Using Hydrogen Bonding to Control Carbamate C−N Rotamer Equilibria
摘要:
In chloroform solution, the syn/anti rotamer ratios for N-(2-pyridyl)carbamates, 3, and N-phenylcarbamates, 4, are close to 0.05. Addition of the double hydrogen bonding acetic acid moderately stabilizes the syn rotamer of 4, but has no measurable effect on the syn/anti ratio for 3. Conversely, the hydrogen bond donor-acceptor-donor triad in 2,6-bis(octylamido)pyridine, 1, strongly stabilizes the syn rotamer of 3, but has no effect on the synlanti ratio for 4. The K-a for syn-3:1 is 10(3)-10(4) times higher than the K-a for anti-3:1. This implies that the alkoxy oxygen in anti-3 is a much poorer hydrogen bond acceptor than the carbonyl oxygen in syn-3, most likely because of a combination of steric and electrostatic factors.
Recognition Properties of Flavin Analogues with Bile Acid-Based Receptors: Role of Steric Effects in Hydrogen Bond Based Molecular Recognition
作者:Prosenjit Chattopadhyay、Rekha Nagpal、Pramod S. Pandey
DOI:10.1071/ch07342
日期:——
The recognitionproperties of 7,8-dimethyl flavin analogues by bile acid-based receptors that contain 2,6-diaminopyridine and the dioctylamide of 2,6-diaminopyridine in CHCl3 were determined. The results show that the bile acid-based receptors bind 7,8-dimethyl flavin analogues less effectively as compared to 7,8-unsubstituted flavins reported earlier, which is contrary to the known fact that the association