TY - JOUR
T1 - Quantifying Electronic Effects of Common Carbohydrate Protecting Groups in a Piperidine Model System
AU - Heuckendorff, Mads
AU - Pedersen, Christian Marcus
AU - Bols, Mikael
PY - 2010/12/17
Y1 - 2010/12/17
N2 - A study of the substituent effects of protecting groups in hydroxypiperidines was carried out and compared with the electronic effects in glycosylation chemistry. 1-Deoxynojirimycin, the aza-sugar analogue of 1-deoxy-D-glucose, was used as a carbohydrate model, and protected with the most common carbohydrate protecting groups. The different stabilization of positive charge on the ring heteroatom was determined by pKa measurements. The protecting groups could be ranked in the following way after their destabilization of the piperidinium ion: benzoylâ¥acetylâ4,6-O- benzylidine>benzylâmethyl>H>3,6-anhydro>tert- butyldimethylsilyl. The observed effects of having protecting groups with different electronic characteristics were found to be in agreement with the "armed-disarmed" concept. Comparison of the pKa of benzylated and benzoylated epimers of 3-hydroxy-6-hydroxymethyl piperidines showed increased stabilization of the piperidinium ion in the axial epimer. The difference between axial and equatorial epimers was larger in the benzylated than in the benzoylated piperidines.
AB - A study of the substituent effects of protecting groups in hydroxypiperidines was carried out and compared with the electronic effects in glycosylation chemistry. 1-Deoxynojirimycin, the aza-sugar analogue of 1-deoxy-D-glucose, was used as a carbohydrate model, and protected with the most common carbohydrate protecting groups. The different stabilization of positive charge on the ring heteroatom was determined by pKa measurements. The protecting groups could be ranked in the following way after their destabilization of the piperidinium ion: benzoylâ¥acetylâ4,6-O- benzylidine>benzylâmethyl>H>3,6-anhydro>tert- butyldimethylsilyl. The observed effects of having protecting groups with different electronic characteristics were found to be in agreement with the "armed-disarmed" concept. Comparison of the pKa of benzylated and benzoylated epimers of 3-hydroxy-6-hydroxymethyl piperidines showed increased stabilization of the piperidinium ion in the axial epimer. The difference between axial and equatorial epimers was larger in the benzylated than in the benzoylated piperidines.
U2 - 10.1002/chem.201002313
DO - 10.1002/chem.201002313
M3 - Journal article
C2 - 21132699
SN - 0947-6539
VL - 16
SP - 13982
EP - 13994
JO - Chemistry: A European Journal
JF - Chemistry: A European Journal
IS - 47
ER -