A New Method for Synthesis of Crown Ether Type Pyridinophanes
摘要:
Bis(acylketene) (3) thermally generated from Meldrum's acid derivative (2) underwent intramolecular [4+2] cycloaddition to produce bridged dehydroacetic acid derivative (4). Heating 4 with methylamine and ammonia afforded crown ether type pyridinophanes (5) and (6) (12-crown-4), respectively. Reaction of the ketene (3) with (ethylene glycol)s afforded macrolactones (11similar to13) in satisfactory yields. Molecular structures of 4 and 6 are discussed based on X-Ray crystallographic analysis.
unsaturation from the poly(lysine) backbone, the more intense the polarized signals when para-hydrogenation is carried out. This is due to (a) the maintenance of short reorientational times on the unsaturated ends, and therefore a sufficiently long T(1) of the protons added during hydrogenation, and (b) the minor effect of steric hindrance by the poly(lysine) backbone that decreases interaction of the
The
X-ray structures of three potential molecular tweezers, C20H24N2O5 (1), C20H20N6O13 (2) and C28H32N2O13
(3), differing
only by the substituents on the terminal aromatic moieties, display three as yet unreported arrays. Hydrogen
bonding with co-crystallized water molecules as well as van der Waals interactions between terminal
aromatic moieties lead to specific packing patterns, namely: (i) a membrane-like architecture of associated molecular tapes in 1·2H2O, (ii) coupled right-handed and left-handed helices in 2·H2O and (iii) a stepped arrangement provided by a back-to-back pairing in (3)2·H2O. Molecular modelling of individual molecules in vacuo shows
that the most stable conformers of 1–3
intrinsically display attractive interactions between the terminal aromatic
groups, which stabilize a pseudocavity suitable for incorporation of a guest compound.
Certain embodiments of the invention provide antioxidant-based diacids and polymers comprising glycol groups as described herein, and methods of use thereof. In certain embodiments the polymers described herein are formulated as microspheres or hydrogels. Described herein is the chemical incorporation of antioxidants, e.g., coumaric acid, ferulic acid, and sinapic acid, into a polymer backbone for use, e.g., in applications for localized release and rapid delivery. As provided, the chemical composition of the linker molecules used (of which hold together two bioactives via ester linkages) may be used to vary the hydrophilicity of the polymer. The bioactive release rate may also be altered for a tunable release delivery system, allowing for increased bioactive release compared to other linkers previously utilized.