133(P-82) 馬鈴薯夏疫病菌代謝産物Solanapyrone Eの合成(ポスター発表の部)

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Solanapyrones were polyketide natural products isolated by Oikawa and Ichihara et al. from Altenzaria solani, a causal fungus of early blight disease to tomato and potato. These unique compounds possess decaline framework with pyrone nucleus and exhibit inhibitory activity against germination of hypocotyl and root of lettuce. Total synthesis of solanapyrone E, one of the solanapyrones having trans-decalin with hydroxymethyl pyrone ring, has been accomplished by domino Michael reaction and by hydroxymethylation of pyrone ring as key transformations. Decaline framework having requisite functionalities for solanapyrone E synthesis was obtained by domino Michael reaction between methyl crotonate and kinetic enolate of optically active acetylcyclohexene derivative prepared by Lipase catalyzed kinetic resolution. Treatment with base provided trans-decalone in which C-2 methyl and C-10 hydrogen were β-syn in each other. After removal of alkoxy group at C-9 by Barton's radical protocol, carbonyl group at C-4 was reduced with L-selectride to give β-axial alcohol which was selectively dehydrated into double bond at C-3 via pyrolysis of xanthate. Base catalyzed isomerization of the α-axial ester at C-1 was accomplished by t-BuOK in DMSO. The ester was then transformed into formyl group. β-Hydroxypyrone unit at C-1 was installed by TiCl_4 promoted condensation of bisTMS enol ether of methyl acetoacetate with the aldehyde followed by Jones oxidation and subsequent DBU catalyzed cyclization. Phenylthiomethyl group was introduced to a position of pyrone carbonyl group by the reaction of paraformaldehyde and thiophenol in the presence of piperidine. After protection of the hydroxy group by methyl ether formation, phenylthio group was oxidized into phenylsulfinyl group. Treatment of the sulfoxide with trifluoroacetic anhydride led to O-acylation of sulfoxide followed by substitution with trifluoroacetoxy anion and completed the total synthesis of solanapyrone E.
天然有機化合物討論会の論文
2000-10-01

133(P-82) 馬鈴薯夏疫病菌代謝産物Solanapyrone Eの合成(ポスター発表の部)

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