Davenport Research Laboratories, Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
Org Lett. 2020 Dec 4;22(23):9210-9214. doi: 10.1021/acs.orglett.0c03369. Epub 2020 Nov 18.
The amidine functionality switches between hydrogen bond donor and acceptor roles depending on pH. Herein, the amidine was incorporated to select amides in cyclo(d-Ala-Pro-d-Phe-Pro-Gly). The unprotonated amidine-containing macrocyclic conformation resembles its oxoamide counterpart. Upon protonation, minimal alterations in the macrocyclic conformation were observed despite changes to the hydrogen bond network. The amidine disrupts hydrogen bonding at minimal steric cost, making it a useful functionality to study the effect of hydrogen bonding on the macrocyclic conformation.
脒基的氢键供体和受体作用取决于 pH 值。在此，脒基被引入以选择环（D-丙氨酰-D-脯氨酰-D-苯丙氨酰-D-甘氨酰）中的酰胺。未质子化的含脒大环构象类似于其氧代酰胺对应物。质子化后，尽管氢键网络发生变化，但大环构象的变化很小。脒基以最小的空间位阻破坏氢键，使其成为研究氢键对大环构象影响的有用功能。
