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A chromogenic substrate 1, 5-bromo-4-chloroindol-3-yl 5-acetamido-3,5-dideoxy-alpha-D-glycero-D-galacto-2-nonulopyranosidon ic acid (X-Neu5Ac), has been synthesized to facilitate the screening of bacterial colonies or plaques for the detection of either natural or mutant neuraminidase activity. Substrate 1 was hydrolyzed by neuraminidase isolated from Clostridium perfringens to release a halogenated indol-3-ol 2 that undergoes rapid aerobic oxidation to form the dark blue pigment, 5,5'-dibromo-4,-4'-dichloroindigo 3. Preliminary kinetic studies indicate that this compound is a good substrate (Km 0.89 x 10(-3) M) for neuraminidase and is quite stable under identical conditions in the absence of enzyme. These results suggest that X-Neu5Ac 1 can be useful to screen for bacterially-encoded enzyme production directly on agar plates.

In this paper, the phrase should be corrected as follows: (page 322, Abstract, line 6) For “remained to be” Read “had been”

A new 1,3,5-phenylene-based metallodendrimer containing a ruthenium bis(terpyridyl) complex was prepared and characterized; the rigid dendritic branches are found to affect the electrochemical properties of the redox-active core.

Two novel analogs of a biosynthetic precursor of lipid A (2) were synthesized. The one analog (3) has acyl groups identical to those of 2, and the other (4) has tetradecanoyl groups in place of the (R)-3-hydroxytetradecanoyl groups of 2. Both 3 and 4 possess an alpha-glycosidically-bound phosphonooxyethyl group in place of the alpha-glycosyl phosphate group of 2. Compounds 3 and 4 exhibited definite antitumor activity against Meth A fibrosarcoma and low toxicity in rabbits, as the original compound 2 does. The replacement of the hydroxytetradecanoyl groups with tetradecanoyl groups barely affected the antitumor activity, but slightly enhanced the toxicity in rabbits.

A rice bran polysaccharide designated RON was subjected either to partial hydrolysis with formic acid or to partial degradation by ultrasonic irradiation. A significant change in the molecular size was also observed during simple chromatography of RON on a strongly acidic ion exchange resin, although the apparent molecular weight of RON had been assumed to be more than 1 x 10(6) daltons (Da). This fact indicates that RON exists as molecular aggregates, presumably mediated by metal cations. Degradation products with average molecular weights above ca. 1 x 10(4) Da which were obtained by any of the three methods still retained the following activities of RON: in vivo antitumor activity against Meth-A fibrosarcoma in mice by oral administration, and in vitro macrophage stimulatory effects to induce tumoricidal activity and interleukin 1 production. This molecular size was proven to be the minimum requisite for these activities because smaller fragments were scarcely active. The aggregation was characteristic of RON but not essential for its antitumor activity because definite, though slightly reduced, activity was exhibited even by the smaller fragments obtained after the ion exchange resin treatment.

Three novel lipid A analogs, which have an alpha- or beta-glycosidically bound phosphonooxyethyl group instead of the alpha-glycosyl phosphate group of natural lipid A, were synthesized. The first analog (2) had an alpha-phosphonooxyethyl group on the identical acylated disaccharide 4'-phosphate structure found in natural lipid A (from Escherichia coli) and hence differed from the latter only in the nature of the acidic group at position 1. The second one (3) had tetradecanoyl groups in place of the two (R)-3-hydroxytetradecanoyl groups bound to the 2- and 3-hydroxyl function of 2, retaining the alpha-phosphonooxyethyl group. The structure of the third analog (4) was the same as that of 3 except that the phosphonooxyethyl group of the former was beta-oriented. Compounds 2 and 3 exhibited potent activity against Meth A at the same level as natural lipid A, whereas 4 showed less activity. This fact revealed that the glycosidic phosphate is not a prerequisite for the antitumor activity of lipopolysaccharide. It can be replaced with a phosphonooxyethyl group without any loss of activity provided that the alpha-anomeric configuration at C-1 is retained. The replacement of the hydroxytetradecanoyl groups with tetradecanoyl groups does not change the activity either.

