Diaminopimelic acid (DAP) analogs bearing isoxazoline moiety as selective inhibitors against meso-diaminopimelate dehydrogenase (m-Ddh) from Porphyromonas gingivalis

Two diastereomeric analogs (1 and 2) of diaminopimelic acid (DAP) bearing an isoxazoline moiety were synthesized and evaluated for their inhibitory activities against meso-diaminopimelate dehydrogenase (m-Ddh) from the periodontal pathogen, Porphyromonas gingivalis. Compound 2 showed promising inhibitory activity against m-Ddh with an IC50 value of 14.9µM at pH 7.8. The two compounds were further tested for their antibacterial activities against a panel of periodontal pathogens, and compound 2 was shown to be selectively potent to P. gingivalis strains W83 and ATCC 33277 with minimum inhibitory concentration (MIC) values of 773µM and 1.875mM, respectively. Molecular modeling studies revealed that the inversion of chirality at the C-5 position of these compounds was the primary reason for their different biological profiles. Based on these preliminary results, we believe that compound 2 has properties consistent with it being a lead compound for developing novel pathogen selective antibiotics to treat periodontal diseases.

A facile synthesis of fully protected meso-diaminopimelic acid (DAP) and its application to the preparation of lipophilic N-acyl iE-DAP

Synthesis of beneficial protected meso-DAP 9 by cross metathesis of the Garner aldehyde-derived vinyl glycine 1b with protected allyl glycine 2 in the presence of Grubbs second-generation catalyst was performed. Preparation of lipophilic N-acyl iE-DAP as potent agonists of NOD 1-mediated immune response from 9 is described.

Stereoselective syntheses of 4-oxa diaminopimelic acid and its protected derivatives via aziridine ring opening

Regio- and stereoselective aziridine ring opening with oxygen nucleophiles derived from serine and threonine provides a route to stereochemically pure 4-oxa-2,6-diaminopimelic acid (oxa-DAP) and its methyl-substituted derivatives. Oxa-DAP is a substrate of DAP epimerase, a key enzyme for biosynthesis of l-lysine and formation of peptidoglycan precursors. Orthogonally protected analogues of lanthionine and beta-methyllanthionine wherein oxygen replaces sulfur were prepared that could be used for solid-supported peptide synthesis to make oxa derivatives of lantibiotics.

A straightforward stereoselective synthesis of meso-, (S,S)- and (R,R)-2,6-diaminopimelic acids from cis-1,4-diacetoxycyclohept-2-ene

A straightforward synthesis of meso-2,6-diaminopimelic acid (DAP) meso-1 was developed from 1,4-diacetoxycyclohept-2-ene (2) via an oxidative ring cleavage. Subsequently, an enantio-divergent synthesis of (S,S)- and (R,R)-1 was performed using a homochiral monoacetate 7 available from 2 by enzymatic desymmetrization.

Meso-Diaminopimelic Acid andMeso-Lanthionine, Amino Acids Specific to Bacterial Peptidoglycans, Activate Human Epithelial Cells through NOD1

Peptidoglycans (PGNs) are ubiquitous constituents of bacterial cell walls and exhibit various immunobiological activities. Two types of minimum essential PGN structures for immunobiological activities were chemically synthesized and designated as muramyldipeptide; N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) and gamma-D-glutamyl-meso-diaminopimelic acid (iE-DAP), which are common constituents of both Gram-positive and Gram-negative bacteria, as well as most Gram-negative and some Gram-positive bacteria, respectively. Recently, intracellular receptors for MDP and iE-DAP have been demonstrated to be nucleotide-binding oligomerization domain (NOD)1 and NOD2, respectively. In this study, we demonstrated that chemically synthesized meso-DAP itself activated human epithelial cells from various tissues, through NOD1 to generate antibacterial factors, PGN recognition proteins and beta-defensin 2, and cytokines in specified cases, although the activities of meso-DAP were generally weaker than those of known NOD agonists. However, stereoisomers of meso-DAP, LL-DAP, and DD-DAP were only slightly activated or remained inactive, respectively. Synthetic meso-lanthionine, which is another diamino-type amino acid specific to PGN of the specified Gram-negative bacteria, was also recognized by NOD1. In human monocytic cells, in the presence of cytochalasin D meso-DAP induced slightly but significantly increased production of cytokines, although the cells did not respond to meso-DAP in the absent of cytochalasin D. Our findings suggest that NOD1 is a special sentinel molecule, especially in the epithelial barrier, allowing the intracellular detection of bacteria through recognizing meso-DAP or comparable moiety of PGN from specified bacteria in cooperation with NOD2, thereby playing a key role in innate immunity.

An efficient RCM-based synthesis of orthogonally protected meso-DAP and FK565

A condensation--ring-close--ring-open sequence was employed for the synthesis of orthogonally protected meso-2,6-diaminopimelic acid, starting from easily accessible chiral synthons. Condensation of suitably protected L-allylglycine and D-vinylglycinol derivatives was followed by Grubbs' ring-closing metathesis to generate the key lactam intermediate. This strategy has been applied to a concise total synthesis of the potent immunostimulatory peptide FK565.

