Synthesis of muramyl peptides containing meso-diaminopimelic acid

FULL PAPER

Synthesis of Muramyl Peptides Containing meso-Diaminopimelic Acid

Niels Kubasch^[a]and Richard R. Schmidt*^[a]

Keywords: Immunochemistry / Natural products / Oxygen heterocycles / Peptides

Chain-extension of

L-glutamate aldehyde 3 by means of the

myl peptides 17, 37, 40, 42, 44, 46, and 49a and 49b, which,

Wittig−Horner reaction furnished the desired C₇dicarboxylic

after deprotection, afforded the desired target molecules mu-

acid derivative, which in turn, after C-C double bond hydro- ramyl-

L

-alanine (38), muramyl-

muramyl- -alanyl- -glutaminide (41), muramyl-

isoglutaminyl- -lysine (43), muramyl- -alanyl- -isoglutami-

nyl-(2S,6R)-2,6-diaminopimelic acid (45), muramyl- -alanyl-

-isoglutaminyl-(2S,6R)-2,6-diaminopimelinyl- -alanine (47),

1,6-anhydromuramyl- -alanyl- -isoglutaminyl-(2S,6R)-2,6-di-

corresponding 1,6-anhydromuramic acid derivative 26 was aminopimelic acid (50a), and 1,6-anhydromuramyl- -alanyl-

isoglutaminyl-(2S,6S)-2,6-diaminiopimelic acid (50b).

L-alanyl-D-glutamic acid (39),

genation and protecting group manipulation, afforded the

2,6-diaminopimelic acid derivatives (S,R)-9 and (S,S)-9, both

with the desired orthogonal protecting group pattern. Syn-

thesis of the muramic acid derivative 15 and attachment of

L

D

L-alanyl-D-

L

D

L

D

an

L-alanine residue furnished muramyl-

L-alanine 18. The

L

D

L

D-

obtained similarly. Treatment of these compounds with pep-

tides 28−30 and with the 2,6-diaminopimelic acid containing

di- and tripeptides 32a, 32b, and 35 gave the protected mura-

( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany,

2002)

Introduction

Bacterial peptidoglycan is a giant macromolecule con-

sisting of linear heteroglycan chains cross-linked by short

peptide chains (Figure 1, A).^[1Ϫ3]The heteroglycan chains

are composed of alternating β(1Ϫ4)-linked N-acetylglucos-

amine (GlcNAc) and N-acetylmuramic acid (MurNAc) res-

idues. The carboxyl group of the MurNAc residue has a

peptide moiety attached to it. In nascent peptidoglycans

this is composed of -alanyl-γ--isoglutaminyl-(α)-(2S,6R)-

2,6-diaminopimelyl (or -lysyl)--alanyl--alanine (Fig-

ure 1, B); however, in mature peptidoglycans one or both

-alanine residues are lost. Neighboring peptidoglycan

chains are interlinked either by direct peptide linkages be-

tween a diamino acid and a -alanine residue or by an addi-

tional short peptide chain between the diamino acid and the

-alanine residue (see AA_nin Figure 1). The biosynthesis

of MurNAc^[4]and of the bacterial peptidoglycan has been

studied extensively,^[5Ϫ7]and the availability of the enzymes

has resulted in the chemoenzymatic synthesis of biosyn-

thetic intermediates α-linked through the anomeric center

of MurNAc to UDP.^[8Ϫ15]

Figure 1. Typical primary structure of bacterial peptidoglycan (A);

structure of the pentapeptide fragment (B); DAA ϭ diamino acid

[generally meso-diaminopimelic acid (as shown in B) or -lysine];

(AA)_nϭ n amino acids, with n ϭ 0Ϫ5

ever, the emergence of bacterial resistance to these antibi-

otics is a good reason to investigate the effects of partial

structures of peptidoglycans further.^[18,19]

Potent cell wall biosynthesis inhibitors have been success-

fully used for the treatment of bacterial infections for more

than fifty years.^[16,17]The antibacterial activity of β-lactams

and also of glycopeptide antibiotics (such as, for instance,

vancomycin) — the most widely used compounds — is due

to inhibition of key steps in cell wall biosynthesis.^[5Ϫ7]How-

Bacterial infections result in an immune response that

starts with the production of proinflammatory mediators

such as cytokines TNF-α and interleukins-1 and -6.^[20,21]

Activation of the immune system by Gram-negative bac-

teria is mainly caused by lipopolysaccharides (LPS) and

muramyl peptides, which seem to have a synergistic ef-

fect.^[22,23]In order to investigate this effect, pure muramyl

peptides with different lengths of peptide chain are re-

quired. These, however, are not readily available from nat-

ural material. Several chemical syntheses of muramyl pep-

[a]

Fachbereich Chemie, Universität Konstanz, Fach M 725,

78457 Konstanz, Germany

Fax: (internat.) ϩ49-7531/88-3135

E-mail: richard.schmidt@uni-konstanz.de

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 WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 1434Ϫ193X/02/0816Ϫ2710 $ 20.00ϩ.50/0 Eur. J. Org. Chem. 2002, 2710Ϫ2726

Synthesis of Muramyl Peptides Containing meso-Diaminopimelic Acid

FULL PAPER

tides and of peptidoglycan di-, tetra-, and octasaccharide the -glutamate-derived part of the molecule had occurred

fragments containing amino acids up to the dipeptide moi- during the various manipulations.

ety have been reported.^[24Ϫ37]The particular target com-

pounds in this paper are muramyl tri- and tetrapeptides

containing, for the first time, meso-2,6-diaminopimelic acid

(Dap^[38]) as a cross-linker in the peptidoglycan network.

The synthesis of the corresponding 1,6-anhydromuramyl

derivatives^[39]— products of lytic transglycosidase in the

process of cell growth — is also reported.^[40]These com-

pounds also exhibit somnogenic properties.^[41]

Results and Discussion

In the muramyl pentapeptide, meso-2,6-diaminopimelic

acid (Dap) is interlinked through the S-configured moiety,

while the amino group of the R-configured moiety serves

as the linker to another muramyl peptide chain. Therefore,

an orthogonally protected (2S,6R)-2,6-diaminopimelic acid

that has lost its meso stereochemistry is required. For this

purpose, a method reported in a preliminary form by Hol-

comb et al.^[42]was essentially followed (Scheme 1). This

method requires the catalytic hydrogenation of a C₇-acryl-

ate intermediate obtained from -glutamate and a C₂-build-

ing block. To this end, Z-protected N-benzyloxycarbonyl--

glutamate (1) was transformed into the oxazolidinone 2,

which furnished aldehyde 3 after reduction of the carb-

oxylate group and periodinane^[43]oxidation of the alcohol

intermediate. This compound could also be obtained in the

same overall yield by transformation of 2 into the acid

chloride 4 with thionyl chloride and subsequent reduction

with LiAl(OtBu)₃H.^[44]A WittigϪHorner reaction with the

Scheme 1. Synthesis of diaminopimelic acid derivatives (S,R)-9 and

phosphoryl glycine derivative 5^[45]in the presence of potas-

(S,S)-9; a) (CH₂O)_n, toluene, ∆ (86%); b) BH₃·SMe₂, 0 °C Ǟ room

temp.; periodinane, room temp. (53%); c) SOCl₂, ∆ (76%); d) LiAl(-

sium hexamethyldisilazane (KHMDS) as base afforded a

OtBu)₃H, THF, Ϫ78 °C (73%); e) KHMDS, THF, Ϫ78 °C Ǟ Ϫ30

6.3:1 mixture of (Z)- and (E)-6. Asymmetric hydrogenation °C [88%, (Z)-6:(E)-6 ϭ 6.3:1]; f) Me₃Si-CH₂-CH₂OH, LiHMDS,

THF, 0 °C (65%); g) [RhCl(PPh₃)₃], H₂, MeOH [90%, (S,R)-

of (Z)-6 with a rhodium catalyst and (S,S)-chiraphos pro-

8:(S,S)-8 ϭ 3:2]; h) Pd(OH)₂/C, H₂, MeOH; Z-Cl, NaHCO₃, THF/

vided only a 3:1 mixture of (S,R)- and (S,S)-8.^[42]Therefore,

H₂O [70%, (S,R)-9:(S,S)-9 ϭ 1:1]; i) TMSE-OH, LiHMDS, THF,

0 °C [70%, (S,R)-9:(S,S)-9 ϭ 3:2]; j) 5  HCl, 100 °C, 1 h; cam-

a simple catalytic hydrogenation with Wilkinson’s catalyst

was performed, affording a 3:2 mixture of (S,R)- and (S,S)-

8 in 90% yield. Treatment of this mixture with trimethylsily-

lethanol in the presence of LiHMDS as base afforded the

phanoyl chloride, NaHCO₃, THF/H₂O; CH₂N₂, Et₂O (65%)

For the synthesis of the required muramic acid derivative

desired target molecules (S,R)- and (S,S)-9, which could 18 (Scheme 2), -glucosamine was transformed into the

readily be separated by medium-pressure liquid chromato- known 2-azido derivative 11.^[26,47]Regioselective 4,6-O-iso-

graphy (MPLC) with toluene/ethyl acetate (5:1) as eluent. propylidenation with acetone dimethyl ketal in the presence

Alternatively, treatment of, for instance, (Z)-6 with trime- of p-toluenesulfonic acid (p-TsOH) as catalyst afforded the

thylsilylethanol [Ǟ (Z)-7] and subsequent hydrogenation as 3-O-unprotected 2-azidoglucose 12. For the attachment of

described above furnished a 1:1 mixture of (S,R)- and (S,S)- the lactic acid residue, by our previously reported proced-

9, although less of the desired (S,R)-9 was obtained by this ure,^[27]the triflate of methyl -lactate 13^[48Ϫ50]was em-

route. The relative stereochemistries of (S,R)-9 and (S,S)-9 ployed. In the presence of sodium hydride as base, this fur-

could readily be confirmed by acid-catalyzed removal of the nished the muramic acid derivative 14 exclusively, with the

TMSE, N-Boc, and N-Z protecting groups, followed by desired stereochemistry. Compound 14 is a highly versatile

camphanoylation of the amino groups and methyl ester intermediate for carbohydrate chain extension because it

formation: the methyl esters of (S,R)-10 are diastereotopic, can readily be transformed into a glycosyl donor and a gly-

while those of (S,S)-10 are homotopic, and this could be cosyl acceptor;^[27,29Ϫ31]however, it is also available for pep-

confirmed by the observation of two separate ¹H NMR sig- tide attachment. Since initial azido group reduction of 14

1

nals for (S,R)-10 and only one H NMR signal for (S,S)- furnishes the undesired six-membered lactam,^[46]the -alan-

10.^[46]These results also indicated that no racemization of ine residue was attached next. To this end, the methyl ester

Eur. J. Org. Chem. 2002, 2710Ϫ2726

2711

N. Kubasch, R. R. Schmidt

FULL PAPER

of 14 was cleaved with lithium hydroxide in aqueous diox- inger procedure^[57]afforded the trans-linked lactam 25^[57]in

ane/methanol,^[30]thus avoiding diastereoisomerization dur- spite of the expected ring strain in the product.

ing the generation of 15. Subsequent treatment with -alan-

ine methyl ester in the presence of EEDQ/NEt₃as condens-

ing agent furnished the muramyl alanine derivative 16 in

high yield. Azido group reduction with hydrogen sulfide in

aqueous pyridine, N-acetylation with acetic anhydride/pyr-

idine (Ǟ 17), and methyl ester cleavage as described above

provided the useful intermediate 18. Because of the in-

creased ring size, lactam formation was not observed in the

transformation of 16 into 17.

Scheme 3. Synthesis of 1,6-anhydroneuramic acid derivatives 26

and 27; a) ref. 28; b) (Bu₃Sn)₂O, MeCN, ∆; I₂, room temp. (89%);

c) TMGA, DMF, H₂O, ∆, 3 days (79% ϩ 15% manno isomer); d)

NaH, CH₂Cl₂(85Ϫ88%); e) H₂S, pyr/H₂O; Ac₂O, pyr (92%); f) Pd/

C, H₂; Ac₂O; MeOH (90%); g) PPh₃, THF/H₂O; Ac₂O, pyr (75%);

h) LiOH, dioxane/MeOH (quant.)

In order to arrive at the target molecules, additional am-

ino acid and di- and tripeptide derivatives were required,

standard protecting group patterns and condensing agents

being employed for their synthesis. Thus, the synthesis of

the -isoglutamine derivative 28 (Scheme 4) followed the

synthesis of the corresponding  isomer.^[58Ϫ60]The Z-pro-

Scheme 2. Synthesis of muramic acid derivative 18; a) refs. 26,27;

tected -alanyl--glutamate derivative 29 was obtained

b) (MeO)₂CMe₂, p-TsOH (quant.); c) NaH, CH₂Cl₂(70Ϫ95%); d)

from Z-protected -alanine and dimethyl -glutamate with

LiOH, dioxane/MeOH (quant.); e) -Ala-OMe·HCl, EEDQ NEt₃,

EEDQ as condensing agent. Similarly, Z-protected methyl

-glutamate and N^ε-Boc-protected methyl -lysine fur-

nished dipeptide 30.

CH₂Cl₂(85%); f) H₂S, Pyr/H₂O; Ac₂O, pyr (89%); g) LiOH, diox-

ane/MeOH (quant.)

For the required 1,6-anhydro analogue of 15 (the known

compound 26^[39]), -glucal was transformed into the 4-O-

benzyl derivative 19 by a literature procedure (Scheme 3).^[28]

Treatment of 19 with bis(tributyltin) oxide and then with

iodine^[51,52]afforded the 1,6-anhydro-2-deoxy-2-iodoglucose

derivative 20^[53]in high yield. Treatment of 20 with tetra-

methylguanidinium azide (TMGA) in DMF as solvent af-

forded, after heating for three days, mainly the desired 2-

azido-2-deoxy--gluco isomer 21,^[54Ϫ56]this reaction taking

place either through formation of a manno-configured ep-

oxide intermediate and regioselective ring-opening by the

azide ion, or by double inversion at C-2 by traces of iod-

ide,^[52]thus furnishing a more reactive intermediate for the

nucleophilic substitution with the azide ion. Transformation

Scheme 4. Building blocks 28Ϫ30

Compounds (S,R)-9 and (S,S)-9 were employed as pre-

of 21 into 22؊24, 26, and 27 followed literature proced- cursors for the synthesis of 2,6-diaminiopimelic acid con-

ures.^[39]Surprisingly, azide reduction of 22 by the Staud- taining peptides (Scheme 5). After hydrogenolytic removal

2712

Eur. J. Org. Chem. 2002, 2710Ϫ2726

Synthesis of Muramyl Peptides Containing meso-Diaminopimelic Acid

FULL PAPER

of the Z-protecting groups of (S,R)-9 and (S,S)-9, treatment

with Z-protected methyl -glutamate in the presence of

PyBOP/NMM as condensing agent afforded the dipeptide

derivatives 31a and 31b in high yields. Again, hydro-

genolysis of the Z group and subsequent treatment with Z-

protected -alanine and PyBOP/NMM as condensing agent

furnished tripeptides 32a and 32b, respectively.

Scheme 6. Synthesis of peptide 35; a) TBAF, THF, room temp., IR

120, H^ϩ; b) -Ala(OMe), PyBOP, NMM, CH₂Cl₂(92%); c) Pd/C,

H₂, MeOH; Z--Glu-OMe, PyBOP, NMM, CH₂Cl₂(86%)

Scheme 7. Synthesis of muramic acid derivative 37; a) 29, Pd/C,

H₂, MeOH; EEDQ, NEt₃(65%); b) -Glu(OMe)₂, PyBOP, NMM,

CH₂Cl₂; c) H₂S, Pyr, H₂O; Ac₂O, Pyr (85%)

Scheme 5. Synthesis of peptides 32a and 32b; a) Pd/C, H₂, MeOH;

Z--Glu-OMe, PyBOP, NMM, CH₂Cl₂; b) Pd/C, H₂, MeOH; Z--

Ala, PyBOP, NMM, CH₂Cl₂

Complete deprotection of the muramyl peptide derivat-

Selective removal of the TMSE group in (S,R)-9 with ives and purification of the desired unprotected target mole-

TBAF (Ǟ 33) followed by condensation with -alanine cules was an important issue. To this end, the methyl ester

methyl ester afforded the protected dipeptide 34 (Scheme 6). moiety in 17 was first cleaved with lithium hydroxide in

Hydrogenolysis of the Z group liberated the amino group aqueous dioxane/methanol, with subsequent acid-catalyzed

of the S-configured part, which afforded tripeptide 35 on removal of the O-isopropylidene and 1-O-TDS groups pro-

condensation with Z-protected methyl glutamate.

viding the desired product 38, which was purified by gel

With these amino acid and peptide compounds in hand, permeation chromatography (GPC with P₂Biogel) and then

ligation with the muramyl residues could be carried out. isolated by lyophilization (Scheme 8). When the same pro-

Thus, hydrogenolysis of the Z group in 29 and subsequent cedure was applied to the protected muramyl peptide 37,

treatment with muramic acid derivative 15, with EEDQ/ the unprotected muramyl dipeptide 39 was obtained as the

NEt₃as condensing agent, afforded the muramyl dipeptide diammonium salt. Compound 39 has physical data in ac-

derivative 36 in good yield (Scheme 7). Treatment of 36 with cordance with material obtained by other procedures.^[25,61]

H₂S in aqueous pyridine and then with acetic anhydride

For the desired muramyl di-, tri-, and tetrapeptides, par-

in pyridine resulted in a smooth transformation into the ticularly those containing the Dpa residue, the precursor

acetylamino derivative 37. The same compound could be was the muramyl -alanine derivative 18 (Scheme 9). Thus,

obtained directly and more efficiently from muramyl--al- treatment of 18 with -isoglutamine derivative 28, -isoglu-

anine derivative 18 and dimethyl -glutamate in the pres- taminyl--lysine derivative 30, and with Dpa-containing di-

ence of PyBOP/NMM as condensing agent.

and tripeptides 31a and 35, respectively, with PyBOP/

Eur. J. Org. Chem. 2002, 2710Ϫ2726

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N. Kubasch, R. R. Schmidt

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For the completion of the synthesis of the desired 1,6-

anhydromuramyl tripeptides 50a and 50b (Scheme 10), sim-

ilar procedures were applied. Hydrogenolytic removal of the

Z groups in 32a and 32b and subsequent condensation with

the 1,6-anhydromuramic acid derivative 26 in the presence

of PyBOP/NMM as condensing agent afforded compounds

48a and 48b, respectively. Hydrogenation of the azido group

and N-acetylation of the generated amino group then af-

forded acetylamino derivatives 49a and 49b. Because the re-

ducing end of the sugar moiety was blocked, the sequence

of the deprotection steps was not as critical as for the previ-

ous compounds. The acid-sensitive protecting groups were

hence removed first, and the methyl esters were then cleaved

with lithium hydroxide in aqueous methanol. For purifica-

tion, 50a was first subjected to ion-exchange chromato-

graphy on RP-18; lyophilization then afforded pure 50a.

For 50b a second ion-exchange chromatography procedure

was carried out, thus providing pure material. All com-

pounds had ¹H and ¹³C NMR spectroscopic data and mass

spectra data in accordance with their assigned structures.

Scheme 8. Synthesis of muramic acid derivatives 38 and 39; a)

LiOH, dioxane/MeOH/H₂O, room temp., pH 9.5Ϫ10.5; TFA/H₂O/

dioxane, 0 °C Ǟ room temp.; GPC (P₂-Biogel, NH₄HCO₃) lyophil-

ization

NMM as condensing agent, afforded the protected mura-

myl peptides 40, 42, 44, and 46 in high yields. Deprotection

and purification of these compounds were important tasks.

The muramyl dipeptide derivative 40 could be deprotected

readily as it contained only acid-sensitive protecting groups.

Hence, treatment of 40 with TFA in aqueous dioxane, with

subsequent GPC and HPLC purification and lyophiliz-

ation, furnished pure muramyl dipeptide (MDP) 41 as an

ammonium salt that could be fully characterized from its

NMR spectroscopic data (in [D₆]DMSO/TFA); these were

Conclusion

Various 2,6-diaminiopimelic acid containing (Dpa-con-

in good agreement with those reported for the free acid of taining) muramyl- and 1,6-anhydromuramyl di-, tri-, and

MDP.^[25,61Ϫ66]The methyl ester group containing com- tetrapeptides were synthesized in good yields. The immuno-

pounds 42, 44, and 46 first required ester cleavage; removal stimulatory properties of these compounds and their com-

of the acid-sensitive protecting groups was then carried out parison with those of the famous muramyl dipeptide will

to afford the target molecules 43, 45, and 47, respectively, be reported in due course.

after purification.

Scheme 9. Synthesis of muramyl peptides 41, 43, 45, and 47; a) Pd/C, H₂, MeOH; 28, 30, 31a, or 35, Py BOP, NMM, CH₂Cl₂; b) TFA/

H₂O/dioxane, 0 °C Ǟ room temp.; GPC (B-2 Biogel, NH₄HCO₃); HPLC (H₂O, MeCN, TFA); lyophilization (68%); c) LiOH, dioxane/

H₂O/MeOH, pH ഠ 10, room temp.; TFA/H₂O/dioxane, 0 °C Ǟ room temp.; GPC (P-2 Biogel NH₄HCO₃); HPLC (H₂O, MeCN, TFA);

lyophilization (64%); d) LiOH, dioxane/H₂O/MeOH, pH ഠ 10, room temp.; TFA/H₂O/dioxane, 0 °C Ǟ room temp.; GPC (P-2 Biogel,

NH₄HCO₃); lyophilization

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Synthesis of Muramyl Peptides Containing meso-Diaminopimelic Acid

FULL PAPER

2.5 cm, flow rate: 10 mL/min; 40 ϫ 4.5 cm, flow rate: 20 mL/min,

detection by Knauer differential refractometer). Analytical HPLC

was performed on a Knauer Eurospher-100 column (5 µm Si, 250

ϫ 4.0 mm ID) on a Merck/Hitachi system (L-6200 pump, D-6000

HPLC manager; detection with an ACS Ltd. 950:14 mass detector,

air flow: 9.0 l/min, air temperature: 110 °C, time const: 0 sec). Pre-

parative HPLC was performed with a sampler (CSI) and gradient

controller (CIM) from Autochrom, a Shimadzu pump (LC-8A), a

Knauer UV detector, and a Knauer Eurospher-100 C18 column (7

µm, 250 ϫ 16 mm). Gel permeation chromatography was per-

formed on a Pharmacia XK16 column (50 ϫ 1.6 cm) filled with

Biorad P2 Biogel (eluent: 30 m aqueous NH₄HCO₃, flow rate:

1 mL/min, detection with a Knauer differential refractometer).

