JMSSJ On-line

JMSSJ On-line, Vol. 42 (1994) No. 2, pp. 117-122

An MO Theoretical Study on Isobutene Loss from Protonated Prenylated Flavonoids		>> Full Text PDF >> References
*Atsushi SHIGIHARA^a) and Mitsuo TAKAYAMA^b)** ^a) Hoshi College of Pharmacy* (2-4-41 Ebara, Shinagawa, Tokyo 142, Japan) ^b) Faculty of Pharmaceutical Sciences, Toho University (2-2-1 Miyama, Funabashi 274, Japan)

The fragmentation mechanism for isobutene loss from the protonated molecules [M+H]⁺ of 6- and 8-prenylated chromanones as the model compounds for 6- and 8-prenylated flavonoids was examined by using the MNDO-PM3 method. Heats of formation of the [M+H]⁺ ions and energy barrier of the fragmentation were estimated. The calculated results rationalized the fact that 6-prenylated flavonoids always show extensive loss of the isobutene from the [M+H]⁺ ion more than the corresponding 8-prenylated flavonoids in their fast-atom bombardment (FAB) spectra. The point is that the proton migration occur through intramolecular hydrogen bonding with low energy barrier prior to the loss of isobutene.

Key words: Fravonoids, Molecular orbital, Fragmentation, FAB, Potential energy