Abstract: A compound of the formula (I) ##STR1## which is identified as an actinonin has now been found to potentiate the immune response in animals bearing Ascites Sarcoma 180 tumor cells.

Abstract: New arphamenine-related compounds are now provided, which are represented by the formula ##STR1## wherein R.sub.1 denots a hydrogen atom or an amino-protecting group, R.sub.2 denotes a dimethylpyrimidinyl group, R.sub.3 denotes a hydrogen atom or a hydroxyl group, and R.sub.4 denotes a hydrogen atom or a carboxyl-protecting group. The new arphamenine-related compounds exhibit a carboxypeptidase-inhibitory activity and also an immunopotentiating activity and are useful for potentiating the immune response in a living animal.

Abstract: New physiologically active substances, arphamenine A and arphamenine B which are generically termed arphamenine are produced from a new microorganism, BMG361-CF4 strain identified as FERM P-6521 or FERM BP-286 or ATCC No. 39373. Arphamenine is useful as a host defence stimulator having an activity to enhance cell-mediated immunity, and also as an anti-tumor agent.

Abstract: New 3-N-acyl derivatives of 3-amino-2-hydroxy-4-phenylbutanoic acid are provided, which exhibit analgesic activity and are affective to enhance the morphine analgesia.

Abstract: 3-Amino-2-hydroxy-4-phenylbutanoic acid and esters thereof as well as new derivatives thereof which are related to bestatin in their chemical structure are active to enhance the immune response in living animals.

Abstract: A process for producing threo-3-amino-2-hydroxybutanoylaminoacetic acids comprises the steps of allowing to react a starting compound represented by the general formula: ##STR1## wherein R.sub.1 represents a naphthyl or a group of the formula: ##STR2## in which R.sub.6 and R.sub.7 represent individually hydrogen, halogen, amino or a protected amino, hydroxy or a protected hydroxy, a lower alkoxy or a lower alkyl and R.sub.2 represents a protected amino, with a starting compound represented by the general formula: ##STR3## wherein R.sub.3 represents hydrogen or an ester residue, to obtain threo-3-protected amino-2-hydroxy-4-oxobutanoic acid or its ester represented by the general formula: ##STR4## wherein R.sub.1, R.sub.2 and R.sub.3 have the same meanings as above, and then reducing the same into threo-3-protected amino-2-hydroxybutanoic acid or its ester represented by the general formula: ##STR5## wherein R.sub.1, R.sub.2 and R.sub.

Abstract: L-Argininal derivatives of the general formula: ##STR1## are disclosed. A method of manufacturing any such derivative is also disclosed. The L-argininal derivative of this invention has a strong inhibitory activity on proteases, such as serine and thiol proteases, and is expected to provide useful medicines, including those which are effective for diseases caused by abnormal elevation of protease activity.

Abstract: A new analgesic agent is now provided, which comprises as the active ingredient 3-amino-2-hydroxy-4-phenylbutanoic acid and some related compounds thereof. These compounds have now found to be effective as inhibitor against enkephalinase and as an agent for enhancing analgesic activity of morphine.

Abstract: Threo-3-protected amino-2-hydroxy-4-oxobutanoic acid or its esters represented by the formula: ##STR1## wherein R.sub.1 represents naphthyl or a group of the formula ##STR2## in which R.sub.6 and R.sub.7 represent individually hydrogen, halogen, amino, an amino protected with acyl, lower alkyloxycarbonyl or carbamoyl, hydroxy or protected with acyl, lower alkyloxycarbonyl or carbamoyl, lower alkoxy, lower alkyl or phenyl group; R.sub.2 represents an amine protected with acyl, lower alkyloxycarbonyl or carbamoyl; and R.sub.3 represents hydrogen, lower alkyl having 1 to 6 carbon atoms or benzyl.

Abstract: 3-Amino-2-hydroxy-4-phenylbutanoic acid and esters thereof as well as new derivatives thereof which are related to bestatin in their chemical structure are active to enhance the immune response in living animals.

Abstract: New physiologically active substances, ebelactone A and ebelactone B which are generally termed ebelactone are produced from a new microorganism, Streptomyces MG7-G1 strain identified FERM-P 5363 or ATCC No. 31860 and ATCC No. 31880. Ebelactone is useful as a host defense stimulator having an activity to enhance cell-mediated immunity, and also as an anti-inflammatory agent.

Abstract: A new compound is produced which has the general formula: ##STR1## wherein R represents hydrogen atom or a lower alkyl group and which exhibits an immunopotentiating activity. This new compound as well as its pharmaceutically acceptable salts and hydrates are useful for immunotherapy and treatment of immune diseases and disorders in living animals including human beings. The new compound can be produced by reduction of a hydroxyterephthalic acid alkyl ester or by esterification of the corresponding 3-hydroxy-4-(hydroxymethyl)-benzoic acid.

