Convenient Glycoside Synthesis of Amino Sugars: Michael-Type Addition to 2-Nitro-D-galactal
作者:Jagattaran Das、Richard R. Schmidt
DOI:10.1002/(sici)1099-0690(199808)1998:8<1609::aid-ejoc1609>3.0.co;2-1
日期:1998.8
-galactal (3) was readily accomplished starting from tri-O-benzyl-D-galactal (1) by acetyl nitrate addition to 2 and base-promoted acetic acid elimination. Addition of alcohols to 3 under conditions of base catalysis afforded 2-deoxy-2-nitrogalactopyranosides 4a–e in high yields; high α-selectivity was obtained with strong bases, whereas weaker bases furnished mainly the corresponding β-galactopyranosides
3,4,6-tri-O-benzyl-2-nitro-D-galactal (3) 的形成很容易从三-O-benzyl-D-galactal (1) 开始,通过乙酰硝酸盐添加到 2 和碱-促进乙酸消除。在碱催化条件下将醇加入到 3 中,以高产率得到 2-脱氧-2-硝基吡喃半乳糖苷 4a-e;用强碱获得高α-选择性,而弱碱主要提供相应的β-吡喃半乳糖苷。以雷尼镍为催化剂,在双糖 4cα 的情况下成功地进行了这些糖苷中的化学选择性硝基还原反应,从而在 N-乙酰化后得到相应的 2-乙酰氨基-2-脱氧衍生物 5cα。