Melting points are uncorrected. Optical rotations were determined

with a Büchi Polar-Monitor (1 dm cell, temperature 20 °C, λ ϭ

589 nm). Unless specified otherwise, ¹H NMR and ¹³C NMR spec-

tra were recorded at room temperature on either Bruker AC 250

Cryospec or Bruker DRX 600 machines. Chemical shifts are given

in δ relative to tetramethylsilane as an internal standard, the coup-

ling constants J are given in Hz. Assignment of peaks was based

upon DQF-Cosy, HMQC, HMBC, and ROESY experiments.

MALDI-TOF mass spectra were recorded on a Kratos Analytical

Kompact MALDI 1 spectrometer with a DHB matrix. FAB mass

spectra were recorded on a modified Finnigan MAT 312/AMD

5000. EI mass spectra were recorded on a Finnigan MAT 312 spec-

trometer.

General Procedure for Z-Cleavage (Procedure A): Pearlman’s cata-

lyst^[67](10%) or Pd/C (10%) was added to a vigorously stirred solu-

tion (0.02Ϫ0.03 ) of the Z-protected peptide in MeOH, main-

tained under a hydrogen atmosphere. Cleavage of the Z group was

normally accomplished within 30 min (as judged by TLC), after

which the suspension was filtered through celite, washed twice with

MeOH, and concentrated. The residue was coevaporated several

times with dry toluene, dried in vacuo for 2 h, and employed in

subsequent peptide couplings without further purification.

Scheme 10. Synthesis of 1,6-anhydromuramylpeptides 50a and 50b;

a) Pd/C, H₂, MeOH; Py BOP, NMM, DMF; b) Pd/C, H₂, MeOH;

Ac₂O; c) TFA, CH₂Cl₂, room temp.; LiOH, H₂O/MeOH, pH ഠ

10, room temp.; Dowex 50 W; RP-18 (MeCN/H₂O); lyophilization

(86%); d) TFA, CH₂Cl₂, room temp.; LiOH, H₂O/MeOH, pH ഠ

10, room temp.; Dowex 50 W; RP-18 (MeCN/H₂O); Dowex 50 W;

lyophilization (77%)

General Procedure for Peptide Couplings in CH₂Cl₂(Procedure B):

The free carboxylic acids and free amines were dried thoroughly as

described in Procedure A, provided that they were not crystalline

or lyophilized. The free acid (1Ϫ1.2 equiv.), free amine (1Ϫ1.2

equiv.), and PyBOP^[68](1.1Ϫ1.3 equiv.) were dissolved in freshly

distilled, dry CH₂Cl₂to give solutions of approximately 0.2  con-

centration (ഠ 0.07  per component). The pH was adjusted to ഠ

9Ϫ9.5 with N-methylmorpholine (NMM) and maintained in this

range during the reaction. The reaction mixture was stirred under

nitrogen at room temperature for 1Ϫ2 h. After completion of the

reaction, the solution was diluted with CH₂Cl₂and extracted sev-

eral times with small portions of saturated NH₄Cl solution. The

combined organic layers were dried over MgSO₄, filtered, and con-

centrated in vacuo. The crude products were purified by flash chro-

matography on silica gel.

Experimental Section

General Methods: Unless specified otherwise, all reactions requiring

anhydrous conditions were performed in flame-dried glassware un-

der an atmosphere of anhydrous nitrogen with starting reagents

that had been dried in vacuo before use. The appropriate solvents

were freshly distilled from sodium/benzophenone (THF) or calcium

hydride (CH₂Cl₂) immediately prior to use. Other chemicals and

reagents were either purchased puriss. p.A. from commercial sup-

pliers or purified by standard techniques. For analytical thin layer

chromatography (TLC), plastic silica gel plates (Merck 60 F254)

were used, and compounds were viewed by irradiation with UV

light and/or by immersion in solutions of ammonium molybdate

(20 g) and Ce(SO₄)₂(400 mg) in 10% H₂SO₄(400 mL) or a 15%

H₂SO₄solution or a 1% ninhydrin solution in EtOH, each followed

by heating. Preparative flash chromatography was performed at a

pressure of 1.3Ϫ1.4 bar on J. T. Baker 60 silica gel

(0.040Ϫ0.063 mm, 230Ϫ400 mesh). Medium-pressure liquid chro-

matography was performed at a pressure of 5Ϫ12 bar on Merck

General Procedure for Peptide Couplings in DMF (Procedure C):

The reaction was performed according to Procedure B, except for

the use of dry DMF (Fluka) instead of CH₂Cl₂. When the reaction

was complete (as judged by TLC), the residue was coevaporated

several times with toluene in order to remove traces of DMF and

then worked up as described above.

General Procedure for Alkaline Ester Saponification (Procedure D):

A solution of the starting ester (0.03Ϫ0.06 ) in a mixture of diox-

ane/MeOH (1:1 v/v) was adjusted exactly to pH 10.0 (pH meter)

by addition of an aqueous LiOH solution (1 ⁾ at room temper-

LiChroprep Si 60 silica gel (0.015Ϫ0.025 mm, column size: 28 ϫ ature. In the event of the solution becoming cloudy, additional

Eur. J. Org. Chem. 2002, 2710Ϫ2726 2715

N. Kubasch, R. R. Schmidt

FULL PAPER

MeOH was added until the solution became clear. The pH should

not drop below 9.5, nor exceed 10.0. Thus, during the reaction,

decreasing pH values were compensated for by addition of base.

Completion of the reaction (as judged by TLC or NMR spectro-

scopy) was generally accomplished within 2Ϫ3 h. The alkaline so-

lution was neutralized with acidic ion exchange resin (Amberlite

IR 120 H^ϩ) and filtered, and the solvents were evaporated to dry-

ness in vacuo.

chromatography (SiO₂, petroleum ether/EtOAc ϭ 4:1) afforded

(Z)-6 (8.58 g, 19.1 mmol, 76%) and (E)-6 (1.32 g, 2.9 mmol, 12%)

in a 6.5:1 ratio as colorless, syrupy compounds.

(Z)-6: TLC (SiO₂): R_fϭ 0.75 (petroleum ether/EtOAc ϭ 1:1).

[α]_Dϭ ϩ63.9 (c ϭ 1, MeOH). ¹H NMR (600 MHz, CDCl₃, 320 K):

δ ϭ 1.39 [s, 9 H, C(CH₃)₃], 2.01, 2.13 (2m, 2 H, 5-CH₂), 2.22Ϫ2.28

3

(m, 2 H, 4-CH₂), 3.70 (s, 3 H, OCH₃), 4.26 [t, J ϭ 4.8 Hz, 1 H,

NCHRC(O)], 5.09Ϫ5.16 (m, 3 H, CH₂Ph, NCHHOC(O)], 5.44 [br.

s, 1 H, NCHHOC(O)], 6.1 (br. s, 1 H, Boc-NH), 6.36 (m, 1 H, 3-

H), 7.28Ϫ7.32 (m, 5 H, Ph) ppm. ¹³C NMR (150.8 MHz, CDCl₃):

δ ϭ 23.7,(1C, 4-C), 28.2 [3C, C(CH₃)₃], 29.2 (1C, 5-C), 52.3 (1C,

OCH₃), 54.5 [1C, NCHRC(O)], 68.1 (1C, CH₂Ph), 77.9 [1C,

NCH₂OC(O)], 80.7 [1C, C(CH₃)₃], 128.3, 128.6, 128.7 (5C, Ph),

132.9 (1C, 3-C), 135.4 (1C, Ph), 152.9, 153.1 [2C, 2 OC(O)N], 165.0

(1C, CO₂CH₃), 172.0 [1C, NCH₂OC(O)] ppm. EI MS (160 °C): m/

z ϭ 448 [M]^ϩ; calcd. 448.5 for C₂₂H₂₈N₂O₈.

(E)-6: TLC (SiO₂): R_fϭ 0.83 (petroleum ether/EtOAc ϭ 1:1).

[α]_Dϭ ϩ52.9 (c ϭ 1, MeOH). ¹H NMR (600 MHz, CDCl₃, 320 K):

δ ϭ 1.39 [s, 9 H, C(CH₃)₃], 1.99, 2.11 (2m, 2 H, 5-CH₂), 2.52Ϫ2.56

(m, 2 H, 4-CH₂), 3.71 (s, 3 H, OCH₃), 4.28 (m, 1 H, NCHRC(O)],

5.11Ϫ5.15 (m, 3 H, CH₂Ph, NCHHOC(O)], 5.44 (br. s, 1 H,

NCHHOC(O)], 6.50 (br. s, 1 H, Boc-NH), 6.62 (br. s, 1 H, 3-H),

7.27Ϫ7.31 (m, 5 H, Ph) ppm. ¹³C NMR (150.8 MHz, CDCl₃): δ ϭ

23.3, (1C, 4-C), 28.3 (3C, C(CH₃)₃], 30.6 (1C, 5-C), 52.2 (1C,

OCH₃), 54.6 (1C, NCHRC(O)], 68.0 (1C, CH₂Ph), 77.9 (1C,

NCH₂OC(O)], 80.5 (1C, C(CH₃)₃], 126.2 (1C, 3-C), 128.3, 128.6,

128.7, 135.5 (6C, Ph), 153.0 (2C, 2 OC(O)N), 164.4 (1C, CO₂CH₃),

171.9 (1C, NCH₂OC(O)] ppm. MALDI MS (positive mode, DHB,

THF): m/z ϭ 471 [M ϩ Na]^ϩ; calcd. 448.5 for C₂₂H₂₈N₂O₈.

General Procedure for the Hydrolysis of Acid-labile Protecting

Groups (Procedure E): An ice-cooled mixture of TFA/dioxane/H₂O

(4:3:3 v/v/v) was added slowly to a stirred solution of the starting

material (0.003Ϫ0.015 ), and the mixture was allowed to warm

to room temperature. The reaction mixture was stirred for 2 h and

then concentrated under vacuum at low temperature (Յ 25 °C) to

a final volume of 1Ϫ1.5 mL. The residue was coevaporated several

times with H₂O and toluene to remove all traces of acid, evaporated

to dryness, dissolved in H₂O, and lyophilized. The crude products

were purified by suitable chromatographic methods.

(S)-3-(3-Benzyloxycarbonyl-5-oxo-1,3-oxazolidin-4-yl)propion-

aldehyde (3). (a) From 2: Under anhydrous conditions, a borane/

dimethyl sulfide complex in THF (2 , 50 mL, 100 mmol, Fluka)

was added slowly at 0 °C over 15Ϫ20 min to a solution of com-

pound 2 (21.63 g, 73.8 mmol) in THF (150 mL). The resulting mix-

ture was stirred at 0 °C for 15 min and then allowed to warm to

room temperature and stirred until no starting material was detect-

able by TLC. The solvent was then evaporated in vacuo (30 °C).

The residue was dissolved in dry CH₂Cl₂(500 mL) and the flask

was put in a water bath (20 °C). DessϪMartin periodinane^[43](49 g,

117 mmol) was added in small portions to keep the temperature

between 20Ϫ40 °C. After complete oxidation of the alcohol (TLC,

SiO₂, R_fϭ 0.32, toluene/acetone ϭ 2:1), the reaction mixture was

diluted with Et₂O (500 mL), treated with 25% NaS₂O₃solution

(250 mL) and 5% NaHCO₃(50 mL), and stirred at 0 °C for 1 h.

The mixture was allowed to warm to room temperature, and the

organic layer was separated and washed twice with H₂O (200 mL)

and saturated NaCl solution (200 mL). The combined organic

layers were dried over MgSO₄, filtered, and concentrated in vacuo.

The residue was purified by flash chromatography [dry (!) silica

gel, petroleum ether/EtOAc ϭ 3:1] to afford the aldehyde 3 (10.8 g,

39.0 mmol, 53%) as a yellow syrup. TLC (SiO₂): R_fϭ 0.61 (toluene/

acetone ϭ 2:1).

1-Methyl 7-[2-(Trimethylsilyl)ethyl] (Z,S)-6-[(Benzyloxycarbonyl)-

amino]-2-[(tert-butyloxycarbonyl)amino]-2-heptenedioate

[(Z)-7]:

Under anhydrous conditions, 610 µL (122 µmol) of a freshly pre-

pared 0.2  solution of LiHMDS (167 mg, 1 mmol, Aldrich, in

5 mL THF) was added dropwise by syringe at 0 °C to oxazolidine

(Z)-6 (210 mg, 0.48 mmol) and 2-(trimethylsilyl)ethanol (85 mg,

0.7 mmol) in THF (10 mL). When the reaction was complete (after

15Ϫ30 min as judged by TLC), the pH was adjusted to ഠ 9 by

addition of saturated NH₄Cl. The organic layer was extracted with

Et₂O (3 ϫ 20 mL), dried (MgSO₄), and concentrated in vacuo.

Purification of the residue by flash chromatography (SiO₂, petro-

leum ether/EtOAc ϭ 4:1) afforded (Z)-7 (167 mg, 0.31 mmol, 65%)

as a light yellow oil. TLC (SiO₂): R_fϭ 0.84 (petroleum ether/

1

EtOAc ϭ 1:1). [α]_Dϭ Ϫ2.4 (c ϭ 1, MeOH). H NMR (600 MHz,

(b) From 4: Aldehyde 3 was prepared according to the procedure

reported by Gelb et al.^[44]The spectroscopic data were identical to

those reported.^[44]

[D₆]DMSO, 298 K): δ ϭ 0.01 [s, 9 H, Si(CH₃)₃], 0.92 [t, ³J ϭ

8.5 Hz,

2 H, OCH₂CH₂Si(CH₃)₃], 1.36 [s, 9 H, C(CH₃)₃],

1.65Ϫ1.69, 1.76Ϫ1.79 (2m, 2 H, 5-CH₂), 2.14Ϫ2.16 (m, 2 H, 4-

3

Methyl (Z,S)-5-(3-Benzyloxycarbonyl-5-oxo-1,3-oxazolidin-4-yl)-2-

[(tert-butyloxycarbonyl)amino]-2-pentenoate [(Z)-6] and Methyl

(E,S)-5-(3-Benzyloxycarbonyl-5-oxo-1,3-oxazolidin-4-yl)-2-[(tert-

butyloxycarbonyl)amino]-2-pentenoate [(E)-6]: Solid KHMDS

(5.0 g, 25 mmol, Aldrich) was placed in a heat-dried flask under a

nitrogen atmosphere. The flask was cooled to Ϫ78 °C and dry THF

(150 mL) was then used to dissolve the base. A solution of 5^[45]

(8.3 g, 28 mmol) in dry THF (150 mL) was added dropwise. The

resulting yellow mixture was warmed to Ϫ55 °C, stirred for 15 min,

then cooled again to Ϫ78 °C. Aldehyde 3 (7.0 g, 25 mmol) in dry

THF (100 mL) was added dropwise to give an orange colored solu-

tion. After complete addition, the reaction mixture was brought to

Ϫ30 °C. At this point the reaction was quenched with saturated

CH₂), 3.64 (s, 3 H, OCH₃), 3.95Ϫ3.98 (m, 1 H, 6-H), 4.11 [t, J ϭ

8.5 Hz, 2 H, OCH₂CH₂Si(CH₃)₃], 4.99Ϫ5.05 (m, 2 H, CH₂Ph), 6.2

(br. s, 1 H, 3-H), 7.31Ϫ7.37 (m, 5 H, Ph), 7.69 (d, ³J_α,NHϭ 7.6 Hz,

1

1 H, Z-NH), 8.3 (br. s, 1 H, Boc-NH) ppm. H NMR (600 MHz,

374 K): δ ϭ 0.03 [s, 9 H, Si(CH₃)₃], 0.94 [t, ³J ϭ 8.1 Hz, 2 H,

OCH₂CH₂Si(CH₃)₃], 1.39 [s, 9 H, C(CH₃)₃], 1.74Ϫ1.76, 1.82Ϫ1.84

(2m, 2 H, 5-CH₂), 2.19Ϫ2.22 (m, 2 H, 4-CH₂), 3.66 (s, 3 H, OCH₃),

4.02 (m, 1 H, 6-H), 4.14 [t, ³J ϭ 8.1 Hz, 2 H, OCH₂CH₂Si(CH₃)₃],

3

5.04 (s, 2 H, CH₂Ph), 6.24 (t, J_γ,δϭ 7.3 Hz, 1 H, 3-H), 7.30Ϫ7.35

(m, 6 H, Ph, NH), 7.88 (s, 1 H, NH) ppm. C₂₆H₄₀N₂O₈Si (536.7):

calcd. C 58.19, H 7.51, N 5.22; found C 58.11, H 7.11, N 5.12.

Methyl

(2R,4ЈS)-5-(3-Benzyloxycarbonyl-5-oxo-1,3-oxazolidin-4-

[(S,R)-8] and

°C, the reaction mixture was extracted with Et₂O (4 ϫ 170 mL), Methyl (2S,4ЈS)-5-(3-Benzyloxycarbonyl-5-oxo-1,3-oxazolidin-4-yl)-

NH₄Cl solution (ഠ 200 mL), resulting in a pH of ഠ 9. At 5Ϫ10 yl)-2-[(tert-butyloxycarbonyl)amino]-pentanoate

and the combined organic layers were dried over MgSO₄, filtered,

and concentrated in vacuo. Purification of the residue by flash

2-[(tert-butyloxycarbonyl)amino]-pentanoate [(S,S)-8]: Wilkinson’s

catalyst (2.0 g, 2 mmol) was added to a solution of the diastereo-

2716

Eur. J. Org. Chem. 2002, 2710Ϫ2726

Synthesis of Muramyl Peptides Containing meso-Diaminopimelic Acid

FULL PAPER

3

meric mixture of (Z)-6 and (E)-6 (7.5 g, 16.8 mmol) in oxygen-free [s, 9 H, Si(CH₃)₃], 0.91 [t, J ϭ 8.3 Hz, 2 H, OCH₂CH₂Si(CH₃)₃],

MeOH (300 mL). The reaction mixture was hydrogenated under 1.32 (m, 2 H, 4-CH₂), 1.36 [s, 9 H, C(CH₃)₃], 1.53Ϫ1.56, 1.59Ϫ1.64

normal pressure, during which time the initially dark red solution (2m, 4 H, 3-CH₂, 5-CH₂), 3.59 (s, 3 H, OCH₃), 3.90Ϫ3.94 (m, 2

3

changed to a light orange color. The reaction was monitored by

NMR spectroscopy, and when it was complete (24Ϫ72 h) the solu-

tion was filtered through Celite, washed twice with MeOH, and

concentrated in vacuo. The residue was purified by flash chromato-

graphy (SiO₂, petroleum ether/EtOAc ϭ 3:1) to give an inseparable

mixture of the R and S isomers (S,R)-8 and (S,S)-8 as a dark brown

syrup (6.8 g, 15.1 mmol, 90%) in a ratio of 3:2, favoring the R iso-

mer as determined by NMR spectroscopy. TLC (SiO₂): R_fϭ 0.83

(petroleum ether/EtOAc ϭ 1:1). ¹H NMR (250 MHz, CDCl₃): δ ϭ

H, 2-H, 6-H), 4.11 [t, J ϭ 8.3 Hz, 2 H, OCH₂CH₂Si(CH₃)₃], 5.02

(m, 2 H, CH₂Ph), 7.18 (d, J_6,NHϭ 7.6 Hz, 1 H, Boc-NH),

3

7.30Ϫ7.35 (m, 5 H, Ph), 7.64 (d, ³J_2,NHϭ 7.6 Hz, 1 H, Z-NH) ppm.

¹³C NMR (150.8 MHz, [D₆]DMSO): δ ϭ Ϫ1.5 [3C, Si(CH₃)₃], 16.8

[1C, OCH₂CH₂Si(CH₃)₃], 21.9 (1C, 4-C), 28.1 [3C, CCH₃)₃], 30.2

(2C, 3-C, 5-C), 51.6 (1C, OCH₃), 53.2, 53.8 (2C, 2-C, 6-C), 62.5

[1C, OCH₂CH₂Si(CH₃)₃], 65.4 (1C, CH₂Ph), 78.1 [1C, C(CH₃)₃],

127.7, 127.8, 128.3, 136.9 (6C, Ph), 155.5, 156.0 [2C, 2 OC(O)NH],

172.2, 172.9 [2C, CO₂CH₃, CO₂(CH₂)₂Si(CH₃)₃] ppm.

1.30Ϫ2.10 (m, 6 H, 3-CH₂, 4-CH₂, 5-CH₂), 1.41 [s, 9 H, C(CH₃)₃], C₂₆H₄₂N₂O₈Si (538.7): calcd. C 57.97, H 7.86, N 5.20; found C

3.69, 3.70 (2s, 3 H, OCH₃), 4.25Ϫ4.29 [m, 2 H, 2-H, NCHRC(O)], 57.88, H 7.76, N 5.03.

