Furanosyl Oxocarbenium Ion Stability and Stereoselectivity |
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| Authors: | Erwin R van?Rijssel Dr Pieter van?Delft Dr Gerrit Lodder Prof Herman S Overkleeft Prof Gijsbert A van der Marel Dr Dmitri V Filippov Dr Jeroen D C Codée |
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| Institution: | Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (The Netherlands) |
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| Abstract: | Lewis acid mediated substitution reactions using D]triethylsilane as a nucleophile at the anomeric center of the four pentofuranoses, ribose, arabinose, xylose, and lyxose, all proceed with good to excellent stereoselectivity to provide the 1,2‐cis adducts. To unravel the stereoelectronic effects underlying the striking stereoselectivity in these reactions we have mapped the energy landscapes of the complete conformational space of the oxocarbenium ions of the four pentofuranoses. The potential energy surface maps provide a detailed picture of the influence of the differently oriented substituents and their mutual interactions on the stability of the oxocarbenium ions and the maps can be used to account for the observed stereoselectivities of the addition reactions. |
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| Keywords: | carbohydrates conformation analysis density functional calculations Lewis acids reaction mechanisms |
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