title: A General Method for Synthesis of Unclosed Cryptands via H-Bond Templated Macrocyclization and Subsequent Mild Postfunctionalization.
abstract: 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.
authors.affiliation: Institute of Organic Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Kajetan
authors.initials: K
authors.lastname: Dabrowa
authors.affiliation: Institute of Organic Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Patryk
authors.initials: P
authors.lastname: Niedbala
authors.affiliation: Faculty of Chemistry, University of Warsaw , Pasteura 1, 02-093 Warsaw, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Majdecki
authors.affiliation: Institute of Organic Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Duszewski
authors.affiliation: Institute of Organic Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Janusz
authors.initials: J
authors.lastname: Jurczak