Synthetic strategy for side chain mono-N-alkylation of Fmoc-amino acids promoted by molecular sieves
摘要:
A new synthetic strategy to alkylate amino groups under mild conditions has been developed. It utilizes only 4 angstrom molecular sieves as base in order to promote the N-alkylation reaction, in presence of the appropriate alkyl halide. The methodology was validated by the simple and efficient side-chain N-alkylation of o-Ns-protected Fmoc-amino acid. One of them was introduced as building block into a peptide sequence, thus allowing the preparation of site-specific alkylated peptide molecules.
Solid-Phase Synthesis of Amine-Bridged Cyclic Enkephalin Analogues via On-Resin Cyclization Utilizing the Fukuyama−Mitsunobu Reaction
摘要:
An efficient solid-phase synthetic route is described for the preparation of 13-membered amine-bridged cyclic enkephalin analogues (ABEs) 1a and 1c-1j (Figure 1) resulting from a sulfonamide-containing peptide whose backbone is bound to a resin. The Fukuyama-Mitsunobu reaction of the 2-nitrobenzenesulfonyl-protected amine bound to the solid support with protected aminoethanol in the presence of triphenylphosphine and diisopropyl azodicarboxylate (DIAD) is utilized to prepare a resin-bound sulfonamide-protected secondary amine. After peptide cyclization, this protected amine functionality becomes the "amine bridge" of the target molecule. In addition, the reagent DIAD was found to be a superior reagent compared to diethyl azodicarboxylate (DEAD) in the solid-phase Fukuyama-Mitsunobu reaction.