A THEORETICAL STUDY OF DACTYLYNE STEREOISOMERS: A MARINE NATURAL PRODUCT FROM APLYSIA DACTYLOMELA

Abstract

Dactylyne is an acetylenic dibromochloro ether from the Persian Gulf sea hare, Aplysia dactylomela. As a result of its unique structure and nontoxic nature; it has been known as a promising pharmacological substance of marine origin. A theoretical study of dactylyne and its stereoisomers, initiated in the hope of understanding more details of its action, is reported here. In the present research, for the first time, a density functional theory (DFT) calculation has been performed on the stereoisomers of dactylyne to determine the most stable configurations in gas phase. The HOMO–LUMO gap, global softness, chemical potential, and electrophilicity index have been calculated for the most stable stereoisomers at the B3LYP level of theory. These DFT-based global reactivity descriptors have been applied to demonstrate the reactive nature of compounds. Moreover, results from the quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis have been employed to support the finding of more reactive stereoisomers. The investigation has indicated that the configuration of stereoisomers has some effects on their electronic and structural properties which control their global reactivity. It is also shown that the most probable interaction sites of dactylyne are in its unsaturated region. In the second part of our study, the effects of some typical substituents on dactylyne reactivity have been investigated theoretically and it has been shown that the strong electron donor groups increase the reactivity of dactylyne more than withdrawing substituent. However, creation of an ionic compound highly influences on reactivity descriptors.