Reagent-Dependent Regioselective Control in Multiple Carbohydrate Esterifications
摘要:
Regioselective control in organotin-mediated multiple acylation of carbohydrates is presented. The acylation reagent could be efficiently used to direct the product formation. Reagent-dependent thermodynamic and kinetic control and dynamic assistance mechanisms are suggested, resulting in the efficient preparation of building blocks that normally require many steps with traditional synthesis.
Tandem Epoxidation‐Alcoholysis or Epoxidation‐Hydrolysis of Glycals Catalyzed by Titanium(IV) Isopropoxide or Venturello’s Phosphotungstate Complex
作者:Pieter Levecque、David W. Gammon、Henok Hadgu Kinfe、Pierre Jacobs、Dirk De Vos、Bert Sels
DOI:10.1002/adsc.200800079
日期:2008.7.7
Venturello’sphosphotungstatecomplex and titanium(IV) isopropoxide [Ti(O-i-Pr)4] were successfully used as catalysts for the epoxidation-alcoholysis of glycals using hydrogen peroxide [H2O2]. Reaction substrates included a range of variously protected glycals and different alcohols were used as solvents. Ti(O-i-Pr)4 was only effective in methanol as solvent, but gave methyl glycosides in high yields
Venturello的磷钨酸盐络合物和异丙醇钛(IV)[Ti(O- i- Pr)4 ]已成功用作使用过氧化氢[H 2 O 2 ]的环氧乙烷缩合醇解的催化剂。反应底物包括各种受保护的糖基,不同的醇用作溶剂。钛(O- i- Pr)4仅在甲醇作为溶剂中有效,但以高收率和高选择性得到甲基糖苷。事实证明,Ventrollo复合物是一种用途广泛且高效的催化剂。除了在醇类溶剂中进行环氧化-醇解以外,它还显示了在双相条件下的活性,以允许长链醇的糖基化,并且在苄基化的葡糖的立体选择性二羟基化中非常有效。
Glycosylation chemistry promoted by iodine monobromide: Efficient synthesis of glycosyl bromides from thioglycosides, and O-glycosides from ‘disarmed’ thioglycosides and glycosyl bromides
作者:K.P. Ravindranathan Kartha、Robert A. Field
DOI:10.1016/s0040-4039(97)10124-1
日期:1997.11
reagent for the conversion of both ‘armed’ and ‘disarmed’ thioglycosides (SMe, SPri, SPh) into glycosylbromides. This reagent is compatible with most common protecting groups, and O-glycosidic linkages. The additional potency of IBr, compared to iodine, as an iodoniumion source also permits the glycosylation of sugar alcohols by ‘disarmed’ glycosylbromides and thioglycosides.