Synthesis and Neuroprotective Biological Evaluation of Quinazolinone Derivatives via Scaffold Hopping

Functionalized sulfonyl anthranilic acid derivatives inhibit replication of all the four dengue serotypes

Dengue virus (DENV), a mosquito-borne flavivirus, continues to be a major public health threat in many countries and no approved antiviral therapeutics are available yet. In this work, we designed and synthesized a series of sulfonyl anthranilic acid (SAA) derivatives using a ligand-based scaffold morphing approach of the 2,1-benzothiazine 2,2-dioxide core, previously used by us to develop DENV polymerase inhibitors resulting devoid of any cell-based antiviral activity. Several derivatives based on the new SAA chemotype exhibited potent inhibition against DENV infection in the cell-based assay but did not inhibit DENV NS5 polymerase activity in the in vitro de novo initiation and elongation assays. Notably, best compounds 26 and 39 showed EC50 values in the range of 0.54-1.36 μM against cells infected with the four dengue serotypes (DENV-1-4). Time-of-drug-addition assay revealed that analogue 26 is a post-entry replication inhibitor that appears to be specific for cells of primate origin, implicating a host target with a high barrier to resistance. In conclusion, SAA derivatives offer a valuable starting point for developing effective Dengue antiviral therapeutics.

tert-Butyl Hydroperoxide Promoted the Reaction of Quinazoline-3-oxides with Primary Amines Affording Quinazolin-4(3H)-ones

An efficient and facile approach for the synthesis of quinazolin-4(3H)-ones via the reaction of quinazoline-3-oxides with primary amines is described. This approach is demonstrated to be applicable for a broad range of substrates and proceeds efficiently under metal-free and mild reaction conditions employing easily available tert-butyl hydroperoxide as the oxidant. Remarkably, 3-(2-(1H-indol-3-yl) ethyl)quinazolin-4(3H)-one 3w, which was conveniently obtained by this process in 70% yield, was an excellent precursor for the synthesis of bioactive evodiamine and rutaempine.

Biology of quinoline and quinazoline alkaloids

Quinoline and quinazoline alkaloids, two important classes of N-based heterocyclic compounds, have attracted scientific and popular interest worldwide since the 19th century. More than 600 compounds have been isolated from nature to date. To build on our two prior reviews, we reexamined the promising molecules described in previous reports and provided updated literature on novel quinoline and quinazoline alkaloids isolated over the past 5 years. This chapter reviews and discusses 205 molecules with a broad range of bioactivities, including antiparasitic and insecticidal, antibacterial and antifungal, cardioprotective, antiviral, anti-inflammatory, and other effects. This survey should provide new clues or possibilities for the discovery of new and better drugs from the original naturally occurring quinoline and quinazoline alkaloids.

An Efficient Regioselective Synthesis of 8-Formylhomoisoflavonoids with Neuroprotective Activity by Enhancing Autophagy

6-Formylisoophiopogonone B (7a) and 8-formylophiopogonone B (7b), two natural products isolated from Ophiopogon japonicus, represent a subgroup of rare 6/8-formyl/methyl-homoisoflavonoid skeletons. Herein we report an efficient method for the synthesis of these formyl/methyl-homoisoflavonoids. The synthesized compounds were evaluated for their neuroprotective effects on the MPP⁺-induced SH-SY5Y cell injury model and showed marked activity. Exploration of the neuroprotective mechanisms of compound 7b led to an increased expression of autophagy marker LC3-II and down-regulation of autophagy substrate p62/SQSTM1. Molecular docking studies showed that 7b may prevent the inhibition of the classic PI3K-AKT-mTOR signaling pathway by interfering with the human HSP90AA1.