利用Pd(0)催化的Stille偶联反应分别从甲基α,d-吡喃葡萄糖苷和甲基α,d-甘露吡喃糖苷分别合成了(+)-4- Epi -Gabosine A 1和(-)-Gabosine A 2关键步骤。另一方面,已经由甲基α,d-吡喃葡萄糖苷和甲基α,d合成了(+)-4-表-葡萄糖苷E 3和(-)-葡萄糖苷E 4。-甘露吡喃糖苷分别通过利用DMAP催化的Morita-Baylis-Hillman反应作为关键步骤。糖衍生的环状烯酮的C-6位上存在乙酰基可防止MBH加合物的芳构化。还描述了一种合理的机制。
Improved synthesis of L-pyranosides utilizing diastereoselective hydroboration/oxidation of 5-enopyranosides was investigated. A unique phenomenon in the diastereoselectivity of the hydroboration was incidentally found. The method was successfully applied to the synthesis of L-iduronicacid.
Highly diastereoselective Morita–Baylis–Hillman chemistry: a remote activation effect in the diastereoface selective synthesis of densely functionalized branched cyclic enones from d-glucose
作者:Vikas Kumar、Partha Ghosal、Pintu Das、Arun K. Shaw
DOI:10.1016/j.tetasy.2012.03.009
日期:2012.4
A highly diastereoselective C-2 alkylation of sugar derived cyclic enone 1 in the presence of diethylaluminium iodide by utilizing Morita-Baylis-Hillman chemistry is reported. While diethylaluminium iodide was found to be a suitable Lewis acid for this transformation, the widely employed TiCl4 was ineffective. A plausible mechanism, which considered the involvement of a Zimmerman-Traxler type of closed transition state and an orthoester intermediate, has been discussed. (C) 2012 Elsevier Ltd. All rights reserved.