Clavamine, a new insecticidal toxin isolated from the venom of Joro spider (Nephila clavata) was totally synthesized in order to confirm the proposed structure. In clavamine, a fragment of glycylalanine is inserted in the structure of NSTX-3, a New Guinean spider toxin. The synthesis determined the chemical structure of clavamine unambiguously.

In a study on structure-activity relationship of spider toxin NSTX-3 obtained from venom of Nephila maculata, nine analogs or fragments of natural toxin were synthesized. Among them, des-Arg- NSTX-3 was found to be the minimum structure for blocking the excitatory transmission in the crustacean neuromuscular synapse. A positive charge of the arginine part was concluded to play the most important role for exhibition of the activity.

A group of spider toxins (JSTX, NSTX, argiopin, argiotoxin etc.) share a basic common structure and have been reported to block strongly quisqualate- and kainate-sensitive glutamate responses in vertebrate and invertebrate nervous systems. They are presumed to be potent antagonists of both quisqualate and kainate receptors and may serve as useful tools for characterizing these receptors. We report here the synthesis of tritium-labeled NSTX-3 and the characterization of its binding sites in the rat brain. We found that high- and low-affinity binding sites exist in the cerebellum (Kd = 7.75 and 202 nM, Bmax = 0.37 and 5.54 pmol/mg protein, respectively). Synthetic NSTX analogs strongly inhibited [3H]NSTX-3 binding in the cerebellum (IC50 = 10(-7)-10(-6) M), whereas competitive agonists of glutamate receptors (AMPA, quisqualate, NMDA, kainate, glutamate and aspartate) exhibited weak or no inhibitory effects.

Total synthesis of lipid A’s of Escherichia coli and many other bacterial species achieved in our laboratory (6, 7, 8) contributed not only to confirm their proposed chemical structures but also to establish unequivocally that these phosphorylated polyacyl glucosamine disaccharide with definite structures are responsible for most of the endotoxic activities of bacterial lipopolysaccharide (LPS) (4, 5). Furthermore, precise study on the biological activities could be carried out in relation to the acylation or phosphorylation patterns of the molecules with these pure synthetic preparations of lipid A’s in hand (12, 13). Immunogenicity and antigenicity of lipid A could be analyzed as well (1, 2). As the results, evidences were obtained which indicated that the toxic and other biological activities of endotoxin could be separated by adequate modification of the structure such as distribution of the acyl groups. One might thus be able to utilize some of the beneficial biological activities by further research in this line.

A site-specific ring opening reaction for the antifungal depsipeptide aureobasidin A occurred on treatment with HF at room temperature for 1 hour. The open-chain peptide thus obtained was recyclized to afford the original aureobasidin A without any modification.

A monolithic long-wavelength receiver optoelectronic integrated circuit (OEIC), which integrates an InGaAs PIN-photodiode (PD) and a GaAs field-effect transistor (FET), has been successfully fabricated on a 3-inch-diameter GaAs substrate using InP-on-GaAs heteroepitaxy, by metalorganic chemical vapor deposition (MOCVD) and conventional GaAs-IC process technology. The epitaxial quality of the PD layer has been improved by use of a low-temperature-grown buffer layer, thermal cyclic annealing and an InGaAs/InP strained-layer superlattice. The integrated PD has low dark current of 10 nA at -5 V bias voltage, and exhibited stable operation at 175°C. The fabricated receiver OEIC has 1.4 GHz bandwidth and sensitivity of -28.1 dBm at the transmission rate of 622 Mb/s with bit error rate of 10-9, which is applicable to practical subscriber optical communication systems.

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.

