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A chemical synthesis was performed of an octapeptide with a phosphonic ester linkage, which corresponds to a variation of the partial sequence of a gene product of erb B-2. The phosphonic ester linkage was successfully prepared through a coupling reaction of magnesium salt of the hydroxypeptide with phosphonochloridate, without damage of the peptide bond. The free aminophosphonic peptide as the final product gave a single peak on the ODS column, and a reasonable ratio of the component amino acids. The reaction series exploited here might be useful as a general procedure for preparation of the phosphonic peptide.

Total synthesis of a lanthionine peptide nisin was achieved by the successive condensations of four segments including cyclic lanthionine peptide parts and the C-terminal linear segment including dehydroalanine, followed by the deprotection procedure with anhydrous HF. Modified reaction conditions for the Hofmann degradation were applied to prepare the dehydroalanine residue from the 2,3-diaminopropionic acid residue. The final deprotection with anhydrous HF proceeded without decomposition of the dehydroamino acid residues which are generally labile in acidic media. The synthetic nisin was completely identical with the natural one in all respects, resulting in a confirmation of the proposed structure.

The structure of ancovenin, a new peptide inhibitor of angiotensin I converting enzyme was determined chemically. Ancovenin is composed of 16 amino acid residues including three lanthionine residues which form a complex tricyclic structure bridged by sulfide bonds. Moreover, this peptide includes dehydroalanine as one of its unusual amino acids. In the present study, plausible mechanisms of the Edman degradation of dehydroalanine and lanthionine-containing peptides were also elucidated.

N-Acetylmuramyl-L-alanyl-D-isoglutamine corresponding to the minimum structure responsible for the immunoadjuvant activity of bacterial cell walls was acylated at the 6-hydroxyl group with various mycolic acids of long carbon chains in order to test their possible antitumor effects. Mycolic acids used were extracted from cell walls of Mycobacterium, Nocardia, and Corynebacterium. All the mycoloyl derivatives synthesized show antitumor activity based on a principle of immunotherapy.

Six analogs of an antituberculous antibiotic capreomycin were synthesized in order to clarify the structure-activity relationship, especially with regard to the significance of the β-amino group in α,β-diaminopropionic acid residue as well as the position of linkage of the branch residue, β-lysine, to the cyclic peptide moiety. All the synthetic products were found to have the same conformations in solution as those of the natural antibiotics in terms of NMR spectra. It was found from their antibacterial activities that an amino group located at β-position of the α,β-diaminopropionic acid residue adjacent to ureidodehydroalanine residue remarkably strengthens the biological activity, and that the position of a branch does not significantly influence the antibacterial potency.

On the N,O-acyl migration reaction of β-hydroxy-α-amino acids with concentrated sulfuric acid, a configuration of the carbon atom carrying hydroxyl group was found to be inverted through the reaction. Thus, threonine residue in peptide was converted to allothreonine residue and vice versa in the selective chemical cleavage of threonine peptide employing the N,O-migration with concentrated sulfuric acid. The reaction mechanism involving SNi elimination of O-sulfate formed as an intermediate was suggested. The inversion did not occur in the N,O-acyl migration reaction with other mineral acids than sulfuric acid.

N-Acetylmuramyl peptides of successive length corresponding to the partial structures of cell wall in Staphylococcus aureus were synthesized in order to elucidate the minimum effective structure responsible for immunoadjuvant activity of bacterial cell walls. In view of the finding that N-acetylmuramyl-L-alanyl-D-isoglutamine was the least structure moiety for exhibition of the activity, nine analogs of either N-acetylmuramyl amino acid or N-acetylmuramyl dipeptide were also synthesized.

Chemical syntheses are described of polyacylated β(1→6) glucosamine disaccharide 1,4′-bis(phosphate), which corresponds to the proposed structure of E. coli lipid A, and of its dephospho derivatives. The synthetic bisphosphate proved to be identical with the corresponding natural specimen. The chemical structure of lipid A was thus established.

Synthesis is described on 6-O-[2-deoxy-2-((R)-3-hydroxytetradecanoylamino)-6-O-tetradecanoyl-β-D-glucopyranosyl]-2-deoxy-2-((R)-3-hydroxytetradecanoylamino)-3,4-di-O-tetradecanoyl-D-glucopyranose which corresponds to the phosphate-less lipid A structure of Salmonella-type bacterial endotoxin.