4.95Ϫ5.20 [m, 3 H, CH₂Ph, NCHHOC(O), Boc-NH], 5.50 [br. s, 1 (S,S)-9: TLC (HPTLC): R_fϭ 0.51 (toluene/EtOAc ϭ 3:1). [α]_D

H, NCHHOC(O)], 7.35Ϫ7.36 (m, 5 H, Ph) ppm. ¹³C NMR Ϫ16.5 (c ϭ 1, MeOH). ¹H NMR (600 MHz, [D₆]DMSO): δ ϭ 0.02

ϭ

3

(62.9 MHz, CDCl₃): δ ϭ 20.2, 20.4 (1C, 4-C), 28.2 (3C, C(CH₃)₃], [s, 9 H, Si(CH₃)₃], 0.92 [t, J ϭ 8.4 Hz, 2 H, OCH₂CH₂Si(CH₃)₃],

30.1, 32.3 (2C, 3-C, 5-C), 52.2 (1C, OCH₃), 53.0 (1C, 2-C), 54.6 1.31Ϫ1.34 (m, 2 H, 4-CH₂), 1.36 [s, 9 H, C(CH₃)₃], 1.56Ϫ1.63 (m,

[1C, NCHRC(O)], 68.0 (1C, CH₂Ph), 77.9 [1C, NCH₂OC(O)], 79.9 4 H, 3-CH₂, 5-CH₂), 3.59 (s, 3 H, OCH₃), 3.89Ϫ3.94 (m, 2 H, 2-

[1C, C(CH₃)₃], 128.0, 128.3, 128.5, 128.6, 128.7, 135.3 (6C, Ph),

152.9, 155.3 [2C,

H, 6-H), 4.11 [t, ³J ϭ 8.3 Hz, 2 H, OCH₂CH₂Si(CH₃)₃], 4.99Ϫ5.04

OC(O)N], 172.0, 172.9 [2C, CO₂CH₃, (m, 2 H, CH₂Ph), 7.17 (d, J_6,NHϭ 7.4 Hz, 1 H, Boc-NH),

3

2

NCH₂OC(O)] ppm. FAB MS (positive mode, glycerol, THF):

7.30Ϫ7.37 (m, 5 H, Ph), 7.63 (d, ³J_2,NHϭ 7.4 Hz, 1 H, Z-NH) ppm.

¹³C NMR (150.8 MHz, [D₆]DMSO): δ ϭ Ϫ1.5 [3C, Si(CH₃)₃], 16.7

[1C, OCH₂CH₂Si(CH₃)₃], 22.1 (1C, 4-C), 27.8, 28.1 [3C, CCH₃)₃],

30.2, 30.2 (2C, 3-C, 5-C), 51.6 (1C, OCH₃), 53.3, 53.8 (2C, 2-C,

6-C), 62.5 [1C, OCH₂CH₂Si(CH₃)₃], 65.4 (1C, CH₂Ph), 78.1 [1C,

C(CH₃)₃], 127.2, 127.7, 127.8, 128.3, 136.9 (6C, Ph), 155.5, 156.0

[2C, 2 OC(O)NH], 172.3, 173.0 [2C, CO₂CH₃, CO₂(CH₂)₂Si(CH₃)₃]

ppm. C₂₆H₄₂N₂O₈Si (538.7): calcd. C 57.97, H 7.86, N 5.20; found

C 58.09, H 7.62, N 5.12.

m/z ϭ 473 [M ϩ Na]^ϩ; calcd. 450.5 for C₂₂H₃₀N₂O₈Si.

7-Methyl 1-[2-(Trimethylsilyl)ethyl] (2S,6R)-N^α-Benzyloxycarbonyl-

N^ε-(tert-butyloxycarbonyl)-2,6-diaminopimelate [(S,R)-9] and 7-

Methyl 1-[2-(Trimethylsilyl)ethyl] (2S,6S)-N^α-Benzyloxycarbonyl-

N^ε-(tert-butyloxycarbonyl)-2,6-diaminopimelate [(S,S)-9]. (a) From

(Z)-7: Pearlman’s catalyst (200 mg) was used (according to Proced-

ure A) for the hydrogenation of compound 7 (4.3 g, 8 mmol) in

MeOH (100 mL). The product mixture (TLC, SiO₂, R_f

ϭ

0.46Ϫ0.51, CHCl₃/MeOH ϭ 9:1) was filtered through celite,

washed with MeOH (2 ϫ 50 mL), evaporated under vacuum, and

dissolved in THF (15 mL). Aqueous NaHCO₃(1 , 15 mL) and

benzyl chloroformate (1.6 g, 10 mmol) were added to the vigor-

ously stirred solution. The reaction mixture was extracted after 1 h

with Et₂O (4 ϫ 50 mL), the combined organic layers were dried

(MgSO₄), and the solvents were evaporated to dryness. Purification

of the crude product by flash chromatography (SiO₂, petroleum

ether/EtOAc ϭ 4:1) gave a mixture of diastereomers (R,S)-9 and

(S,S)-9 in a 1:1 ratio and as a colorless oil (3.0 g, 5.6 mmol, 70%).

Thexyldimethylsilyl 2-Azido-2-deoxy-4,6-O-isopropylidene-β-D-

glucopyranoside (12): Dry p-toluenesulfonic acid (60 mg,

0.33 mmol) was added to a solution of 11^[47](10.0 g, 28.82 mmol)

in 2,2-dimethoxypropane (40 mL), and the mixture was then stirred

overnight at room temperature. After complete consumption of the

starting material (as judged by TLC), the solution was neutralized

with triethylamine and concentrated in vacuo. Purification of the

residue by flash chromatography (SiO₂, toluene/acetone ϭ 20:1)

afforded 12 (10.9 g, 28.12 mmol, 98%) as a colorless syrup. TLC

(SiO₂): R_fϭ 0.41 (toluene/acetone ϭ 10:1). [α]_Dϭ Ϫ18.2 (c ϭ 1,

CHCl₃). ¹H NMR (250 MHz, CDCl₃): δ ϭ 0.15, 0.17 [2s, 6 H,

Si(CH₃)₂], 0.85 (s, 6 H, 2 CH₃), 0.87 [d, ³J ϭ 6.3 Hz, 6 H,

CH(CH₃)₂], 1.41, 1.49 [2s, 6 H, C(CH₃)₂], 1.64 [quint, ³J ϭ 6.9 Hz,

1 H, CH(CH₃)₂], 2.78 (br. s, 1 H, OH), 3.20 (m, 1 H, 5-H), 3.24

(b) From (S,R)/(S,S)-8: This reaction was performed as described

for (Z)-7. 2-(Trimethylsilyl)ethanol (2.4 mL, 17 mmol) and

LiHMDS (0.2 , 22 mL, 4.4 mmol) were added at 0 °C to a solu-

tion of the oxazolidinones (S,R)/(S,S)-8 (5 g, 11 mmol) in THF

(60 mL). Purification of the products by flash chromatography

(SiO₂, petroleum ether/EtOAc ϭ 3:2) afforded a mixture of diaster-

eomers (S,R)-9 and (S,S)-9 in a 3:2 ratio and as a colorless oil

(4.2 g, 7.8 mmol, 70%).

3

(dd, J_2,3ഠ J_1,2ϭ 7.6 Hz, 1 H, 2-H), 3.45 (t, J_3,4ϭ 9.3 Hz, 1 H,

3

2

3-H), 3.56 (t, J_4,5ϭ 9.1 Hz, 1 H, 4-H), 3.76 (t, J_6,6Јϭ 10.7 Hz, 1

H, 6-H), 3.85 (dd, J_5,6Јϭ 5.7, J_6,6Јϭ 10.8 Hz, 1 H, 6Ј-H), 4.54

(d, J_1,2ϭ 7.6 Hz, 1 H, 1-H) ppm. C₁₇H₃₃N₃O₅Si (387.6): calcd. C

3

2

3

52.69, H 8.58, N 10.84; found C 52.66, H 8.71, N 10.38.

(c) Separation of Diastereomers (S,R)-9 and (S,S)-9: The diastere-

omeric mixture (450 mg) in 4.5 mL eluent (toluene/EtOAc ϭ 5:1)

was subjected to MPLC (40 ϫ 4.5 cm). The products generally

eluted at t_Rϭ 45.9 min [(S,S)-9] and t_Rϭ 50.1 min [(S,R)-9]. Pure

fractions were collected, while mixed fractions were reinjected for

final separation.

Thexyldimethylsilyl

[(1R)-1-(methoxycarbonyl)ethyl]-β-

2-Azido-2-deoxy-4,6-O-isopropylidene-3-O-

-glucopyranoside (14): Methyl

D

(S)-2-(trifluoromethanesulfonyloxy)propionate (13,^[48Ϫ50]0.79 g,

3.3 mmol) was used for the alkylation of 12 (1 g, 2.6 mmol), as

published previously.^[27]Purification of the crude product by flash

chromatography (SiO₂, petroleum ether/EtOAc ϭ 15:1) afforded 14

in variable yields (0.85Ϫ1.18 g, 1.8Ϫ2.5 mmol, 70Ϫ95%) as a light

yellow syrup. TLC (SiO₂): R_fϭ 0.68 (toluene/acetone ϭ 10:1).

(d) HPLC analysis of MPLC separation: A sample (0.1 mL) of each

MPLC fraction was dried in vacuo and then dissolved in toluene

(40 µL). From each solution, 20 µL were subjected to HPLC ana-

1

[α]_Dϭ Ϫ35.5 (c ϭ 1, CHCl₃). H NMR (250 MHz, CDCl₃): δ ϭ

0.12, 0.14 [2s, 6 H, Si(CH₃)₂], 0.84 (s, 6 H, 2 CH₃), 0.86 [d, J ϭ

lysis (toluene/EtOAc ϭ 9:1, 1 mL/min). Compounds (S,R)-9 (t_R

12.5 min) and (S,S)-9 (t_Rϭ 10.8 min) were fully separated.

ϭ

3

6.7 Hz, 6 H, CH(CH₃)₂], 1.36 [s, 3 H, C(CH₃)₂], 1.37 (d, J_α,β

ϭ

(S,R)-9: TLC (HPTLC): R_fϭ 0.48 (toluene/EtOAc ϭ 3:1). [α]_D

Ϫ4.9 (c ϭ 1, MeOH). H NMR (600 MHz, [D₆]DMSO): δ ϭ 0.02

ϭ

6.7 Hz, 3 H, Lac-β-CH₃), 1.46 [s, 3 H, C(CH₃)₂], 1.62 [m, ³J ϭ

1

3

6.7 Hz, 1 H, CH(CH₃)₂], 3.15 (m, 1 H, 5-H), 3.25 (dd, J_1,2ϭ 7.6,

Eur. J. Org. Chem. 2002, 2710Ϫ2726

2717

N. Kubasch, R. R. Schmidt

FULL PAPER

³J_2,3ϭ 9.5 Hz, 1 H, 2-H), 3.37 (dd, J_2,3ഠ J_3,4ϭ 9.4 Hz, 1 H, 3-

[D₆]DMSO): δ ϭ 0.11, 0.13 [2s, 6 H, Si(CH₃)₂], 0.83Ϫ0.87 (m, 12

H, 4 CH₃), 1.34Ϫ1.39 [m, 6 H, Lac-β-CH₃, C(CH₃)₂], 1.44Ϫ1.45

10.7 Hz, 1 H, 6-H), 3.75 (s, 3 H, OCH₃), 3.83 (dd, J_5,6Јϭ 5.7, (m, 3 H, Ala-β-CH₃), 1.50Ϫ1.52 [m, 3 H, C(CH₃)₂], 1.59Ϫ1.62 [m,

3

2

H), 3.64 (dd, J_3,4

ഠ

³J_4,5ϭ 9.3 Hz, 1 H, 4-H), 3.73 (t, J_6,6Ј

ϭ

3

²J_6,6Јϭ 10.7 Hz, 1 H, 6Ј-H), 4.37 (q, J_α,βϭ 6.8 Hz, 1 H, Lac-α-

1 H, CH(CH₃)₂], 1.93 (s, 3 H, NHAc), 3.28Ϫ3.32 (m, 1 H, 5-H),

3

H), 4.45 (d, ³J_1,2ϭ 7.6 Hz, 1 H, 1-H) ppm. C₂₁H₃₉N₃O₇Si (473.6): 3.39Ϫ3.43 (m, 1 H, 2-H), 3.62 (t, J_3,4

ഠ

³J_4,5ϭ 9.3 Hz, 1 H, 4-

3

calcd. C 53.25, H 8.30, N 8.87; found C 53.35, H 8.26, N 8.62.

H), 3.76 (s, 3 H, OCH₃), 3.74Ϫ3.78 (m, 1 H, 6-H), 3.85Ϫ3.91 (m,

3

2 H, 3-H, 6Ј-H), 4.14 (q, J_α,βϭ 6.7 Hz, 1 H, Lac-α-H), 4.49 (dq,

Thexyldimethylsilyl 2-Azido-3-O-[(1R)-1-carboxyethyl]-2-deoxy-4,6-

O-isopropylidene-β-D-glucopyranoside (15): Saponification of

methyl ester 14 (200 mg, 0.42 mmol) according to Procedure D af-

forded the free acid 15 (193 mg, 0.42 mmol, quant.) as a glassy,

colorless solid. The solid was coevaporated several times with tolu-

ene, dried in vacuo, and then used directly in the next step.

3

³J_α,βഠ J_α,NHϭ 7.2 Hz, 1 H, Ala-α-H), 5.00 (d, J_1,2ϭ 7.8 Hz, 1

3

H, 1-H), 5.76 (d, J_NH,2ϭ 8.1 Hz, 1 H, NHAc), 7.29 (d, J_NH,α

ϭ

7.1 Hz, 1 H, Ala-NH) ppm. ¹³C NMR (150.8 MHz, [D₆]DMSO):

δ ϭ Ϫ3.5, Ϫ1.9 [2C, Si(CH₃)₂], 18.2, 18.5, 18.5, 19.0, 19.5, 19.9,

20.0 [7C, CCH₃, Ala-β-C, Lac-β-C, C(CH₃)₂CH(CH₃)₂], 23.8 [1C,

NHC(O)CH₃], 24.7 [1C, C(CH₃)₂CH(CH₃)₂], 29.1 (1C, CCH₃),

34.0 [1C, C(CH₃)₂CH(CH₃)₂], 48.0 (1C, Ala-α-C), 52.4 (1C,

OCH₃), 59.7 (1C, 2-C), 62.2 (1C, 6-C), 67.0 (1C, 5-C), 74.7 (1C, 4-

C), 78.1 (1C, Lac-α-C), 79.5 (1C, 3-C), 95.4 (1C, 1-C), 99.3 (1C,

CCH₃), 170.5 [1C, NHC(O)CH₃], 173.2, 173.5 [2C, C(O)NH,

CO₂CH₃] ppm. FAB MS (positive mode, NBA, glycerol): m/z ϭ

561 [M ϩ H]^ϩ, 583 [M ϩ Na]^ϩ. C₂₆H₄₈N₂O₉Si (560.8): calcd. C

55.69, H 8.63, N 5.00; found C 55.42, H 8.67, N 4.34.

TLC (SiO₂): R_fϭ 0.83 (CHCl₃/MeOH ϭ 3:1). ¹H NMR (250 MHz,

CDCl₃): δ ϭ 0.15, 0.18 [2s, 6 H, Si(CH₃)₂], 0.85 (s, 6 H, 2 CH₃),

3

0.86 [d, J ϭ 6.7 Hz, 6 H, CH(CH₃)₂], 1.37 [s, 3 H, C(CH₃)₂], 1.44

3

(d, J_α,βϭ 7.0 Hz, 3 H, Lac-β-CH₃), 1.49 [s, 3 H, C(CH₃)₂], 1.61

3

[quint, J ϭ 6.8 Hz, 1 H, CH(CH₃)₂], 3.16Ϫ3.24 (m, 2 H, 3-H, 5-

H), 3.34 (dd, ³J_1,2ϭ 7.4, ³J_2,3ϭ 10.0 Hz, 1 H, 2-H), 3.66 (t, ³J_3,4ϭ

2

9.3 Hz, 1 H, 4-H), 3.75 (t, J_6,6Јϭ 10.1 Hz, 1 H, 6-H), 3.86 (dd,

2

3

³J_5,6Јϭ 5.6, J_6,6Јϭ 10.9 Hz, 1 H, 6Ј-H), 4.41 (q, J_α,βϭ 7.0 Hz,

Thexyldimethylsilyl 2-Acetamido-2-deoxy-4,6-O-isopropylidene-3-

O-[(2R)-propionyl-(L-alanine)-2-yl]-β-D-glucopyranoside (18): Sa-

3

1 H, Lac-α-H), 4.64 (d, J_1,2ϭ 7.4 Hz, 1 H, 1-H); calcd. 459.6

for C₂₀H₃₇N₃O₇Si.

ponification of the methyl ester 17 (700 mg, 1.25 mmol) according

to Procedure D afforded the free acid 18 (680 mg, 1.25 mmol, qu-

ant.) as a glassy, colorless solid. The solid was coevaporated several

times with toluene, dried in vacuo, and then used directly in the

next step. A sample was purified for analysis by flash chromato-

graphy (SiO₂, EtOAc/MeOH ϭ 3:1). TLC (SiO₂): R_fϭ 0.71 (acet-

one/AcOH ϭ 98:2). [α]_Dϭ ϩ11.9 (c ϭ 1, CHCl₃). ¹H NMR

(250 MHz, CDCl₃/[D₄]MeOH ϭ 10:1): δ ϭ 0.04, 0.06 [2s, 6 H,

Si(CH₃)₂], 0.76 (2s, 6 H, 2 CH₃), 0.78 [d, ³J ϭ 7.0 Hz, 6 H,

CH(CH₃)₂], 1.26Ϫ1.33 [m, 9 H, Lac-β-CH₃, Ala-β-CH₃, C(CH₃)₂],

Thexyldimethylsilyl

2-Azido-2-deoxy-4,6-O-isopropylidene-3-O-

-glucopyranoside

[(2R)-propionyl-( -alanine methyl ester)-2-yl]-β-

L

D

(16): EEDQ (4.64 g, 18.8 mmol) and triethylamine (1.26 g,

12.5 mmol) were added to a stirred solution of the acid 15 (5.76 g,

12.5 mmol) and -alanine methyl ester hydrochloride (1.74 g,

12.5 mmol) in dry CH₂Cl₂(150 mL). After 18 h, complete con-

sumption of the acid was observed by TLC. The solution was di-

luted with CH₂Cl₂(100 mL) and washed with HCl (2 , 3 ϫ

75 mL), saturated NaHCO₃(2 ϫ 100 mL), and H₂O (2 ϫ 100 mL).

The organic layer was dried (MgSO₄) and filtered, and the solvents

were evaporated in vacuo. Purification of the crude product by

flash chromatography (SiO₂, petroleum ether/EtOAc, 4:1) afforded

16 (5.78 g, 10.6 mmol, 85%) as a colorless syrup. TLC (SiO₂): R_fϭ

0.48 (petroleum ether/EtOAc ϭ 2:1). [α]_Dϭ Ϫ2.2 (c ϭ 1, CHCl₃).

¹H NMR (250 MHz, CDCl₃): δ ϭ 0.15, 0.17 [2s, 6 H, Si(CH₃)₂],

3

1.43 [s, 3 H, C(CH₃)₂], 1.54 [quint, J ϭ 6.9 Hz, 1 H, CH(CH₃)₂],

1.85 (s, 3 H, NHAc), 3.15Ϫ3.25 (m, 1 H, 5-H), 3.53Ϫ3.84 (m, 5 H,

3

2-H, 3-H, 4-H, 6-H, 6Ј-H), 3.97 (q, J_α,βϭ 6.8 Hz, 1 H, Lac-α-H),

3

4.11 (m, 1 H, Ala-α-H), 4.79 (d, J_1,2ϭ 6.8 Hz, 1 H, 1-H), 7.56 (d,

³J ϭ 6.9 Hz, 1 H, NH), 7.64 (d, ³J ϭ 8.2 Hz, 1 H, NH) ppm.

C₂₅H₄₆N₂O₉Si·H₂O (564.7): calcd. C 53.17, H 8.57, N 4.96; found

C 53.06, H 8.17, N 4.26.

3

0.85 (s, 6 H, 2 CH₃), 0.86 [d, J ϭ 6.7 Hz, 6 H, CH(CH₃)₂], 1.35

3

[s, 3 H, C(CH₃)₂], 1.37 (d, J_α,βϭ 6.7 Hz, 3 H, Lac-β-CH₃), 1.44

1,6-Anhydro-4-O-benzyl-2-deoxy-2-iodo-β-D-glucopyranose (20): Bi-

3

(d, J_α,βϭ 7.5 Hz, 3 H, Ala-β-CH₃), 1.48 [s, 3 H, C(CH₃)₂], 1.64

s(tributyltin) oxide (0.61 g, 1.02 mmol) and pulverized, dry mol.

3

˚

[quint, J ϭ 6.9 Hz, 1 H, CH(CH₃)₂], 3.12Ϫ3.22 (m, 2 H, 3-H, 5-

sieves (3 A, 0.8 g) were added to a solution of glucal 19 (0.3 g,

H), 3.31 (dd, ³J_1,2ϭ 7.5, ³J_2,3ϭ 9.9 Hz, 1 H, 2-H), 3.64 (dd, ³J_3,4

ഠ

1.27 mmol) in dry MeCN (20 mL), and the mixture was heated

under reflux for 3 h. The reaction mixture was then allowed to cool

to ambient temperature, iodine was added (0.39 g, 1.52 mmol), and

the mixture was stirred for another 45 min. After filtration and

removal of the solvent, flash chromatography (SiO₂, petroleum

ether/EtOAc ϭ 5:1Ǟ3:2) of the residue afforded 20, which crystal-

lized from petroleum ether/EtOAc (ഠ 95:5 v/v) at Ϫ50 °C as light

yellow crystals (0.41 g, 1.13 mmol, 89%). The spectroscopic data

were identical to those reported previously.^[53]

³J_4,5ϭ 9.4 Hz, 1 H, 4-H), 3.73 (t, ²J_6,6Јϭ 10.4 Hz, 1 H, 6-H), 3.73

(s, 3 H, OCH₃), 3.84 (dd, ³J_5,6Јϭ 5.6, ²J_6,6Јϭ 10.8 Hz, 1 H, 6Ј-H),

3

4.31 (q, J_α,βϭ 6.9 Hz, 1 H, Lac-α-H), 4.58 (dq, J_α,NHഠ J_α,β

ϭ

3

8.1 Hz, 1 H, Ala-α-H), 4.59 (d, J_1,2ϭ 7.5 Hz, 1 H, 1-H), 7.90 (d,

³J_α,NHϭ 7.5 Hz, 1 H, Ala-NH) ppm. FAB MS (positive mode,

NBA, glycerol): m/z ϭ 545 [M ϩ H]^ϩ, 567 [M ϩ Na]^ϩ.

