Hiroyuki Ishiwata

Isolation, structure, and synthesis of dolastatin D, a cytotoxic cyclic depsipeptide from the sea gare Dolabella auricularia

Abstract Dolastatin D ( 1 ), a cytotoxic cyclic depsipeptide possessing the novel β-amino acid (2 R ,3 R )-3-amino-2-methylbutanoic acid [(2 R ,3 R ]- 3 ] as a component, has been isolated from the Japanese sea hare Dolabella auricularia . The absolute stereostructure of 1 was elucidated on the basis of spectroscopic analysis and chemical degradation and was further confirmed by synthesis.

Total synthesis of optically active integerrimine, a twelve-membered dilactonic pyrrolizidine alkaloid of retronecine type

Abstract A total synthesis of the natural enantiomer of integerrimine (1), a twelve-membered dilactonic pyrrolizidine alkaloid of retronecine type has been achieved through the enantioselective synthesis and regioselective coupling of (+)-retronecine (4) and (+)-integerrinecic acid (methylthio)methyl ether (6).

Regioselective oxidation of β-hydroxyazo compounds to β-hydroxyazoxy compounds and its application to syntheses of maniwamycins A and B

Abstract A new preparation of β-hydroxyazo compounds and regioselectivities on their oxidation to β-hydroxyazoxy compounds have been described. A new synthesis of antifungal antibiotic maniwamycin A and the first synthesis of maniwamycin B by using this methodology have been also described.

Three sesquiterpene alkaloids from Euonymus alatus forma Striatus

Abstract Three new sesquiterpene alkaloids, alatusamine, neoalatamine and alatusinine, were isolated from the fruits of Euonymus alatus forma striatus and their structures elucidated by spectroscopic and chemical methods.

Total synthesis of optically active integerrimine, a twelve-membered dilactonic pyrrolizidine alkaloid of retronecine type. III: Regioselective elaboration of the unsymmetrical twelve-membered dilactone and total synthesis of (−)-integerrimine

Abstract The first enantioselective synthesis of optically active integerrimine, the twelve-membered dilactonic pyrrolizidine alkaloid has been achieved.

Synthesis of bracken ultimate carcinogen analogues possessing a DNA binding moiety and their DNA cleaving activities

Two bracken ultimate carcinogen analogues possessing a DNA binding moiety, 4 and 5, have been synthesized and have been found to cleave DNA more effectively than the control compounds, 21 and 22, that have no DNA binding moiety.

Synthesis of novel antibiotic Maniwamycin A

Abstract Novel antifungal antibiotic maniwamycin A was synthesized in optically active form.