A synthetic adjuvant, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), failed to produce polyarthritis with a wide dose range in a water-in-oil emulsion of mineral oil such as liquid paraffin, Drakeol, or heavy mineral oil. MDP, however, produced moderate to severe arthritis with almost 100% incidence in a water-in-oil emulsion made up of Difco incomplete adjuvant, which consists of Bavol F as an oil vehicle and Arlacel A as an emulsifier. N-acetylmuramyl-L-alanyl-L-isoglutamine did not produce arthritis, whereas 4,6-diacetyl-MDP produced the disease. Bacterial peptidoglycans, such as disaccharide peptides which were N-acetylglucosaminyl-N-acetylmuramyl-L-alanyl-D-isoglutaminyl-meso-diaminopimelyl-D-alanine and N-acetylglucosaminyl-6,o-acetyl-N-acetylmuramyl-L-alanyl-D-isoglutaminyl-meso-diaminopimelyl-D-alanine, also produced polyarthritis with low incidence in Difco oil but not in the other mineral oils described above. MDP and bacterial disaccharide peptides were able to produce the disease even in the latter mineral oil only when the concentration of Arlacel A was increased from 15% to 20 to 30% in the oil. We concluded that one of the minimal essential structures responsible for development of this disease is MDP, although the role of the oil vehicle remained uncertain, and there is no direct correlation between granulona formation and arthritogenicity of MDP.

The structure of lepidopteran was determined by sequential analysis using the Edman method for the whole molecule as well as several fragment peptides obtained by enzymatic and chemical cleavages. Consequently, lepidopteran was found to be a mixture of congeners composed of 35 amino acids possessing one replaceable amino acid residue of lysine with δ-hydroxylysine.

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.

To confirm the revised lipid A structure of Escherichia coli and to establish the structure responsible for its functions, biological activities of the synthetic compounds based on the presented structure of E. coli lipid A were investigated. Compound 506, 2-deoxy-6-O-(2-deoxy-2-[(R)-3-dodecanoyloxytetradecanoylamino]-3-O [(R)3-tetradecanoyloxytetradecanoyl]-beta-D-glucopyranosyl]-3-O-[(R) -3-hydroxytetradecanoyl]-2-[(R)-3-hydroxytetradecanoylamino]-alpha -D-glucopyranose 1,4'-bis(phosphate), exhibited activities identical to those of natural E. coli lipid A in eliciting Shwartzman reaction and tests on lethality, pyrogenicity, interferon- and tumor necrosis factor-inducing activities as well as in B-cell activating activity and Limulus amebocyte lysate gelating activity. With the exception of the Shwartzman reaction the monophosphorylated synthetic compounds at either the 1 or 4' position showed slightly lower activities than the compound with the bisphosphorylated compound (Compound 506). The compound without the phosphate group showed no or only very weak activities. The structural requirements for each activity (i.e. binding position and composition of fatty acids and presence of phosphate groups) are discussed taking into account the results of previous investigations.

In the previous paper [Eur. J. Biochem. 124, 405 (1982)], we demonstrated that chemically synthesized lipid-A analogues such as the 1-monophosphate or 1,4'-diphosphate of 6-O-(2-deoxy-2-tetradecanoylamino-6-O-tetradecanoyl-D-glucopyra nos yl)-2-deoxy-2-tetradecanolyamino-3,4-di-O-tetradecanoyl-D-gluco pyr anose enhanced immunogenicity of liposomal model membranes sensitized with amphipathic antigen when they were incorporated in the same liposomes. Here we extend the observation by testing the recently synthesized analogues including diglucosamine analogues carrying hydroxy and acyloxy fatty acids. Among the analogues tested, those which showed higher adjuvant and mitogenic activities in the liposomal system were N-acylated and O-acylated beta-1,6-linked D-glucosamine disaccharides carrying either amide-bound 3-hydroxytetradecanoic acids in addition to phosphate in position 1 of the reducing sugar or amide-bound 3-tetradecanoyloxytetradecanoic acids. The analogue carrying both amide-bound 3-hydroxytetradecanoic acids and phosphate in position 4 of the non-reducing sugar showed weak adjuvant activity and marginal mitogenic activity.