C₂₄H₄₄N₄O₈Si (544.7): calcd. C 52.92, H 8.14, N 10.29; found C

53.14, H 8.16, N 9.74.

Thexyldimethylsilyl 2-Acetamido-2-deoxy-4,6-O-isopropylidene-3-

O-[(2R)-propionyl-(L-alanine methyl ester)-2-yl]-β-D-glucopyrano-

1,6-Anhydro-2-azido-4-O-benzyl-2-deoxy-β-

Tetramethyl guanidinium azide (32.1 g, 0.2 mol, Merck) was added

side (17): A stream of H₂S was bubbled through a stirred solution to the iodide 20 (10.5 g, 29 mmol) in dry DMF (100 mL). Under

D-glucopyranose (21):

of azide 16 (100 mg, 0.18 mmol) in pyridine (4 mL) and H₂O

an atmosphere of nitrogen, the reaction mixture was stirred at 50

(1 mL) for 15 min. After 24 h the solvent was removed under va-

°C (30 min) and then heated to 120 °C (72 h). After removal of the

cuum and the residue was stirred for 12 h in a 1:1 mixture of Ac₂O solvent in vacuo, the residue was dissolved in EtOAc (1000 mL)

and pyridine (8 mL, v/v). Removal of the solvent in vacuo afforded

the crude product, which was purified by flash chromatography

(SiO₂, toluene/acetone ϭ 5:1) to give 17 (90 mg, 0.16 mmol, 89%)

as a light yellow foam. TLC (SiO₂): R_fϭ 0.71 (toluene/acetone ϭ

1:1). [α]_Dϭ Ϫ18.6 (c ϭ 1, MeOH). ¹H NMR (600 MHz,

and extracted with H₂O (3 ϫ 200 mL). The organic layer was dried

(MgSO₄), filtered, and concentrated under vacuum. Flash chroma-

tography (SiO₂, toluene/EtOAc ϭ 6:1Ǟ5:1) afforded 21 (6.3 g,

22.8 mmol, 79%), which crystallized from toluene as colorless crys-

tals. TLC (SiO₂): R_fϭ 0.33 (CH₂Cl₂/EtOAc ϭ 9:1). m.p.: 97Ϫ98

2718

Eur. J. Org. Chem. 2002, 2710Ϫ2726

Synthesis of Muramyl Peptides Containing meso-Diaminopimelic Acid

FULL PAPER

°C; ref.:^[54]m.p.: 96 °C. The analytical data were identical to those 1.04 mmol) according to Procedures A and B. Purification of the

reported previously.^[54,55]

product by flash chromatography (SiO₂, toluene/EtOAc ϭ 2:1) af-

forded dipeptide 31a (673 mg, 0.99 mmol, 96%) as a colorless

syrup. TLC (SiO₂): R_fϭ 0.75 (toluene/acetone ϭ 1:1). [α]_Dϭ ϩ3.5

2-Acetamido-1,6-anhydro-4-O-benzyl-2-deoxy-3-O-[(1R)-1-(meth-

oxycarbonyl)ethyl]-β-D-glucopyranose (23): The azide 22 (110 mg,

1

(c ϭ 1, MeOH). H NMR (600 MHz, [D₆]DMSO): δ ϭ 0.01 [s, 9

0.3 mmol) was transformed into the acetamino derivative as de-

scribed for compound 17. Purification of the crude product by flash

chromatography (SiO₂, toluene/EtOAc ϭ 1:1) afforded 23 (105 mg,

0.28 mmol, 92%). The spectroscopic and analytical data were ident-

ical to those reported previously.^[39]

3

H, Si(CH₃)₃], 0.92 [t, J ϭ 8.4 Hz, 2 H, OCH₂CH₂Si(CH₃)₃], 1.32

(m, 2 H, 4-CH₂), 1.36 [s, 9 H, C(CH₃)₃], 1.52Ϫ1.54, 1.61Ϫ1.62 (2m,

4 H, 3-CH₂, 5-CH₂), 1.77, 1.93 (2m, 2 H, Glu-β-CH₂), 2.20 (t,

³J_β,γϭ 7.5 Hz, 2 H, Glu-γ-CH₂), 3.59, 3.62 (2s, 6 H, 2 OCH₃), 3.90

(m, 1 H, 6-H), 4.04 (m, 1 H, Glu-α-H), 4.07Ϫ4.14 [m, 3 H, 2-H,

3

OCH₂CH₂Si(CH₃)₃], 5.02 (m, 2 H, CH₂Ph), 7.17 (d, J_α,NH

ϭ

2-Amino-1,6-anhydro-4-O-benzyl-3-O-[(1R)-1-carboxyethyl]-2-

deoxy-β-D-glucopyranose 1Ј,2-Lactam (25): Triphenylphosphane

3

7.7 Hz, 1 H, Boc-NH), 7.31Ϫ7.36 (m, 5 H, Ph), 7.71 (d, J_α,NH

ϭ

3

7.6 Hz, 1 H, Z-NH), 8.15 (d, J_α,NHϭ 7.3 Hz, 1 H, 2-NH) ppm.

¹³C NMR (150.8 MHz, [D₆]DMSO): δ ϭ Ϫ1.5 [3C, Si(CH₃)₃], 16.8

[1C, OCH₂CH₂Si(CH₃)₃], 21.9 (1C, 4-C), 26.6 (1C, Glu-β-C), 28.1

[3C, C(CH₃)₃], 30.2, 30.4 (2C, 3-C, 5-C), 31.2 (1C, Glu-γ-C), 51.7,

51.8, 51.9 (2C, 2 OCH₃, 2-C), 53.2 (1C, 6-C), 53.5 (1C, Glu-α-C),

62.4 [1C, OCH₂CH₂Si(CH₃)₃], 65.5 (1C, CH₂Ph), 78.2 [1C,

C(CH₃)₃], 127.1, 127.7, 127.8, 128.3, 136.9 (6C, Ph), 155.5, 156.0

[2C, 2 OC(O)NH], 171.3, 172.1, 172.6, 173.0 [4C, 2 CO₂CH₃,

C(O)NH, CO₂(CH₂)₂Si(CH₃)₃] ppm. FAB MS (positive mode,

NBA, glycerol, CHCl₃): m/z ϭ 704 [M ϩ Na]^ϩ. C₃₂H₅₁N₃O₁₁Si

(681.9): calcd. C 56.37, H 7.54, N 6.16; found C 56.26, H 7.52,

N 5.50.

(173 mg, 0.66 mmol) was added to a stirred solution of azide 22

(200 mg, 0.55 mmol) in THF (5 mL) and H₂O (0.5 mL). After 48 h

the pH was adjusted with glacial AcOH (pH 5) and the solvent

was removed in vacuo. The residue was coevaporated with toluene

(3 ϫ 10 mL) and then acetylated (Ac₂O/pyridine ϭ 1:1; v/v, 8 mL,

20 h). The solvent was removed in vacuo and the residue was puri-

fied by flash chromatography (SiO₂, toluene/EtOAc ϭ 1:1) to af-

ford lactam 25 (126 mg, 0.41 mmol, 75%) as a colorless solid, which

crystallized from toluene. The analytical data were identical to

those reported previously.^[57]

tert-Butyl N-Benzyloxycarbonyl-D-isoglutaminate: The amide

28^[58,59]was synthesized as described for the corresponding  iso-

mer.^[60]

7-Methyl 1-[2-(Trimethylsilyl)ethyl] (2S,6S)-N^α-(N-Benzyloxycar-

bonyl-D

-isoglutamyl α-methyl ester)-N^ε-(tert-butyloxycarbonyl)-2,6-

Dimethyl (N-Benzyloxycarbonyl-L-alanyl)-D-glutamate (29): Di-

diaminopimelate (31b): Compound (S,S)-9 (230 mg, 0.43 mmol)

was hydrogenated according to Procedure A, and then coupled

peptide 29 (8.64 g, 22.7 mmol, 96%) was synthesized from dimethyl

-glutamate (5 g, 23.5 mmol), N-benzyloxycarbonyl--alanine

(5.25 g, 23.5 mmol), and EEDQ (8.73 g, 35.3 mmol) as described

for compound 16. It was isolated as a colorless, amorphous solid.

with

1-methyl

N-benzyloxycarbonyl--glutamate

(140 mg,

0.47 mmol) (Procedure B). Purification by flash chromatography

(SiO₂, toluene/EtOAc ϭ 2:1) afforded 31b (279 mg, 0.41 mmol,

96%) as a colorless syrup. TLC (SiO₂): R_fϭ 0.75 (toluene/acet-

one ϭ 1:1). [α]_Dϭ Ϫ6.1 (c ϭ 1, MeOH). ¹H NMR (600 MHz,

TLC (SiO₂): R_fϭ 0.23 (petroleum ether/EtOAc ϭ 1:1). [α]_D

ϭ

Ϫ23.6 (c ϭ 0.5, CHCl₃). ¹H NMR (250 MHz, CDCl₃): δ ϭ 1.37

3

(d, J_α,βϭ 7.1 Hz, 3 H, Ala-β-CH₃), 1.92Ϫ2.04, 2.15Ϫ2.25 (2m, 2

3

[D₆]DMSO): δ ϭ 0.01 [s, 9 H, Si(CH₃)₃], 0.92 [t, J ϭ 8.4 Hz, 2 H,

H, Glu-β-CH₂), 2.32Ϫ2.40 (m, 2 H, Glu-γ-CH₂), 3.65, 3.71 (2s, 6

OCH₂CH₂Si(CH₃)₃], 1.31 (m, 2 H, 4-CH₂), 1.36 [s, 9 H, C(CH₃)₃],

1.53Ϫ1.60 (m, 4 H, 3-CH₂, 5-CH₂), 1.76, 1.94 (2m, 2 H, Glu-β-

CH₂), 2.20 (t, ³J_β,γϭ 7.5 Hz, 2 H, Glu-γ-CH₂), 3.59, 3.62 (2s, 6 H,

2 OCH₃), 3.89 (m, 1 H, 6-H), 4.04 (m, 1 H, Glu-α-H), 4.08Ϫ4.13

[m, 3 H, 2-H, OCH₂CH₂Si(CH₃)₃], 5.02 (m, 2 H, CH₂Ph), 7.17 (d,

³J_α,NHϭ 7.6 Hz, 1 H, Boc-NH), 7.31Ϫ7.37 (m, 5 H, Ph), 7.71 (d,

3

H, 2 OCH₃), 4.26 (m, 1 H, Glu-α-H), 4.57 (dq, J ϭ 7.9 Hz, 1 H,

Ala-α-H), 5.10 (s, 2 H, CH₂Ph), 5.28, 6.80 (2bd, 2 H, 2 NH),

7.28Ϫ7.35 (m, 5 H, Ph). MALDI MS (positive mode, DHB, THF):

m/z ϭ 382 [M ϩ H]^ϩ, 404 [M ϩ Na]^ϩ, 420 [M ϩ K]^ϩ; calcd. 380.4

for C₁₈H₂₄N₂O₇.

3

³J_α,NHϭ 7.6 Hz, 1 H, Z-NH), 8.16 (d, J_α,NHϭ 7.3 Hz, 1 H, 2-

D

Methyl N^α-(N-Benzyloxycarbonyl- -isoglutamyl α-methyl ester)-N^ε-

NH) ppm. ¹³C NMR (150.8 MHz, [D₆]DMSO): δ ϭ Ϫ1.5 [3C,

Si(CH₃)₃], 16.7 [1C, OCH₂CH₂Si(CH₃)₃], 22.1 (1C, 4-C), 26.6 (1C,

Glu-β-C), 28.1 [3C, C(CH₃)₃], 30.2, 30.4 (2C, 3-C, 5-C), 31.1 (1C,

Glu-γ-C), 51.6 (2C, 2 OCH₃), 51.8 (1C, 2-C), 53.4 (1C, 6-C), 53.5

(1C, Glu-α-C), 62.4 [1C, OCH₂CH₂Si(CH₃)₃], 65.5 (1C, CH₂Ph),

78.2 [1C, C(CH₃)₃], 127.7, 128.3, 136.8 (6C, Ph), 155.5, 156.0 [2C,

2 OC(O)NH], 171.4, 172.1, 172.6, 173.0 [4C, 2 CO₂CH₃, C(O)NH,

CO₂(CH₂)₂Si(CH₃)₃] ppm. C₃₂H₅₁N₃O₁₁Si·1.5 H₂O (708.9): calcd.

C 54.20, H 7.68, N 5.93; found C 54.41, H 7.73, N 4.95.

(tert-butyloxycarbonyl)- -lysinate (30): 1-Methyl N-benzyloxycar-

L

bonyl--glutamate (200 mg, 0.68 mmol) and methyl N^ε-(tert-bu-

tyloxycarbonyl)--lysine hydrochloride (195 mg, 0.68 mmol) were

coupled according to Procedure B. Purification of the crude prod-

uct by flash chromatography (SiO₂, toluene/acetone ϭ 1:1) afforded

the dipeptide 30 (342 mg, 0.64 mmol, 94%) as a colorless, amorph-

ous solid. TLC (SiO₂): R_fϭ 0.51 (toluene/acetone ϭ 1:1). [α]_D

ϭ

ϩ1 (c ϭ 1, MeOH). ¹H NMR (250 MHz, [D₆]DMSO): δ ϭ

1.18Ϫ1.41 (m, 4 H, Lys-γ-CH₂, Lys-δ-CH₂), 1.35 [s, 9 H, C(CH₃)₃],

1.50Ϫ1.68 (m, 2 H, Lys-β-CH₂), 1.70Ϫ2.03 (2m, 2 H, Glu-β-CH₂),

7-Methyl 1-[2-(Trimethylsilyl)ethyl] (2S,6R)-N^α-[(N-Benzyloxycar-

3

2.21 (t, J_β,γϭ 7.0 Hz, 2 H, Glu-γ-CH₂), 2.87 (q, J ϭ 6.4 Hz, 2

H, Lys-ε-CH₂), 3.59, 3.62 (2s, 6 H, 2 OCH₃), 4.03, 4.16 (2m, 2 H,

Glu-α-H, Lys-α-H), 5.02 (s, 2 H, CH₂Ph), 6.77 (t, ³J_ε,NHϭ 6.4 Hz,

1 H, Lys-ε-NH), 7.25Ϫ7.42 (m, 5 H, Ph), 7.74 (d, ³J_α,NHϭ 8.6 Hz,

bonyl-L-alanyl)-D

-isoglutamyl α-methyl ester]-N^ε-(tert-butyloxycar-

bonyl)-2,6-diaminopimelate (32a): The dipeptide 31a (419 mg,

0.61 mmol) was hydrogenated (Procedure A) and coupled with N-

benzyloxycarbonyl--alanine (170 mg, 0.76 mmol) (Procedure B).

Purification of the crude product by flash chromatography (SiO₂,

toluene/acetone ϭ 2:1) afforded the tripeptide 32a (423 mg,

0.56 mmol, 92%) as a colorless foam. TLC (SiO₂): R_fϭ 0.69 (tolu-

3

1 H, Z-NH), 8.21 (d, J_α,NHϭ 7.0 Hz, 1 H, Lys-α-NH) ppm.

C₂₆H₃₉N₃O₉(537.6): calcd. C 58.09, H 7.31, N 7.82; found C 58.03,

H 7.52, N 7.51.

7-Methyl 1-[2-(Trimethylsilyl)ethyl] (2S,6R)-N^α-(N-Benzyloxycar- ene/acetone ϭ 1:1). [α]_Dϭ Ϫ5.6 (c ϭ 2, MeOH). ¹H NMR

3

bonyl-

D

-isoglutamyl α-methyl ester)-N^ε-(tert-butyloxycarbonyl)-2,6-

(600 MHz, [D₆]DMSO): δ ϭ 0.01 [s, 9 H, Si(CH₃)₃], 0.92 [t, J ϭ

diaminopimelate (31a): 1-Methyl N-benzyloxycarbonyl--glutamate

8.3 Hz, 2 H, OCH₂CH₂Si(CH₃)₃], 1.21 (d, ³J_α,βϭ 7.1 Hz, 3 H, Ala-

(370 mg, 1.25 mmol) was coupled with compound (S,R)-9 (560 mg, β-CH₃), 1.31 (m, 2 H, 4-CH₂), 1.36 [s, 9 H, C(CH₃)₃], 1.52Ϫ1.56,

Eur. J. Org. Chem. 2002, 2710Ϫ2726 2719

N. Kubasch, R. R. Schmidt

1.60Ϫ1.63 (2m, 4 H, 3-CH₂, 5-CH₂), 1.78Ϫ1.81, 1.91Ϫ1.93 (2m, 2 9 H, C(CH₃)₃], 1.45Ϫ1.65 (m, 4 H, 3-CH₂, 5-CH₂), 3.59, 3.60 (2s,

FULL PAPER

3

H, Glu-β-CH₂), 2.15 (t, J_β,γϭ 7.4 Hz, 2 H, Glu-γ-CH₂), 3.59,

6 H, 2 OCH₃), 3.83Ϫ3.92, 3.97Ϫ4.05 (2m, 2 H, 2-H, 6-H), 4.25

3.62 (2s, 6 H, 2 OCH₃), 3.90 (m, 1 H, 6-H), 4.08Ϫ4.13 [m, 4 H, (dq, ³J_α,βഠ ³J_α,NHϭ 7.2 Hz, 1 H, Ala-α-H), 5.01 (s, 2 H, CH₂Ph),

OCH₂CH₂Si(CH₃)₃, Ala-α-H, 2-H], 4.23 (q, J_α,βϭ 5.8 Hz, 1 H,

Glu-α-H), 5.01 (2d, J ϭ 12.3 Hz, 2 H, CH₂Ph), 7.18 (d, J_α,NH

3

7.21 (d, J_NH,αϭ 7.7 Hz, 1 H, NH), 7.25Ϫ7.39 (m, 6 H, Ph, NH),

2

3

ϭ

8.34 (d, J_NH,αϭ 7.3 Hz, 1 H, NH) ppm. ¹³C NMR (150.8 MHz,

7.7 Hz, 1 H, Boc-NH), 7.30 (br. d, 1 H, Z-NH), 7.34 (m, 5 H, Ph), [D₆]DMSO): δ ϭ 17.1 (1C, Ala-β-C), 21.9 (1C, 4-C), 27.8, 28.1

3

8.16 (d, J_α,NHϭ 7.4 Hz, 1 H, 2-NH), 8.24 (d, J_α,NHϭ 7.4 Hz, 1

H, Glu-NH) ppm. ¹³C NMR (150.8 MHz, [D₆]DMSO): δ ϭ Ϫ1.5 51.8 (2C, 2 OCH₃), 53.5, 54.0 (2C, 2-C, 6-C), 65.3 (1C, CH₂Ph),

[3C, Si(CH₃)₃], 16.7 [1C, OCH₂CH₂Si(CH₃)₃], 18.5 (1C, Ala-β-C), 78.1 [1C, C(CH₃)₃], 127.0, 127.6, 127.7, 128.3, 137.0 (6C, Ph),

21.9 (1C, 4-C), 27.0 (1C, Glu-β-C), 28.1 [3C, C(CH₃)₃], 30.2, 30.3 155.5, 155.8 [2C, 2 OC(O)NH], 171.6, 172.8, 173.1 [3C, 2 CO₂CH₃,

[3C, C(CH₃)₃], 30.3, 31.7 (2C, 3-C, 5-C), 47.4 (1C, Ala-α-C), 51.6,

(2C, 3-C, 5-C), 31.1 (1C, Glu-γ-C), 49.8 (1C, Ala-α-C), 51.6 (1C,

Glu-α-C), 51.6 (2C, 2 OCH₃), 51.8 (1C, 2-C), 53.2 (1C, 6-C), 62.4

[1C, OCH₂CH₂Si(CH₃)₃], 65.3 (1C, CH₂Ph), 78.1 [1C, C(CH₃)₃],

127.7, 128.3, 137.0 (6C, Ph), 154.0, 155.5 [2C, 2 OC(O)NH], 171.3,

172.1 [5C, 2 CO₂CH₃, 2 C(O)NH, CO₂(CH₂)₂Si(CH₃)₃] ppm.

C₃₅H₅₆N₄O₁₂Si·0.3H₂O (752.9): calcd. C 55.41, H 7.53, N 7.39;

found C 55.36, H 7.61, N 7.04.

C(O)NH]. MALDI MS (positive mode, DHB, THF): m/z ϭ 546

[M ϩ Na]^ϩ; calcd. 523.6 for C₂₅H₃₇N₃O₉.

Methyl [7-Methyl (2S,6R)-N^α-(N-Benzyloxycarbonyl-

α-methyl ester)-N^ε-(tert-butyloxycarbonyl)-2,6-diaminopimelyl]-

D-isoglutamyl

D-

alaninate (35): The dipeptide 34 (200 mg, 0.38 mmol) was hydro-

genated (Procedure A) and coupled with 1-methyl N-benzyloxycar-

bonyl--glutamate (218 mg, 0.42 mmol) according to Procedure B.

