Photoelectron spectra of some antibiotic building blocks: 2-azetidinone and thiazolidine-carboxylic acid.
X-ray photoelectron spectra of the core and valence levels of the fundamental building blocks of β-lactam antibiotics have been investigated and compared with theoretical calculations. The spectra of the compounds 2-azetidinone and the 2- and 4-isomers of thiazolidine-carboxylic acid are interpreted in the light of theoretical calculations. The spectra of the two isomers of thiazolidine-carboxylic acid are rather similar, as expected, but show clear effects due to isomerization. Both isomers are analogues of proline, which is well-known to populate several low energy conformers in the gas phase. We have investigated the low energy conformers of thiazolidine-4-carboxylic acid theoretically in more detail and find some spectroscopic evidence that multiple conformers may be present. The measured valence levels are assigned for all three compounds, and the character of the frontier orbitals is identified and analyzed.
eChemistry Laboratory, Faculty of Life and Social Sciences, Swinburne University of Technology, Melbourne, Victoria 3122, Australia.
Marawan
M
Ahmed
Aravindhan
A
Ganesan
Feng
F
Wang
Vitaliy
V
Feyer
Oksana
O
Plekan
Kevin C
KC
Prince
D000900:Anti-Bacterial Agents / Q000737:chemistry*; D001384:Azetidines / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D011392:Proline / Q000031:analogs & derivatives* / Q000737:chemistry; D011789:Quantum Theory; D053778:Thiazolidines / Q000737:chemistry*
C116379:2-azetidinone; D000900:Anti-Bacterial Agents; D001384:Azetidines; D053778:Thiazolidines; C021760:thiazolidine-2-carboxylic acid; D011392:Proline; C003438:thiazolidine-4-carboxylic acid