-HB,cis,A of cp), 0.37 – 0.32 (m, 1 H, 3- C=O), 173.8 (s, C=O), 173.1 (s, C=O), 172.9 (s, C=O), 135.6
HB,cis,B of cp). – 13C NMR (125 MHz, CD3OD): δ = 176.24 (s, Ph), 128.5 (d, Ph), 128.2 (d, Ph), 128.1 (d, Ph), 74.6 (d, 2-
(s, C=O), 176.15 (s, C=O), 175.1 (s, C=O), 175.0 (s, C=O), C of Lac), 70.6 (t, CH2O), 66.6 (t, CH2-Ph), 52.6 (d, 2-C of
174.7 (s, C=O), 77.4 (d, 2-Ccis,A of Lac), 77.0 (d, 2-Ctrans,A iGln), 49.5 (d, 2-C of Ala), 36.5 (t, 2-C of oct), 31.7 (t, oct),
of Lac), 76.32 (d, 2-Ccis,B of Lac), 76.26 (d, 2-Ctrans,B of 30.7 (t, 4-C of iGln), 29.2 (t, oct), 29.0 (t, oct), 28.6 (t, 2-C of
Lac), 72.9 (t, CH2Otrans,A), 72.2 (t, CH2Otrans,B), 70.2 (t, cp), 26.6 (t, 3-C of iGln), 25.7 (t, oct), 22.6 (t, oct), 20.4 (d, 1-
CH2Ocis,A), 69.9 (t, CH2Ocis,B), 53.93 (d, 2-C of iGln), 53.90 C of cp), 18.1 (q, Me), 17.3 (q, Me), 14.1 (q, Me of oct), 10.3
(d, 2-C of iGln), 53.8 (d, 2-C of iGln), 50.62 (d, 2-C of Ala), (dd, 3-C of cp). – MS (EI, 70 eV): m/z (%) = 505 (1), 475
50.59 (d, 2-C of Ala), 50.6 (d, 2-C of Ala), 31.8 (t, 4-C of (1), 458 (1), 448 (1), 430 (3), 404 (4), 380 (9), 363 (7), 346
iGln), 29.1 (d, 2-Ctrans of cp), 28.2 (t, 3-C of iGln), 28.0 (d, (3), 335 (3), 313 (16), 285 (14), 257 (11), 237 (11), 229 (45),
2-Ccis,A of cp), 27.7 (d, 2-Ccis,B of cp), 22.5 (q, Ac), 22.4 (q, 211 (11), 192 (99), 185 (8), 144 (21), 127 (17), 113 (56), 91
Ac), 21.1, 20.6, 20.3, 19.1, 18.9, 17.9, 17.8, 17.5 (Me or 1- (73), 69 (100). – Analysis for C30H46N4O7 (574.72): calcd.
C of cp), 11.1 (dd, 3-Ctrans,A of cp), 10.8 (dd, 3-Ctrans,B of C 62.69, H 8.07, N 9.75; found C 62.47, H 8.19, N 9.84.
cp), 10.7 (dd, 3-Ccis,A of cp), 9.5 (dd, 3-Ccis,B of cp). – MS
(EI, 70 eV): m/z (%) = 400 (1), 382 (2), 356 (1), 323 (1), 290
Data for trans-9b: white amorphous solid. – RF (ethyl
acetate/methanol 10:1) 0.16. – IR (KBr): ν = 3405s,
(1), 272 (12), 255 (15), 227 (62), 210 (2), 195 (2), 184 (6),
3285s, 3065w, 2930m, 2855m, 1730m, 1675s, 1645s, 1545s,
156 (7), 144 (29), 112 (100). – Analysis for C17H28N4O7
1455m, 1420m, 1390m, 1310m, 1245m, 1170m, 1105m,
(400.44): calcd. C 50.99, H 7.04, N 14.06; found C 50.78,
H 7.23, N 13.88.