Flash chromatography (SiO₂, toluene/EtOAc ϭ 2:1) afforded the

tripeptide 35 (217 mg, 0.33 mmol, 86%) as a colorless syrup. TLC

7-Methyl 1-[2-(Trimethylsilyl)ethyl] (2S,6S)-N^α-[(N-Benzyloxycar-

bonyl-L-alanyl)-D

-isoglutamyl α-methyl ester]-N^ε-(tert-butyloxycar-

bonyl)-2,6-diaminopimelate (32b): Compound 31b (514 mg, (SiO₂): R_fϭ 0.39 (toluene/acetone ϭ 1:1). [α]_Dϭ ϩ11.1 (c ϭ 1,

3

0.75 mmol) was deprotected according to Procedure A. Peptide

coupling (Procedure B) with N-benzyloxycarbonyl--alanine

(202 mg, 0.91 mmol) afforded the tripeptide 32b, which was puri-

fied by flash chromatography (SiO₂, toluene/acetone ϭ 2:1) to give

MeOH). ¹H NMR (600 MHz, [D₆]DMSO): δ ϭ 1.25 (t, J_α,β

ϭ

7.2 Hz, 3 H, Ala-β-CH₃), 1.31 (m, 2 H, 4-CH₂), 1.36 [s, 9 H,

C(CH₃)3], 1.42Ϫ1.45, 1.53Ϫ1.60 (2m, 4 H, 3-CH₂, 5-CH₂), 1.76,

1.93 (2m, 2 H, Glu-β-CH₂), 2.21 (t, J_β,γϭ 7.1 Hz, 2 H, Glu-γ-

3

a colorless foam (499 mg, 0.66 mmol, 89%). TLC (SiO₂): R_fϭ 0.69 CH₂), 3.59, 3.60, 3.62 (3s, 9 H, 3 OCH₃), 3.87 (m, 1 H, 6-H), 4.02

1

(toluene/acetone ϭ 1:1). [α]_Dϭ Ϫ13.7 (c ϭ 1, MeOH). H NMR

(m, 1 H, Glu-α-H), 4.24Ϫ4.28 (m, 2 H, 2-H, Ala-α-H), 5.02 (m, 2

3

(600 MHz, [D₆]DMSO): δ ϭ 0.01 [s, 9 H, Si(CH₃)₃], 0.92 [t, J ϭ

H, CH₂Ph), 7.15 (d, J_α,NHϭ 7.7 Hz, 1 H, Boc-NH), 7.29Ϫ7.37

8.5 Hz, 2 H, OCH₂CH₂Si(CH₃)₃], 1.20 (d, ³J_α,βϭ 7.1 Hz, 3 H, Ala- (m, 5 H, Ph), 7.71 (d, J_α,NHϭ 7.6 Hz, 1 H, Z-NH), 7.89 (d,

3

β-CH₃), 1.31 (m, 2 H, 4-CH₂), 1.36 [s, 9 H, C(CH₃)₃], 1.54Ϫ1.62 ³J_α,NHϭ 8.3 Hz, 1 H, 2-NH), 8.30 (d, J_α,NHϭ 7.2 Hz, 1 H, Ala-

3

(m, 4 H, 3-CH₂, 5-CH₂), 1.79, 1.92 (2m, 2 H, Glu-β-CH₂), 2.16 (t, NH) ppm. ¹³C NMR (150.8 MHz, [D₆]DMSO): δ ϭ 17.0 (1C, Ala-

³J_β,γϭ 7.5 Hz, 2 H, Glu-γ-CH₂), 3.59, 3.61 (2s, 6 H, 2 OCH₃), 3.89 β-CH₂), 21.7 (1C, 4-C), 26.8 (1C, Glu-β-C), 28.1 [3C, C(CH₃)₃],

(m, 1 H, 6-H), 4.07Ϫ4.22 [m, 4 H, OCH₂CH₂Si(CH₃)₃, Ala-α-H, 2-

30.3, 31.9 (2C, 3-C, 5-C), 31.3 (1C, Glu-γ-C), 47.4 (1C, Ala-α-C),

H], 4.23 (q, ³J_α,βϭ 5.8 Hz, 1 H, Glu-α-H), 5.01 (2d, ²J ϭ 10.1 Hz, 2 51.6, 51.8 (4C, 3 OCH₃, 2-C), 53.5 (2C, 6-C, Glu-α-C), 65.5 (1C,

3

H, CH₂Ph), 7.20 (d, J_α,NHϭ 7.7 Hz, 1 H, Boc-NH), 7.30 (br. d, CH₂Ph), 78.1 [1C, C(CH₃)₃], 127.7, 127.8, 128.3, 136.8 (6C, Ph),

3

1 H, Z-NH), 7.32Ϫ7.38 (m, 5 H, Ph), 8.17 (d, J_α,NHϭ 7.4 Hz, 1 156.0 [2C, 2 OC(O)NH], 171.0, 171.3, 172.6, 172.8, 173.1 [5C, 3

H, 2-NH), 8.26 (d, ³J_α,NHϭ 7.6 Hz, 1 H, Glu-NH) ppm. ¹³C NMR CO₂CH₃, 2 C(O)NH] ppm. FAB MS (positive mode, NBA,

(150.8 MHz, [D₆]DMSO): δ ϭ Ϫ1.5 [3C, Si(CH₃)₃], 16.7 [1C, glycerol): m/z ϭ 667 [M ϩ H]^ϩ, 689 [M ϩ Na]^ϩ. C₃₁H₄₆N₄O₁₂

OCH₂CH₂Si(CH₃)₃], 18.5 (1C, Ala-β-C), 22.1 (1C, 4-C), 27.0 (1C,

(666.7): calcd. C 55.85, H 6.95, N 8.40; found C 55.81, H 7.01,

Glu-β-C), 28.1 [3C, C(CH₃)₃], 30.2, 30.4 (2C, 3-C, 5-C), 31.1 (1C, N 8.27.

Glu-γ-C), 49.8 (1C, Ala-α-C), 51.6 (1C, Glu-α-C), 51.7 (2C, 2

Thexyldimethylsilyl

[(2R)-propionyl-( -alanyl-

2-Azido-2-deoxy-4,6-O-isopropylidene-3-O-

-glutamic acid dimethyl ester)-2-yl]-β-D-

OCH₃), 51.8 (1C, 2-C), 53.4 (1C, 6-C), 62.5 [1C, OCH₂CH₂S-

i(CH₃)₃], 65.3 (1C, CH₂Ph), 78.2 [1C, C(CH₃)₃], 127.7, 127.8, 128.3,

137.0 (6C, Ph), 155.5 [2C, 2 OC(O)NH], 171.4, 172.2, 172.7, 173.1

L

D

glucopyranoside (36): The Z-protected dipeptide 29 (0.95 g,

3.3 mmol) was hydrogenated (Procedure A) and then coupled with

15 (1.28 g, 2.8 mmol) and EEDQ (1.03 g, 4.19 mmol) as described

for compound 16. Purification by flash chromatography (SiO₂,

toluene/acetone ϭ 7:1) afforded compound 36 (1.25 g, 1.82 mmol,

65%) as a colorless syrup. TLC (SiO₂): R_fϭ 0.78 (toluene/acet-

[5C,

2

CO₂CH₃,

2

C(O)NH, CO₂(CH₂)₂Si(CH₃)₃] ppm.

C₃₅H₅₆N₄O₁₂Si (752.9): calcd. C 55.83, H 7.41, N 7.44; found C

55.89, H 7.27, N 7.63.

Methyl [7-Methyl (2S,6R)-N^α-Benzyloxycarbonyl-N^ε-(tert-butyloxy-

carbonyl)-2,6-diaminopimelyl]-D

-alaninate (34): TBAF in THF (1 , one ϭ 1:1). [α]_Dϭ Ϫ25.3 (c ϭ 1, CHCl₃). ¹H NMR (250 MHz,

0.7 mL, 0.7 mmol) was added to a stirred solution of the β-silyl

ester (S,R)-9 (350 mg, 0.65 mmol) in dry THF (35 mL). The reac-

tion was monitored by TLC until consumption of the starting mat-

CDCl₃): δ ϭ 0.14, 0.17 [2s, 6 H, Si(CH₃)₂], 0.84 (s, 6 H, 2 CH₃),

0.86 [d, J ϭ 6.1 Hz, 6 H, CH(CH₃)₂], 1.36 [s, 3 H, C(CH₃)₂], 1.39

3

(d, J_α,βϭ 6.9 Hz, 3 H, Lac-β-CH₃), 1.41 (d, J_α,βϭ 7.1 Hz, 3 H,

erial was complete. After neutralization of the reaction mixture Ala-β-CH₃), 1.48 [s, 3 H, C(CH₃)₂], 1.63 [m, ³J ϭ 6.8 Hz, 1 H,

(Amberlite, IR 120 H^ϩ), the solution was filtered, concentrated,

and flushed through a short column (SiO₂, EtOAc/MeOH ϭ 3:1). 2.33Ϫ2.48 (m, 2 H, Glu-γ-CH₂), 3.11Ϫ3.22 (m, 2 H, 3-H, 5-H),

The eluent was concentrated and dried, and the obtained crude

33 was directly coupled with -alanine methyl ester hydrochloride

(100 mg, 0.72 mmol) according to Procedure B. Purification of the

crude product by flash chromatography (SiO₂, petroleum ether/

EtOAc ϭ 1:1) afforded 34 (313 mg, 0.60 mmol, 92%) as a colorless

CH(CH₃)₂], 1.89Ϫ2.03, 2.13Ϫ2.29 (2m, 2 H, Glu-β-CH₂),

3

3.30 (dd, J_1,2ϭ 7.5, J_2,3ϭ 9.9 Hz, 1 H, 2-H), 3.64 (t, J_3,4ഠ

³J_4,5ϭ 9.6 Hz, 1 H, 4-H), 3.65, 3.70 (2s, 6 H, 2 OCH₃), 3.74 (t,

²J_6,6Јϭ 10.8, J_5,6ϭ 10.2 Hz, 1 H, 6-H), 3.84 (dd, J_6,6Јϭ 10.8,

3

2

³J_5,6Јϭ 5.5 Hz, 1 H, 6Ј-H), 4.34 (q, J_α,βϭ 6.9 Hz, 1 H, Lac-α-H),

3

4.46 (dq, J_α,βഠ ³J_α,NHϭ 7.1 Hz, 1 H, Ala-α-H), 4.53Ϫ4.60 (m, 1

3

syrup. TLC (SiO₂): R_fϭ 0.63 (toluene/acetone ϭ 1:1). [α]_D

ϭ

H, Glu-α-H), 4.60 (d, J_1,2ϭ 7.5 Hz, 1 H, 1-H), 7.01 (d, J_NH,αϭ

8.0 Hz, 1 H, Glu-NH), 7.76 (d, J_NH,αϭ 7.1 Hz, 1 H, Ala-NH)

ϩ11.7 (c ϭ 1, MeOH). ¹H NMR (250 MHz, [D₆]DMSO): δ ϭ 1.25

3

(d, J_α,βϭ 7.2 Hz, 3 H, Ala-β-CH₃), 1.32 (m, 2 H, 4-CH₂), 1.36 [s, ppm. EI MS (195 °C): m/z ϭ 602 [M Ϫ thexyl]^ϩ, 656 [M Ϫ

2720

Eur. J. Org. Chem. 2002, 2710Ϫ2726

Synthesis of Muramyl Peptides Containing meso-Diaminopimelic Acid

FULL PAPER

OCH₃]^ϩ, 672 [M

C₃₀H₅₃N₅O₁₁Si.

Ϫ

CH₃]^ϩ, 687 [M]^ϩ; calcd. 687.9 for fied with 1  LiOH according to Procedure D. The residue was

treated with TFA/dioxane/H₂O (10 mL, Procedure E) to remove

the remaining protecting groups. Purification of the crude product

Thexyldimethylsilyl 2-Acetamido-2-deoxy-4,6-O-isopropylidene-3-

O-[(2R)-propionyl-( -alanyl- -glutamic acid dimethyl ester)-2-yl]-β-

-glucopyranoside (37). (a) From 36: The reduction and acetylation

of azide 36 (670 mg, 0.97 mmol) was performed as described for

compound 17. Flash chromatography (SiO₂, toluene/acetone ϭ

5:2) afforded the acetamide 37 (585 mg, 0.83 mmol, 85%) as a col-

orless foam.

by gel chromatography (t_Rϭ 43.6 min) afforded 39 (39 mg, 74

µmol, 71%) as a colorless lyophilizate (from water). TLC (RP-18):

R_fϭ 0.79 (MeCN/H₂O/TFA ϭ 6:1:1). [α]_Dϭ ϩ22.8 (c ϭ 0.5,

L

D

1

H₂O). H NMR (600 MHz, [D₆]DMSO ϩ TFA): δ (α anomer) ϭ

1.18Ϫ1.25 (m, 6 H, Ala-β-CH₃, Lac-β-CH₃), 1.76 (m, 1 H, Glu-β-

CH₂), 1.78 (s, 3 H, NHAc), 1.98 (m, 1 H, Glu-β-CH₂), 2.24 (m, 2

3

H, Glu-γ-CH₂), 3.25 (t, J_3,4ഠ J_4,5ϭ 9.2 Hz, 1 H, 4-H), 3.45 (t,

3

2

³J_2,3

ഠ ϭ

³J_3,4ϭ 8.9 Hz, 1 H, 3-H), 3.50 (dd, J_5,6ϭ 5.8, J_6,6Ј

(b) From 18: The Z-protected dimethyl glutamate (100 mg,

0.26 mmol) was hydrogenated (Procedure A) and coupled with the

free acid 18 (156 mg, 0.29 mmol) according to Procedure B. Extrac-

tive workup and purification of the crude product by flash chroma-

tography (SiO₂, toluene/acetone ϭ 5:2) afforded 37 (168 mg,

0.24 mmol, 92%) as a colorless foam. TLC (SiO₂): R_fϭ 0.34 (tolu-

ene/acetone ϭ 3:2). [α]_Dϭ Ϫ2.6 (c ϭ 1, MeOH). ¹H NMR

(600 MHz, CDCl₃): δ ϭ 0.08, 0.10 [2s, 6 H, Si(CH₃)₂], 0.81Ϫ0.85

(m, 12 H, 4 CH₃), 1.34Ϫ1.41 [m, 9 H, Lac-β-CH₃, Ala-β-CH₃,

C(CH₃)₂], 1.48 [s, 3 H, C(CH₃)₂], 1.56Ϫ1.61 [m, 1 H, CH(CH₃)₂],

1.92 (s, 3 H, NHAc), 1.97Ϫ2.03, 2.18Ϫ2.24 (2m, 2 H, Glu-β-CH₂),

12.2 Hz, 1 H, 6-H), 3.59Ϫ3.61 (m, 2 H, 5-H, 6Ј-H), 3.66Ϫ3.67 (m,

3

1 H, 2-H), 4.20Ϫ4.23 (m, 1 H, Glu-α-H), 4.28 (q, J_α,βϭ 6.7 Hz,

3

1 H, Lac-α-H), 4.33Ϫ4.34 (m, 1 H, Ala-α-H), 4.97 (d, J_1,2

ϭ

3

3.3 Hz, 1 H, 1-H), 7.58 (d, J_α,NHϭ 7.8 Hz, 1 H, Ala-NH), 8.02

3

(d, J_2,NHϭ 7.9 Hz, 1 H, NHAc), 8.22 (d, J_α,NHϭ 8.0 Hz, 1 H,

Glu-NH) ppm. ¹³C NMR (150.8 MHz, [D₆]DMSO ϩ TFA): δ ϭ

19.07, 19.13 (2C, Ala-β-C, Lac-β-C), 22.7 [1C, NHC(O)CH₃], 26.6

(1C, Glu-β-C), 30.0 (1C, Glu-γ-C), 47.8 (1C, Ala-α-C), 51.1 (1C,

Glu-α-C), 53.7 (1C, 2-C), 61.0 (1C, 6-C), 70.2 (1C, 4-C), 72.4 (1C,

5-C), 76.4 (1C, Lac-α-C), 78.9 (1C, 3-C), 90.7 (1C, 1-C), 196.6,

172.2, 172.7, 173.2, 173.7 [5C, NHC(O)CH₃, 2 C(O)NH, 2 CO₂H]

ppm. FAB MS (positive mode, glycerol, DMSO): m/z ϭ 494 [M Ϫ

2.34Ϫ2.41 (m, 2 H, Glu-γ-CH₂), 3.27Ϫ3.32 (m, 2 H, 2-H, 5-H),

3

3.59 (t, J_3,4

ഠ

³J_4,5ϭ 9.1 Hz, 1 H, 4-H), 3.66, 3.72 (2s, 6 H, 2

2

ϩ

2NH₄ϩ 3H^ϩ]^ϩ, 516 [M Ϫ 2NH₄ϩ 2H^ϩϩ Na^ϩ]^ϩ, 626 [M Ϫ

OCH₃), 3.74Ϫ3.76 (m, 1 H, 6-H), 3.83Ϫ3.86 (dd, J_6,6Јϭ 10.8,

³J_5,6ϭ 5.4 Hz, 1 H, 6Ј-H), 3.95 (t, J_2,3ഠ J_3,4ϭ 9.1 Hz, 1 H, 3-

3

2NH₄ϩ 2H^ϩϩ Cs^ϩ]^ϩ; calcd. 527.5 for C₁₉H₃₇N₅O₁₂.

ϩ

3

H), 4.15 (q, J_α,βϭ 6.7 Hz, 1 H, Lac-α-H), 4.40 (dq, J_α,β

ഠ

³J_α,NHϭ 7.0 Hz, 1 H, Ala-α-H), 4.55Ϫ4.59 (m, 1 H, Glu-α-H), Thexyldimethylsilyl 2-Acetamido-2-deoxy-4,6-O-isopropylidene-3-

3

5.04 (d, J_1,2ϭ 7.8 Hz, 1 H, 1-H), 6.10 (d, J_NH,2ϭ 7.8 Hz, 1 H,

O-{(2R)-propionyl-[

L

-alanyl-

D-isoglutamine γ-tert-butyl ester]-2-yl}-

NHAc), 6.97 (d, ³J_NH,αϭ 7.8 Hz, 1 H, Glu-NH), 7.29 (d, ³J_NH,αϭ β-

D-glucopyranoside (40): The glutamine 28 (91 mg, 0.27 mmol) was

7.0 Hz, 1 H, Ala-NH) ppm. ¹³C NMR (150.8 MHz, CDCl₃): δ ϭ hydrogenated (Procedure A) and coupled with the free acid 18

Ϫ3.5, Ϫ1.9 [2C, Si(CH₃)₂], 17.9, 18.5, 19.0, 19.5, 19.9, 20.0 [7C, (148 mg, 0.27 mmol) according to Procedure B. Flash chromato-

CCH₃, Ala-β-C, Lac-β-C, C(CH₃)₂CH(CH₃)₂], 23.8 [1C, graphy (SiO₂, toluene/acetone

NHC(O)CH₃], 24.7 [1C, C(CH₃)₂CH(CH₃)₂], 27.0 (1C, Glu-β-C), 0.24 mmol, 89%) as a colorless solid. TLC (SiO₂): R_fϭ 0.58

29.1 (1C, CCH₃),

29.9 (1C, Glu-γ-C), 34.0 [1C, (EtOAc/MeOH ϭ 9:1). [α]_Dϭ Ϫ3.7 (c ϭ 1, MeOH). ¹H NMR

ϭ 1:1) afforded 40 (176 mg,

C(CH₃)₂CH(CH₃)₂], 48.9 (1C, Ala-α-C), 51.7 (1C, Glu-α-C), 51.9, (600 MHz, [D₆]DMSO): δ ϭ 0.07, 0.08 [2s, 6 H, Si(CH₃)₂], 0.76 (s,

52.6 (2C, 2 OCH₃), 59.9 (1C, 2-C), 62.2 (1C, 6-C), 66.7 (1C, 5-C), 6 H, 2 CH₃), 0.80 [d, ³J ϭ 7.2 Hz, 6 H, CH(CH₃)2], 1.20 (d, ³J_α,βϭ

3

74.9 (1C, 4-C), 77.9 (1C, Lac-α-C), 79.2 (1C, 3-C), 95.1 (1C, 1-C), 6.6 Hz, 3 H, Lac-β-CH₃), 1.25 (d, J_α,β, 3 H, Ala-β-CH₃), 1.31 [s,

99.3 (1C, CCH₃), 170.8 [1C, NHC(O)CH₃], 172.0, 172.2, 173.1, 3 H, C(CH₃)₂], 1.37 [s, 9 H, C(CH₃)₃], 1.45 [s, 3 H, C(CH₃)₂], 1.53

3

173.8 ]4C, 2 C(O)NH, 2 CO₂CH₃] ppm. C₃₂H₅₇N₃O₁₂Si (703.9): [quint, J ϭ 7.2 Hz, 1 H, CH(CH₃)₂], 1.54Ϫ1.71 (m, 1 H, Glu-β-

calcd. C 54.60, H 8.16, N 5.97; found C 54.27, H 8.21, N 6.02.

CH₂), 1.76 (s, 3 H, NHAc), 1.86Ϫ1.95 (m, 1 H, Glu-β-CH₂), 2.17

(t, ³J_β,γϭ 8.2 Hz, 2 H, Glu-γ-CH₂), 3.18Ϫ3.21 (m, 1 H, 5-H), 3.41

(t, ³J_2,3ഠ ³J_3,4ϭ 9.4 Hz, 1 H, 3-H), 3.60 (t, ³J_3,4ഠ ³J_4,5ϭ 9.2 Hz,

Ammonium N-Acetylmuramyl- -alanine (38): The free acid 18

L

(127 mg, 0.23 mmol) was treated with TFA/dioxane/H₂O (15 mL)

according to Procedure E. The crude product was purified by gel

chromatography (t_Rϭ 46.2 min) to afford 38 (80 mg, 0.21 mmol,

90%) as a light yellow lyophilizate (from water). TLC (RP-18): R_fϭ

3

1 H, 4-H), 3.64Ϫ3.68 (m, 1 H, 2-H), 3.72 (t, J_6,6Јϭ 10.8, J_5,6

ϭ

10.3 Hz, 1 H, 6-H), 3.76 (dd, ²J_6,6Јϭ 10.8, ³J_5,6Јϭ 6.0 Hz, 1 H, 6Ј-

3

H), 3.97 (q, J_α,βϭ 6.6 Hz, 1 H, Lac-α-H), 4.10Ϫ4.14 (m, 1 H,

3

Glu-α-H), 4.23 (dq, J_α,βഠ J_α,NHϭ 6.6 Hz, 1 H, Ala-α-H), 4.63

1

0.83 (MeCN/H₂O/TFA ϭ 6:1:1). [α]_Dϭ ϩ18.2 (c ϭ 0.5, H₂O). H

3

(d, J_1,2ϭ 7.9 Hz, 1 H, 1-H), 7.06 [s, 1 H, C(O)NH₂], 7.24 (d,

NMR (600 MHz, [D₆]DMSO ϩ TFA): δ (α anomer) ϭ 1.20Ϫ1.30

(m, 6 H, Lac-β-CH₃, Ala-β-CH₃), 1.79 (s, 3 H, NHAc), 3.27 (t,

³J_NH,αϭ 6.8 Hz, 1 H, Ala-NH), 7.28 [s, 1 H, C(O)NH₂], 7.83 (d,

3

³J_2,NHϭ 9.3 Hz, 1 H, NHAc), 8.06 (d, J_NH,αϭ 8.2 Hz, 1 H, Glu-

3

³J_3,4ഠ J_4,5ϭ 9.2 Hz, 1 H, 4-H), 3.44 (t, J_2,3ഠ J_3,4ϭ 8.8 Hz, 1

NH) ppm. FAB MS (positive mode, NBA, glycerol, dioxane):

m/z ϭ 731 [M ϩ H]^ϩ, 753 [M ϩ Na]^ϩ; calcd. 731.0 for

C₃₄H₆₂N₄O₁₁Si.

