Takeshi Kawamata

Sesquiterpene lactones of Gaillardia pulchella

Abstract A Japanese cultivar of Gaillardia pulchella Foug. contained, in addition to the pseudoguaianolides, pulchellin(I) and neopulchellin(II), the guaianolide, gaillardin(III) apparently accompanied by its epimer neogaillardin(IV) and an unidentified basic principle different from pulchellidine(V) and neopulchellidine(VI). A possible biogenetic scheme for the sesquiterpene lactones including eudesmanolides, pulchellin-B, -C, -E and -F(VII) is proposed.

Enzymatic resolution of cis- and trans-1,2,3,4,6,7,8,8a-octahydro-8a-methyl-6-oxo-naphthyl acetate derivatives

Abstract Extensive screenings using commercially available enzymes were performed in relation to the asymmetric hydrolysis reactions of the (±)- cis- ( 1 , 3 and 5 ) and (±)- trans -1,2,3,4,6,7,8,8a-octahydro-8a-methyl-6- oxo -naphthyl acetates ( 7 , 9 and 11 ). The combinations of enzymes from plants and cis -equatorial compounds as well as the combinations of lipases from microorganisms and trans -axial-5-methoxycarbonyl acetate showed high enantiomeric ratio in asymmetric hydrolysis. However, the enantiomeric ratio of the combinations of lipases from microorganisms and trans -axial isomers except trans -axial-5-methoxycarbonyl derivative was less satisfactory. High E values (>200) were observed when β-amylase from wheat and lipase from Candida cylindracea were used for the (±)- cis -acetate 1 and the (±)- trans -isomer 7 , respectively, to obtain the corresponding chiral products with high enantiomeric ratios (>99:1).

A novel rearrangement from eudesmanolide to adamantanone

Abstract A novel cyclization-skeletal rearrangement from a eudesmanolide, 3-desoxy-4β, 5αH-hexahydro-l-α-santonin(1) to an adamantanone, 2, 5, 9-trimethyltetracyclo [6. 3. 1. 01,6. 05,10]dodecan-11-one(2) was found to occur as the result of a most unusual reaction. The structure of 2 was elucidated by the X-ray diffraction method.

Ambrosic Acid, a New Irritant Principle from the Pollen of the Ragweed Ambrosia arthemisiifolia

In connection with our studies on the physiologically active substance in the genus of Gaillardia, Arthemisia and their relatives in Compositae, we have recently investigated a poisonous principle in the common ragweed, Ambrosia arthemisiifolia (Butakusa.) Since this plant was introduced into Japan from North America almost one century ago, it has made a wide distribution over the Japanese islands and been notorious for a cause of pollen allergy (hay fever) and also as a poisonous weed in cattle feed.