85(P-18) (-)-Vallesamidineの全合成(ポスター発表の部)

概要

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Vallesamidine (1) was isolated from Vallesia dichotoma Ruiz et Pav in 1965 and its structure and absolute configuration were determined by Djerassi et al. in 1968. This structure is disclosed to be a unique and abnormal indole alkaloid including 2,2,3-trialkylindoline skeleton. We report here first asymmetric total synthesis of (-)-Vallesamidine through indoline derivative 15a and its selenide (17a) by the aid of reductive radical ring closure reaction. Starting from the known lactone (7), we synthesized carboxylic acid derivative (12), a chiral C_9-unit corresponding to non-tryptamine building block of Vallesamidine. Condensation of 12 with tryptamine in acetic acid gave 14a and its diastreoisomer 14b, the stereochemistry of which was characterized by detail studies on those NMR spectra. The primary hydroxy group in the side chain of 15a, presumed to be natural form, was converted into the corresponding selenide (17a) in two steps under the usual way. Treatment of the selenide (17a) with a mixture of n-Bu_3SnH and AIBN in toluene at 100℃ gave a single product in 92% yield, which was followed by the successive N-methylation and LAH reduction to give (-)-Vallesamidine (1). The structure of the synthetic material was confirmed by comparison with the physical data reported by Heathcock.
天然有機化合物討論会の論文
2002-09-01