Hitoshi Minato

Studies on sesquiterpenoids—IX: Structure of ligularol and ligularone from Ligularia sibirica Cass

Abstract Two crystalline sesquiterpenes having a furan ring, named ligularol and ligularone, have been isolated from Ligularia sibirica Cass. Ligularol and ligularone were characterized as 6β-hydroxyfuranoeremophilane (petasalbine) and 6-oxofuranoeremophilane, respectively.

Components of the root of Lindera strychnifolia Vill.—IX : Structres of lindestrene and linderene acetate☆

Abstract In addition to the four known sesquiterpenes (I–IV) two new ones have been isolated from the root of Lindera strychnifolia Vill. One of the new sesquiterpenes was named “lindestrene” and is represented by V, and another was shown to be an acetate of lindren (I).

Studies on sesquiterpenoids—XIX : Structure and absolute configuration of liguloxide, liguloxidol and liguloxidol acetate

Abstract Three closely related sesquiterpene oxides of the guaiane series, named liguloxide (III), liguloxidol (IV) and liguloxidol acetate (V), have been isolated from the aerial parts of Ligularia fischeri Turcz. The absolute configuration of these compounds has been clarified on the basis of the correlation of liguloxide (III) with the known guaioxide (XIX) by epimerization of the C-4 methyl group of the latter compound with the aid of microbial hydroxylation at that position.

Studies on the steroidal components of domestic plants—XLI : Constituents of Reineckia carnea kunth (6) structure of reineckiagenin, isoreineckiagenin and isocarneagenin☆☆☆★

Abstract Convallamarogenin (Ia), isorhodeasapogenin (IIIa), isoreineckiagenin (VIIa), reineckiagenin (VIIIa) and isocarneagenin (XIIIa) were isolated from Reineckia carnea kunth . The three sapogenins, isoreineckiagenin, reineckiagenin and isocarneagenin are new and are the only known stereoidal sapogenins isolated from a plant source containing a hydroxyl group in the F-ring.

Saponins isolated from Bupleurum falcatum L.; components of saikosaponin b.

The components of the saikosaponins a and b derived from the root of Bupleurum falcatum L. have been re-investigated. Saikosaponin b has been shown to consist of 16α, 23, 28-trihydroxyoleana-11,13(18)-dien-3β-yl D-glucopyranosyl-(1 → 3)-β-D-fucopyranoside (II)(saikosaponin b2) and 16α, 23,28-trihydroxy-11α-methoxy-olean-12-en-3β-yl D-glucopyranosyl-(1 → 3)-β-D-fucopyranoside (V)(saikosaponin b4), and saikosaponin a contains 16β, 23,28-trihydroxy-11α-methoxyolean-12-en-3β-yl D-glucopyranosyl-(1 → 3)-β-D-fucopyrano-side (XXI)(saikosaponin b3) and a small amount of 16β, 23,28-trihydroxyoleana-11,13(18)-dien-3β-yl D-glucopyranosyl-(1 → 3)-β-D-fucopyranoside (XXII)(saikosaponin b1).

Microbial transformation of sesquiterpenoids—I : Structure elucidation of guaioxide with the aid of microbial hydroxylation

Abstract Guaioxide is a saturated sesquiterpene oxide, for which four possible structures have been suggested. Attempted microbial hydroxylation of the compound was successful, this led to a way to open its oxide linkage under mild conditions, and to a decision of the stereochemistry II for guaioxide.

Studies on the metabolites of Verticillium sp. Structures of verticillins A, B, and C

Three new antibiotics, verticillins A (Ia), B (XVIII), and C have been isolated from Verticillium sp. Stereo-structures of verticillins A and B, which are derivatives of bi-(3,11 a-epidithio-1.4-dioxopyrazino[1′,2′ : 1,5]pyrrolo-[2,3-b]indol-10b-yl), have been elucidated by chemical and physicochemical methods. Verticillin C is thought to be an epitrithio-analogue of verticillin B.

A new method for the synthesis of furan compounds

A number of furans have been synthesised in good yield from α,β-unsaturated γ-lactones by use of dialkylaluminium hydrides. This method is simpler and more efficient than earlier methods.

Studies on sesquiterpenoids. Part XIV. Total synthesis of (±)-atractylon

The structure of a furanosesquiterpene, atractylon, isolated from Atractylis ovata Thunb and Atractylodes japonica Koizumi, was established by Yosioka and his co-workers. As starting material for the synthesis of atractylon, 2,3,4,6,7,8-hexahydro-2-oxonaphthalene has been used, and 4,4a,5,6,7,8,8a,9-octahydro-3,8a-dimethyl-5-methylenenaphtho[2,3-b] furan has been synthesised. This racemic compound is identical with atractylon, by comparison of infrared spectra.

Studies on sesquiterpenoids. Part XVIII. Total synthesis of (±)-carabrone

To confirm the structure of carabrone (I), a cyclopropanoid sesquiterpene lactone isolated from Carpesium abrotanoides Linn., (±)-perhydro-5aα-methyl-3-methylene-5α-(3-oxobutyl)cyclopropa[f]benzofuran-2-one (I) has been synthesised. The i.r. spectrum and gas chromatographic retention time of this racemic compound were identical with those of carabrone.