The ground- and excited-state intramolecular proton transfer processes of 2-（2-R （R=OH, NH2, SH） phenyl （or pyridyl）） benzoxazoles （or benzothiazoles） are investigated by the DFT methods. The calculated results indicate that in the ground state there is a high correlation （R=0.9950） between the proton transfer barrier and the intramolecular hydrogen bonds （IMHB） strength. The increase of the strength of IMHB in the proton transfer processes leads to a larger barrier contributions. Intramolecular proton transfer process pathway is along with the minimal difference of change value in the IMHB angle. In the excited-state, there is a similar relationship between the IMHB and the bartier.
Density functional calculations have been carried out on a series of fluorinated empty cages XnFn （n=2-20） with X=Si, Ge, and Sn. It indicates that the fullerene-like cage structure with pentagons turns out to be the most stable with n increasing, and the stability of the XnFn isomers increases with the number of five-membered rings. The HOMO-LUMO gap for Ge （n=6, 10） cages is found to be even larger than the values for Si cages, though in bulk Ge has a smaller band gap than Si. Moreover, calculation of the Gibbs free energy of oligomerization reaction of SiF→1/n （SiF）n showed that this reaction is exothermic even at 900 K, indicating the favorability of their formation from the SiF monomer.
The 1,3-dipolar cycloaddition reactions of nitrilimine with thiazolo[3,2-a]pyrimidine derivatives was investigated. Bis-cycloadducts were obtained through a domino 1,3-dipolar cycloaddition/ring-opening/ring-opening/ 1,3-dipolar cycloaddition processes. The structures of the products were characterized thoroughly by NMR, IR, MS, elemental analysis together with X-ray crystallographic analysis.
In the work, aminophenylboronic acid （APB）-functionalized magnetic mesoporous silica, which holds the attractive features of high magnetic responsivity and large surface area, was developed to enrich glycopeptides. At first, magnetic mesoporous silica nanocomposites were prepared. And then, the nanocomposites were functioned with glycidoxypropyltrimethoxysilane （GLYMO） for boronic acid immobilization. Due to that the boronic acid group on the surface of magnetic mesoporous silica nanocomposites can form tight yet reversible covalent bond with glycopeptides containing cis-1,2-diols groups, the magnetic mesoporous silica nanocomposites were successfully applied to selective enrichment of glycopeptides. APB functionalized magnetic mesoporous silica was also demonstrated to have high selectivity for the glycopeptides in the presence of a 10-fold excess bovine serum albumin （BSA） over horseradish peroxidase （HRP） in the tryptic digest. We also find that magnetic rnesoporous silica has better sensitivity in HRP digest compared with that of commercial aminophenylboronic acid-functionalized magnetic nanoparticles beads. The limit of detection for glycopeptides from glycoprotein HRP is about 0.01 ng/μL.
The 1,3-dipolar cycloaddition of an azomethine ylide generated by a decarboxylative route from sarcosine and acenaphthenequinone to 7-arylmethylidene-3-aryl-3,4-dihydro-2H-thiazolo[3,2-aJ[1,3,5]triazin-6（7H）-ones afforded novel dispiro[acenaphthylene-1,2’-pyrrolidine]-3＇,7″-[1,3]thiazolo[3,2-a][1,3,5]triazines in moderate yields. The structures of the products were determined and characterized thoroughly by NMR, MS, IR, elemental analysis and X-ray crystallographic analysis. The results of experiment indicated that this 1,3-dipolar cycloaddition proceeded with high stereoselectivity and regioselectivity.