Thirty two semisynthetic tuberactinomycins were prepared by introduction of various amino acids to amino group of tuberactinamine N, a cyclic peptide moiety of tuberactinomycin N and O, which was isolated from natural tuberactinomycin N by acid treatment with liberation of γ-hydroxy-β-lysine of the branched part. Among introduced amino acids, β-amino acids were synthesized from corresponding α-amino acids by modified Arndt-Eistert reaction. After couplings of N-protected amino acids with tuberactinamine N, deprotections were carried out to give semisynthetic tuberactinomycins. From their minimum inhibitory concentrations against many bacteria, it was suggested that a branched part effects significantly to the strength of antimicrobial activities though most important active site must locate in the cyclic peptide moiety, and basicity and/or hydrophobicity of the branched part seemed to strengthen the antibacterial activity especially.

6-Phosphate of N-acetylmuramyl-L-alanyl-D-isoglutamine and its lipophilic derivatives, i.e., 6-(octadecyl hydrogenphosphate) and 6-(2-docosyltetracosyl hydrogenphosphate) were synthesized after the structural feature of mycobacterial cell walls for the purpose to modify and possibly to enhance the immunostimulating activity of the muramyl dipeptide which is the minimum requisite for the activity. As expected, the latter more lipophilic phosphate showed a high activity in a tumor regression test.

Total syntheses of [Ala3, Ala4]-, [Ala3]-, and [Ala4]-tuberactinomycin O corresponding to deoxy analogs of natural antibiotic tuberactinomycin O were achieved for the purpose of elucidation of relationship between chemical structure and biological activity. Cyclization of the pentapeptide intermediates at two different positions was investigated. Minimum inhibitory concentrations of the synthetic analogs against Mycobacterium or Corynebacterium indicated that both hydroxy groups of two serine residues of tuberactinomycins are not required for antibacterial activity, nor participated to drug-resistancy of bacilli. These analogs were found to have the same conformations in solution as those of natural antibiotic from the results of NMR, ORD, and CD measurements.

Various structural analogs of N-acetylmuramyl-L-alanyl-D-isoglutamine, which had been shown to be the minimum structure required for the immunoadjuvant activity of bacterial cell walls, were synthesized in order to investigate in more detail the relationship between the activity and chemical structures. Particularly, the compounds of the structures corresponding to the cell walls of special bacteria without immunoadjuvant activity were prepared in this study. Several novel procedures including the preparation of a branched glutamyl peptide were newly exploited to accomplish the syntheses of muramyl peptides with complicated structures. As a result of this synthetic study, new informations were obtained on the structural requirement for the immunoadjucant activity.

threo-3-Methyl-D-cysteine as a moiety of β-methyllanthionine in the peptide antibiotic nisin was synthesized stereospecifically. The reaction of (2R,3R)-3-methyl-2-aziridinecarboxylic acid derivative prepared from D-threonine with thiobenzoic acid gave the β-mercapto α-amino acid derivative of the same configuration as the starting material. A stereochemistry of the product was retained as a result of double inversion mechanism through the reactions. Thus, we could prepare threo-3-methyl-D-cysteine, i.e., (2S,3S)-2-amino-3-mercaptobutanoic acid which is required for the synthetic study of nisin.

A novel method was established for the determination of true optical purity of amino acid residues in peptides. Hydrolysis in deuterium chloride followed by mass fragmentographic detection enables very accurate analysis without disturbance by racemization in the hydrolysis procedure.

Four analogs of an antibiotic althiomycin were synthesized in order to clarify the structure-activity relationships, especially with regard to two asymmetric centers and the aldoxime configuration. The antibiotic activity of de(hydroxymethyl) analog is comparable to that of the original antibiotic for Gram-positive bacteria.