Synthesis of enantiomerically and diastereomerically pure 2(S)-amino-6(R)-hydroxy-1,7-heptanedioic acid dimethyl ester hydrochloride from cycloheptadiene

The complete carbon framework of enantiomerically and diastereomerically pure 2(S)-amino-6(R)-hydroxy-1,7-heptanedioic acid dimethyl ester hydrochloride was derived from cycloheptadiene in six steps utilizing an amino acid-derived acylnitroso Diels-Alder reaction as the key step. This versatile amino diester has been previously used to synthesize amino-differentiated diaminopimelic acid (DAP) and biologically active analogues. In addition, after formation of a novel aminoxy diketopiperazine, the newly formed carboxyl groups were differentiated by a novel transpeptidation of the amino acid that directed the stereochemistry of the initial cycloaddition.

Vinylogous amide analogues of diaminopimelic acid (DAP) as inhibitors of enzymes involved in bacterial lysine biosynthesis

[reaction: see text] Vinylogous amides 5 and 6 have been synthesized from L-propargyl glycine and tested against diaminopimelate (DAP) enzymes involved in bacterial lysine biosynthesis. Both are reversible inhibitors of DAP D-dehydrogenase and DAP epimerase with IC(50) values in the 500 microM range. Compound 5 shows competitive inhibition against the L-dihydrodipicolinate (DHDP) reductase with a K(i) value of 32 microM, which is comparable to the planar dipicolinate 16 (K(i) = 26 microM), the best known inhibitor of the enzyme.

New convenient synthesis of immunostimulating peptides containing meso-diaminopimelic acid. Syntheses of FK-565 and FK-156

A new improved synthesis of two immunostimulating peptides: FK-156 (D-lactyl-alanyl-gamma-D-glutamyl-(L)-meso-2,6-diaminopimelyl-(L)- glycine) and FK-565 (heptanoyl-gamma-D-glutamyl-(L)-meso-2,6-diaminopimelyl-(L)- D-alanine) is described. A proper differentiation between the two chiral amino acid moieties of diaminopimelic acid was accomplished by selective enzymatic hydrolysis of one methyl ester group of the L-centre of Z2-meso-A2pm(OMe)2 (2). Utilization of a commercially available protease and diester 2 as an enzyme substrate made possible the relatively simple synthesis of a key intermediate 4 and considerably simplified the final deprotection steps. Aminolysis of the N-carboxyanhydride (4) with D-AlaONBzl or GlyONBzl was chosen to obtain the appropriate dipeptides with one free amino group as convenient intermediates for further peptide synthesis. The BOP reagent, used for peptide bond formation, secured good yields and high chemical and chiral purity of the peptides. A modification of alanine deamination procedure leading to a significant increase of D-Lac(OAc) yield is presented.

Inhibition of Escherichia coli growth and diaminopimelic acid epimerase by 3-chlorodiaminopimelic acid

The diaminopimelic acid (DAP) analog, 3-chloro-DAP, was synthesized and tested as the racemic acid for antibacterial activity and for inhibition of DAP epimerase. 3-Chloro-DAP was a potent inhibitor of DAP epimerase purified from Escherichia coli (Ki = 200 nM), and it is argued that 3-chloro-DAP is converted to a tight-binding transition state analog at the active site of this enzyme. Furthermore, 3-chloro-DAP inhibited growth of two E. coli mutants. In one of the mutants known for supersusceptibility to beta-lactams, inhibition was not seen until the mid-log phase of growth, while in the other mutant, a DAP auxotroph, inhibition occurred much earlier. Growth inhibition was reversed by DAP in both strains. In the auxotroph, the reversal was specific for meso-DAP, indicating that DAP epimerase was the target for 3-chloro-DAP. Thus we suggest a novel mechanism of bacterial growth inhibition which depends on DAP epimerase inhibition by a DAP analog.

Studies on a new immunoactive peptide, FK-156. IV. Synthesis of FK-156 and its geometric isomer

For the structural confirmation of FK-156, two possible structures, 1 and its geometric isomer 2, were synthesized. Di-Z-meso-diaminopimelic acid (4) was converted into 14 via a sequence of reactions involving, as key steps, an enzyme-mediated asymmetric hydrolysis (6 leads to 7), followed by carbobenzyloxylation using a copper chelate procedure (7 leads to 8). Condensation of 14 and the appropriately protected lactoyl dipeptide 17 and removal of the protecting groups of the resulting 18 afforded 1. Protection of 7 to 22, followed by coupling to glycine via an azide method, gave 25. Derivatization of 25 to 29 and condensation with 17 gave 30, which was deprotected to yield 2. Compound 1 proved to be identical in all respects with the natural product.