Takeo Sakan

Structure and stereochemistry of boschniakine, boschnialactone, and boschnialinic acid, an oxidation product of boschnialactone

Abstract Boschniakine, C10H11NO, and boschnialactone, C9H14O2, were isolated as the physiologically active principles of Boschniakia rossica Hunt, and their absolute structures have been determined. Four optically active stereoisomers of boschnialinic acid (2-carboxy-3-methylcyclopentylacetic acid), one of which is an oxidation product of boschnialactone, have been synthesized and their stereochemistries established.

Revisions of the absolute configurations of C-8 methyl groups in dehydroiridodiol, neonepetalactone, and matatabiether from Actinidia polygama miq

Abstract The absolute configurations of C-8 Me groups in dehydro-iridodiol, neonepetalactone, and matatabiether isolated from the cat- and lacewmg-attracting plant Actinidia polygama Miq. were revised to the S configurations on the basis of chemical transformations and unambiguous syntheses.

STUDIES ON THE SESQUITERPENOIDS OF HYPOLEPIS PUNCTATA METT. II

Abstract Hypacrone ( 1 ), a new seco-illudoid sesquiterpene, was isolated from a fern, Hypolepis punctata Mett., as its characteristic acrid principle. The structure is proposed on the spectral basis and the transformation into pterosins, illudoid constituents of the same plant.

Studies on the sesquiterpenoids of hypolepis punctata mett.—II : The total synthesis of hypacrone

Hypacrone (1), a new seco-illudoid, was synthesized by several steps, including a cross aldol condensation of two major moieties, a diketone (2) and a cyclopentenone derivative (11).

Total synthesis of nagilactone F, biologically active nor-diterpenoid dilactone isolated from podocarpus nagi

Abstract Nagilactone F was synthesized from (+)-podocarpic acid of the established structure. This work constitutes the first total synthesis of the biologically active norditerpenoid dilactones in Podocarpus plants.

The synthesis of oosponol and oospoglycol

Oosponol and (–)-oospoglycol (of about 66% optical purity) have been synthesized from 8-hydroxyisocoumarin-4-carboxylic acid (= oospoic acid).

STRATEGY IN ORGANIC SYNTHESIS

In this paper, several designs and the concepts in syntheses of natural products performed in our laboratory are described. 1) Syntheses of cat attractants under thermodynamically controlled conditions; 2) Synthesis of verbenalin, an iridoid glycoside, under kinetically controlled conditions; 3) Preparations of bioactive substances by oxidative degradation of carotenoids, as an example of interpretation and utilization of abnormal reactions; 4) Syntheses of ketones based on mimic enzymatic reactions.