Compound 1 was least active due to the presence of two olefinic double bonds in conjugation with the carbonyl group of ring A at C-3.
While in compound 2 the carbonyl group of ring A forms bidentate interaction with the side chain guanidinium moiety of Arg38.
As evident from results the OH group of ring A is not involved in hydrogen bonding and therefore its absence in case of 5a increased the binding affinity, while the ortho hydroxyl group of ring B increased binding affinity as it is involved in hydrogen bonding with the target.
The addition operation of I in ring R constitutes a subgroup of additive group of ring R. RI ⊆ R, i.e., for ∀a ∈ R and b ∈ R, it satisfies ab ∈ R.
The addition operation of I in ring R constitutes a subgroup of additive group of ring R. IR ⊆ R, i.e., for ∀a ∈ R and b ∈ R, it satisfies ba ∈ R.
Our docking results revealed the importance of Arg38 in the vicinity of carbonyl group of ring A, which plays a vital role in protein-ligand complex formation and stabilization.
The exocyclic aminomethyl group of ring-I adopts the gt exocyclic rotamer conformation around physiological pHs while the gg exocyclic rotamer conformation predominates in acidic solutions near and below pH 4.5.
The nonempty subset I ⊆ R in ring R is called the left ideal in R, if I satisfies the following two conditions [13]: (1) The addition operation of I in ring R constitutes a subgroup of additive group of ring R. (2) RI ⊆ R, i.e., for ∀a ∈ R and b ∈ R, it satisfies ab ∈ R. .
The nonempty subset I ⊆ R in ring R is called the right ideal in R, if I satisfies the following two conditions [13]: (1) The addition operation of I in ring R constitutes a subgroup of additive group of ring R. (2) IR ⊆ R, i.e., for ∀a ∈ R and b ∈ R, it satisfies ba ∈ R. .
Our study shows that some of the modifications in the synthetic compounds, such as the introduction of an ortho-cyano-substituted benzyl group and a short chain alkyl ester at the 28-carboxyl, as well as the introduction of an acetyl group at the 3-hydroxyl group of ring A, could enhance antibacterial activity.
