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Research has been conducted on bisannulated acridines. The biosynthetic origin of these compounds and their structural and biological activities have been investigated, and the results are reported.

Results reveal that the transition states of the proton transfer reactions are not in balance despite the absence of correlation between the degree of imbalance and the pi-acceptor strength of the Y group.

An ab initio study of two series of carbon-to-carbon proton transfer reactions is conducted to examine the degree of aromaticity of [C.sub.4][H.sub.4]X (X = CH(-), NH, S, O, PH) and the antiaromaticity of [C.sub.4][H.sub.4]X (X = AlH, BH) is expressed at the transition state of the proton transfer and its effect on the respective intrinsic barriers. The results revealed a disproportionately large degree of aromaticity at the transition state for the aromatic systems and a disproportionately small degree of transition state antiaromaticity for the antiaromatic systems.

A systematic analysis of the candidate structures of spiroleucettadine, a sponge with a bicyclic core meager in H-atoms, is performed by using density functional theory calculations. The results have provided a revised structure of spiroleucettadine, a bicyclic sponge alkaloid with a scarcity of H-atoms in its core.

The experimental data on the kinetic and thermodynamic acidities of pentacarbonyl(cyclobutenylidene)chromium complexes in acetonitrile is presented. Results of the gas phase ab initio calculations indicate that in the gas phase, the effect of antiaromaticity on the thermodynamic acidities is large but strongly attenuated in acetonitrile.

Research has been conducted on carbon-to-carbon proton-transfer. The authors describe the results of ab initio study of the proton-transfer identity in the gas phase, and discuss the effects of the cyano group on the proton-transfer barriers, transition state structure and acidities.