Abstract: This invention provides tetrapeptide derivatives of the formula (I): ##STR1## wherein R.sup.1 and R.sup.2 are methyl, 1-methylethyl, 2-methylpropyl, 1-hydroxyethyl, 2-carboxyethyl or 4-aminobutyl and Y is ##STR2## wherein R.sup.3 is methyl, 1-methylethyl, 2-methylpropyl, 1-methylpropyl, hydroxymethyl, 1-hydroxyethyl, carboxymethyl, 2-carboxyethyl, 4-aminobutyl, 3-guanidinopropyl, benzyl or p-hydroxybenzyl excluding the compounds in which R.sup.1 and R.sup.2 are each 1-methylethyl and also R.sup.3 is carboxymethyl or 2-carboxyethyl, the first and leftmost .beta.-amino acid moiety in said tetrapeptide derivatives having the (2S,3R)-configuration and a primary amino group and the second, third and fourth .alpha.-amino acid moieties in said tetrapeptide derivatives having the L-configuration. These compounds have an inhibitory activity on several types of aminopeptidases.

Abstract: A process for producing threo-3-amino-2-hydroxybutanoylaminoacetic acids comprises the steps of allowing to react a starting compound represented by the general formula: ##STR1## wherein R.sub.1 represents a naphthyl or a group of the formula: ##STR2## in which R.sub.6 and R.sub.7 represent individually hydrogen, halogen, amino or a protected amino, hydroxy or a protected hydroxy, a lower alkoxy or a lower alkyl and R.sub.2 represents a protected amino, with a starting compound represented by the general formula: ##STR3## wherein R.sub.3 represents hydrogen or an ester residue, to obtain threo-3-protected amino-2-hydroxy-4-oxobutanoic acid or its ester represented by the general formula: ##STR4## wherein R.sub.1, R.sub.2 and R.sub.3 have the same meanings as above, and then reducing the same into threo-3-protected amino-2-hydroxybutanoic acid or its ester represented by the general formula: ##STR5## wherein R.sub.1, R.sub.2 and R.sub.

Abstract: A new physiologically active substance named esterastin is now provided, which inhibits the activity of esterase and is useful as an immunosuppressive drug. Esterastin is produced by cultivating a micro-organism Streptomyces MD4-C1 identified as FERM-P 3723 or ATCC. 31336 in a culture medium under aerobic conditions and recovering it from the resulting culture.

Abstract: Bestatin, which is [(2S,3R)-3-amino-2-hydroxy-4-phenylbutanoyl]-L-leucine, and related compounds which inhibit aminopeptidase B, leucino aminopeptidase and Bleomycin hydrolase, enhance the anti-tumor effect of Bleomycin and exhibit an antifertility effect were synthesized and tested.

Abstract: A new compound having the formula ##STR1## and now designated forphenicinol is produced, which exhibits an immunopotentiating activity. This new compound as well as its pharmaceutically acceptable salts and hydrates are useful for immunotherapy and treatment of immune diseases and disorders in living animals, including human beings. The new compound can be produced by hydrolysis of the corresponding aminonitrile compound of the formula ##STR2## or by reduction of forphenicine.

Abstract: Three, new physiologically active derivatives of esterastin are now provided, which inhibit the activity of esterase similarly to the parent esterastin and further exhibit a higher inhibiting activity against cholesterol esterase than the parent esterastin. These three new derivatives are tetrahydroesterastin which is produced by catalytic hydrogenation of esterastin; 3,5-di-hydroxy-2-hexylhexadeca-7,10-dienoic 1,3-lactone which is produced by alkaline hydrolysis of esterastin; and 3,5-di-hydroxy-2-hexylhexadecanoic 1,3-lactone which is produced either by alkaline hydrolysis of said tetrahydroesterastin or by catalytic hydrogenation of the product of the alkaline hydrolysis of esterastin.

Abstract: Bestatin, which is [(2S,3R)-3-amino-2-hydroxy-4-phenylbutanoyl]-L-leucine, and related compounds which inhibit aminopeptidase B, leucino aminopeptidase and Bleomycin hydrolase, enhance the anti-tumor effect of Bleomycin and exhibit an antifertility effect were synthesized and tested.

Abstract: A new physiologically active substance named esterastin is now provided, which inhibits the activity of esterase and is useful as an immunosuppressive drug. Esterastin is produced by cultivating a microorganism Streptomyces MD4-C1 identified as FERM-P 3723 or ATCC. 31336 in a culture medium under aerobic conditions and recovering it from the resulting culture.