Study of mass spectra of the esterification products synthesized from N-protected amino acids and 2,6-bishydroxylmethyl pyridine
✍ Scribed by Yantao Chen; Wenting Hua; Meiyu He; Xiaoran He; Qiyi Xing
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 126 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0951-4198
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✦ Synopsis
Using the condensation of N-protected amino acids with 2,6-bishydroxylmethyl pyridine, we synthesized six di-esters and four mono-esters. All ten esters are new compounds. They are all important intermediate compounds for synthesis of macrocylic compounds containing amino acid and pyridyl units. Because there are several complex sites in these macrocycles, they may be useful as enzyme models or as templates in asymmetric resolution. This paper reports fast-atom bombardment (FAB) mass spectrometry of these two kinds of esterification products, and electron impact (EI) of four mono-esters. Their FAB mass spectrometric behavior was studied with the aid of both mass-analyzed ion kinetic energy spectrometry and high-resolution data. The EI fragmentation mechanisms of the mono-esters are also studied with the aid of mass-analyzed ion kinetic energy spectrometry and high-resolution data. We discovered that, under FAB conditions, each mono-ester yields (2MH] ions, and the ionizing proton is connected with the nitrogen atom in the pyridine ring. Through the high-resolution analysis of compound 10 under EI, we found two kinds of ions at m/z 139. One is a 2,6-bishydroxylmethyl pyridine residue, which is more stable than the other residue formed by the loss of one oxygen atom from p-toluenesulfonyl ion. Also of importance is the fact that a H-atom rearrangement proceeds via a four-membered ring intermediate under both FAB and EI conditions.