25018-67-1Relevant articles and documents
A mild acetolysis procedure for the regioselective removal of isopropylidene in di-O-isopropylidene-protected pyranoside systems
Zhang, Pengfei,Ling, Chang-Chun
, p. 7 - 13 (2017/04/06)
A mild acetolysis method for the regioselective removal of isopropylidene group from di-O-isopropylidene-protected hexopyranosides is reported. O-Isopropylidene-protected intermediates play an important role in carbohydrate chemistry, as they are often found in commercially available furanosyl and pyranosyl materials, and some of them contain more than one O-isopropylidene groups. Methods that permit regioselective removal of O-isopropylidene groups are extremely valuable, as the number of steps in the total synthesis of complex oligosaccharides could be significantly decreased. Here we report that trifluoroacetic acid (TFA)/acetic anhydride (Ac2O) can be used to regioselectively convert one of the two O-isopropylidene groups to vicinal di-O-acetates in the di-O-isopropylidene-protected galacto- and fructo-pyranosyl systems, and the reagent is compatible with some common functionalities such as sulfonate esters, bromide, azide etc.
Concise synthesis of chiral N -Benzyl-α,α-Diarylprolinols through shi asymmetric epoxidation
Li, Jie,Zhou, Hai,Weng, Jiangsen,Wang, Mingwen,Ge, Chengsheng,Tu, Wujie
supporting information, p. 805 - 808 (2014/04/03)
A concise and practical synthesis of chiral N-benzyl-α,α- diaryl-2-prolinols was developed through Shi asymmetric epoxidation, followed by double nucleophilic substitution of bromo-containing olefins. A series of enantioenriched N-benzyl-α,α-diaryl-2-prolinols were obtained with excellent enantioselectivities (96% ee) in moderate to good yields (40-76% yield). For the first time, enantiopure N-benzyl-α,α-diphenyl-2- prolinol was obtained from bromo-containing olefin using this methodology. Georg Thieme Verlag Stuttgart, New York.
Acetalation studies. Part IX. Reaction of sucrose and some related sugars with acetone in the presence of iodine; a novel cleavage-isopropylidenation method
Verhart, Cor G. J.,Caris, Brigitte M. G.,Zwanenburg, Binne,Chittenden, Gordon J. F.
, p. 348 - 352 (2007/10/02)
An efficient cleavage-isopropylidenation reaction of sucrose, catalyzed by iodine, is described.Related D-fructofuranosyl-containing oligosaccharides and their individual monosaccharide units were treated in a similar manner to yield isopropylidenated monosaccharide derivatives.The reaction conditions are particularly mild and selective.Some mechanistic aspects of the procedure are also discussed.