The effects of polyclonal B cell activation (PBA) of cell walls and their cell wall fractions obtained from several kinds of gram-positive bacteria were studied using the anti-sheep red blood cell (SRBC) or anti-trinitrophenylated (TNP) SRBC plaque forming cell (PFC) responses of cultured spleen cells from Balb/c, athymic nu/nu, their littermates (nu/+), C3H/He (LPS-responder), C3H/HeJ (LPS-non-responder), (CBA/N × Balb/c) F1 male with an X-linked defect in B cell function and the F1 female mice. The cell walls of Staphylococcus epidermidis (ATCC 155), Lactobacillus plantarum (ATCC 8014), Micrococcus lysodeikticus (NCTC 2665), Mycobacterium rhodochrous (ATCC 184), Streptomyces gardneri (ATCC 23911) and Nocardia corynebacteriodes (ATCC 14898) had the ability to induce polyclonal B cell responses in the spleen cells of Balb/c, nu/nu, nu/+, C3H/He and C3H/HeJ mice. The cell wall fractions prepared by enzymatic digestion from the cell walls of S. epidermidis, S. gardneri or N. corynebacteriodes were also capable of inducing polyclonal B cell responses. The responses of spleen cells from (CBA/N × Balb/c) F1 male mice to these active preparations, except the cell walls of M. rhodochrous, were much lower than those of the F1 female mice. These findings indicate that the majority of the cell wall preparations lacks PBA ability for spleen cells with the CBA/N defect, except for the cell walls of M. rhodochrous which possess this ability. The PBA-ability of synthetic peptidoglycan, muramyl dipeptide (N-acetylmuramyl-L-alanyl-D-isoglutamine, MDP), was also examined, and a similar activity was observed in MDP.

Thirteen 6-O-acyl-N-acetylmuramyl-L-alanyl-D-isoglutamines (6-O-acyl-MDPs), including four inactive D-isoasparagine and L-isoglutamine analogs, were tested for their pyrogenicity and immunopotentiating activity to stimulate primary humoral and cellular immune responses in guinea pigs to a model protein antigen, ovalbumin, when administered in various vehicles. Among them, derivatives whose muramic acid residue was substituted by alpha-branched (and beta-hydroxylated) higher fatty acids at the carbon-6 position, especially 6-O-(2-tetradecylhexadecanoyl)-MDP (B3O-MDP) and, to a lesser extent, 6-O-(3-hydroxy-2-docosylhexacosanoyl)-MDP (BH48-MDP) and its L-serine analog [BH48-MDP(L-Ser)], were found to exert strong adjuvant activity in both the induction of delayed-type hypersensitivity and the stimulation of circulating precipitating antibody levels when combined with nonirritating vehicles (liposomes, squalene-in-water emulsion, and phosphate-buffered saline). These vehicles did not efficiently support the adjuvant activity of MDP, the parent molecule of the above lipophilic derivatives. Pyrogenicity tests showed that introduction of alpha-branched higher fatty acid groups but not of straight, long-chain fatty acids at the 6-position of the muramic acid residue resulted in marked decrease of the pyrogenicity inherent to MDP via intravenous administration.

For elucidation of a relationship between chemical structure and biologic activity of lipid A, syntheses of 13 derivatives of glucosamine beta (1-6) disaccharide, which were acylated at 3, 4, and 6'-hydroxyl groups and/or phosphorylated at positions 1 and 4', were carried out. The results showed the importance of the presence of the phosphate group at either position 1 or 4' and of the beta-hydroxyl group in acyl function, particularly in N-linked fatty acids, for the exhibition of biologic activities characteristic of lipid A. New evidence on the positions of fatty acids in natural lipid A of Escherichia coli species obtained by means of 2D-H nuclear magnetic resonance was also demonstrated; the findings indicate that the 3'-hydroxyl group is acylated and the 6'-hydroxyl group in the molecule must be free.

The structure of the lipid A component of E. coli lippopolysaccharide was determined by means of chemical and 2D-NMR methods unequivocally to be a glucosamine β(1′-6)-disaccharide 1,4′-diphosphate acylated at the two hydroxyl (positions C-3 and −3′) and the two amino groups.

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.

