Oligosaccharide Analogues of Polysaccharides. Part 2. Regioselective deprotection of monosaccharide-derived monomers and dimers
作者:Jawad Alzeer、Andrea Vasella
DOI:10.1002/hlca.19950780117
日期:1995.2.8
led to 24 and 22. The structure of 24 was established by X-ray analysis (Fig.), showing a C(6)–C(5′) distance of 5.2 Å. The conditions for deprotecting 2 were applied to 21, and led to 25 (AgNO2/KCN), 26 (aq. NaOH), 27 (Bu4NF), and 29 (HCl/MeOH; Scheme 3). Attempted deprotection of the propargylic-ether moiety with BuLi, however, failed. The dimer 27 was further deprotected to 28. Acetolytic (Ac2O/Me3SiOTf)
在ME 3的SiC(1)的双- (三甲基硅烷基)的键乙炔anhydroalditol 2被选择性地用BuLi切割以产生3 / 4,而硝酸银2 / KCN在MeOH裂解我3的SiC(2')键,导致5(方案1)。两个Me 3 Si基团都用NaOH在MeOH中的溶液(7)除去,(i-Pr)3 Si基团用HCl水溶液选择性地裂解。MeOH(6);m / z(MH)。用Bu 4 NF(8)除去所有的甲硅烷基取代基。乙酰分解将9转化为13,将其脱甲硅烷基以14,而硫解的9导致了混合物11 / 12。四乙酸酯14也已经从9经由10获得。的任一氧化二聚化3或5,或它们的混合物的3 / 5的产率只有同二聚体15和16(方案2); 用AgNO 2 / KCN处理16能产生17,脱保护的过程比裂解Me 3 SiC(2')基团慢得多。2。的iodoalkyne 20,具有所需的交叉耦合5根据Cadiot-Chodkiewicz,的制备是通过脱保护3