The formation of macrocyclic compounds with O,O- and O,N-acetal units

Poly(acetal)s are prepared in polycondensation of methyl α-D-mannopyranoside (IX) and terephthalaldehyde (IV) or 1,4-bis(formyl-phenoxy)butanes (XIV) catalyzed by acid. The composition highly depends on the reaction conditions, structure of comonomers and nature of catalyst leading to the formation of chiral macrocycles and linear macromolecules. The regioselective polycondensation was examined by ¹H NMR spectroscopy. The structures of polycondensation products were also identified by electrospray mass spectrometry (ESI-MS) and MALDI-TOF mass spectroscopy. The polycondensation of terephthalaldehyde with 2-amino-2-hydroxymethyl-1,3-propanediol [or 2,2′(1,4-phenylene)-bis-1,3- (4,4-dihydroxymethyl)oxazolidine (bis-oxazolidine)] and 2-amino-2-methyl-1,3- propanediol under acidic catalysts leads to the formation of macrocyclic compounds. ESI-MS measurements were used to study the details of polymer structure and support the nature of oxazolidine-acetal and 2-(1′,4′- phenylene)-5-methyl-1-aza-3,7-dioxabicyclo[3.3.0]octane as the repeating units in all macromolecules (both cyclic and linear).