Kinzo Watanabe

Ent-kauranes and other constituents of three Helianthus species

Abstract Aerial parts of Helianthus debilis subsp. cucumerifolius, H. occidentalis and H. simulans afforded a variety of known and some unknown ent-kauranoic acids. H. occidentalis gave, in addition, ciliaric acid and a new biogenetically related atisane derivative occidentalic acid. H. simulans gave the heliangolide leptocarpin and the flavone hymenoxin in addition to ent-kauranes. Several of the diterpenoids from these species inhibited larval growth of the sunflower moth.

Stereochemistry of strictic acid and related furano-diterpenes from conyza japonica and grangea maderaspatana

Abstract Extraction of Conyza japonica gave strictic acid, ent-2β-hydroxy-15,16-epoxy-3,13(16),14-clerodatrien-18-oic acid and 5,7-dihydroxy-3,8,4′-trimethoxyflavone. Extraction of Grangea maderaspatana gave (-)-hardwickiic acid, ent-15,16-epoxy-1,3,13(16),14-clerodatetraen-18-oic acid and 3-hydroxy-8-acetoxypentadeca-1,9,14-trien-4,6-diyne. The structure of ent-2β-hydroxy-15,16-epoxy-3,13(16),14-cleroclatrien-18-oic acid was deduced by spectroscopic methods and by partial synthesis from (-)-hardwickiic acid and the stereochemistries of strictic acid and (ent-15,16-epoxy-1,3,13(16),14-clerodatraen-18-oic acid were established by correlation with ent-2β-hydroxy-15,16-epoxy-3,13(16),14-clerodatrien-18-oic acid.

Sesquiterpene alcohols and triterpenoids from Liatris microcephala

Abstract Liatris microcephala gave the sesquiterpene alcohols (+)-T-cadinol,α-cadinol, oplopanol and oplodiol, the benzofuran euparin and the triterpenes lupeyl acetate, taraxasteryl acetate, and 30-nor-taraxaster-20-en-3β-yl acetate.

Cycloartanes from Lindheimera texana

Abstract The following new cycloartanes were isolated from the aerial parts of Lindheimera texana: (16S,23S)- and (16S,23R)-16,23-epoxycycloart-24-en-3-one, (3S,16S,23S)- and (3S,16S,23R)-16,23-epoxycycloart-24-en-3ol, (16S,23R)-16,23-epoxy-23,25-epidioxycycloartan-3-one, (16S)-23,24,25,26,27-pentanorcycloartan-3-one-16,22-olide, (16S,23S,24R)- or (16S,23R,24S)-23,24-epoxycycloartan-3-one-16,25-diol and (16S,23ζ,24ζ)-cycloartan-3-one-16,23,24,25-tetrol. Structures were established by chemical transformations and spectroscopic methods and, in the case of (16S,23R)-16,23-epoxy-23,25-epidioxycycloartan-3-one, by X-ray crystallography. Norambreinolide, several known labdanes and oleanolic acid were also isolated.

Diterpenes of helianthus rigidus and H. Salicifolius

Abstract The chloroform extract of Helianthus rigidus gave ciliaric acid and 16-hydroxy-11-kauren-19-oic acid. H. salicifolius furnished these compounds as well as (−)-kauranol.

New 5-methylcoumarins from Ethulia conyzoides

Abstract The isolation of three new terpenoid 5-methylcoumarins in the form of diastereomeric mixtures from a north Indian collection of Ethulia conyzoides is reported. Stereochemistries were deduced by X-ray analysis of a pure acetate isomer obtained on acetylation of one of the diastereomeric mixtures.

Stereochemistry of chapliatrin and its congeners from Liatris gracilis

Abstract Re-examination of Liatris gracilis afforded the known sesquiterpene lactones chapliatrin, isochapliatrin, acetlisochapliatrin, five new closely related 5,10-epoxygermacranolides and a new eudesmanolide. The stereochemistry of the 5,10-epoxygermacranolides has been settled by an X-ray analysis of isochapliatrin.

Ineupatoriol, a thiophene analogue of ichthyothereol, from Inula eupatorioides

Abstract Ineupatoriol, a thiophene analogue of ichthyothereol, was isolated from Inula eupatorioides . The absolute stereochemistry is that of ichthyothereol.

3-Germacren-612-olides, from an undescribed liatris taxon

Abstract A previously undescribed variant of Liatris gracilis whose taxonomic status is still uncertain furnished a series of 3-germacren-6,12-olides different from the chapliatrin analogues found in authentic L. gracilis. The stereochemistry of one of the new sesquiterpene lactones was established by X-ray diffraction. A eudesmanolide previously isolated from L. gracilis was also found in the variant.