1
1070w cm−1. – H NMR (400 MHz, CDCl3): δ = 8.19 (d,
J = 7.5 Hz, 1 H, NH), 7.36 – 7.29 (m, 5 H, Ph), 7.23 (d,
J = 8.1 Hz, 1 H, NH), 7.15 (br, 1 H, NH), 5.78 (br, 1 H,
NH), 5.38 (br, 1 H, NH), 5.09 (AB system, J = 12.3 Hz, 2
H, CH2-Ph), 4.46 (qd, J = 7.5 Hz, 1 H, CH, Ala), 4.45 –
4.41 (m, 1 H, CH of iGln), 3.86 (q, J = 6.7 Hz, 1 H, CH
of Lac), 3.71 (dd, J = 11.7, 4.6 Hz, 1 H, HA-CH2O), 3.32
(dd, J = 11.7, 10.4 Hz, 1 H, HB-CH2O), 2.79 – 2.76 (m, 1 H,
2-H of cp), 2.61 – 2.53 (m, 1 H, 4-HA of iGln), 2.48 – 2.40
(m, 1 H, 4-HB of iGln), 2.28 – 2.20 (m, 1 H, 3-HA of iGln),
2.10 (t, J = 7.7 Hz, 2 H, oct), 2.07 – 1.98 (m, 1 H, 3-HB of
iGln), 1.61 – 1.55 (m, 2 H, 3-H oct), 1.44 (d, J = 7.1 Hz, 3
H, Me), 1.38 (d, J = 6.6 Hz, 3 H, Me), 1.31 – 1.20 (m, 9 H,
1-H of cp and oct), 1.07 – 1.01 (m, 1 H, 3-HA of cp), 0.85 (t,
J = 6.7 Hz, 3 H, Me, oct), 0.39 – 0.35 (m, 1 H, 3-HB of cp).
Benzyl N-[(2R) 2-{[cis-(2-octanoylamino)cyclopropyl]meth-
oxy}propionyl-L-alanyl-D-isoglutaminate (cis-9a) and benz-
yl N-[(2R) 2-{[trans-(2-octanoylamino)cyclopropyl]meth-
oxy}propionyl]-L-alanyl-D-isoglutaminate (trans-9b)
Following the procedure given for the synthesis of 7 from
6 (1.40 g, 2.55 mmol) in abs. ethyl acetate (25 ml) deprotec-
tion was performed with hydrochloric acid in ethyl acetate
(3.6 N, 4.7 ml, 16.9 mol) followed by acylation with oc-
tanoyl chloride (0.62 g, 3.83 mmol) / triethylamine (2.58 g,
25.5 mmol) in abs. dichloromethane (40 ml). Chromatogra-
phy (silica gel, ethyl acetate/methanol 19:1 → 10:1) gave di-
asteromer trans-9a (80 mg, 5%), diastereomer cis-9b (60 mg,
4%) and a mixture of stereoisomers (960 mg, 66%).
–
13C NMR (100 MHz, CDCl3): δ = 175.8 (s, C=O), 174.2
Data for cis-9a: white amorphous solid. – RF (ethyl (s, C=O), 173.5 (s, C=O), 173.3 (s, C=O), 172.6 (s, C=O),
acetate/methanol 10:1) 0.16. – IR (KBr): ν = 3405s, 135.6 (s, Ph), 128.5 (d, Ph), 128.2 (d, Ph), 128.1 (d, Ph), 77.4
3285s, 3065w, 2930m, 2855m, 1730m, 1675s, 1645s, 1545s, (d, 2-C of Lac), 69.9 (t, CH2O), 66.7 (t, CH2-Ph), 53.0 (d,
1455m, 1420m, 1390m, 1310m, 1245m, 1170m, 1105m, 2-C of iGln), 49.2 (d, 2C of Ala), 36.7 (t, 2-C of oct), 31.7 (t,
1070w cm−1. – 1H NMR (400 MHz, CDCl3): δ = 8.19 (d, oct), 30.5 (t, 4-C of iGln), 29.2 (t, oct), 29.0 (t, oct), 27.1 (d,
J = 6.8 Hz, 1 H, NH), 7.36 – 7.27 (m, 6 H, NH and Ph), 7.06 2-C of cp), 26.7 (t, 3-C of iGln), 26.9 (t, oct), 18.9 (d, 1-C of
(br, 1 H, NH), 5.89 (br, 1 H, NH), 5.88 (br, 1 H, NH), 5.09 cp), 17.5 (q, Me), 17.4 (q, Me), 14.1 (q, Me of oct), 10.0 (dd,
(AB system, J = 12.3 Hz, 2 H, CH2-Ph), 4.50 – 4.40 (m, 1 H, 3- of cp). – MS (EI, 70 eV): m/z (%) = 505 (1), 475 (1), 458
CH of iGln), 4.32 (qd, J = 6.9 Hz, 1 H, CH of Ala), 4.19 (q, (1), 448 (1), 430 (4), 404 (6), 380 (12), 363 (3), 346 (4), 335
J = 6.6 Hz, 1 H, CH of Lac), 3.59 (dd, J = 11.3, 4.9 Hz, 1 (1), 313 (10), 285 (12), 257 (15), 237 (11), 229 (52), 211 (9),
H, HA-CH2O), 3.07 (dd, J = 11.3, 8.8 Hz, 1 H, HB-CH2O), 192 (82), 185 (4), 144 (17), 127 (21), 113 (43), 91 (63), 69
2.76 – 2.72 (m, 1 H, 2-H of cp), 2.56 – 2.47 (m, 1 H, 4-HA (100). – Analysis for C30H46N4O7 (574.72): calcd. C 62.69,
of iGln), 2.46 – 2.39 (m, 1 H, 4-HB of iGln), 2.25 – 2.19 (m, H 8.07, N 9.75; found C 62.52, H 8.23, N 9.86.