Conformational analyses of peptide antibiotics tuberactinomycins were performed by NMR spectroscopy of 100 MHz. Studies on temperature dependence and deuterium exchange in amide proton resonances revealed the presence of an intramolecular hydrogen bond participated with α-amide proton of the guanidino amino acid residue in the cyclic part of each molecule. The same result was obtained in tuberactinamine N, which is the cyclopeptide moiety without amino acid side chain in tuberactinomycins N and O. The common rigid structure fixed by hydrogen bonding in the cyclic part seems to be a requisite for the exhibition of microbial activity in tuberactinomycin family.

A cyclic guanidino amino acid, L-epicapreomycidine, isolated from hydrolyzates of protease inhibitors such as chymostatin and elastatinal was synthesized. This amino acid is a diastereomer of L-capreomycidine which is a component amino acid of tuberactinomycin N,O and capreomycin. A new synthetic route from β-hydroxy-DL-orni thine via an aziridine compound to DL-capreomycidine was applied to the synthesis of L-epicapreomycidine starting from erythro-β-hydroxy-L-ornithine. A convenient and one-step technique to obtain L-erythro form from a mixture of four diastereomers of β-hydroxyornithine by means of enzymatic reaction was newly exploited. The synthetic L-epicapreomycidine obtained was identical with natural one in all respects, thus confirming the proposed structure.

Seven acyl derivatives of N-acetylmuramyl-L-alanyl-D-isoglutamine, which had previously been shown to be a minimum structure required for the immunoadjuvant activity, were synthesized in order to evaluate the significance of lipophilicity on the adjuvant activity and on the possible antitumor effect. Among them, are included 6-O-docosanoyl, stearoyl, lauroyl, octanoyl, butyryl, acetyl, and 4,6-di-O-acetyl derivatives. Some of these compounds were found to serve an improvement in the administration method to living body.

As a basic study in the synthetic approach to immunoactive cell wall peptidoglycan whose backbone is a β(1–4)-linked saccharide of alternating glucosamine and muramic acid, methods for the direct condensation of these sugar components were studied and O-(N-acetyl-β-muramyl)-(1→4)-N-acetyl-D-glucosamine and O-(N-acetyl-β-D-glucosaminyl)-(1→4)-N-acetylmuramic acid were synthesized. In the synthesis of the latter disaccharide, previous formation of an ester bond between the carboxyl group of muramic acid and the 6-hydroxyl group of glucosamine proved to facilitate the glycoside bond fromation between these sugar moieties.

For the investigation on the action mechanism of immunoadjuvant active N-acetylmuramyl-L-alanyl-D-isoglutamine, its labeled compound, i.e., N-acetylmuramyl-L-[U-14C]alanyl-D-isoglutamine was synthesized. For this purpose, an entirely novel synthetic route for the muramyl dipeptide was exploited using cold materials and applied to the preparation of the labeled compound. A convenient synthetic procedure of isoglutamine derivatives is also described.

In the series of synthetic study on peptide antibiotic nisin, a bicyclic sulfide part ring D-E in this molecule was successfully synthesized. Conjunctive sulfide rings were constructed either by one step or stepwise desulfurization reaction from corresponding disulfides by use of hexaethylphosphorus triamide. Thus, all of the ring moieties in nisin were prepared for total synthesis of this antibiotic

An amino acid composition of the pep tide antibiotic longicatenamycin was investigated. Four new amino acids, i.e., thero-β-hydroxy-L-glutamic acid, L-2-amino-5-rnethylhexanoic acid, L-2-amino-6-methylheptanoic acid, and L-2-amino-7-methyloctanoic acid, which were reported by Shoji et al., were reconfirmed by comparison with the synthetic specimens. Racemic forms of the latter three amino acids were synthesized through acetaminomalonate method. Furthermore, 5-chloro-D-tryptophan was newly isolated from the hydrolyzate of the antibiotic. This structure was assigned by NMR, MS and ORD. A steric configuration of this amino acid was certified by degradation to D-aspartic acid through ozonization. 5-Chloro-DL-tryptophan was synthesized from 3-cyanopropionaldehyde and p-chlorophenylhydrazine by Fischer’s indole synthesis.

