アルデヒド‐アルドース誘導体を基質とするテトラヒドロフラン環形成反応

Abstract

Reaction of allylsilane with 2, 3; 4, 5-di- O-isopropylidene-aldehydo-D-arabinose in the presence of boron trifluoride etherate afforded an unexpected product, which was identified as a tetrahydrofuran derivative, as a major component along with a small amount of homoallyl alcohol. This tetrahydrofuran formation probably proceeds via cyclization of the β-silyl cation intermediate accompanied by migration of the isopropylidene group. The scope of this reaction was investigated : When 2, 3-O-isopropylidene derivatives of D-erythrose, D-ribose, L-rhamnose, and D-mannose were used as the aldehyde in the reaction of allylsilane, the tetrahydrofuran derivatives were obtained in moderate yields, whereas aldehydes derived from D-xylose, 6-deoxy-D-glucose, and D-glucose gave the homoallyl alcohols as major products. Similar cyclization proceeded employing disubstituted terminal olefins, vinyl ethers, and vinyl sulfides instead of allylsilane to afford the corresonding tetrahydrofurans in good to high yields. Especially, the reaction using β-substituted vinyl ethers and sulfides provided a stereoselective route to 2-C-substituted 2-deoxyfuranosides, which were utilized for synthesizing 2-C-substi-tuted 2-deoxyhexoses and 2'-substituted 2'-deoxynucleosides.