103(P-54) ヘミアセタールを経由するパラジウム(II)錯体による立体選択的ヘテロ環化反応と糖合成(ポスター発表の部)

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We recently reported the intramolecular substitution of an ally alcohol by a heteroatom using a palladium(II) catalyst without activation of the allylic alcohol. We report here highly stereoselective intramolecular cyclization of 7- and 8-formyl allylic alcohols using palladium (II) catalyst in the presence of alcohol via unstable hemiacetal intermediates, in which cyclization occurs without activation of the allylic alcohol in this case too. Stereoselective Cyclization using Pd(II)-catalyst via Hemiacetal Intermediates Treatment of 7-hydroxy-3-phenyl-5-hexenal (4) with 5mol% bis(benzonitrile)palladium (II) chloride in THE in the presence of ethanol afforded 6-membered cyclic acetals 5 in 65% yield as a 84:16 mixture of stereoisomers. And substrate 6 was successfully converted to the 7 membered ring 7. To demonstrate the synthetic potential of this method, we have synthesized furanose derivatives. Total synthesis of D-ribose and the synthetic studies of deoxy-D-ribose The optically active aldehyde 16 was prepared from (Z)-2-butene-1,4-diol using asymmetric esterification. Treatment of aldehyde 16 and methanol with Pd (II) catalyst gave the cyclized product 17. Finally, ozonolysis, reduction and deprotection of 17 was afforded 2,3-isopropyridene-D-ribose (18). The aldehyde 24 was prepared from 1-malic acid in 8 steps. Treatement of 24 and methanol with Pd(II) catalyst gave the key intermediate 25 for synthesis of deoxy-D-ribose.
天然有機化合物討論会の論文
2002-09-01

103(P-54) ヘミアセタールを経由するパラジウム(II)錯体による立体選択的ヘテロ環化反応と糖合成(ポスター発表の部)

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