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Featured researches published by I. Ninomiya.


Tetrahedron | 2000

Radical Cyclization in Heterocycle Synthesis. Part 10: A Concise Synthesis of (−)-Kainic Acid via Sulfanyl Radical Addition–Cyclization–Elimination Reaction

Okiko Miyata; Yoshiki Ozawa; I. Ninomiya; Takeaki Naito

Abstract Sulfanyl radical addition–cyclization–elimination of diallylamines in the presence of thiophenol and AIBN gave the 2,3,4-trisubstituted pyrrolidine in high yield. This reaction was extended to a radical cyclization using a catalytic amount of thiophenol. A successful application was demonstrated by the asymmetric synthesis of (−)-kainic acid.


Tetrahedron Letters | 1995

A novel and concise synthesis of aminocyclopentitols and 1-deoxynojirimycin via radical cyclization of oxime ethers

Toshiko Kiguchi; Kazumi Tajiri; I. Ninomiya; Takeaki Naito; Hajime Hiramatsu

Abstract Tributyltin hydride-induced radical cyclization of the oxime ether 3 derived from D -glucose proceeded smoothly to give two amino alcohols 4 and 5 which were converted into two aminocyclopentitol pentaacetates 8 and 12 and 1-deoxynojirimycin known as glycosidase inhibitors.


Tetrahedron | 1997

Asymmetric construction of two contiguous stereocenters by diastereoface differentiating addition reaction of thiols to chiral imides: Formal synthesis of (+)-diltiazem

Okiko Miyata; Tetsuro Shinada; I. Ninomiya; Takeaki Naito

Abstract A high degree of diastereoselectivity has been achieved on the asymmetric construction of two contiguous stereocenters by the conjugate addition of thiols to α,β-unsaturated imides possessing Evanss chiral auxiliary. Addition reactions of thiophenol to chiral E-and Z-2-methylcrotonyl imides 4 proceeded with high diastereoface selectivities. Diastereoselectivities were discussed when E- and Z-imides4 and 5 were used as the substrates. A successful application was demonstrated by the formal synthesis of a clinically useful cardiac drug, (+)-diltiazem.


Tetrahedron | 2000

Radical Cyclization in Heterocycle Synthesis. Part 9: A Novel Synthesis of Aminocyclitols and Related Compounds via Stannyl Radical Cyclization of Oxime Ethers Derived from Sugars

Toshiko Kiguchi; Kazumi Tajiri; I. Ninomiya; Takeaki Naito

Abstract Stannyl radical addition–cyclization of oxime ethers derived from d -glucose, d -galactose, and d -xylose proceeded smoothly to afford alkoxyamino alcohols which were effectively converted into two types of glycosidase inhibitors or its candidates such as aminocyclitols, 1-deoxynojirimycin, and 1-deoxygalactostatin via reductive ring-expansion of trans alkoxyamino alcohols.


Tetrahedron | 1998

Total synthesis of (+)-azimic acid, (+)-julifloridine, and proposed structure ofN-methyljulifloridine via cycloaddition of nitrone to a chiral dipolarophile

Toshiko Kiguchi; Mitsuko Shirakawa; Rina Honda; I. Ninomiya; Takeaki Naito

Abstract A combination of 1, 3-dipolar cycloaddition of Z-nitrones to the chiral dipolarophile and subsequent ring transformation of the resulting adducts to the piperidinols has provided a new practical synthesis of 2, 6-disubstituted 3-piperidinol alkaloids, (+)-azimic acid, (+)-julifloridine, and the proposed structure ofN-methyljulifloridine. Download : Download full-size image


Tetrahedron Letters | 1996

Hydroximate as a synthetically useful functional group: A novel synthesis of lactones using hydroximates as a tether

Okiko Miyata; Atsuko Nishiguchi; I. Ninomiya; Takeaki Naito; Keiichi Aoe; Kimio Okamura

Abstract Hydroximate has proved to be a potential functional group by realizing the radical cyclization of the dienes connected with the hydroximates 4 and 10 followed by conversion of the resulting cyclic hydroximates 5, 6, 11 , and 12 to lactones 13 and 14 .


The Alkaloids: Chemistry and Biology | 1998

Chapter 8 Pseudodistomins: Structure, Synthesis, and Pharmacology

I. Ninomiya; Toshiko Kiguchi; Takeaki Naito

Publisher Summary The chapter discusses pseudodistomins, their occurrence, structure, synthesis, and pharmacology. The first paper regarding the series of natural products appeared in 1987 on the isolation and structure proposal of pseudodistomins A and B. The structures of pseudodistomins A and B were proposed based mainly on the assignment of their 1 H and 13 C NMR spectra. Pseudodistomins A and B were readily hydrogenated at the dienyl group in their side chains to afford an identical tetrahydro-pseudodistomin, which played a key role in their initial structure determination. Four syntheses of this structure have been reported, almost at the same time, in 1992–1994. Natsume e t al. had developed a new type of carbon–carbon bond forming reaction using singlet oxygen and succeeded in applying this reaction to hydropyridines and then to tetrahydro-pseudodistomin. Pharmacological results were reported on the components from the other tunicates, such as Pseudodistoma cruciparta , Pseudodistoma novaezelandiae, and Pseudodistoma crucigaster .


Journal of Heterocyclic Chemistry | 1989

Synthesis of 6H,8H‐isoquino[2,3‐c][1,3]benzothiazin‐8‐ones

Lajos Fodor; János Szabó; Gábor Bernáth; Pál Sohár; David B. MacLean; Richard W. Smith; I. Ninomiya; Takeaki Naito


Chemical & Pharmaceutical Bulletin | 1997

Radical Cyclization in Heterocycle Synthesis. II. Total Synthesis of (±)-Anantine and (±)-Isoanatine

Takeaki Naito; Yuko Honda; Vanida Bhavakul; Sayaka Yamaguchi; Azusa Fujiwara; Okiko Miyata; I. Ninomiya


Chemical & Pharmaceutical Bulletin | 1996

A NOVEL SYNTHESIS OF (+)-AZIMIC ACID

Toshiko Kiguchi; Mitsuko Shirakawa; I. Ninomiya; Takeaki Naito

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Takeaki Naito

Kobe Pharmaceutical University

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Toshiko Kiguchi

Kobe Pharmaceutical University

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Kazumi Tajiri

Kobe Pharmaceutical University

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Mitsuko Shirakawa

Kobe Pharmaceutical University

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Atsuko Nishiguchi

Kobe Pharmaceutical University

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Gábor Bernáth

Hungarian Academy of Sciences

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Pál Sohár

Eötvös Loránd University

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