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Direct assignment of the relative configuration in 1,3,n-methyl-branched carbon chains by (1)H NMR spectroscopy
Yvonne Schmidt1, Bernhard Breit
1Institut für Organische Chemie und Biochemie, Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs-Universität Freiburg, Alberstrasse 21, 79104 Freiburg, Germany.
Abstract:
On the basis of the assignment of methylene proton signals in (1)H NMR and determination of the chemical shift difference (Deltadelta), the relative configuration of 1,3,n-methyl-branched deoxypropionates can be determined directly. Comparison of the chemical shifts in the corresponding syn- and anti-configured compound pairs shows remarkable differences, while the absolute values depend on the presence and nature of adjacent functional groups. The determination of the Deltadelta values provides a reliable assessment of the relative configuration in 1,3,n-methyl-branched polypropionate chains and is even valid for macrocycles.
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