This short review article briefly summarized recent trend of the chemistry of metallacycle that contains metal-heteroatom bond in their ring system (namely heterometallacycle). Oxametallacycles and azametallacycles are typical compounds. These heterometallacycles have been classified by the term of ring-size, and structure, reactivity, and catalytic activity of various kinds of heterometallacycles have been reviewed.

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Compactsized, multifunctional 2- (N-cyanoimino) thiazolidine (NCT) (1) derivatives exhibited wide range reactivities depending on the N (3) -substituent and the reagents used. 3-Acyl-NCTs (4) were proved to be excellent acylating reagents for amines, alcohols, and thiols. NCT derivatives were converted to various heterocyclic compounds, e.g.., imidazo [2, 1-b] thiazoles (7), 2-aminothiazolo [3, 2-b] -1, 2, 4-triazole (8), triazoles (12, 13), 2, 4-diamino-s-triazines (17, 18, 21), and 1, 2, 4-thiadiazin-3-ones (25). In addition, the regioselectivity of hydride reduction of 5 could be controlled by changing the reagents. Other interesting alkyl or acyl migrations were also observed in the reaction of 5 and 6, and a new synthetic pathway to an anti-ulcer agent, cimetidine (43), was developed utilizing an alkyl migration reaction.

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Conjugated heterocycles fused with strained bicyclic skeletons are of considerable interest owing to their effect of angular strain for the physical and chemical properties. In the case with a fused norbornadiene, possible through-space and through-bond interactions of π electrons and the behavior of a cationic intermediate resulting by an electrophilic reaction of the olefin moiety are also of interest. In this context, we have synthesized five- and six-membered heteroaromatics fused with norbornadiene or 2-azanorbornene, and a 1, 4-dihydropyrazine fused with two bornene skeletons. Unusual spectral and redox properties and peculiar cycloaddition reactions probably due to the angular strain of fused rings, as well as the behavior of norbornenyl cations of fused pyridazines and pyrazines are described.

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The present paper mainly describes recent progress in the chemistry of chiral porphyrins and metalloporphyrins with molecular asymmetry. I first show synthetic methodologies for chiral porphyrins with molecular asymmetry from prochiral porphyrins, and then provide the examples of enantioselective reactions and recognitions by using the chiral strapped porphyrins and metalloporphyrins ; (1) asymmetric catalytic oxidation of olefins and sulfides, (2) asymmetric Michael addition of thiol to enone, (3) highly enantioselective recognition of amino acid derivatives, (4) helix-sense selective recognition of poly (glutamic acid), and (5) enantioselective reconstitution with apocytochrome b₅₆₂. I also demonstrate that the porphyrin ligand of chiral double-decker complexes rotates in response to external stimuli (e.g., heat, proton), by taking advantage of successful resolution of the enantiomers.

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Glycopeptides and glycoproteins have received much attention due to their biological interests in cell recognition and cell adhesion.
Recently we have developed a new chemo-enzymatic synthetic strategy for glycopeptide and glycoprotein. In this article we describe our new methodology including 1) a new synthetic method of glycosylasparagine derivatives by the reaction of glycosyl azide and aspartic acid in the presence of tertially phosphine, 2) solid-phase synthesis of [Asn (G1cNAc)] -peptide without protecting the hydroxyl functions using dimethylphosphinothioic mixed anhydride method, 3) peptide elongation by peptide thioester method, and 4) transglycosylation reaction using endo-β-N-acetylglucosaminidase from Mucor hiemalis (Endo-M). By these methods, we synthesized eel calcitonin (32 amino acids) analog having natural complex-type sugar chain (11 sugar residues).

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From the viewpoint of agricultural situations in Japan, safe agrochemicals for mammals and useful livings in environment have been strongly preferred. Among several hundred compounds prepared, the present authors found a novel chloroacetanilide “Thenylchlor” which shows high herbicidal activity at the dosage of 27 g/1, 000 m² (10 are) for barnyardgrass in paddy field. Thenylchlor is extraordinarily secure herbicide, being judged from the results of toxicity studies and the studies related to environment. To launch Thenylchlor in the market, we made quite a big effort for the economical production of the key intermediate, “3-methoxythiophene” and the final product, “Thenylchlor” and established a series of epoch-making processes. Getting the registration in 1993, we commercialized Thenylchlor as mixed flowables. The sales are growing smoothly year by year, and the major sales product, “Kusamets Flowable”, became a top three best seller among many herbicides for paddy field rice in 1996.

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