Alkali metal-mediated proline aggregation in solution observed by coldspray ionization mass spectrometry

Organic Letters

Volumn 4, Issue 3, 2002, Pages 347-350

  Kunimura, Miki ^a   Sakamoto, Shigeru ^a   Yamaguchi, Kentaro ^a,b  

^a CHIBA UNIVERSITY   (Japan)

^b JAPAN SCIENCE AND TECHNOLOGY AGENCY   (Japan)

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ARTICLE;

EID: 0001714965     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol017028f     Document Type: Article

References (22)

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12. +, was mainly observed by conventional ESI-MS for these amino acids. Ion peaks in the higher mass range, including the chain structure, are presumably not observed because of thermal decomposition caused by the heat of the desolvation chamber.
13. Jönsson, P.-G.; Kvick, Å. Acta Crystallogr. 1972, B28, 1827.
14. Torii, K.; Iitaka, Y. Acta Crystallogr. 1970, B26, 1317.
15. Torii, K.; Iitaka, Y. Acta Crystallogr. 1973, B29, 2799.
16. This result suggests an induced fit between the cyclic L-proline cluster (host) and metal cation (guest). If the guest fits in the middle of the host cavity (tetramer), the complex would exhibit a rather flat shape (Figure 3b) and no other aggregation should be observed. However, when the guest is too large to fit in the middle of the cavity, the guest should be located out of the host plane (Figure 3a). Then, the metal ion of this complex will be able to aggregate with another cyclic cluster (trimer) (Figure 3c). The structures appear to depend on the radius of the metal cation and the size of the cavity in the cyclic L-proline cluster.
17. All calculations were carried out using the HyperChem ver. 5.01 program system with a Gateway Select personal computer.
18. Anderson, W. P.; Edwards, E. D.; Zerner, M. C. Inorg. Chem. 1986, 25, 2728.
19. The geometry of the clusters was obtained by minimizing the total energy using the Polak-Ribiere optimization procedure.
20. Stewart, J. J. P. Quantum Chemistry Program Exchange, No. 455, Indiana University, IN.
21. + were mainly observed by means of conventional ESI-MS measurement.
22. Interaction with L-proline was not observed in the case of lithium, presumably because the ion radius is much smaller than the cavity of the trimeric L-proline cluster.