Synthesis and conformational studies of amide-linked cyclic homooligomers of a thymidine-based nucleoside amino acid

Cyclic homooligomers of a thymidine-based nucleoside amino acid were synthesized from the linear dimer using BOP reagent in the presence of DIPEA under dilute conditions. Conformational analysis by NMR and constrained MD studies revealed that all the cyclic products had symmetrical structures. The NH and CO groups in these molecules point in opposite directions with near perpendicular orientation with respect to the plane of the macrocyclic ring having CO on the same side as the base.