IQUIR   05412
INSTITUTO DE QUIMICA ROSARIO
Unidad Ejecutora - UE
artículos
Título:
Regioselectivity of the glycosylation of N-dimethylmaleoyl-protected hexosamine acceptors. An experimental and DFT approach.
Autor/es:
MARÍA I. COLOMBO; EDMUNDO A. RÚVEDA; CARLOS A. STORTZ
Revista:
ORGANIC & BIOMOLECULAR CHEMISTRY
Editorial:
ROYAL SOC CHEMISTRY
Referencias:
Año: 2011 vol. 9 p. 3020 - 3025
ISSN:
1477-0520
Resumen:
Both anomers of the methyl glycoside of 6-O-benzyl-N-dimethylmaleoyl-D-allosamine (6 and 7) are
glycosylated exclusively on O3 when reacting with the trichloroacetimidate of peracetylated
a-D-galactopyranose (5). This regioselectivity is expected for 6, the a-anomer, as a strong hydrogen
bond of its H(O)3 with the carbonyl group of the dimethylmaleoyl group occurs, as shown by NMR
temperature dependence. However, this hydrogen bond was not encountered experimentally for 7, the
b-anomer. A DFT study of the energies implied in an analog of the glycosylation reaction charged
intermediate has explained neatly this behavior, in terms of strong hydrogen bonds occurring at these
charged intermediates. This approach explains both the experimental regioselectivities found for 6 and
7, but furthermore the calculations have shown a marked agreement with the regioselectivities found for
other related compounds in the literature.