Yoshio Kitahara

Growth and germination inhibitors in rice husks

Abstract A search for growth and germination inhibitors in rice husk ( Oryza sativa L. cv Koshihikari) revealed four compounds, ineketone, S (+)-dehydrovomifoliol, momilactone-C and p -coumaric acid, in addition to the previously known momilactones-A and -B. The isolation and structural determination of these inhibitors are reported. The flavonoid tricin and three steroids were also detected in the husk but none showed any inhibitory activity.

Constituents of genus petasites—IV : Bakkenolide-A, a sesquiterpene of novel carbon skeleton

Abstract A group of a new type of sesquiterpene, named bakkenolide-A, B, C, D, and E was isolated from the buds of Petasites japonicus (Sieb. et Zucc.) Maxim. subsp. giganteus (Fr. Schm.) Kitam. (Japanese name, Akita-buki). They have a novel spiro-γ-lactone grouping. The structure and stereochemistry including absolute configuration was established for bakkenolide-A (B-A) ( 1 ) on the basis of chemical degradations (Chart 1, 2) and physical measurements. The C 11 -dicarboxylic acid ( 5 ), a main degradation product of B-A during potassium permanganate oxidation, was instrumental in determination of the full structure. The absolute configuration was based on the transformation of B-A to the known perhydroindanone derivative ( 12 ).

Interconversion between hibaene and kaurene

Abstract Hibaene-α-epoxide, upon treatment with BF 3 -etherate in benzene, undergoes skeletal rearrangement into the kaurane ring system, giving an unsaturated alcohol or a glycol, respectively. The unsaturated alcohol, after conversion to the corresponding unsaturated ketone, affords kaurane, isokaurene, and kaurane by Huang-Minlon reduction. It has also been found that an equilibrium mixture of kaurene, isokaurene and hibaene, in the ratio of 2:3:5, is produced when either kaurane or hibaene is heated in boiling xylene in the presence of iodine; thus the interconversion between hibaene and kaurene has been achieved. The stereochemistry of the intermediates in the transformation of hibaene to kaurene has been established.

Cyclization of polyenes: XII. Direct brominative ring closure of polyenes

Abstract In connection with a program directed toward the biogenetic-type synthesis of bromine-containing terpenoids, we have developed a new reagent system which provides for selective brominative cyclization of polyenes. The mechanism of Br + -formation in nature is discussed on the basis of the new reagent system.

The coumarin heraclenol as a growth inhibitor in parsley seeds

Abstract By the aid of germination assay with lettuce seeds, the germination inhibitors in the parsley seeds were investigated. One of the inhibitors was revealed to be heraclenol.

Cyclization of polyenes: VI. Biogenetic-type synthesis of levantenolides isolated from Turkish tobacco☆

Abstract Keto acid (VII) was assumed to be a precursor in the biogenesis of levantenolides (IV and V). The syntheses of the analogous compounds (IX and X) and their cyclization to IV and V were carried out as follows. Reaction of farnesyl bromide (XV and XX) with 2,2′-di-3-methylfurylmercury afforded the corresponding furano derivatives (XVI and XXI), which were photo-oxidized to butenolide derivatives (IX and X). Biogenetic-type cyclization of IX and X with stannic chloride afforded IV, V, and XIX in moderate yields.

Cyclization of polyenes—V : Synthesis of α-chamigrene by the cyclization of cis- and trans-monocyclofarnesols☆

Abstract Trans-Monocyclofarnesic acid (IXa) was obtained from dihydro-β-ionone (X) and triethyl phosphono-acetate in moderate yield. Cis-Monocyclofarnesic acid (IXb) was separated from the mixture of the Wittig reaction. Cyclization of both cis- and trans-monocyclofarnesols with iodine afforded α chamigrene (V).

Abscisic acid from Pinus densiflora pollen

Abstract (+)-Abscisic acid was isolated as the methyl ester from Pinus densiflora pollen and identified spectroscopically.

Mass spectra of bakkenolides and their derivatives

Abstract Mass spectra (including high resolutions) of bakkenolides and their derivatives (I–X) were measured and the common fragmentation patterns discussed with the help of metastable ions. Fragmentation of B-A(I) is characterized by a McLafferty-type rearrangement, whereas oxygen functions at 1 and 9-positions of B-A take part in the fragmentation of bakkenolides-B, C, D and E.

Chemical components of callus tissues of pumpkins

Abstract Chemical components of callus and other tissues (leaf, stem, root and seed) of pumpkin were investigated to find the specificity of callus tissues. The isolated and identified compounds were squalene, 3 sterols, a triterpene, a fatty alcohol and hydroquinone; the last two being specifically found in the callus. On the other hand, Δ 7,25 stigmastadienol and chlorophyll could not be identified in the callus. Fatty acids were detected in all the tissues in a different ratio.