A Novel Pentose Synthesis via Palladium(II)-Catalyzed Cyclization of an Unstable Hemiacetal
作者:Masahiro Miyazawa、Yoshiro Hirai、Ken-ichiro Awasaguchi、Koichi Inoue、Koji Nakamura、Hajime Yokoyama、Ikuyo Uoya
DOI:10.3987/com-10-12001
日期:——
-hexenal and methanol gave substituted furanoside in moderate yield, exclusively via 5-exo-mode cyclization, without the need for a reoxidant. New stereogenic centers at C1 and C4 on the tetrahydrofuran ring showed preferential 1R and 4R stereochemistry due to anomeric effect (n o -σ * c-o ) and A 1,2 strain, respectively. This methodology was applied to stereocontrolled synthesis of pentoses: D-ribose
PdCl 2 (PhCN) 2 (5 mol%)-催化由 (E,2S,3R)-2,3-异亚丙基二氧基-6-(四氢-2H-吡喃-2-基)-4-己烯醛衍生的半缩醛环化甲醇以中等收率产生取代的呋喃糖苷,仅通过 5-外模式环化,无需再氧化剂。由于异头效应(无 -σ * co )和 A 1,2 应变,四氢呋喃环上 C1 和 C4 处的新立体中心分别显示出优先的 1R 和 4R 立体化学。该方法应用于戊糖的立体控制合成:D-核糖和 L-来苏糖。