Sadao Sakamura

Potato tuber-inducing activities of jasmonic acid and related compounds

Salicylic acid (SA) induced potato tuberization in vitro at concentrations greater than 10−5 M. A comparison of the tuber-inducing activities of various related compounds suggested that derivatives of benzoic acid with a free carboxyl group and a substituent at the C-2 position of the benzene ring have this activity. Although SA had the strongest activity among the compounds tested, the activity was about one thousandth of that of natural jasmonic acid (1R,2S-jasmonic acid) in terms of the threshold concentration for activity. Spraying SA to leaves of plants grown under tuber-noninducing conditions (long days) induced tuberization. However, the natural occurrence of SA was not detected in the leaves of potato plants that had been grown under tuber-inducing conditions (short days) and had begun to form tubers. The results seem to exclude the possibility of the involvement of SA in the natural tuberization of potato plants.

Solanapyrones A, B and C, phytotoxic metabolites from the fungus Alternaria solani

On the basis of spectroscopic data and chemical reaction, structures 1, 2 and 3 are proposed for solanapyrones A, B and C, phytotoxins from the fungus Alternaria solani, parasite of potato.

Four fungitoxic C-18 hydroxy unsaturated fatty acids from stromata of epichloe typhina

Abstract Four fungitoxic C-18 hydroxy unsaturated fatty acids ( 1 )–( 4 ) have been isolated from stromata of Epichloe typhina . Their structures including the absolute configuration have been elucidated from spectral data.

Bitter triterpenoids from the fungus Ganoderma applanatum

Six novel triterpenoids, ganoderenic acid, furanoganoderic acid and ganoderic acid derivatives, some of which are bitter principles, were isolated from the fruiting body of the fungus Ganoderma applanatum. Their structures were determined mainly by spectroscopic and chemical methods.

Triterpenoids from the fungus Ganoderma lucidum

Ten novel components, ganoderic acid, ganoderenic acid and lucidenic acid derivatives, were isolated from the fruiting body of the fungus Ganoderma lucidum. Their structures were elucidated mainly by spectroscopic and chemical methods.

Three phenolic acid derivatives from stromata of Epichloe typhina on Phleum pratense

Abstract Three new phenolic acid derivatives, 1,3- O -di- trans - p -coumaroylglycerol, 1,2- O -di- trans - p -coumaroylglycerol and chokorin were isolated from stromata of Epichloe typhina on timothy plants Phleum pratense . Their structures were established by spectroscopic and chemical means.

Synthesis of (±)-solanapyrone A

Abstract The first synthesis of solanapyrone A ( 1 ), a phytotoxin from Alternaria solani , has been completed through the intramolecular Diels-Alder reaction.

A ring B aromatic sterol from stromata of Epichloe typhina

Abstract A sterol with an aromatized B ring was isolated from stromata of Epichloe typhina growing on Phleum pratense . The structure was established as 1(10→6) abeo -ergosta-5,7,9,22-tetraen-3α-ol by spectral analysis and synthesis.

Structure and absolute configuration of solanapyrone D: a new clue to the occurrence of biological Diels–Alder reactions

The structure and absolute configuration of solanapyrone D (2) offers further indirect evidence that solanapyrone A (1) and D (2) are biosynthesized via intramolecular Diels–Alder reactions.

Synthesis of pyrenocines A, B and pyrenochaetic acid A

Abstract Starting from 5-acetyl-4-hydroxy-6-methyl-α-pyrone, three phytotoxins, pyrenocines A, B and pyrenochaetic acid A were synthesized. Retro-Diels-Alder reaction was successfully applied in the synthesis of pyrenochaetic acid A.