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R. Csuk – G. Go¨the · Synthesis of Spacered Cyclopropanoid Muramyldipeptide Analogues
1253
(2R) 2-{[cis-2-(octanoylamino)cyclopropyl]methoxy}prop-
ionyl-L-alanyl-D-isoglutamine (cis-10a)
scribed above followed by chromatography (silica gel, chlo-
roform/ethanol/acetic acid 70:25.5) gave 10b (31 mg, 82%)
as a white amorphous solid. – RF (chloroform/ethanol/acetic
acid 70:25:5) 0.43. – IR (KBr): ν = 3405s, 2955s, 2925s,
2855s, 1730m, 1655s, 1555s, 1455m, 1260m, 1110m,
Hydrogenolysis of 9a (75 mg, 0.13 mmol) in ethanol
(30 ml) in the presence of Pd/C as described above followed
by chromatography (silica gel, chloroform/ethanol/acetic
acid 70:25:5) gave 10 (60 mg, 95%) as a white amorphous
solid. RF (chloroform, ethanol/acetic acid 70:20:5) 0.42. –
IR (KBr): ν = 3290s, 2930m, 2860m, 1650s, 1555s, 1455m,
1260m, 1210w, 1170w, 1110m cm−1. – 1H NMR (400 MHz,
DMSO-d6): δ = 8.60 (br, 1H, NH), 8.01 (d, J = 7.3 Hz, 1 H,
NH), 7.95 (d, J = 4.6 Hz, 1 H, NH), 7.33 (br, 1 H, NH),
7.00 (br, 1 H, NH), 4.23 (qd, J = 7.0 Hz, 1 H, CH of Ala),
4.10 – 4.03 (m, 1 H, CH of iGln), 3.97 (q, J = 6.4 Hz, 1 H,
CH of Lac), 3.47 (dd, J = 10.9, 5.9 Hz, 1 H, HA-CH2O de-
termined in CD3OD), 3.31 (m, 1 H, HB-CH2O, determined
in CD3OD), 2.62 – 2.58 (m, 2-H of cp), 2.05 – 1.95 (m, 4 H,
H4-H of iGln, 2-H of oct), 1.94 – 1.84 (m, 1 H, HA-3 of iGln),
1.75 – 1.68 (m, 1 H, HB-3 of iGln), 1.49 – 1.42 (m, 2 H, 3-
H of oct), 1.29 – 1.18 (m, 14 H, Me, Me, Oct), 1.10 – 1.02
(m, 1H, 1-H of cp), 0.84 (t, J = 6.7 Hz, 3 H, Me of oct),
0.61 – 0.51 (m, 2 H, 3-H of cp). – 13C NMR (100 MHz,
CD3OD): δ = 177.5 (s, C=O), 186.7 (s, C=O), 176.2 (s,
C=O), 176.0 (s, C=O), 174.8 (s, C=O), 76.3 (2-C of Lac),
72.2 (t, CH2O), 54.5 (d, 2-C of iGln), 50.6 (d, 2-C of Ala),
36.9 (t, 2-C of oct), 32.9 (t, oct), 30.7 (t, 4-C of iGln), 30.3
(t, oct), 30.1 (t, oct), 29.2 (t, 3-C of oct), 29.1 (d, 2-C of cp),
27.0 (t, oct), 23.7 (t, oct), 20.5 (d, 1-C of cp), 19.0 (q, Me),
17.9 (q, Me of oct), 11.0 (dd, 3-C of cp). – HPLC-MS (ESI,
4.1 kV, 8 µl/min N2, methanol): m/z (%) = 1007.4 [M2K]+
(100), 991.5 [M2Na]+ (86), 969.5 [M2H]+ (7), 523.5 [MK]+
(49), 507.9 [MNa]+ (55), 485.5 [MH]+ (22). – HRMS for
C23H40N4O7: calcd. 484.2898; found 484.2897. – Analysis
for C23H40N4O7 (484.60): calcd. C 57.01, H 8.32, N 5.11;
found C 57.13, H 8.54, N 11.41.