3

2

H, 3-H), 3.51 (dd, J_5,6ϭ 5.7, J_6,6Јϭ 12.2 Hz, 1 H, 6-H),

3.59Ϫ3.65 (m, 3 H, 2-H, 5-H, 6Ј-H), 4.19Ϫ4.23 (m, 1 H, Ala-α-H),

3

4.31 (q, J_α,βϭ 6.7 Hz, 1 H, Lac-α-H), 4.42 (d, J_1,2ϭ 8.2 Hz, 0.9

3

H, 1-H_β), 5.01 (d, J_1,2ϭ 3.4 Hz, 0.1 H, 1-H_α), 7.70 (d, J_α,NH

ϭ

Ammonium N-Acetyl-muramyl-L-alanyl-D-isoglutaminate (41):

7.5 Hz, 1 H, Ala-NH), 8.09 (d, ³J_2,NHϭ 7.5 Hz, 1 H, NHAc) ppm.

¹³C NMR (150.8 MHz, [D₆]DMSO ϩ TFA): δ ϭ 17.4 (1C, Ala-β-

C), 19.2 (1C, Lac-β-C), 22.8 [1C, NHC(O)CH₃], 47.4 (1C, Ala-α-

C), 53.8 (1C, 2-C), 61.0 (1C, 6-C), 70.3 (1C, 4-C), 72.4 (1C, 5-C),

76.2 (1C, Lac-α-C), 78.7 (1C, 3-C), 90.6 (1C, 1-C), 169.8, 174.0 [3C,

OC(O)NH, NHC(O)CH₃, CO₂H] ppm. FAB MS (positive mode,

Compound 40 (70 mg, 96 µmol) was treated with TFA/dioxane/

H₂O (10 mL) according to Procedure E and then purified by gel

chromatography (t_Rϭ 49.8 min). To remove remaining minor im-

purities, the crude product was subjected to HPLC (flow rate:

10 mL/min; A: 0.1% TFA, B: MeCN ϩ 0.1% TFA, gradient:

0Ϫ10 min: 99% A, 10Ϫ30 min: 99Ϫ90% A, 30Ϫ40 min: 90Ϫ5% A;

glycerol, DMSO): m/z ϭ 365 [M Ϫ NH₄ϩ H^ϩ]^ϩ, 387 [M Ϫ

ϩ

detection: UV 230 nm). The product eluted in two fractions (t_R

ϭ

NH₄ϩ Na^ϩ]^ϩ; calcd. 381.4 for C₁₄H₂₇N₃O₉.

ϩ

14.9 min; t_Rϭ 24.2 min), which were identified by MALDI-MS

and NMR spectroscopy. Repeated lyophilization from NH₄HCO₃

buffer (30 m) and H₂O afforded 41 (33 mg, 65 µmol, 68%) as a

Diammonium N-Acetyl-muramyl-L-alanyl-D-glutamate (39): A solu-

tion of 37 (70 mg, 99 µmol) in dioxane/MeOH (15 mL) was saponi-

Eur. J. Org. Chem. 2002, 2710Ϫ2726

2721

N. Kubasch, R. R. Schmidt

FULL PAPER

light yellow lyophilizate. TLC (RP18): R_fϭ 0.37 (MeCN/H₂O/

Lys-δ-CH₂), 1.70 (m, 1 H, Lys-β-CH₂), 1.75Ϫ1.79 (m, 1 H, Glu-β-

1

TFA ϭ 8:1:1). [α]_Dϭ ϩ20.2 (c ϭ 0.5, H₂O). H NMR (600 MHz, CH₂), 1.79 (s, 3 H, NHAc), 1.96 (m, 1 H, Glu-β-CH₂), 2.18 (t,

3

[D₆]DMSO ϩ TFA): δ (α anomer) ϭ 1.22 (d, J_α,βϭ 7.0 Hz, 3 H, ³J_β,γϭ 7.7 Hz, 2 H, Glu-γ-CH₂), 2.75 (m, 2 H, Lys-ε-CH₂), 3.25

3

Ala-β-CH₃), 1.24 (d, J_α,βϭ 6.7 Hz, 3 H, Lac-β-CH₃), 1.70, 1.95 (t, ³J_3,4ഠ ³J_4,5ϭ 9.1 Hz, 1 H, 4-H), 3.46 (t, ³J_2,3ഠ ³J_3,4ϭ 8.9 Hz,

(2m, 2 H, Glu-β-CH₂), 1.78 (s, 3 H, NHAc), 2.20 (t, ³J_β,γϭ 7.8 Hz,

1 H, 3-H), 3.51 (dd, J_5,6ϭ 5.5, J_6,6Јϭ 12.0 Hz, 1 H, 6-H),

3

2

3

2 H, Glu-γ-CH₂), 3.26 (t, J_3,4ഠ J_4,5ϭ 9.2 Hz, 1 H, 4-H), 3.44 3.60Ϫ3.62 (m, 2 H, 5-H, 6Ј-H), 3.69 (m, 1 H, 2-H), 4.15Ϫ4.19 (m,

3

2

3

(t, J_2,3ഠ J_3,4ϭ 8.9 Hz, 1 H, 3-H), 3.50 (dd, J_5,6ϭ 5.5, J_6,6Ј

ϭ

2 H, Glu-α-H, Lys-α-H), 4.27 (q, J_α,βϭ 6.6 Hz, 1 H, Lac-α-H),

3

12.2 Hz, 1 H, 6-H), 3.59Ϫ3.61 (m, 2 H, 5-H, 6Ј-H), 3.67 (m, 1 H,

4.35Ϫ4.38 (m, 1 H, Ala-α-H), 4.96 (d, J_1,2ϭ 3.5 Hz, 1 H, 1-H),

2-H), 4.14Ϫ4.17 (m, 1 H, Glu-α-H), 4.26Ϫ4.28 (m, 2 H, Lac-α-H,

7.56 (d, ³J_α,NHϭ 7.9 Hz, 1 H, Ala-NH), 7.63 (s, 3 H, Lys-ε-NH₃^ϩ),

3

Ala-α-H), 4.97 (d, J_1,2ϭ 3.1 Hz, 1 H, 1-H), 7.00, 7.28 [2s, 2 H,

8.03 (d, J_2,NHϭ 8.1 Hz, 1 H, NHAc), 8.07 (d, J_α,NHϭ 7.9 Hz, 1

3

C(O)NH₂], 7.61 (d, J_α,NHϭ 6.9 Hz, 1 H, Ala-NH), 8.00 (d, H, Lys-α-NH), 8.25 (d, J_α,NHϭ 7.8 Hz, 1 H, Glu-NH) ppm. ¹³C

3

³J_2,NHϭ 7.9 Hz, 1 H, NHAc), 8.10 (d, J_α,NHϭ 8.2 Hz, 1 H, Glu- NMR (150.8 MHz, [D₆]DMSO ϩ TFA): δ ϭ 19.1, 19.2 (2C, Ala-

NH) ppm. ¹³C NMR (150.8 MHz, [D₆]DMSO ϩ TFA): δ ϭ 18.3 β-C, Lac-β-C), 22.5 (1C, Lys-γ-C), 22.7 [1C, NHC(O)CH₃], 26.7

(1C, Ala-β-C), 19.1 (1C, Lac-β-C), 22.7 [1C, NHC(O)CH₃], 27.1 (1C, Lys-δ-C), 27.4 (1C, Glu-β-C), 30.6 (1C, Lys-β-C), 31.6 (1C,

(1C, Glu-β-C), 30.1 (1C, Glu-γ-C), 48.2 (1C, Ala-α-C), 51.7 (1C,

Glu-α-C), 53.6 (1C, 2-C), 60.9 (1C, 6-C), 70.0 (1C, 4-C), 72.3 (1C,

Glu-γ-C), 38.9 (1C, Lys-ε-C), 47.7 (1C, Ala-α-C), 51.7 (1C, Glu-α-

C), 53.8 (1C, 2-C), 61.1 (1C, 6-C), 70.0 (1C, 4-C), 72.4 (1C, 5-C),

5-C), 76.2 (1C, Lac-α-C), 78.8 (1C, 3-C), 90.6 (1C, 1-C), 169.5, 76.5 (1C, Lac-α-C), 78.9 (1C, 3-C), 90.8 (1C, 1-C), 169.8, 171.6,

172.1, 173.1, 173.8 [5C, NHC(O)CH₃, 2 C(O)NH, C(O)NH₂, 172.7, 173.3, 173.8 [6C, NHC(O)CH₃, 3 C(O)NH, 2 CO₂H] ppm.

CO₂H] ppm. FAB MS (positive mode, glycerol, AcOH/H₂O ϭ 1:1):

FAB MS (positive mode, glycerol, AcOH/H₂O ϭ 1:1): m/z ϭ 622

m/z ϭ 493 [M Ϫ NH₄^ϩϩ H^ϩ]^ϩ, 515 [M Ϫ NH₄^ϩϩ Na^ϩ]^ϩ; calcd. [M Ϫ NH₄ϩ H^ϩ]^ϩ, 644 [M Ϫ NH₄ϩ Na^ϩ]^ϩ; calcd. 638.7

ϩ

509.5 for C₁₉H₃₅N₅O₁₁.

for C₂₅H₄₆N₆O₁₃.

Thexyldimethylsilyl 2-Acetamido-2-deoxy-4,6-O-isopropylidene-3-

D

-isoglutamyl α-methyl ester-N^ε-(tert-

Thexyldimethylsilyl 2-Acetamido-2-deoxy-4,6-O-isopropylidene-3-

O-{(2R)-propionyl-[L-alanyl-

O-{(2R)-propionyl-[

methyl)-1-(2-trimethylsilylethyl)

bonyl)-2,6-diaminopimelate]-2-yl}-β-

L

-alanyl-(

D

-isoglutamyl

α-methyl

ester)-(7-

butyloxycarbonyl)-D-lysine α-methyl ester]-2-yl}-β-L-glucopyrano-

(2S,6R)-N^ε-(tert-butyloxycar-

D-glucopyranoside (44): The di-

side (42): The dipeptide 30 (145 mg, 0.27 mmol) was coupled with

the free acid 18 (148 mg, 0.27 mmol) according to Procedures A

and B. Purification of the crude product by flash chromatography

(SiO₂, toluene/acetone ϭ 1:1) afforded 42 (210 mg, 0.23 mmol,

85%) as a colorless solid. TLC (SiO₂): R_fϭ 0.34 (toluene/acetone ϭ

peptide 31a (75 mg, 0.11 mmol) was hydrogenated (Procedure A)

and coupled with the free acid 18 (58 mg, 0.11 mmol) (Procedure

B). Purification of the crude product by flash chromatography

(SiO₂, toluene/acetone ϭ 1:1) afforded 44 (99 mg, 0.09 mmol, 84%)

as a colorless, waxy solid. TLC (SiO₂): R_fϭ 0.46 (toluene/acet-

one ϭ 1:1). [α]_Dϭ Ϫ6.1 (c ϭ 1, MeOH). ¹H NMR (600 MHz,

[D₆]DMSO): δ ϭ 0.01 [s, 9 H, Si(CH₃)₃], 0.07, 0.08 [2s, 6 H,

Si(CH₃)₂], 0.76 (s, 6 H, 2 CH₃), 0.80 [d, ³J ϭ 6.8 Hz, 6 H,

CH(CH₃)₂], 0.92 [t, ³J ϭ 8.4 Hz, 2 H, OCH₂CH₂Si(CH₃)₃], 1.20

1:1). [α]_D

ϭ Ϫ3.3 (c ϭ

1, MeOH). ¹H NMR (600 MHz,

[D₆]DMSO): δ ϭ 0.07, 0.08 [2s, 6 H, Si(CH₃)₂], 0.76 (s, 6 H, 2

3

CH₃), 0.80 [d, J ϭ 6.8 Hz, 6 H, CH(CH₃)₂], 1.13Ϫ1.26 (m, 8 H,

Lac-β-CH₃, Ala-β-CH₃, Lys-γ-CH₂), 1.30 [s, 3 H, C(CH₃)₂],

1.31Ϫ1.34 (m, 2 H, Lys-δ-CH₂), 1.35 [s, 9 H, C(CH₃)₃], 1.46 [s, 3

H, C(CH₃)₂], 1.52Ϫ1.55 [m, 2 H, CH(CH₃)₂, Lys-β-CH₂], 1.63 (m,

1 H, Lys-β-CH₂), 1.75 (s, 3 H, NHAc), 1.92 (m, 2 H, Glu-β-CH₂),

3

(d, J_α,βϭ 6.7 Hz, 3 H, Lac-β-CH₃), 1.25 (d, J_α,βϭ 6.9 Hz, 3 H,

Ala-β-CH₃), 1.30 [s, 3 H, C(CH₃)₂], 1.31 (m, 2 H, DAP-4-CH₂),

1.36 [s, 9 H, C(CH₃)₃], 1.45 [s, 3 H, C(CH₃)₂], 1.52Ϫ1.62 [2m, 5 H,

DAP-3-CH₂, DAP-5-CH₂, CH(CH₃)₂], 1.75 (s, 3 H, NHAc), 1.76,

3

2.16 (t, J_β,γϭ 7.8 Hz, 2 H, Glu-γ-CH₂), 2.85Ϫ2.87 (m, 2 H, Lys-

3

ε-CH₂), 3.19Ϫ3.22 (m, 1 H, 5-H), 3.41 (t, J_2,3ഠ J_3,4ϭ 8.6 Hz, 1

H, 3-H), 3.59Ϫ3.61 (m, 1 H, 4-H), 3.60, 3.62 (2s, 6 H, 2 OCH₃),

3

2

ഠ

³J_5,6ϭ 10.3 Hz, 1 H, 6-H),

1.93 (2m, 2 H, Glu-β-CH₂), 2.16 (t, J_β,γϭ 7.5 Hz, 2 H, Glu-γ-

3.65 (m, 1 H, 2-H), 3.72 (t, J_6,6Ј

3

CH₂), 3.19 (m, 1 H, 5-H), 3.42 (t, J_2,3ഠ J_3,4ϭ 9.3 Hz, 1 H, 3-

H), 3.59, 3.61 (2s, 6 H, 2 OCH₃), 3.59Ϫ3.66 (m, 2 H, 2-H, 4-H),

3.71Ϫ3.80 (m, 2 H, 6-H, 6Ј-H), 3.91 (m, 1 H, DAP-6-H), 3.98 (q,

3.74Ϫ3.77 (m, 1 H, 6Ј-H), 3.98 (q, J_α,βϭ 6.6 Hz, 1 H, Lac-α-H),

3

4.16 (m, 1 H, Lys-α-H), 4.21 (m, 1 H, Glu-α-H), 4.32 (dq, J_α,β

ഠ

³J_α,NHϭ 7.3 Hz, 1 H, Ala-α-H), 4.62 (d, J_1,2ϭ 8.0 Hz, 1 H, 1-

3

³J_α,βϭ 6.7 Hz, 1 H, Lac-α-H), 4.08Ϫ4.14 [m, 3 H, DAP-2-H,

H), 6.74 (br. t, 1 H, Lys-ε-NH), 7.21 (d, ³J_NH,αϭ 7.8 Hz, 1 H, Ala-

3

OCH₂CH₂Si(CH₃)₃], 4.21 (m, 1 H, Glu-α-H), 4.33 (dq, J_α,β

ഠ

NH), 7.80 (d, J_2,NHϭ 9.6 Hz, 1 H, NHAc), 8.18 (d, J_NH,α

ϭ

³J_α,NHϭ 7.2 Hz, 1 H, Ala-α-H), 4.62 (d, J_1,2ϭ 7.8 Hz, 1 H, 1-

3

7.8 Hz, 1 H, Lys-α-NH), 8.37 (d, J_NH,αϭ 7.8 Hz, 1 H, Glu-NH)

ppm. FAB MS (positive mode, NBA, glycerol, dioxane): m/z ϭ 932

[M ϩ H]^ϩ, 954 [M ϩ Na]^ϩ; calcd. 932.2 for C₄₃H₇₇N₅O₁₅Si.

3

H), 7.17 (d, J_α,NHϭ 7.7 Hz, 1 H, Boc-NH), 7.22 (d, J_α,NH

ϭ

7.8 Hz, 1 H, Ala-NH), 7.79 (d, ³J_2,NHϭ 9.3 Hz, 1 H, NHAc), 8.15

(d, ³J_α,NHϭ 7.1 Hz, 1 H, DAP-2-NH), 8.36 (d, J_α,NHϭ 7.6 Hz, 1

3

Ammonium

N-Acetyl-muramyl-L-alanyl-(D-isoglutamyl)-L-lysine

H, Glu-NH) ppm. ¹³C NMR (150.8 MHz, [D₆]DMSO): δ ϭ Ϫ3.5,

(43): Compound 42 (69 mg, 74 µmol) was dissolved in dioxane/ Ϫ2.0 [2C, Si(CH₃)₂], Ϫ1.6 [3C, Si(CH₃)₃], 16.7 [1C, OCH₂CH₂S-

MeOH (10 mL) and saponified with 1  LiOH according to Pro- i(CH₃)₃], 18.3, 18.4, 18.9, 18.9, 19.0, 19.6, 19.7 [7C, CCH₃, Ala-

cedure D. The residue was treated with TFA/dioxane/H₂O (10 mL)

to remove the remaining protecting groups (Procedure E). The

crude product was purified by gel chromatography (t_Rϭ 41.4 min),

followed by HPLC as described for 41. The product eluted in two

fractions (t_Rϭ 25.0 min; t_Rϭ 28.4 min), which were lyophilized

β-C, Lac-β-C, C(CH₃)₂CH(CH₃)₂], 21.9 (1C, DAP-4-C), 23.0 [1C,

NHC(O)CH₃], 24.2 [1C, C(CH₃)₂CH(CH₃)₂], 26.9 (1C, Glu-β-C),

28.1 [3C, C(CH₃)₃], 28.9 (1C, CCH₃), 30.2, 30.3 (2C, DAP-3-C,

DAP-5-C), 31.1 (1C, Glu-γ-C), 33.4 [1C, C(CH₃)₂CH(CH₃)₂], 47.5

(1C, Ala-α-C), 51.5, 51.6, 51.8 (4C, Glu-α-C, DAP-2-C, 2 OCH₃),

repeatedly from NH₄HCO₃buffer (30 m) and H₂O to afford 43 53.2 (1C, DAP-6-C), 56.5 (1C, 2-C), 61.4 (1C, 6-C), 62.4 [1C,

(30 mg, 47 µmol, 64%) as a light yellow lyophilizate. TLC (RP-18): OCH₂CH₂Si(CH₃)₃], 66.6 (1C, 5-C), 73.4 (1C, 4-C), 77.1 (1C, Lac-

R_fϭ 0.44 (MeCN/H₂O/TFA ϭ 8:1:1). [α]_Dϭ ϩ5.6 (c ϭ 0.5 H₂O). α-C), 78.1 [1C, C(CH₃)₃], 79.5 (1C, 3-C), 96.4 (1C, 1-C), 98.8 (1C,

¹H NMR (600 MHz, [D₆]DMSO ϩ TFA): δ (α anomer) ϭ 1.22 (d,

³J_α,βϭ 7.0 Hz, 3 H, Ala-β-CH₃), 1.25 (d, ³J_α,βϭ 6.7 Hz, 3 H, Lac-

CCH₃), 155.4 (1C, 2 OC(O)NH), 169.1 [1C, NHC(O)CH₃], 171.2,

171.5 [2C, 2 C(O)NH], 172.0 [3C, 2 CO₂CH₃, CO₂(CH₂)₂Si(CH₃)₃],

β-CH₃), 1.33 (m, 2 H, Lys-γ-CH₂), 1.50Ϫ1.55 (m, 3 H, Lys-β-CH₂, 172.9 [1C, C(O)NH] ppm. FAB MS (positive mode, NBA,

2722 Eur. J. Org. Chem. 2002, 2710Ϫ2726

Synthesis of Muramyl Peptides Containing meso-Diaminopimelic Acid

FULL PAPER

glycerol): m/z ϭ 1098 [M ϩ Na]^ϩ. C₄₉H₈₉N₅O₁₇Si₂(1076.4): calcd.

H), 4.62 (d, J_1,2ϭ 7.9 Hz, 1 H, 1-H), 7.15 (d, J_α,NHϭ 7.6 Hz, 1

3

C 54.67, H 8.33, N 6.51; found C 54.69, H 8.15, N 6.04.

