Abstract
Chemical desymmetrization reactions of meso-diols are highly effective for the precise and efficient synthesis of chiral molecules. However, even though enzyme-catalyzed desymmetric glycosylations are frequently found in nature, there is no method for highly diastereoselective desymmetric chemical glycosylation of meso-diols. Herein, we report a highly diastereoselective desymmetric 1,2-cis-glycosylation of meso-diols found in myo-inositol 1,3,5-orthoesters using a boronic acid catalyst based on predictions of regioselectivity by density functional theory (DFT) calculations. The enantiotopic hydroxyl groups of the meso-diols are clearly differentiated by the stereochemistry at the C2 position of the glycosyl donor with excellent regioselectivities. In addition, the present method is successfully applied to the synthesis of core structures of phosphatidylinositolmannosides (PIMs) and glycosylphosphatidylinositol (GPI) anchors, and common β-mannoside structures of the LLBM-782 series of antibiotics.
Highlights
Chemical desymmetrization reactions of meso-diols are highly effective for the precise and efficient synthesis of chiral molecules
We expect that the glycosylation of a 1,2anhydro donor and a meso-diol using a boronic acid catalyst will give a 1,2-cis-glycoside with high stereoselectivity via the SNi-type mechanism, and the regioselectivity will be predictable by analyzing transition states with density functional theory (DFT) calculations
The present method is successfully applied to the synthesis of core structures of phosphatidylinositolmannosides (PIMs) and glycosylphosphatidylinositol (GPI) anchors, and common βmannoside structure of the LLBM-782 series of antibiotics
Summary
PhO OPh α(1,6)-D-Glucoside 82%, α(1,6) only α(1,6)-D-Glucoside 90%, α(1,6) only α(1,6)-D-Glucoside 75%, α(1,6) only. A boronic or borinic acid catalyst in the glycosylation gives excellent 1,2-cis-stereoselectivities. The SNi-type mechanism and the transition states are supported by mechanistic studies. We expect that the glycosylation of a 1,2anhydro donor and a meso-diol using a boronic acid catalyst will give a 1,2-cis-glycoside with high stereoselectivity via the SNi-type mechanism, and the regioselectivity will be predictable by analyzing transition states with density functional theory (DFT) calculations. We report a highly diastereoselective desymmetric 1,2-cis-glycosylation of meso-diols found in myoinositol 1,3,5-orthoesters using a boronic acid catalyst based on predictions of regioselectivity by DFT calculations (Fig. 1c). The enantiotopic hydroxyl groups of the meso-diols are clearly differentiated by the stereochemistry at the C2 position of the 1,2anhydro glycosyl donor with excellent regioselectivity. The present method is successfully applied to the synthesis of core structures of phosphatidylinositolmannosides (PIMs) and glycosylphosphatidylinositol (GPI) anchors, and common βmannoside structure of the LLBM-782 series of antibiotics
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