Re-mutant lipopolysaccharide (Re LPS) of Salmonella minnesota profoundly inhibited the growth of murine B-cell lines, designated CYG34 and CYG101, established from long term bone-marrow culture. When CYG101 cells were cultured together with Re LPS at concentrations of 2-100μg/ml, the cell proliferation was dose-dependently suppressed. Re LPS hardly or slightly affected the growth of a murine T-cell line, BW5147, pre-B cell lines, 70Z/3 and CYG 8, and a myeloma cell line, X63Ag8. S-form LPS of Escherichia coli and S. typhimurium, Re-mutant LPS of S. minnesota and natural lipid A of E. coil, S. typhimurium and S. minnesota also inhibited the growth of CYG101 cells. However, degraded polysaccharide of S-form LPS of S. typhimurium did not inhibit the cell growth. Synthetic compounds 406, corresponding to a biosynthetic disaccharide lipid A precursor, and 506, corresponding to lipid A of the E. coli type, also inhibited the growth of CYG101 cells. These results suggest that the growth inhibition of cell lines by LPS is selective or specific to the cell line and that the lipid A portion of LPS is involved in this growth inhibition. Double acyl groups of lipid A may not play any role in the inhibition of cell growth.

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.

Silkworm, Bombyx mori , produces self-denfense substance lepidopteran in a haemolymph when it is vaccinated with killed Escherichia coli . Lepidopteran family contains at least three congeners A, B and C, all of which were isolated and determined in amino acid sequences. Furthermore, total synthesis of lepidopteran A was achieved. For elucidation of structure-activity relationship of lepidopteran, twenty one different kinds of peptide fragments were then synthesized. From results of antibacterial tests for those peptides, it is concluded that N-terminal region particularly the Arg -Trp2 sequence is very important for exhibition of the biological activity. The minimal sequence of lepidopteran providing significant bioactivity is the peptide fragment (1–18). α-Helix content in the peptide chain does not necessarily guarantee a manifestation of the activity. An important factor to strengthen the activity seems to be a hydrophobicity in the molecule in addition to the N-terminal region. The assumption was confirmed by preparation of long aliphatic amide of the fragment (1–18) which showed almost comparable activity to that of the original lepidopteran.

Title compounds ( 1a,b ) and an analogous disaccharide ( 2a ) were synthesized via a reaction of a ketosidic fluoride of 3-deoxy-D- manno -2-octulosonic acid (KDO) ( 3 ) with phosphorylated acyl glucosamine di- and monosaccharides.

Total Synthesis of antibiotic althiomycin has been achieved starting from D-cysteine. The imide bond between thiazoline and the pyrrolinone part was constructed by coupling reaction of sodium salt of pyrrolinone with cysteine active ester or by photoreaction with diketene. The hydroxymethyl group attached on the carbon adjacent to C-2 of the thiazoline ring, was introduced by aldol condensation posterior to the thiazoline ring formation. The thiazole part was introduced in a final step in whole process of the total synthesis of the antibiotic. The synthetic althiomycin was identical with the natural antibiotic in all respects.

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.

A synthetic route was established to construct the proposed structure of lipid A which consists of β (1–6) glucosamine disaccharide 1,4′-diphosphate O,N-acylated with (R)-3-hydroxy- or (R)-3-acyloxytetradecanoic acid.

Two antigens, cholera toxin (CT) and a synthetic albumin-conjugated 16-residue peptide derived from the circumsporozoite (CS) protein of Plasmodium falciparum sporozoites, were tested as immunogens in rabbits. The malaria peptide-albumin conjugate by itself was completely nonimmunogenic, and although cholera toxin was immunogenic it also expressed considerable native toxicity. After attachment of CT to liposomes containing ganglioside GM1, toxicity of CT was completely eliminated and antigenicity was enhanced. Therefore liposomes may be capable of reducing toxicity of certain potentially dangerous antigens such as toxins. After incorporation of the malaria peptide-albumin conjugate into liposomes a high titre of specific antibodies was induced against the malaria peptide but not against albumin. These antibodies also reacted with native CS protein. Three adjuvants, including lipid A and two types of lipophilic muramyl dipeptide, were compared and found to be effective in liposomes. Based on the conversion of synthetic P. falciparum CS peptide from a nonimmunogenic to an immunogenic form and on the 'toxoiding' effect of liposomes for CT, it is concluded that liposomes should be considered as being a useful carrier for antigens and adjuvants for vaccines for poorly antigenic or toxic substances.