H, Boc-NH), 7.21 (d, J_α,NHϭ 7.8 Hz, 1 H, Ala-NH), 7.80 (d,

³J_2,NHϭ 9.3 Hz, 1 H, NHAc), 7.89 (d, ³J_α,NHϭ 8.1 Hz, 1 H, DAP-

3

Diammonium N-Acetyl-muramyl-L-alanyl-D-isoglutamyl-(2S,6R)-

2-NH), 8.31 (d, J_α,NHϭ 7.1 Hz, 1 H, -Ala-NH), 8.38 (d,

³J_α,NHϭ 7.6 Hz, 1 H, Glu-NH) ppm. ¹³C NMR (150.8 MHz,

[D₆]DMSO): δ ϭ Ϫ3.5, Ϫ2.0 [2C, Si(CH₃)₂], 17.0, 18.3, 18.4, 18.8,

18.9, 19.0, 19.7, 19.8 [8C, -Ala-β-C, Ala-β-C, Lac-β-C, CCH₃,

C(CH₃)₂CH(CH₃)₂], 21.7 (1C, DAP-4-C), 23.0 [1C, NHC(O)CH₃],

24.2 [1C, C(CH₃)₂CH(CH₃)₂], 27.1 (1C, Glu-β-C), 28.1 [3C,

C(CH₃)₃], 28.9 (1C, CCH₃), 30.3, 31.9 (2C, DAP-3-C, DAP-5-C),

31.2 (1C, Glu-γ-C), 33.4 [1C, C(CH₃)₂CH(CH₃)₂], 47.4 (1C, -Ala-

α-C), 47.6 (1C, Ala-α-C), 51.5, 51.6, 51.8 (5C, Glu-α-C, DAP-2-C,

3 OCH₃), 53.5 (1C, DAP-6-C), 56.5 (1C, 2-C), 61.4 (1C, 6-C), 66.6

(1C, 5-C), 73.4 (1C, 4-C), 77.1 (1C, Lac-α-C), 78.1 [1C, C(CH₃)₃],

79.5 (1C, 3-C), 96.4 (1C, 1-C), 98.8 (1C, CCH₃), 155.6 [1C,

2,6-diaminopimelate (45): A solution of 44 (30 mg, 28 µmol) in di-

oxane/MeOH (15 mL) was saponified with 1  LiOH according to

Procedure D. The residue was treated with a TFA/dioxane/H₂O

mixture (10 mL) according to Procedure E to remove the remaining

protecting groups. After completion of the reaction (as determined

by NMR spectroscopy) and removal of the solvent, the crude prod-

uct was purified by gel chromatography (t_Rϭ 45.5 min). The frac-

tions containing the product (as judged by MALDI) were concen-

trated to a volume of 3Ϫ4 mL and lyophilized several times from

H₂O to afford 45 (16 mg, 23 µmol, 83%) as a colorless lyophilizate.

TLC (RP18): R_fϭ 0.17 (MeCN/H₂O ϭ 4:1). [α]_Dϭ ϩ6.6 (c ϭ 0.5,

1

H₂O). H NMR (600 MHz, [D₆]DMSO ϩ TFA): δ (α anomer) ϭ

OC(O)NH], 169.2 [1C, NHC(O)CH₃], 170.9, 171.4 [2C,

2

3

1.22 (d, J_α,βϭ 6.8 Hz, 3 H, Ala-β-CH₃), 1.24 (d, J_α,βϭ 6.6 Hz,

3 H, Lac-β-CH₃), 1.38Ϫ1.42 (m, 2 H, DAP-4-CH₂), 1.54Ϫ1.56 (m,

1 H, DAP-3-CH₂), 1.71Ϫ1.76 (m, 4 H, DAP-3-CH₂, DAP-5-CH₂,

Glu-β-CH₂), 1.78 (s, 3 H, NHAc), 1.93Ϫ1.96 (m, 1 H, Glu-β-CH₂),

C(O)NH], 172.1 (3C, 3 CO₂CH₃), 172.8, 173.1 [2C, 2 C(O)NH]

ppm. FAB MS (positive mode, NBA, glycerol): m/z ϭ 1083 [M ϩ

Na]^ϩ. C₄₈H₈₄N₆O₁₈Si·H₂O (1079.3): calcd. C 53.41, H 8.03, N

7.79; found C 53.72, H 7.91, N 7.59.

3

2.15Ϫ2.21 (m, 2 H, Glu-γ-CH₂), 3.25 (t, J_3,4ഠ J_4,5ϭ 9.0 Hz, 1

H, 4-H), 3.45 (t, ³J_2,3ഠ ³J_3,4ϭ 9.1 Hz, 1 H, 3-H), 3.50 (dd, ³J_5,6ϭ

Diammonium N-Acetylmuramyl-

-alanine (47): A solution of 46 (60 mg, 57 µmol)

1 H, 2-H), 3.88 (m, 1 H, DAP-6-H), 4.12Ϫ4.21 (m, 2 H, Glu-α-H, in dioxane/MeOH (16 mL) was saponified with 1  LiOH (Proced-

L-alanyl-D-isoglutamyl-(2S,6S)-2,6-

5.7, ²J_6,6Јϭ 11.7 Hz, 1 H, 6-H), 3.61 (m, 2 H, 5-H, 6Ј-H), 3.68 (m, diaminopimelyl-

D

3

DAP-2-H), 4.27 (q, J_α,βϭ 6.7 Hz, 1 H, Lac-α-H), 4.34Ϫ4.38 (m,

ure D). The residue was treated with TFA/dioxane/H₂O (15 mL)

1 H, Ala-α-H), 4.95 (d, ³J_1,2ϭ 3.4 Hz, 1 H, 1-H), 7.55 (d, ³J_α,NHϭ according to Procedure E. Purification of the crude product by gel

8.0 Hz, 1 H, Ala-NH), 8.02 (d, ³J_2,NHϭ 8.1 Hz, 1 H, NHAc), 8.10

(d, ³J_α,NHϭ 7.9 Hz, 1 H, DAP-2-NH), 8.18 (br. d, ³J_α,NHϭ 5.1 Hz,

chromatography (t_Rϭ 41.2 min) afforded 47 (33 mg, 43 µmol,

76%) as a colorless lyophilizate (from water). TLC (RP-18): R_fϭ

1

1 H, DAP-6-NH₃^ϩ), 8.27 (d, ³J_α,NHϭ 7.9 Hz, 1 H, Glu-NH) ppm. 0.21 (MeCN/H₂O ϭ 4:1). [α]_Dϭ ϩ2.6 (c ϭ 0.5, H₂O). H NMR

¹³C NMR (150.8 MHz, [D₆]DMSO ϩ TFA): δ ϭ 19.4 (1C, Ala-β- (600 MHz, [D₆]DMSO ϩ TFA): δ (α anomer) ϭ 1.99Ϫ1.25 (m, 9

C), 19.5 (1C, Lac-β-C), 21.5 (1C, DAP-4-C), 23.1 [1C,

H, Lac-β-CH₃, Ala-β-CH₃, -Ala-β-CH₃), 1.36 (m, 2 H, DAP-4-

NHC(O)CH₃], 27.7 (1C, Glu-β-C), 30.0 (1C, DAP-5-C), 30.9 (1C, CH₂), 1.49, 1.63 (2m, 2 H, DAP-3-CH₂), 1.69Ϫ1.82 (m, 3 H, DAP-

DAP-3-C), 31.9 (1C, Glu-γ-C), 48.0 (1C, Ala-α-C), 52.0 (2C, Glu- 5-CH₂, Glu-β-CH₂), 1.78 (s, 3 H, NHAc), 1.98 (m, 1 H, Glu-β-

3

α-C, DAP-2-C), 52.2 (1C, DAP-6-C), 54.1 (1C, 2-C) 61.3 (1C, 6-

C), 70.4 (1C, 4-C), 72.7 (1C, 5-C), 76.7 (1C, Lac-α-C), 79.2 (1C, 3-

CH₂), 2.17 (m, 2 H, Glu-γ-CH₂), 3.25 (t, J_3,4ഠ J_4,5ϭ 9.1 Hz, 1

H, 4-H), 3.45 (t, ³J_2,3ഠ ³J_3,4ϭ 9.1 Hz, 1 H, 3-H), 3.51 (dd, ³J_5,6ϭ

C), 91.0 (1C, 1-C), 169.9, 171.4, 171.9, 172.4, 172.9, 173.5, 173.9 5.2, ²J_6,6Јϭ 11.9 Hz, 1 H, 6-H), 3.61 (m, 2 H, 5-H, 6Ј-H), 3.69 (m,

[7C, NHC(O)CH₃, 3 C(O)NH, 3 CO₂H] ppm. FAB MS (positive

mode, glycerol, DMSO): m/z ϭ 666 [M Ϫ 2NH₄^ϩϩ 3H^ϩ]^ϩ; calcd.

699.7 for C₂₆H₄₉N₇O₁₅.

1 H, 2-H), 3.84 (m, 1 H, DAP-6-H), 4.17Ϫ4.22 (m, 2 H, Ala-α-H,

Glu-α-H), 4.26Ϫ4.29 (m, 2 H, Lac-α-H, DAP-2-H), 4.32Ϫ4.38 (m,

3

1 H, -Ala-α-H), 4.96 (d, J_1,2ϭ 3.0 Hz, 1 H, 1-H), 7.56 (d,

3

³J_α,NHϭ 7.8 Hz, 1 H, -Ala-NH), 7.94 (d, J_α,NHϭ 8.1 Hz, 1 H,

3

Thexyldimethylsilyl 2-Acetamido-2-deoxy-4,6-O-isopropylidene-3-

DAP-2-NH), 8.04 (d, J_2,NHϭ 8.0 Hz, 1 H, NHAc), 8.13 (d,

³J_α,NHϭ 7.2 Hz, 1 H, Ala-NH), 8.18 (br. s, 3 H, DAP-6-NH₃^ϩ),

O-(2R)-propionyl-[

methyl)-1-(2-trimethylsilylethyl)-{(2S,6R)-N^ε-(tert-butyloxy-

carbonyl)-2,6-diaminopimelyl)-( -alanine methyl ester)]-2-yl}-β-D-

L-alanyl-(D-isoglutamyl

α-methyl

ester)-(7-

3

8.26 (d, J_α,NHϭ 7.8 Hz, 1 H, Glu-NH) ppm. ¹³C NMR

D

(150.8 MHz, [D₆]DMSO ϩ TFA): δ ϭ 17.4, 19.08, 19.14 (3C, Lac-

β-C, Ala-β-C, -Ala-β-C), 20.9 (1C, DAP-4-C), 21.1 [1C,

NHC(O)CH₃], 27.5 (1C, Glu-β-C), 29.8 (1C, DAP-5-C), 31.7 (1C,

Glu-γ-C), 31.9 (1C, DAP-3-C), 47.6 (1C, Ala-α-C), 47.8 (1C, -

Ala-α-C), 51.7 (1C, Glu-α-C), 52.0 (2C, DAP-2-C, DAP-6-C), 53.8

(1C, 2-C), 61.0 (1C, 6-C), 70.0 (1C, 4-C), 72.4 (1C, 5-C), 76.6 (1C,

Lac-α-C), 79.1 (1C, 3-C), 90.7 (1C, 1-C), 169.7, 171.2, 171.4, 171.5,

172.2, 172.3, 172.7, 173.3, 174.1 [8C, NHC(O)CH₃, 4 C(O)NH, 3

CO₂H] ppm. FAB MS (positive mode, glycerol, MeCN/0.1%

glucopyranoside (46): The tripeptide 35 (150 mg, 0.23 mmol) was

hydrogenated (Procedure A) and coupled with compound 18

(130 mg, 0.23 mmol) according to Procedure B. Purification of the

crude product by flash chromatography (SiO₂, toluene/ethanol/

acetone ϭ 8:2:1) and MPLC (25 ϫ 1.6 cm, toluene/acetone ϭ 1:1.1)

afforded 46 (219 mg, 0.21 mmol, 90%) as a light yellow solid. TLC

(SiO₂): R_fϭ 0.40 (toluene/acetone ϭ 1:1). [α]_Dϭ ϩ4.9 (c ϭ 1,

MeOH). ¹H NMR (600 MHz, [D₆]DMSO): δ ϭ 0.07, 0.08 [2s, 6

H, Si(CH₃)₂], 0.76 (s, 6 H, 2 CH₃), 0.80 [d, ³J ϭ 6.8 Hz, 6 H,

TFA ϭ 1:1): m/z ϭ 737 [M Ϫ 2NH₄ϩ 3H^ϩ]^ϩ, 759 [M Ϫ 2NH₄

ϩ

3

ϩ 2H^ϩϩ Na^ϩ]^ϩ, 775 [M Ϫ 2NH₄ϩ 2H^ϩϩ K^ϩ]^ϩ, 869 [M Ϫ

ϩ

CH(CH₃)₂], 1.20 (d, J_α,βϭ 6.7 Hz, 3 H, Lac-β-CH₃), 1.20Ϫ1.27

2NH₄ϩ 2H^ϩϩ Cs^ϩ]^ϩ; calcd. 770.8 for C₂₉H₅₄N₈O₁₆.

ϩ

(m, 8 H, Ala-β-CH₃, -Ala-β-CH₃, DAP-4-CH₂), 1.30 [s, 3 H,

C(CH₃)₂], 1.36 [s, 9 H, C(CH₃)₃], 1.45 [s, 3 H, C(CH₃)₂], 1.52Ϫ1.59

[m, 5 H, DAP-3-CH₂, DAP-5-CH₂, CH(CH₃)₂], 1.75 (s, 3 H,

1,6-Anhydro-2-azido-4-O-benzyl-2-deoxy-3-O-{(2R)-propionyl-[

-isoglutamyl α-methyl ester)-(7-methyl)-1-(2-trimethyl-

silylethyl) (2S,6R)-N^ε-(tert-butyloxycarbonyl)-2,6-diaminopimelate]-

1 H, 3-H), 3.58Ϫ3.68 (m, 2 H, 2-H, 4-H), 3.60, 3.61 (2s, 6 H, 2 2-yl}-β- -glucopyranose (48a): The tripeptide 32a (245 mg,

L-

NHAc), 1.74Ϫ1.78, 1.92Ϫ1.95 (2m, 2 H, Glu-β-CH₂), 2.16 (m, 2 alanyl-(

D

3

H, Glu-γ-CH₂), 3.19 (m, 1 H, 5-H), 3.42 (t, J_2,3ഠ ³J_3,4ϭ 9.4 Hz,

D

2

3

OCH₃), 3.72 (t, J_6,6Јϭ 10.5, J_5,6ϭ 10.2 Hz, 1 H, 6-H), 3.76 (dd,

0.33 mmol) was hydrogenated (Procedure A) and coupled with

²J_6,6Јϭ 10.5, J_5,6Јϭ 5.5 Hz, 1 H, 6Ј-H), 3.87 (m, 1 H, DAP-6-H), compound 26 (137 mg, 0.39 mmol) according to Procedure C. Puri-

3.98 (q, J_α,βϭ 6.7 Hz, 1 H, Lac-α-H), 4.21 (m, 1 H, Glu-α-H), fication of the crude product by flash chromatography (SiO₂, tolu-

3

4.24Ϫ4.27 (m, 2 H, DAP-2-H, -Ala-α-H), 4.32 (m, 1 H, Ala-α-

Eur. J. Org. Chem. 2002, 2710Ϫ2726

ene/acetone ϭ 3:2) afforded 48a (277 mg, 0.29 mmol, 89%) as a

2723

N. Kubasch, R. R. Schmidt

FULL PAPER

colorless foam. TLC (SiO₂): R_fϭ 0.47 (toluene/acetone ϭ 3:2).

(1C, 4-C), 74.4 (1C, Lac-α-C), 75.9 (1C, 5-C), 78.2 [1C, C(CH₃)₃],

1

[α]_Dϭ ϩ15.9 (c ϭ 1, MeOH). H NMR (600 MHz, [D₆]DMSO): 79.1 (1C, 3-C), 100.1 (1C, 1-C), 155.5 [1C, OC(O)NH], 169.2 [1C,

3

δ ϭ 0.01 [s, 9 H, Si(CH₃)₃], 0.92 [t, J ϭ 8.4 Hz, 2 H, OCH₂CH₂Si- NHC(O)CH₃], 171.3, 172.2, 172.2, 173.0 [6C, 2 CO₂CH₃, 3

3

(CH₃)₃], 1.21 (d, J_α,βϭ 6.7 Hz, 3 H, Lac-β-CH₃), 1.23 (d, J_α,β

ϭ

C(O)NH, CO₂(CH₂)₂Si(CH₃)₃] ppm. C₃₈H₆₅N₅O₁₆Si (876.0):

7.0 Hz, 3 H, Ala-β-CH₃), 1.32Ϫ1.35 (m, 2 H, DAP-4-CH₂), 1.36 calcd. C 52.10, H 7.48, N 7.99; found C 52.20, H 7.91, N 7.51.

[s, 9 H, C(CH₃)₃], 1.48Ϫ1.57, 1.59Ϫ1.65 (2m, 4 H, DAP-3-CH₂,

Diammonium (N-Acetyl-1,6-anhydro-muramyl)-L D-iso-

-alanyl-N^α-(

DAP-5-CH₂), 1.72Ϫ1.82, 1.89Ϫ1.95 (2m, 2 H, Glu-β-CH₂), 2.16

(t, J_β,γϭ 7.7 Hz, 2 H, Glu-γ-CH₂), 3.34 (s, 1 H, 2-H), 3.47 (s, 1

3

glutamyl)-(2S,6R)-2,6-diaminopimelate (50a). (a) Synthesis: A solu-

tion of compound 49a (80 mg, 91 µmol) in 50% TFA/CH₂Cl₂

(16 mL) was stirred for 3Ϫ4 h in order to remove the Boc and

TMSE groups. When reaction was complete (as judged by NMR

spectroscopy), the solution was concentrated at low temperature

(25 °C) to a volume of 0.5 mL. Remaining TFA was removed by

coevaporation with dry toluene (5 ϫ 5 mL), and the residue was

then dissolved in H₂O/MeOH (2:1, v/v, 21 mL) for saponification

with 1  LiOH according to Procedure D. After completion of the

reaction (as judged by NMR spectroscopy, 4 days), glacial AcOH

was used to neutralize the solution and the solvent was removed at

low temperature.

(b) Purification: The crude product was purified by ion-exchange

chromatography (Dowex 50 W X2) on resin that had been washed

successively with MeOH, 25% aqueous NH₃, H₂O, 1  aqueous

HCl, and H₂O until neutral. The acidified crude product was ap-

plied to the column, then washed with H₂O until the eluent was

neutral. Aqueous NH₃(1% of a 25% NH₃solution in H₂O) was

used to elute the product, which was detected by TLC (ninhydrin).

The eluent was concentrated to 1Ϫ2 mL, lyophilized, and applied

to a reversed-phase column (RP-18, MeCN/H₂O ϭ 6:1) to afford

50a (53 mg, 78 µmol, 86%) as a colorless lyophilizate. TLC (RP-

H, 4-H), 3.56 (s, 1 H, 3-H), 3.60, 3.61 (2s, 6 H, 2 OCH₃), 3.62Ϫ3.63

(m, 1 H, 6-H), 3.88Ϫ3.95 (m, 1 H, DAP-6-H), 4.00Ϫ4.03 (m, 2 H,

Lac-α-H, 6Ј-H), 4.08Ϫ4.11 [m, 3 H, OCH₂CH₂Si(CH₃)₃, DAP-2-

H], 4.24 (m, 1 H, Glu-α-H), 4.38 (m, 1 H, Ala-α-H), 4.64 (m, 2 H,

CH₂Ph), 4.76 (d, ³J_5,6ϭ 5.3 Hz, 1 H, 5-H), 5.54 (s, 1 H, 1-H), 7.17

3

(d, J_α,NHϭ 7.7 Hz, 1 H, Boc-NH), 7.24Ϫ7.38 (m, 5 H, Ph), 7.73

3

(d, J_α,NHϭ 8.0 Hz, 1 H, Ala-NH), 8.16 (d, J_α,NHϭ 7.4 Hz, 1 H,

DAP-2-NH), 8.34 (d, J_α,NHϭ 7.6 Hz, 1 H, Glu-NH) ppm. ¹³C

3

NMR (150.8 MHz, [D₆]DMSO): δ ϭ Ϫ1.5 [3C, Si(CH₃)₃], 16.7

[1C, OCH₂CH₂Si(CH₃)₃], 18.2 (1C, Lac-β-C), 18.9 (1C, Ala-β-C),

21.9 (1C, DAP-4-C), 27.0 (1C, Glu-β-C), 28.1 [3C, CCH₃)₃], 30.2,

30.3 (2C, DAP-3-C, DAP-5-C), 31.0 (1C, Glu-γ-C), 47.5 (1C, Ala-

α-C), 51.5 (1C, Glu-α-C), 51.6 (2C, 2 OCH₃), 51.8 (1C, DAP-2-C),

53.2 (1C, DAP-6-C), 58.3 (1C, 2-C), 62.4 [1C, OCH₂CH₂Si(CH₃)₃],

64.8 (1C, 6-C), 70.3 (1C, CH₂Ph), 73.4 (1C, 5-c), 75.1, 75.1 (2C,

Lac-α-C, 4-C), 75.4 (1C, 3-C), 78.1 [1C, C(CH₃)₃], 99.5 (1C, 1-C),

128.2, 127.6, 127.5, 137.9 (6C, Ph), 155.5 [1C, OC(O)NH], 171.1,

171.2, 172.0, 173.0 [6C,

2

CO₂CH₃,

3

C(O)NH,

CO₂(CH₂)₂Si(CH₃)₃] ppm. C₄₃H₆₇N₇O₁₅Si (950.1): calcd. C 54.36,

H 7.11, N 10.32; found C 54.38, H 6.81, N 10.36.

2-Acetamido-1,6-anhydro-2-deoxy-3-O-{(2R)-propionyl-[

-isoglutamyl α-methyl ester)-(7-methyl)-1-(2-trimethylsilylethyl)

(2S,6R)-N^ε-(tert-butyloxycarbonyl)-2,6-diaminopimelate]-2-yl}-β-

L-alanyl-

18): R_fϭ 0.23 (MeCN/H₂O ϭ 5:1). [α]_Dϭ Ϫ14.4 (c ϭ 0.5, H₂O).

