61733-82-2Relevant academic research and scientific papers
Stabilization of Azapeptides by Namide···H-NamideHydrogen Bonds
Baruah, Kalpita,Sahariah, Biswajit,Sakpal, Sushil S.,Deka, Jugal Kishore Rai,Bar, Arun Kumar,Bagchi, Sayan,Sarma, Bani Kanta
supporting information, p. 4949 - 4954 (2021/06/28)
An unusual Namide···H-Namide hydrogen bond (HB) was previously proposed to stabilize the azapeptide β-Turns. Herein we provide experimental evidence for the Namide···H-Namide HB and show that this HB endows a stabilization of 1-3 kcal·mol-1 and enforces the trans-cis-Trans (t-c-T) and cis-cis-Trans (c-c-T) amide bond conformations in azapeptides and N-methyl-Azapeptides, respectively. Our results indicate that these Namide···H-Namide HBs can have stabilizing contributions even in short azapeptides that cannot fold to form β-Turns.
N-(Acetamido)thiourea based simple neutral hydrogen-bonding receptors for anions
Liu, Wen-Xia,Yang, Rui,Li, Ai-Fang,Li, Zhao,Gao, Yu-Feng,Luo, Xing-Xing,Ruan, Yi-Bin,Jiang, Yun-Bao
experimental part, p. 4021 - 4028 (2009/12/06)
N-(Acetamido)-N′-phenylthioureas (4-6) were found to be efficient anion receptors with higher anion affinity than their N-benzamido-N′- phenylthiourea counterparts (1 and 2). The N′-phenylthiourea moiety in 4-6 was shown to be the chromophore with an absorption maximum at ca. 270 nm. It was found that, in the presence of anions, the absorption at ca. 270 nm of 4-6 (except 5f) in acetonitrile (MeCN) was blue shifted and enhanced while a red-shifted shoulder appeared at ca. 295 nm, together with an isosbestic point at ca. 240 nm. The 1:1 anion binding constants of 4-6, for example at 10 6-107 M-1 order of magnitude for AcO - in MeCN, were found to be higher than those of 1 and 2, although the acidity of the thioureido -NH protons in 4-6 is lower than that in 1 and 2. 1H NMR data indicates that the N-N single bond in 4-6 is twisted but less than that in 1 and 2. A conformation change at the N-N single bond of 4-6 was suggested to occur upon anion binding which leads to a planar hydrogen-bonding network in the anion binding complex in which a charge transfer takes place with the N-acyl moiety being the electron acceptor. Variations in the CD signals of a proline derivative 6 bearing a chiral center in the N-amido moiety provide direct evidence for this conformation change upon its binding with anions in MeCN. The amplified effect of substituent X at the N′-phenyl ring of 5 on the anion binding constant supports the conclusion of anion-binding switched charge transfer in the anion binding complex. 1H NMR and absorption titrations for 5 indicated that the anion-receptor interaction was of a hydrogen-bonding nature until the N′-phenyl substituent X is as electron-withdrawing as m-CF3 (5e). With X being the more electron-withdrawing p-NO2 (5f), deprotonation of the thioureido -NH occurs in the presence of anion. Results reported here confirm that N-amidothioureas derived from both N-aliphatic and N-aromatic amides can in general be a family of efficient hydrogen-bonding receptors, with the aliphatic N-amido derivatives being more efficient. This provides a wider structural diversity for designing thiourea-based functional molecules such as anion receptors and organocatalysts. Preliminary experiments confirm that 6 could catalyse efficiently the reduction of nitrostyrene in CH2Cl2 and MeCN.
Superior reactivity of thiosemicarbazides in the synthesis of 2-amino-1,3,4-oxadiazoles
Dolman, Sarah J.,Gosselin, Francis,O'Shea, Paul D.,Davies, Ian W.
, p. 9548 - 9551 (2007/10/03)
(Chemical Equation Presented) A facile and general protocol for the preparation of 2-amino-1,3,4-oxadiazoles is reported. This method relies on a tosyl chloride/pyridine-mediated cyclization of a thiosemicarbazide, which is readily prepared by acylation o
The rapid preparation of 2-aminosulfonamide-1,3,4-oxadiazoles using polymer-supported reagents and microwave heating
Baxendale, Ian R.,Ley, Steven V.,Martinelli, Marisa
, p. 5323 - 5349 (2007/10/03)
Herein, we report on the preparation of a library of 5-substituted-2-amino- 1,3,4-oxadiazoles and the corresponding thiadiazole analogues. Presented is a one-pot preparation of the 2-aminosulfonylated analogues through a three component coupling of an acylhydrazine, an isocyanate and sulfonyl chloride promoted by a polymer-supported phosphazine base under microwave dielectric heating. Also described is the optimization process and details pertaining to the elucidation of the reaction products.
An efficient synthesis of 1,3,4-oxadiazoles from N,N′-diacylhydrazines using Ph3P·Br2, Ph3P·CCl4 or Ph3P·CBr4 adducts as condensing agents
Mazurkiewicz,Grymel
, p. 77 - 82 (2007/10/03)
1,3,4-Oxadiazoles including 2-amino derivatives were effectively synthesized by treatment of N,N′-diacylhydrazines or N-acylsemicarbazides with Ph3P·Br2, Ph3P·CCl4 or Ph3P·CBr4 adducts in the presence of Et3N in CH2Cl2 under mild conditions.
NEW METAL COMPLEXES OF SOME DIPOSITIVE METAL IONS WITH THIOSEMICARBAZIDE AND SEMICARBAZIDE DERIVATIVES
El-Asmy, Ahmed Abdel-Hamid,Bekheit, Magdy Mohamed,Ibrahim, Kamal Mohamed,Mostafa, Mohsen Mahmoud
, p. 391 - 402 (2007/10/02)
The preparation and characterization of some dipositive metal ions with 1-acetyl-4-phenyl-3-thiosemicarbazide (ATSC) and 1-acetyl-4-phenyl-3-semicarbazide (ASC) are reported.The data of elemental analyses, molar conductivities, polarographic, magnetic mea
