Hiroyasu Tabuchi

Synthesis of (−)-probetaenone I: structural confirmation of biosynthetic precursor of betaenone B

(–)-Probetaenone I (1) has been synthesized by an intramolecular Diels–Alder reaction and, thereby, its structure has been clearly confirmed; in the biosynthesis of betaenone B (2) the stereochemistry of the C-8 hydroxylation of (1) was proved to involve retention of configuration.

Total synthesis of alternaric acid

A total synthesis of alternaic acid (1) has been achieved. Key reactions include the Julia olefination of tertiary aldehyde 4 and phenylsulfone 5, and novel one-pot construction of 3-acyl-4-hydroxy-5,6-dihydropyrone via Fries type rearrangement of O-enolacyl group of β-keto-δ-valerolactone toward α-position of the δ-lactone. The absolute configuration of alternaric acid has been shown to be that illustrated in structure 1.

Stereochemistry of alternaric acid ; Synthesis of the C(9)-C(14) fragment

Abstract The stereochemistry of alternaric acid (1) has been elucidated by stereoselective synthesis of four diastereoisomers of C(9)-C(14) fragment 2, which had been obtained as degradation product during structural studies.

Biosynthetic study of alternaric acid: isolation of plausible biosynthetic intermediates and origins of the hydrogen and oxygen atoms

In further isolation studies of alternaric acids, new less-oxidized analogues, (1OE)-10,11-dideoxy-10,11-dehydro-6,19-dihydroalternaric acid 5 and 10,11-dideoxy-6,19-dihydroalternaric acid 6, have been isolated from Alternaric solani, which is a causal fungus of early blight disease on potato and tomato. The structures have been elucidated by spectroscopic analysis. HPLC analysis of the acidic extracts of the cultural filtrates which had been treated with specific cytochrome P-450 inhibitors were employed, and also incorporation of sodium [1-13C,18O2]- and [1-13C,2H3]-acetate into the metabolites have been carried out. In addition, treatment of the fungus with the inhibitors resulted in the generation of a plausible precursor, which we have named proalternaric acid 17. The structure and stereochemistry of 7 have been determined by spectroscopic analysis and chemical synthesis from the analogue 3. From the results of these experiments, plausible biosynthetic routes to alternaric acid 1 are postulated.

Structures and stereochemistries of new compounds related to alternaric acid

Three alternaric acid-related compounds, viz., 10-deoxyalternaric acid 2, 10-deoxy-6,19-dihydroalternaric acid 3, and 10-deoxy-6,8,9,19-tetrahydroalternaric acid 4, have been isolated from Alternaric solani which is a causal fungus of early blight disease on potato and tomato. The structures and stereochemistries of these compounds have been determined by spectral studies and chemical correlations. The structure–activity relationships of alternaric acid 1 and plausible biosynthetic routes from these compounds to alternaric acid 1 are also discussed.