3

¹H NMR (600 MHz, [D₆]DMSO ϩ TFA): δ ϭ 1.22 (d, J_α,β

ϭ

(

D

6.7 Hz, 3 H, Lac-β-CH₃), 1.23 (d, ³J_α,βϭ 6.9 Hz, 3 H, Ala-β-CH₃),

1.36Ϫ1.42 (m, 2 H, DAP-4-CH₂), 1.53Ϫ1.56 (m, 1 H, DAP-3-

CH₂), 1.68Ϫ1.76 (m, 2 H, DAP-3-CH₂, DAP-5-CH₂, Glu-β-CH₂),

1.84 (s, 3 H, NHAc), 1.93Ϫ1.97 (m, 1 H, Glu-β-CH₂), 2.14Ϫ2.18

(m, 2 H, Glu-γ-CH₂), 3.23 (s, 1 H, 3-H), 3.51 (s, 1 H, 4-H), 3.61

D-

glucopyranose (49a): Pd/C (32 mg) and Ac₂O (52 mg, 0.51 mmol)

were added to a solution of azide 48a (320 mg, 0.34 mmol) in

MeOH (32 mL). The reaction mixture was hydrogenated according

to Procedure A. After completion (as judged by TLC), the solution

was filtered through Celite and evaporated, and the residue was

purified by flash chromatography over a short column (SiO₂, acet-

one). The pure acetamide 49a (286 mg, 0.33 mmol, 97%) was af-

forded as a colorless lyophilizate (from dioxane). TLC (SiO₂): R_fϭ

0.49 (toluene/acetone ϭ 1:3). [α]_Dϭ Ϫ17.3 (c ϭ 1, MeOH). ¹H

NMR (600 MHz, [D₆]DMSO): δ ϭ 0.01 [s, 9 H, Si(CH₃)₃], 0.92 [t,

3

(t, ³J_5,6ϭ 5.9, ²J_6,6Јϭ 7.3 Hz, 1 H, 6-H), 3.65 (d, J_2,NHϭ 8.7 Hz,

1 H, 2-H), 3.87 (m, 1 H, DAP-6-H), 4.05Ϫ4.09 (m, 2 H, 6Ј-H, Lac-

α-H), 4.13 (dt, ³J ϭ 4.9, ³J_α,NHϭ 8.5 Hz, 1 H, DAP-2-H), 4.18 (dt,

3

³J ϭ 5.2, J_α,NHϭ 8.4 Hz, 1 H, Glu-α-H), 4.38 (dq, J_α,β

ഠ

³J_α,NHϭ 7.6 Hz, 1 H, Ala-α-H), 4.48 (d, J_5,6ϭ 5.8 Hz, 1 H, 5-

H), 5.27 (s, 1 H, 1-H), 7.71 (d, J_α,NHϭ 8.3 Hz, 1 H, Ala-NH),

3

³J ϭ 8.4 Hz, 2 H, OCH₂CH₂Si(CH₃)₃], 1.22 (d, J_α,βϭ 7.1 Hz, 3

3

7.74 (d, J_2,NHϭ 8.6 Hz, 1 H, NHAc), 8.13 (d, J_α,NHϭ 7.9 Hz, 1

H, Lac-β-CH₃), 1.24 (d, ³J_α,βϭ 7.4 Hz, 3 H, Ala-β-CH₃), 1.31 (m,

2 H, DAP-4-CH₂), 1.36 [s, 9 H, C(CH₃)₃], 1.52Ϫ1.54, 1.61Ϫ1.62

H, DAP-2-NH), 8.20 (bd, J_α,NHϭ 5.2 Hz, 3 H, DAP-6-NH₃^ϩ),

3

8.28 (d, J_α,NHϭ 7.9 Hz, 1 H, Glu-NH) ppm. ¹³C NMR

3

(2m, 4 H, DAP-3-CH₂, DAP-5-CH₂), 1.76 (m, 1 H, Glu-β-CH₂),

(150.8 MHz, [D₆]DMSO ϩ TFA): δ ϭ 17.9 (1C, Lac-β-C), 19.2

(1C, Ala-β-C), 21.2 (1C, DAP-4-C), 22.5 [1C, NHC(O)CH₃], 27.3

(1C, Glu-β-C), 29.7 (1C, DAP-5-C), 30.6 (1C, DAP-3-C), 31.5 (1C,

Glu-γ-C), 47.5 (1C, Ala-α-C), 48.8 (1C, 2-C), 51.6 (1C, Glu-α-C),

51.7 (1C, DAP-2-C), 51.8 (1C, DAP-6-C), 64.9 (1C, 6-C), 69.2 (1C,

4-C), 74.5 (1C, Lac-α-C), 76.0 (1C, 5-C), 79.2 (1C, 3-C), 100.2 (1C,

1-C), 169.3 [1C, NHC(O)CH₃], 171.1, 171.4, 171.6, 172.1, 173.2,

3

1.84 (s, 3 H, NHAc), 1.93 (m, 1 H, Glu-β-CH₂), 2.16 (t, J_β,γ

7.6 Hz, 2 H, Glu-γ-CH₂), 3.23 (s, 1 H, 3-H), 3.51 (d, J_4,OH

ϭ

3

ϭ

5.0 Hz, 1 H, 4-H), 3.60, 3.62 (2s, 6 H, 2 OCH₃), 3.60Ϫ3.62 (m, 1

3

H, 6-H), 3.65 (d, J_2,NHϭ 8.5 Hz, 1 H, 2-H), 3.90 (m, 1 H, DAP-

6-H), 4.05 (d, J ϭ 7.4 Hz, 1 H, 6Ј-H), 4.07Ϫ4.13 [m, 4 H, Lac-α-

H, OCH₂CH₂Si(CH₃)₃, DAP-2-H], 4.23 (m, 1 H, Glu-α-H), 4.37

(dq, ³J_α,βഠ ³J_α,NHϭ 7.5 Hz, 1 H, Ala-α-H), 4.48 (d, ³J_5,6ϭ 5.2 Hz,

173.6 [6C, 3 CO₂H, 3 C(O)NH] ppm. FAB MS (positive mode,

3

ϩ

1 H, 5-H), 5.27 (s, 1 H, 1-H), 5.29 (d, J_4,OHϭ 5.8 Hz, 1 H, 4-

glycerol, MeOH/AcOH/H₂O ϭ 1:1:1): m/z ϭ 648 [M Ϫ 2NH₄

ϩ

3

3H^ϩ]^ϩ; calcd. 681.3 for C₂₆H₄₇N₇O₁₄.

OH), 7.20 (d, J_α,NHϭ 7.8 Hz, 1 H, Boc-NH), 7.70 (d, J_α,NH

ϭ

8.3 Hz, 1 H, Ala-NH), 7.73 (d, ³J_2,NHϭ 8.6 Hz, 1 H, NHAc), 8.19

(d, J_α,NHϭ 7.3 Hz, 1 H, DAP-2-NH), 8.39 (d, ³J_α,NHϭ 7.6 Hz, 1 1,6-Anhydro-2-azido-4-O-benzyl-2-deoxy-3-O-{(2R)-propionyl-[

L

-

3

H, Glu-NH) ppm. ¹³C NMR (150.8 MHz, [D₆]DMSO): δ ϭ Ϫ1.5 alanyl-(

[3C, Si(CH₃)₃], 16.7 [1C, OCH₂CH₂Si(CH₃)₃], 17.8 (1C, Lac-β-C), silylethyl)

19.1 (1C, Ala-β-C), 21.9 (1C, DAP-4-C), 22.5 [1C, NHC(O)CH₃], melate}]-2-yl}-β-

27.0 (1C, Glu-β-C), 28.1 [3C, C(CH₃)₃], 30.2, 30.3 (2C, DAP-3-C,

DAP-5-C), 31.1 (1C, Glu-γ-C), 47.4 (1C, Ala-α-C), 48.8 (1C, 2-C), compound 26 (225 mg, 0.64 mmol) according to Procedure C. The

51.5 (1C, Glu-α-C), 51.7 (2C, 2 OCH₃), 51.9 (1C, DAP-2-C), 53.2 reaction was complete after 10 h, as determined by TLC. Purifica-

(1C, DAP-6-C), 62.5 [1C, OCH₂CH₂Si(CH₃)₃], 64.8 (1C, 6-C), 69.1 tion of the crude product by flash chromatography (SiO₂, toluene/

D-isoglutamyl α-methyl ester)-(7-methyl)-1-(2-trimethyl-

(2S,6S)-N^ε-(tert-butyloxycarbonyl)-2,6-diaminopi-

-glucopyranose (48b): The tripeptide 32b (400 mg,

D

0.54 mmol) was hydrogenated (Procedure A) and coupled with

2724

Eur. J. Org. Chem. 2002, 2710Ϫ2726

Synthesis of Muramyl Peptides Containing meso-Diaminopimelic Acid

acetone ϭ 3:2) afforded 48b (423 mg, 0.45 mmol, 83%) as a color- C), 47.4 (1C, Ala-α-C), 48.8 (1C, 2-C), 51.5 (1C, Glu-α-C), 51.7,

FULL PAPER

less foam. TLC (SiO₂): R_fϭ 0.47 (toluene/acetone ϭ 3:2). [α]_D

ϭ

51.9 (3C, 2 OCH₃, DAP-2-C), 53.4 (1C, DAP-6-C), 62.5 [1C,

OCH₂CH₂Si(CH₃)₃], 64.8 (1C, 6-C), 69.1 (1C, 4-C), 74.4 (1C, Lac-

α-C), 75.9 (1C, 5-C), 78.2 [1C, C(CH₃)₃], 79.1 (1C, 3-C), 100.1 (1C,

1-C), 155.5 [1C, OC(O)NH], 169.2 [1C, NHC(O)CH₃], 171.3,

172.1, 172.2 [6C, 2 CO₂CH₃, 3 C(O)NH, CO₂(CH₂)₂Si(CH₃)₃]

ϩ9.1 (c ϭ 1.1, MeOH). ¹H NMR (600 MHz, [D₆]DMSO): δ ϭ

0.01 [s, 9 H, Si(CH₃)₃], 0.92 [t, ³J ϭ 8.5 Hz, 2 H, OCH₂CH₂S-

3

i(CH₃)₃], 1.21 (d, J_α,βϭ 6.7 Hz, 3 H, Lac-β-CH₃), 1.23 (d, ³J_α,β

ϭ

7.0 Hz, 3 H, Ala-β-CH₃), 1.31 (m, 2 H, DAP-4-CH₂), 1.36 [s, 9 H,

C(CH₃)₃], 1.53Ϫ1.62 (m,

1.76Ϫ1.79, 1.91Ϫ1.94 (2m, 2 H, Glu-β-CH₂), 2.16 (t, J_β,γ

4

H, DAP-3-CH₂, DAP-5-CH₂), ppm. C₃₈H₆₅N₅O₁₆Si·0.5 H₂O (884.4): calcd. C 51.61, H 7.41, N

3

ϭ

7.92; found C 51.70, H 7.75, N 7.49.

7.8 Hz, 2 H, Glu-γ-CH₂), 3.36 (s, 1 H, 2-H), 3.46 (s, 1 H, 4-H),

3.56 (s, 1 H, 3-H), 3.59, 3.60 (2s, 6 H, 2 OCH₃), 3.63 (t, J ϭ 7.1 Hz,

1 H, 6-H), 3.87Ϫ3.89 (m, 1 H, DAP-6-H), 4.00Ϫ4.03 (m, 2 H, Lac-

α-H, 6Ј-H), 4.08Ϫ4.12 [m, 3 H, OCH₂CH₂Si(CH₃)₃, DAP-2-H],

Diammonium (N-Acetyl-1,6-anhydromuramyl)-L D-iso-

-alanyl-N^α-(

glutamyl)-(2S,6S)-2,6-diaminopimelate (50b): This reaction was per-

formed as described for compound 50a. A solution of compound

49b (127 mg, 145 µmol) in 50% TFA/CH₂Cl₂(20 mL) was stirred

for 2 h in order to remove the Boc and TMSE groups. After re-

moval of the solvent, the residue was saponified with LiOH in H₂O/

MeOH (1 , 2:1, v/v, 30 mL) and stirred for 4 days. The crude

product was subsequently purified by ion-exchange chromato-

graphy (Dowex 50 W X2), reversed-phase chromatography (RP-18,

MeCN/H₂O ϭ 6:1), and again by ion-exchange chromatography

(Dowex 50 W X2) as described above. The pure product 50b

(76 mg, 112 µmol, 77%) was obtained as a light yellow lyophilizate.

TLC (RP-18): R_fϭ 0.24 (MeCN/H₂O ϭ 5:1). [α]_Dϭ Ϫ23.2 (c ϭ

3

4.24 (q, J_α,βϭ 5.6 Hz, 1 H, Glu-α-H), 4.37 (dq, J_α,βഠ J_α,NH

ϭ

3

7.4 Hz, 1 H, Ala-α-H), 4.64 (m, 2 H, CH₂Ph), 4.76 (d, J_5,6

ϭ

3

5.4 Hz, 1 H, 5-H), 5.54 (s, 1 H, 1-H), 7.20 (d, J_α,NHϭ 7.7 Hz, 1

3

H, Boc-NH), 7.28Ϫ7.38 (m, 5 H, Ph), 7.74 (d, J_α,NHϭ 8.0 Hz, 1

3

H, Ala-NH), 8.18 (d, J_α,NHϭ 7.4 Hz, 1 H, DAP-2-NH), 8.36 (d,

³J_α,NHϭ 7.7 Hz, 1 H, Glu-NH) ppm. ¹³C NMR (150.8 MHz,

[D₆]DMSO): δ ϭ Ϫ1.5 [3C, Si(CH₃)₃], 16.8 [1C, OCH₂CH₂Si-

(CH₃)₃], 18.2 (1C, Lac-β-C), 18.9 (1C, Ala-β-C), 22.1 (1C, DAP-

4-C), 27.0 (1C, Glu-β-C), 28.1 [3C, C(CH₃)₃], 30.2, 30.4 (2C, DAP-

3-C, DAP-5-C), 31.1 (1C, Glu-γ-C), 47.5 (1C, Ala-α-C), 51.5 (1C,

Glu-α-C), 51.7, 51.9 (3C, 2 OCH₃, DAP-2-C), 53.4 (1C, DAP-6-

C), 58.3 (1C, 2-C), 62.5 [1C, OCH₂CH₂Si(CH₃)₃], 64.8 (1C, 6-C),

70.3 (1C, CH₂Ph), 73.4 (1C, 5-C), 75.1, 75.4 (3C, Lac-α-C, 4-C, 3-

C), 78.2 [1C, C(CH₃)₃], 99.5 (1C, 1-C), 127.5, 127.6, 128.2, 137.9

(6C, Ph), 155.5 [1C, OC(O)NH], 171.1, 171.3, 172.1, 172.1, 173.1

1

0.5, H₂O). H NMR (600 MHz, [D₆]DMSO ϩ TFA): δ ϭ 1.22 (d,

³J_α,βϭ 7.1 Hz, 3 H, Lac-β-CH₃), 1.23 (d, ³J_α,βϭ 8.4 Hz, 3 H, Ala-

β-CH₃), 1.35, 1.46 (2m, 2 H, DAP-4-CH₂), 1.56 (m, 1 H, DAP-3-

CH₂), 1.67Ϫ1.79 (m, 4 H, DAP-3-CH₂, DAP-5-CH₂, Glu-β-CH₂),

1.84 (s, 3 H, NHAc), 1.95Ϫ1.97 (m, 1 H, Glu-β-CH₂), 2.15Ϫ2.19

(m, 2 H, Glu-γ-CH₂), 3.23 (s, 1 H, 3-H), 3.51 (s, 1 H, 4-H), 3.60

[6C,

2

CO₂CH₃,

3

C(O)NH, CO₂(CH₂)₂Si(CH₃)₃] ppm.

3

(m, 1 H, 6-H), 3.67 (d, J_2,NHϭ 8.4 Hz, 1 H, 2-H), 3.87 (m, 1 H,

C₄₃H₆₇N₇O₁₅Si (950.1): calcd. C 54.36, H 7.11, N 10.32; found C

54.69, H 7.47, N 10.30.

3

DAP-6-H), 4.06Ϫ4.09 (m, 2 H, 6Ј-H, Lac-α-H), 4.13 (dt, J ϭ 4.9,

3

³J_α,NHϭ 8.2 Hz, 1 H, DAP-2-H), 4.19 (dt, ³J ϭ 5.4, J_α,NH

ϭ

3

8.1 Hz, 1 H, Glu-α-H), 4.38 (dq, J_α,β

ഠ

³J_α,NHϭ 7.4 Hz, 1 H,

Ala-α-H), 4.47 (d, J_5,6ϭ 4.9 Hz, 1 H, 5-H), 5.27 (s, 1 H, 1-H),

2-Acetamido-1,6-anhydro-2-deoxy-3-O-{(2R)-propionyl-[

-isoglutamyl α-methyl ester)-(7-methyl)-1-(2-trimethylsilylethyl)

(2S,6S)-N^ε-(tert-butyloxycarbonyl)-2,6-diaminopimelate]-2-yl}-β-

L-alanyl-

3

(

D

3

7.72 (d, J_α,NHϭ 7.3 Hz, 1 H, Ala-NH), 7.73 (d, J_2,NHϭ 7.9 Hz,

D-

1 H, NHAc), 8.11 (d, ³J_α,NHϭ 7.6 Hz, 1 H, DAP-2-NH), 8.19 (br.

glucopyranose (49b): Pd/C (28 mg) and Ac₂O (45 mg, 0.44 mmol)

were added to a solution of azide 48b (280 mg, 0.30 mmol) in

MeOH (20 mL). The reaction mixture was hydrogenated according

to Procedure A. After completion (as judged by TLC), the solution

was filtered through Celite and evaporated, and the residue was

purified by flash chromatography over a short column (SiO₂, tolu-

ene/acetone ϭ 1:3). The pure acetamide 49b (255 mg, 0.29 mmol,

98%) was obtained as a colorless lyophilizate (from dioxane). TLC

(SiO₂): R_fϭ 0.53 (toluene/acetone ϭ 1:3). [α]_Dϭ Ϫ22.3 (c ϭ 1,

MeOH). ¹H NMR (600 MHz, [D₆]DMSO): δ ϭ 0.01 [s, 9 H,

3

s, 3 H, DAP-6-NH₃^ϩ), 8.26 (d, J_α,NHϭ 7.8 Hz, 1 H, Glu-NH)

ppm. ¹³C NMR (150.8 MHz, [D₆]DMSO ϩ TFA): δ ϭ 18.1 (1C,

Lac-β-C), 19.3 (1C, Ala-β-C), 21.5 (1C, DAP-4-C), 22.6 [1C,

NHC(O)CH₃], 27.5 (1C, Glu-β-C), 29.9 (1C, DAP-5-C), 30.8 (1C,

DAP-3-C), 31.7 (1C, Glu-γ-C), 47.8 (1C, Ala-α-C), 49.1 (1C, 2-C),

51.9 (1C, Glu-α-C, DAP-2-C), 52.1 (1C, DAP-6-C), 65.1 (1C, 6-C),

69.4 (1C, 4-C), 74.8 (1C, Lac-α-C), 76.2 (1C, 5-C), 79.4 (1C, 3-C),

100.4 (1C, 1-C), 169.6 [1C, NHC(O)CH₃], 171.4, 171.8, 171.9,

172.3, 173.5, 173.9 [6C, 3 CO₂H, 3 C(O)NH] ppm. FAB MS (posit-

ive mode, glycerol, MeCN/0.1% TFA ϭ 1:1): m/z ϭ 648 [M Ϫ

3

Si(CH₃)₃], 0.92 [t, J ϭ 8.4 Hz, 2 H, OCH₂CH₂Si(CH₃)₃], 1.22 (d,

2NH₄ϩ 3H^ϩ]^ϩ; calcd. 681.3 for C₂₆H₄₇N₇O₁₄.

ϩ

3

³J_α,βϭ 7.0 Hz, 3 H, Lac-β-CH₃), 1.23 (d, J_α,βϭ 7.1 Hz, 3 H,

Ala-β-CH₃), 1.31 (m, 2 H, DAP-4-CH₂), 1.36 [s, 9 H, C(CH₃)₃],

1.55Ϫ1.60 (m, 4 H, DAP-3-CH₂, DAP-5-CH₂), 1.75Ϫ1.79 (m, 1 H,

Glu-β-CH₂), 1.84 (s, 3 H, NHAc), 1.91Ϫ1.95 (m, 1 H, Glu-β-CH₂),

Acknowledgments

3

This work was supported by the Deutsche Forschungsgemeinschaft

and the Fonds der Chemischen Industrie. The help of Dr. A. Geyer

and A. Friemel in structural assignments is gratefully acknow-

ledged.

2.16 (t, J_β,γϭ 7.7 Hz, 2 H, Glu-γ-CH₂), 3.23 (s, 1 H, 3-H), 3.51

3

(d, J_4,OHϭ 5.1 Hz, 1 H, 4-H), 3.60, 3.62 (2s, 6 H, 2 OCH₃),

3.60Ϫ3.62 (m, 1 H, 6-H), 3.65 (d, ³J_2,NHϭ 8.5 Hz, 1 H, 2-H), 3.88

(m, 1 H, DAP-6-H), 4.05 (d, J ϭ 7.3 Hz, 1 H, 6Ј-H), 4.07Ϫ4.13

[m, 4 H, Lac-α-H, OCH₂CH₂Si(CH₃)₃, DAP-2-H], 4.23 (m, 1 H,

3

[1]

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3

glycan, Chapman and Hall Ltd., London 1980.

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T. D. H. Bugg, C. T. Walsh, Nat. Prod. Rep. 1992, 199Ϫ216.

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(d, J_α,NHϭ 8.3 Hz, 1 H, Ala-NH), 7.73 (d, J_2,NHϭ 8.6 Hz, 1 H,

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³J_α,NHϭ 7.6 Hz, 1 H, Glu-NH) ppm. ¹³C NMR (150.8 MHz,

[D₆]DMSO): δ ϭ Ϫ1.5 [3C, Si(CH₃)₃], 16.8 [1C, OCH₂CH₂S-

i(CH₃)₃], 17.8 (1C, Lac-β-C), 19.1 (1C, Ala-β-C), 22.1 (1C, DAP-

4-C), 22.5 [1C, NHC(O)CH₃], 26.9 (1C, Glu-β-C), 28.1 [3C,

C(CH₃)₃], 30.2, 30.4 (2C, DAP-3-C, DAP-5-C), 31.1 (1C, Glu-γ-

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2725

N. Kubasch, R. R. Schmidt

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Received March 8, 2002

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The synthesis of 1,6-anhydromuramyl dipeptides has been re-

[O02124]

2726

Eur. J. Org. Chem. 2002, 2710Ϫ2726

Article Doi

Synthesis of muramyl peptides containing meso-diaminopimelic acid

DOI: 10.1002/1099-0690(200208)2002:16<2710::AID-EJOC2710>3.0.CO;2-8

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Article abstract of DOI:10.1002/1099-0690(200208)2002:16<2710::AID-EJOC2710>3.0.CO;2-8

Full text of DOI:10.1002/1099-0690(200208)2002:16<2710::AID-EJOC2710>3.0.CO;2-8

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