Oligosaccharide Analogues of Polysaccharides. Part 3. A new protecting group for alkynes: Orthogonally protected dialkynes
作者:Chengzhi Cai、Andrea Vasella
DOI:10.1002/hlca.19950780319
日期:1995.5.10
hydroxysulfide 16 with 15. The OH group of 27 was protected to yield the [dimethyl(oxy)propyl]dimethylsilyl}acetylenes (DOPSA's) 21, 28, and 29. The orthogonally protected acetylenes 20–22, 28, and 29 were de-trimethylsilylated to the new monoprotected acetylene synthons 30–34. The scope of the orthogonal protection was checked by regioselective deprotection of the dialkynes 39–42 (Scheme 4), prepared by alkylation
通过在质子溶剂中(4)用碱处理,或在暴露OH基团之后,在质子惰性溶剂中用催化量的碱(5和8)处理3型二元炔(方案1)的区域选择性脱保护。在ME 3的Si-保护12(方案2)是惰性的催化丁基锂/ THF其转化11到9,而ķ 2 CO 3 / MeOH中转化的两个10到9,和12到13,表明需要更受阻的(羟丙基)甲硅烷基取代基。17–19(方案3)中的碳负离子的C-甲硅烷基化反应生成15的碳负离子导致20-22,但以合理的收率仅获得22。因此,关键中间体27是通过逆布鲁克重排23制备的,该逆向布鲁克重排是通过将羟基硫化物16与15进行甲硅烷基化而制得的。OH基团的27是受保护的,得到[ d imethyl(氧)p丙基]二甲基甲硅烷}乙炔(DOPSA的)21,28和29。正交保护的乙炔20–22、28和29被去三甲基甲硅烷基化为新的单保护的乙炔合成子30–34。正交的保护范围是由dialkyn