A General Method for Synthesis of Unclosed Cryptands via H‑Bond Templated Macrocyclization and Subsequent Mild Postfunctionalization
journal contributionposted on 2015-10-02, 00:00 authored by Kajetan Dabrowa, Patryk Niedbala, Maciej Majdecki, Piotr Duszewski, Janusz Jurczak
A practical four-step synthesis of a model 26-membered N-Boc-protected macrocycle, starting from commercially available and inexpensive materials, is reported. The crucial macrocyclization step does not require high-dilution conditions and is completed in a short time (8 h). The high yield of macrocyclization (61%) is achieved owing to templation by intramolecular H-bonds and a chloride anion, which both help to adopt a favorable folded conformation of the open-chain intermediate. Finally, mild, selective, and efficient incorporation of intraannular amide function leading to five diversely functionalized unclosed cryptands (UCs) is described.
chloride anionGeneral MethodSubsequent Mild Postfunctionalizationhigh-dilution conditionsopen-chainintraannular amide functionmodel 26- membered N-Boc-protected macrocyclediversely functionalized unclosed cryptandsTemplatedMacrocyclizationfour-step synthesisUnclosed CryptandsmaterialconformationtemplationincorporationUCSynthesimacrocyclization stepintramolecular H-bonds