Computational study of the molecular structure and reactive sites of the R and S isomers of persin diene

In this work the molecular structure and some electronic properties of the R and S isomers of persin diene, by means of DFT employing the PBE1/CBSB2**//PBE1/CBSB4 model chemistry, were studied and compared with the purpose to establish the reactive sites of this compound and their possible relationship with biological activity. It was found that the reactive sites of R isomer are the C4 of ketone group, which represent the preferential site for nucleophilic and radical attacks, and the C12 and C16 of the cis,cis-1,4-pentadiene system for electrophilic attack. The S isomer has the same reactive sites, and only differs of the R isomer in that the O4, in addition to C4, also represents an important reactive site for the radical attack. We suggest that the reason by which the R isomer is active whereas the S isomer inactive, is the selectivity of the receptor molecule that reacts with diene. Two factors that could favor such selectivity are: the torsion angles formed by the atoms in reactive sites of diene, as well as the fact that molecular orbital phases are oriented in an inverted direction in the reactive sites of the intermediates of both isomers, especially those which are derived from 4-ketone group.