TY - JOUR
T1 - Selective activation of glycosyl donors utilising electrochemical techniques
T2 - A study of the thermodynamic oxidation potentials of a range of chalcoglycosides
AU - France, Robert R.
AU - Wadhawan, Jay D.
AU - Fairbanks, Antony J.
AU - Compton, Richard G.
AU - Rees, Neil
PY - 2004/8/7
Y1 - 2004/8/7
N2 - A series of six chalcoglycosides (phenyl-2,3,4,6-tetra-0-benzoyl-1-seleno-β-D-glucopyranoside, phenyl-2,3,4,6-tetraO-benzyl-1-seleno-β-D-glucopyranoside, phenyl-2,3,4,6-tetra-O-benzyl-1-thio-β-D-glucopyranoside, p-tolyl-2,3,4,6-O-benzoyl-1-thio-β-D-glucopyranoside, p-tolyl-2,3,4,6-O-benzyl-1-thio-β-D-glucopyranoside, and phenyl-2,3,4,6-O-benzyl-β-D-glucopyranoside) are voltammetrically interrogated in dimethyl sulfoxide, so as to determine their formal (i.e. thermodynamic) redox potentials. The electrochemical oxidation of the chalcoglycoside is shown to follow an overall EC-type mechanism, in which the electro-generated cation radical undergoes an irreversible carbon-chalcogen bond rupture to produce the corresponding glycosyl cation, which may react further. The kinetics of the initial heterogeneous electron transfer process and subsequent irreversible homogeneous chemical degradation of the radical cation are reported, with values for the standard electrochemical rate constant k0 in the order of 10-2 cm s-1 and the first order homogeneous rate constant, k1, of the order of 103 s-1. The formal oxidation potentials were found to vary according to the identity of the chalcogenide, such that OPh > SPh > STol > SePh.
AB - A series of six chalcoglycosides (phenyl-2,3,4,6-tetra-0-benzoyl-1-seleno-β-D-glucopyranoside, phenyl-2,3,4,6-tetraO-benzyl-1-seleno-β-D-glucopyranoside, phenyl-2,3,4,6-tetra-O-benzyl-1-thio-β-D-glucopyranoside, p-tolyl-2,3,4,6-O-benzoyl-1-thio-β-D-glucopyranoside, p-tolyl-2,3,4,6-O-benzyl-1-thio-β-D-glucopyranoside, and phenyl-2,3,4,6-O-benzyl-β-D-glucopyranoside) are voltammetrically interrogated in dimethyl sulfoxide, so as to determine their formal (i.e. thermodynamic) redox potentials. The electrochemical oxidation of the chalcoglycoside is shown to follow an overall EC-type mechanism, in which the electro-generated cation radical undergoes an irreversible carbon-chalcogen bond rupture to produce the corresponding glycosyl cation, which may react further. The kinetics of the initial heterogeneous electron transfer process and subsequent irreversible homogeneous chemical degradation of the radical cation are reported, with values for the standard electrochemical rate constant k0 in the order of 10-2 cm s-1 and the first order homogeneous rate constant, k1, of the order of 103 s-1. The formal oxidation potentials were found to vary according to the identity of the chalcogenide, such that OPh > SPh > STol > SePh.
UR - http://www.scopus.com/inward/record.url?scp=4344592359&partnerID=8YFLogxK
U2 - 10.1039/b316720h
DO - 10.1039/b316720h
M3 - Article
C2 - 15280954
AN - SCOPUS:4344592359
SN - 1477-0520
VL - 2
SP - 2188
EP - 2194
JO - Organic and Biomolecular Chemistry
JF - Organic and Biomolecular Chemistry
IS - 15
ER -