Two disaccharide dipeptides, i.e., O-(N-acetyl-β-D-glucosaminyl)-(1→4)-N-acetylmuramyl-L-alanyl-D-isoglutamine (2) and O-(N-acetyl-β-muramyl-L-alanyl-D-isoglutamine)-(1→4)-N-acetyl-D-glucosamine (3), which correspond to partial structures of cell wall peptidoglycan were synthesized via the same glucosamine disaccharide as a common intermediate. Thus, selective introduction of lactic acid moiety on either one of the sugar moieties of the intermediate gave two disaccharides respectively which contain muramic acid on either reducing or nonreducing side. Coupling of the peptide moiety followed by deprotection afforded 2 and 3. The results of biological tests showed that both 2 and 3 have the same magnitude of immunostimulating activities as those of N-acetylmuramyl-L-alanyl-D-isoglutamine which is the minimum structure required for expression of the activities.

Hypusine, a new basic amino acid occurring in the homogenate of bovine brain tissue, was synthesized to determine the absolute structure. Nα-Benzyloxycarbonyl-L-lysine benzyl ester was coupled with (S)- or (R)-4-benzyloxycarbonylamino-1-bromo-2-butanol derived from L- or D-malic acid, respectively. The products were deprotected by catalytic hydrogenation. One of the synthetic compounds, i.e., (2S,9R)-2,11-diamino-9-hydroxy-7-azaundecanoic acid, was completely identical with natural hypusine in all respects.

Cyclic guanidino amino acid, capreomycidine, is a component of antituberculous peptides, capreomycin and tuberactinomycin N and O. Its epimer was also found in protease inhibitors, chymostatin and elastatinal. A new synthetic approach to DL-capreomycidine via β-hydroxyornithine was studied for the purpose of total synthesis of capreomycidine and epicapreomycidine of natural forms or its hydroxy derivative, tuberactidine.

2,2′-N:3,3′-O-Tetrakis[(R)-3-hydroxytetradecanoyl]-β(1-6)-D-glucosamine disaccharide 1,4′-bis(phosphate) and its dephospho derivatives were synthesized. The bisphosphate prepared was shown to be identical with a natural biosynthetic precursor of lipid A which corresponds to the lipophilic part of lipopolysaccharide (LPS) in bacterial cell wall. The synthetic bis- and monophosphates exhibited many of typical endotoxic activities of LPS. Consequently, this work established the chemical structure of the biosynthetic precursor of lipid A and elucidated the fundamental structure required for the expression of these activities.

α-Glycosyl phosphates and 4-phosphates of N-acylglucosamine derivatives were prepared in high yields via the reaction of corresponding O-lithium salts with dibenzyl or diphenyl phosphorochloridate at low temperature.

Four stereoisomers of β-methyllanthionine were synthesized by coupling of N-enzyloxycarbonyl-3-methyl-D-cysteine with β-chloroalanine. 1H NMR analysis and retention time in amino acid analysis were studied on these compounds.

For the purpose of the verification of an expectation that the structural analogs of D-alanyl-D-alanine which participates in the biosynthesis of cell wall peptides might inhibit the growth of microorganisms, alanyl-1-aminoethanesulfonic acid was synthesized by the mixed anhydride method. Four diastereomers were separated and their absolute configurations were deduced on the basis of X-ray analysis. None of these dipeptide analogs and their benzyloxycarbonyl or t-butoxycarbonyl derivatives showed appreciable activity against E. coli.

The title compound was synthesized and identified with a partial hydrolysis product from natural streptothricin. This work confirmed the presence of the proposed glycosyl guanidine structure in the antibiotic and established a method for its preparation.

Several linear and branched all-trans-multiprenylacetic acids were synthesised, and introduced to the 6 position of the sugar moiety of muramyl dipeptide and its analog, via an amino acid as a linking unit. Compared with the saturated stearoyl derivative, all the compounds having a multiprenylacetyl group exhibited more potent adjuvant activity on the induction of delayed-type hypersensitivity to N-acetyl-3-(4-arsonophenylazo)-L-tyrosine. The derivatives with larger branched side chains tended to have increased activity.

γ-Hydroxy-β-lysine is a new basic amino acid isolated from the hydrolyzates of antitubercular peptides, tuberactinomycin A and N. In order to confirm the structure and establish the stereochemistry of the amino acid, two diastereoisomers of γ-hydroxy-DL-β-lysine were synthesized by Arndt-Eistert synthesis via β-hiydroxyornithine. Synthetic erythro and threo isomers were found to be identical spectroscopically and chromatographically with the corresponding forms obtained from the antibiotics respectively.

