Ring Opening Metathesis Polymerization of Bicyclic α,β‐Unsaturated Anhydrides for Ready‐to‐be‐grafted Polymers Having Tailored pH‐Responsive Degradability

Polymers having α,β‐unsaturated anhydrides as repeating units were synthesized by ring opening metathesis polymerization (ROMP). The anhydride moieties were ready‐to‐be‐grafted with amines to form acid‐labile cis‐α,β‐unsaturated acid amide linkages. The pH‐responsive reversible de‐grafting can be controlled by changing the intramolecular accessibility between acid and amide groups. The alendronate‐grafted ROMP polymers showed distinct pH‐dependent cytotoxicity according to the anhydride structures.     

Frustrated Helicity: Joining the Diverging Ends of a Stable Aromatic Amide Helix to Form a Fluxional Macrocycle

Macrocyclization of a stable two‐turn helical aromatic pentamide, that is, an object with diverging ends that are not prone to cyclization, was made possible by the transient introduction of disruptors of helicity in the form of acid‐labile dimethoxybenzyl tertiary amide substituents. After removal of the helicity disruptors, NMR, X‐ray crystallography, and computational studies show that the macrocycle possesses a strained structure that tries to gain as high a helical content as possible despite being cyclic. Two points of disruption of helicity remain, in particular a cis amide bond. This point of disruption of helicity can propagate along the cycle in a fluxional manner according to defined trajectories to produce ten degenerate conformations.     

Reduction of N,N‐Dimethylcarboxamides to Aldehydes by Sodium Hydride–Iodide Composite

A new and concise protocol for selective reduction of N,N‐dimethylamides into aldehydes was established using sodium hydride (NaH) in the presence of sodium iodide (NaI) under mild reaction conditions. The present protocol with the NaH‐NaI composite allows for reduction of not only aromatic and heteroaromatic but also aliphatic N,N‐dimethylamides with wide substituent compatibility. Retention of α‐chirality in the reduction of α‐enantioriched amides was accomplished. Use of sodium deuteride (NaD) offers a new step‐economical alternative to prepare deuterated aldehydes with high deuterium incorporation rate. The NaH‐NaI composite exhibits unique chemoselectivity for reduction of N,N‐dimethylamides over ketones.     

Effect of temperature on the behavior of osmotic and activity coefficients of amides in aqueous solutions

The osmotic coefficients of acetamide, propionamide and butyramide in water were measured at 293.15, 298.15 and 308.15 K using the isopiestic method. The activity coefficients were calculated for the aliphatic amides and the pairwise free energy coefficients for solute-solute interactions were determined according to the McMillan-Mayer theory. The osmotic and activity coefficients of amides are discussed in terms of solute-solute interactions.     

14N NQR study of nicotinamide and related compounds

14N nuclear quadrupole resonance (NQR) frequencies have been measured in picolinamide, nicotinamide, isonicotinamide, 2,6-pyridine dicarboxamide, and acetamide by double resonance. The 14N NQR spectra in picolinamide, nicotinamide, isonicotinamide, and 2,6-pyridine dicarboxamide show the presence of two distinct nitrogen positions: the ring position with the quadrupole coupling constant about 4,5 MHz and the amide position with the quadrupole coupling constant about 2.6 MHz. The NQR data are related to the structure of the investigated compounds and to the N--H...O hydrogen bonds.