Construction of molecular switching system based on dipeptide framework

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The dipeptide sequence α-aminoisobutyryl-L-proline (Aib-L-Pro) adopts only two conformations, i.e., a folded (β-turn) conformation and an unfolded rather extended conformation. Based on this unique nature, it was attempted to utilize the Aib-L-Pro-based dipeptide for the construction of molecular switching system. The protected dipeptides possessing protected amino group in each side chain was designed, to which functional groups could be introduced for enabling their cooperative functioning. By the coupling of protected L/D-α,γ-diamino-α-methylbutyric acid (L/D-MeDab) derivative and protected L-4α/β-aminoproline [L-Pro(4β-NH_2] derivative, Boc-DL-DabMe(4-Cbz-NH)-L-Pro(4β-CbzNH)-OEt was synthesized. As for the function which could be manifested and controlled, we have chosen cooperative functioning of two Zn(II)-complexed bispicolylamino groups to cleave phosphodiester linkage of ribonucleotide model substrate. The activity could be controlled by conformational control of the dipeptide using interterminal host-guest inclusion.