Ethyl 2-(1-benzyloxycarbonylaminoethyl)-R-Δ2-thiazoline-4-carboxylate (III), ethyl 2-(1-benzyloxycarbonylamino-2-methyl-n-butyl)-R-Δ2-thiazoline-4-carboxylate (VI) and their acid amide derivatives (V, VII and VIII) were prepared by either the iminoether coupling method or the dehydration method. As a general character of thiazoline peptide, it was found that the amino acid residue connected to thiazoline ring at N-terminal side is completely racemized at the stage of thiazoline ring formation, and further epimerized, in the case of isoleucine, by treatment with the basic reagent.

Synthesis of thiazoline peptide from cysteine peptide by dehydration with hydrochloric acid in non-aqueous solvent was investigated. By this method, ethyl 2-benzyloxycarbonylaminomethyl-R-Δ2-thiazoline-4-carboxylate and 2 - benzyloxycarbonylaminomethyl-R-Δ2-thiazoline-4-carbonyl-L-leucine ethyl ester were prepared and isolated in pure states. This synthetic method could give a promising route to a total synthesis of bacitracin A. However, the cysteine residue in the latter thiazoline peptide ester was found to be easily racemized under the basic condition.

Tuberactidine (III) is a guanidino amino acid component of an ti tubercular pep tides, tuberactinomycin A and B, while the known guanidino amino acid capreomycidine (V) is involved in tuberactinomycin N and O. The structure of tuberactidine was assigned to be α-(4-hydroxy-2-iminohexahydro-6-pyrimidinyl)glycine and its stereochemistry was also established. During isolation of tuberactidine from an eluate in the column chromatography of tuberactinomycin hydrolyzate, it was converted to Nα-formyltuberactidine dimer (I). In this dimer, structural alternation between a carbinolamine form of cyclol type and an amide lactone form was noticed depending to a pH of the solution. I was hydrolyzed to tuberactidine and viomycidine (IV) with hydrobromic acid. In addition, a plausible pathway for the formation of viocidic acid (VII), one of the artifacts formed during hydrolysis of tuberactinomycin, was proposed.

For the purpose of synthesis of antibiotic bacitracin of six amino acids-membered ring formula, the following intermediate peptides, i.e., cyclo-(Nα-benzy]oxycarbonyl-L-lysyl-Nδ-cyclopentyloxycarbonyl-D-ornithyl-L-isojeucyl-D-phenylalanyl-L-histidyl-α-methyl-L-aspartyl) (III) and Nα-benzyloxycarbonyl-Ne-t-butyloxycarbonyl-L-lysyl-Nδ-cyclopentyloxycarbonyl-D-ornithyl-L-isoleucyl-D-phenylalanyl-Nim-benzyl-L-histidyl-L-aspartyl-D-isoasparagine benzyl ester (IV) were prepared. In this synthesis, cyclopentyloxycarbonyl group was introduced to protect δ-amino group of ornithine residue and cleavability of this protecting group for hydrogen fluoride was investigated.

A protected heptapeptide, the formyl-L-isoleucyl-e-benzyloxycarbonyl-L-lysyl-δ-5-tosyl-D-ornithyl-L-isoleucyl-D-phenylalanyl-im-benzyl-L-histidyl-L-aspartic acid α-methyl-β-benzyl ester, was synthesized by the azide method and the carbodiimide method. It is an intermediate peptide for the total synthesis of the antibiotic bacitracin A, the structure of which is still ambiguous at a few points. β-Benzyl benzyloxycarbonyl-L-aspartate was prepared by a novel method similar to that used in the synthesis of γ-benzyl glutamate. The α-methyl-β-benzyl L-aspartate prepared could be useful in the synthesis of branched aspartic acid peptide. Phenomena of dimorphism were observed in crystals of δ-tosyl-D-ornithine and δ-tosyl-D-ornithyl-L-isoleucyl-D-phenylalanine ethyl ester hydrobromide, and two crystal forms of each compound were isolated in pure states.

