Abstract: Addition compounds having the formula ##STR1## wherein R.sub.1 represents an aliphatic oxycarbonyl group, benzyloxycarbonyl group which can have nuclear substituents, or benzoyl, aromatic sulfonyl or aromatic sulfinyl group; R.sub.2 represents methyl, isopropyl, isobutyl, isoamyl or benzyl group; R.sub.3 represents a lower alkoxyl, benzyloxy or benzhydryloxy group and n represents 1 or 2 are produced by reacting an N-substituted monoaminodicarboxylic acid having the formula ##STR2## with an amino carboxylic acid ester having the formula ##STR3## in the presence of a protease.

Abstract: Protease is recovered by reacting a first amino acid whose amino group is protected with a protective group with a second amino acid whose carboxyl group is protected with a protective group, in an aqueous medium in the presence of a protease to result a peptide synthesis to deposit the addition compound of a dipeptide and said second C-terminal protected amino acid; dissolving said addition compound into the aqueous medium by adding a polar organic solvent which is miscible with water and separating an insoluble material from the resulting suspension by a solid-liquid separation to isolate the protease.

Abstract: Protease is recovered by reacting a first amino acid whose amino group is protected with a protective group with a second amino acid whose carboxyl group is protected with a protective group, in an aqueous medium in the presence of a protease to result a peptide synthesis to deposit the addition compound of a dipeptide and said second C-terminal protected amino acid; dissolving said addition compound by adding an organic solvent to a precipitate separated from the reaction mixture and isolating the protease from an organic solvent suspension or dissolving said addition compound by adding a water immiscible organic solvent and separating the organic solvent phase by a liquid-liquid separation.The addition compound can be dissolved in an organic solvent after separating the precipitate from the reaction mixture.The addition compound can be also dissolved by adding a water-immiscible organic solvent to the reaction mixture and the organic solvent phase can be separated from the aqueous phase.

Abstract: Addition compounds having the formula ##STR1## wherein R.sub.1 represents an aliphatic oxycarbonyl group, benzyloxycarbonyl group which can have nuclear substituents, or benzoyl, aromatic sulfonyl or aromatic sulfinyl group; R.sub.2 represents methyl, isopropyl, isobutyl, isoamyl or benzyl group; R.sub.3 represents a lower alkoxyl, benzyloxy or benzhydryloxy group and n represents 1 or 2 together with methods for preparing (I) and for decomposing (I) into the constituent dipeptide esters and amino acid esters.

Abstract: A peptide having the formulaX--A--B--Ywherein A and B are the same or different and represent an amino acid residue or a peptide residue; X represents an amino protective group and Y represents a carboxyl protective group, is prepared by reacting an amino acid or peptide having an N-terminal protective group or a salt thereof of the formula:X--A--OHwith an amino acid or peptide having a C-terminal protective group or a salt thereof of the formula:H--B--Yin the presence of metalloproteinase in an aqueous solution having a pH which maintains the enzyme activity of said metalloproteinase.

Abstract: A peptide having the formulaX--A--B--Ywherein A and B are the same or different and represent an amino acid residue or a peptide residue; X represents an amino protective group and Y represents a carboxyl protective group, is prepared by reacting an amino acid or peptide having an N-terminal protective group or a salt thereof of the formula:X--A--OHwith an amino acid or peptide having a C-terminal protective group or a salt thereof of the formula:H--B--Yin the presence of metalloproteinase in an aqueous solution having a pH which maintains the enzyme activity of said metalloproteinase.

Abstract: A novel process for producing allyl alcohol derivatives having the formula ##STR1## wherein R.sup.1 represents a hydrogen atom or a lower alkyl group; and R.sup.2 represents an alkyl group which can have an inert substituent; and X represents a hydrogen atom, a hydroxy, an alkoxy, a tetrahydropyranyloxy or a silyloxy group; which are useful intermediates for the syntheses of prostaglandins and analogous compounds is disclosed. In the process, the allyl alcohol derivatives are produced starting from .beta.-keto-esters and azides through a series of reactions.

Abstract: A peptide having the formulaX--A--B--Y--wherein A and B are the same or different and each represents an amino acid residue or a peptide residue, X represents an amino protective group, Y represents a carboxyl protective group selected from the group consisting of tertiary alkoxy, and benzyloxy, benzylamino and benzhydrylamino which can be substituted with an inert substituent, is prepared by a process which comprises reacting an amino acid or peptide having an N-terminal protective group, or a salt thereof of the formula:X--A--OHwith an amino acid or peptide having a C-terminal protective group or a salt thereof of the formula:H--B--Yin the presence of a thiol proteinase or serine proteinase enzyme in an aqueous solution having a pH sufficient to maintain the enzyme activity of said thiol proteinase or serine proteinase.

Abstract: A novel process for producing 3-formylcyclopentanone derivatives which are useful intermediates for syntheses of five-membered ring compounds such as prostaglandins is disclosed. In the process, 3-formylcyclopentanone derivatives are produced starting from .beta.-dicarbonyl compounds and azides through several-step reactions.