The biological activities of synthetic glycolipids, which were chemically synthesized and based on the structure of lipid A of the lipopolysaccharide (LPS) from Escherichia coli, were examined with special reference to their adjuvant activity on the induction of delayed-type hypersensitivity, activity on the induction of tumour necrotic factor (TNF) and tumour regressive activity on line 10 hepatoma in strain 2 guinea pigs. Among them, a compound structurally corresponding to free E. coli lipid A (compound 506) as well as LPS exhibited potent adjuvant activity in the induction of delayed-type hypersensitivity in guinea pigs and TNF inducing activity in the sera of mice which were presensitized with Propionibacterium acnes. Compound 506 showed potent lethal toxicity in the intravenous administration of BALB/c mice presensitized with P. acnes. The regressive activity on line 10 hepatoma was observed by the multiple intralesional injection of squalane-treated compounds 504 and 505 in strain 2 guinea pigs.

The first total synthesis of streptothricin F was achieved and its structure was unequivocally confirmed.

A pentaacyl precursor of lipid A biosynthesis, termed precursor Ib, and a structural isomer have been chemically synthesized. These compounds were, in comparison to synthetic Escherichia-coli type lipid A or lipopolysaccharide, analyzed for their activity in typical endotoxin test systems. It was found that both precursor Ib and the isomer exhibited similar or only slightly lower pyrogenic, lethal and Shwartzman-phenomenon-inducing activity than lipid A. All preparations were comparable in their B-lymphocyte mitogenicity, macrophage-activating capacity and immunoreactivity towards lipid A antisera. The proton nuclear magnetic resonance spectra of the 1-dephospho derivative of synthetic and bacterial precursor Ib were indistinguishable proving that the previously proposed structure for precursor Ib is correct.

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.

Two new ureido amino acids, lividine ( 1 ) and grateloupine ( 2 ), were isolated from Grateloupia livida and Grateloupia filicina respectively. The structures of both amino acids were assumed mainly by NMR spectra and determined as N w -carbamoyl-L-citrulline for lividine and as N -carbamoyl- Y -aminobutyric acid for grateloupine by comparison with the synthetic compounds respectively.

The peptide N -acetylmuramyl- l -alanyl- d -isoglutamine (MDP), which has adjuvant activities, and 17 of its derivatives and analogs were synthesized and assayed to elucidate the structure necessary for adjuvant activity in induction of experimental allergic encephalomyelitis (EAE) in guinea pigs. The results revealed the importance of the d configuration and the α-carboxamide group of the isoglutaminyl residue of MDP for adjuvant activity. Replacement of the l -alanyl residue of MDP by d -alanine, but not by l -serine or glycine, resulted in a marked decrease in the activity. The β-methyl glycoside of MDP was found to be more active than the α-methyl derivative. 6- O -Stearoyl- N -acetylmuramyl- l -alanyl- d -isoglutamme showed activity.

Synthetic and biological studies continued in our laboratories con- tributed to elucidate the chemical structure and biological functions of en- dotoxin, which is lipopolysaccharide (LPS) located at the cell surface of gram-negative bacteria. In this paper the effect of structural variation on the biological activities is discussed of lipophilic part of LPS. The recent result of our synthetic approach toward the most simple LPS isolated and characterized from Escherichia goJ Re mutant cells is also described. ~~~~~~ O-hOH)r

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.

A new inhibitor of angiotensin I converting enzyme, I5B2, was isolated from the culture broth of Actinomadura sp. No. 937ZE-1. This compound contains N-methylvaline, tyrosine and 1-amino-2-(4-hydroxyphenyl)ethylphosphonic acid. The microorganism also produced another inhibitor, I5B1, which is identical with K-4 isolated from Actinomadura sp. as an antihypertensive agent.