1
1070w cm−1. – H NMR (400 MHz, DMSO-d6): δ = 8.80
(br, 1 H, NH), 7.99 (br, 1 H, NH), 7.92 (d, J = 7.1 Hz,
1 H, NH), 7.30 (br, 1 H, NH), 6.93 (br, 1 H, NH), 4.19
(qd, J = 7.1 Hz, 1 H, CH of Ala), 4.02 – 3.98 (m, 1 H, CH
of iGln), 3.74 (q, J = 6.8 Hz, 1 H, CH of Lac), 3.56 (dd,
J = 11.0, 5.7 Hz, 1 H, HA-CH2O, determined in CD3OD),
3.38 (dd, J = 11.0, 8.9 Hz, 1 H, HB-CH2O, determined in
CD3OD), 2.75 – 2.69 (m, 1 H, 2-H of cp), 2.02 – 1.96 (m,
4 H, 4-H of iGln and 2-H of oct), 1.88 – 1.80 (m, 1 H, 3-
HA of iGln), 1.75 – 1.65 (m, 1 H, 3-HB of iGln), 1.47 – 1.38
(m,2 H, 3-H of oct), 1.30 – 1.11 (m, 14 H, 1-H of cp, 2
x Me and oct), 1.10 – 1.00 (m, 1 H, 3-HA of cp), 0.81 (t,
J = 6.9 Hz, Me of oct), 0.46 – 0.42 (m, 1 H, 3-HB of cp).
–
13C NMR (100 MHz, CD3OD): δ = 178.2 (s, C=O), 176.7
(s, C=O), 176.4 (s, C=O), 174.8 (s, C=O), 77.6 (d, 2-C of
Lac), 70.3 (t, CH2O), 54.6 (d, 2-C of iGln), 50.7 (d, 2-C
of Ala), 36.9 (t, 2-C of oct), 32.9 (t, oct), 30.7 (t, 4-C of
iGln), 30.3 (t, oct), 30.2 (t, oct), 29.3 (t, 3-C of iGln), 28.0
(d, 2-C of cp), 27.1 (t, oct), 23.7 (t, oct), 19.2 (d, 1-C of cp),
18.1 (q, Me), 17.8 (q, Me), 14.4 (q, Me of oct), 9.6 (dd, 3-
C of cp). – HPLC-MS (ESI, 4.1 kV, 8 µl/min N2, methanol):
m/z (%) = 1007.4 [M2K]+ (100), 991.4 [M2Na]+ (83), 969.5
[M2H]+ (6), 523.7 [MK]+ (71), 507.8 [MNa]+ (100), 485.5
[MH]+ (29). – HRMS for C23H40N4O7: calcd. 484.2898;
found 484.2898. – Analysis for C23H40N4O7 (484.60):
calcd. C 57.01, H 8.32, N 5.11; found C 56.82, H 8.47,
N 11.46.
Acknowledgments
(2R) 2-{[trans-2-(Octanoylamino)cyclopropyl]methoxy}-
propionyl-L-alanyl-D-isoglutamine (trans-10b)
Financial support by the Fonds der Chemischen Industrie
is gratefully acknowledged. We like to thank Dr. R. Kluge
for the ESI-MS measurements and Dr. D. Stro¨hl for numer-
ous NMR spectra.
Hydrogenolysis of 9b (45 mg, 0.08 mmol) in ethanol
(25 ml) in the presence of Pd/C (10%, 20 mg) as de-
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