Threonine peptide was converted to an oxazolidone derivative via an O-chlorocarbonyl derivative by treatment with phosgene and dimethylaniline followed by refluxing in xylene, wherever the threonin...

In the synthetic study of bacitracins, peptide fragments corresponding to a branched part of bacitracin F, i.e., (S)-2-(2-methylbutyryl)thiazole-4-carboxylic acid 1-succinimidyl ester (III) and L-leucyl-γ-t-butyl-D-glutamyl-L-isoleucine (IV), were prepared. As a macrocyclic part of bacitracin A and F of cycloheptapeptide formula, cyclo- (Nα-benzyloxycarbonyl-L-lysyl-Nδ-cyclopentyloxycarbonyl-D-ornithyl-L-isoleucyl-D-phenylalanyl-L-histidyl-β-benzyl-D-aspartyl-L-asparaginyl) (V) was synthesized through cyanomethyl ester method.

Asparagine peptide was selectively cleaved by the Hofmann rearrangement followed by an alkaline treatment at the peptide linkage in which an amino group of the asparagine residue participated. Upon reaction of N-benzyloxycarbonyl-L-alanyl-L-asparagine with one equivalent of bromine and three equivalents of aqueous sodium hydroxide solution at 60°C, 1-(N-benzyloxycarbonyl-L-alanyl)-2-oxoimidazolidine-5-carboxylic acid was obtained in quantitative yield. When this was treated with an aqueous methanolic sodium hydroxide solution at room temperature, a cleavage reaction occurred to give N-benzyloxycarbonyl-L-alanine and 2-oxo-imidazolidine-5-carboxylic acid. Under the same condition of the rearrangement, N-benzyl-oxycarbonyl-L-asparaginyl-L-phenylalanine was converted to 1-benzyloxycarbonyl-2-oxoimidazo-lidine-5-carbonylphenylalanine. Since glutamine peptide could not give the corresponding ring compound, this cleavage reaction was found to be specific to asparagine peptide.

For a total synthesis of bacitracian A, a synthetic method to secure unprotected thiazoline peptides must be established. 2-Aminomethyl-R-Δ2-thiazoline-4-carboxamide, 2-aminomethyl-R-Δ2-thiazoline-4-carboxylic acid, 2-aminomethyl-R-Δ2-thiazoline-4-carbonyl-L-leucine were synthesized by either the iminoether coupling method or by the dehydration method using N-benzyloxycarbonyl group and benzyl ester as protecting groups.

An optical active 2-(2-methylbutyryl)thiazole-4-carboxylic acid obtained from bacitracin F by an acid hydrolysis was synthesized starting from L-isoleucine. Applying the usual methods for the peptide synthesis, 2-(2-methylbutyryl)thiazole-4-carbonyl-L-leucyl-D-glutamic acid α-methyl-γ-t-butyl ester corresponding to the N-terminal tetrapeptide of bacitracin F, was then synthesized from the thiazole carboxylic acid. UV spectrum of the synthetic tetrapeptide was very similar to that of bacitracin F.

For the purpose of a total synthesis of bacitracin A, a synthetic method of the thiazoline peptide was investigated. A benzyloxycarbonylaminoalkylimino ethyl ether derived from glycine, L-alanine, L-valine, L-leucine or L-isoleucine was coupled with ethyl L-cysteinate hydrochloride to afford the corresponding thiazoline peptide, that is, a dehydrated form of cysteine peptide. While L-cystine was obtained from acid hydrolyzates of those thiazoline peptides, hydrolysis of them after treatment with alkali or ammonia gave DL-cystine. Furthermore, alkaline treatment caused a racemization of the amino acid residue adjacent to the thiazoline ring too.

A new amino acid named galantinamic acid was found as one of the constituent amino acids in a peptide antibiotic galantin I. The primary structure of galantinamic acid was determined chemically and spectrometrically to be 6,10-diamino-2,3,5-trihydroxydecanoic acid.

4-Azidobutyryl esters formed from hydroxyl compounds and 4-azidobutyryl chloride were shown to be cleaved via reduction to 4-aminobutyrate followed by intramolecular O→N-acyl migrations to regenerate the free hydroxyl groups. High susceptibility of azide group to reduction enables the selective removal of this acyl group leaving many other functional groups unchanged.