In an earlier fast atom bombardment mass spectroscopy study of polyether antibiotics containing a β-hemiketal carboxylic acid group, the base peak was found to originate from the unusual fragmentation process where both CO2 and H2O were lost from the metal-adduct molecular ion. In this paper, the details of this fragmentation process are studied by ab initio molecular orbital calculations, which indicate that the concerted loss of both CO2 and H2O is much favored over sequential losses of CO2 and H2O.
SiegelM. M.McGahrenW. J.TomerK. B., and ChangT. T., Biomed. Envir. Mass Spectrom.14, 29 (1987).
2.
HehreW. J.RadomL.SchleyerP. v. R., and PopleJ. A., Ab Initio Molecular Orbital Theory (John Wiley, New York, 1986).
3.
ClarkJ., A Handbook of Computational Chemistry (John Wiley, New York, 1985).
4.
BinkleyJ. S.FrischM. J.DeFreesD. J.RaghavachariK.WhitesideR. A.SchelgelH. B.FluderE. M., and PopleJ. A., GAUSSIAN82 Revision H Version (Carnegie-Mellon University, Pittsburgh, 1985).
5.
LiuC. M.HermannT. E.DowneyA.ProserB. La T.ScheldknechtE.PalleroniN. J.WestleyJ. W., and MillerP. A., J. Antibiotics36, 343 (1983).
6.
Cf.: DewarM. J. S., The Molecular Orbital Theory of Organic Chemistry (McGraw-Hill, New York, 1969), Chap. 8.
