[Synthesis of dihydroquinopymaric acid conjugates with amino acids]

New Molecules of Diterpene Origin with Inhibitory Properties toward α-Glucosidase

The incidence of diabetes mellitus (DM), one of the most common chronic metabolic disorders, has increased dramatically over the past decade and has resulted in higher rates of morbidity and mortality worldwide. The enzyme, α-Glucosidase (α-GLy), is considered a therapeutic target for the treatment of type 2 DM. Herein, we synthesized arylidene, heterocyclic, cyanoetoxy- and propargylated derivatives of quinopimaric acid (levopimaric acid diene adduct with p-benzoquinone) 1-50 and, first, evaluated their ability to inhibit α-GLy. Among the tested compounds, quinopimaric acid 1, 2,3-dihydroquinopimaric acid 8 and its amide and heterocyclic derivatives 9, 30, 33, 39, 44, with IC50 values of 35.57-65.98 μM, emerged as being good inhibitors of α-GLy. Arylidene 1β-hydroxy and 1β,13α-epoxy methyl dihydroquinopimarate derivatives 6, 7, 26-29, thiadiazole 32, 1a,4a-dehydroquinopimaric acid 40 and its indole, nitrile and propargyl hybrids 35-38, 42, 45, 48, and 50 showed excellent inhibitory activities. The most active compounds 38, 45, 48, and 50 displayed IC50 values of 0.15 to 0.68 μM, being 1206 to 266 more active than acarbose (IC50 of 181.02 μM). Kinetic analysis revealed the most active diterpene indole with an alkyne substituent 45 as a competitive inhibitor with Ki of 50.45 μM. Molecular modeling supported this finding and suggested that the indole core plays a key role in the binding. Compound 45 also has favorable pharmacokinetic and safety properties, according to the computational ADMET profiling. The results suggested that quinopimaric acid derivatives should be considered as potential candidates for novel alternative therapies in the treatment of type 2 diabetes.

Synthesis and evaluation of diterpenic Mannich bases as antiviral agents against influenza A and SARS-CoV-2

A chemical library was constructed based on the resin acids (abietic, dehydroabietic, and 12-formylabietic) and its diene adducts (maleopimaric and quinopimaric acid derivatives). The one-pot three-component CuCl-catalyzed aminomethylation of the abietane diterpenoid propargyl derivatives was carried out by formaldehyde and secondary amines (diethylamine, pyrrolidine, morpholine, and homopiperazine). All compounds were tested for cytotoxicity and antiviral activity against influenza virus A/Puerto Rico/8/34 (H1N1) in MDCK cells and SARS-CoV-2 pseudovirus in BHK-21-hACE2 cells. Among 21 tested compounds, six derivatives demonstrated a selectivity index (SI) higher than 10, and their IC₅₀ values ranged from 0.19 to 5.0 μM. Moreover, two derivatives exhibited potent anti-SARS-CoV-2 infection activity. The antiviral activity and toxicity strongly depended on the nature of the diterpene core and heterocyclic substituent. Compounds 12 and 21 bearing pyrrolidine moieties demonstrated the highest virus-inhibiting activity with SIs of 128.6 and 146.8, respectively, and appeared to be most effective when added at the time points 0-10 and 1-10 h of the viral life cycle. Molecular docking and dynamics modeling were adopted to investigate the binding mode of compound 12 into the binding pocket of influenza A virus M2 protein. Compound 9 with a pyrrolidine group at C20 of 17-formylabietic acid was a promising anti-SARS-CoV-2 agent with an EC₅₀ of 10.97 µM and a good SI value > 18.2. Collectively, our data suggested the potency of diterpenic Mannich bases as effective anti-influenza and anti-COVID-19 compounds.

Synthesis and antiviral activity of maleopimaric and quinopimaric acids' derivatives

A series of maleopimaric and quinopimaric acids' derivatives modified in the E-ring, at the carbonyl- and carboxyl-groups were synthesized and evaluated for their activity in vitro against respiratory viruses (influenza; rhinovirus; adenovirus; and SARS), papilloma virus, and hepatitis B and C viruses. The antiviral screening of levopimaric acid diene adducts derivatives was carried out with minimal effect on SARS and influenza type B viruses. Excellent antiviral activity of the ozonolysis product of maleopimaric acid and dihydroquinopimaric methyl-(2-methoxycarbonyl)ethylene amide was found toward papilloma virus (HPV-11 strain) with the selectivity index of SI 30 and 20, respectively. Methyl (2-methoxycarbonyl)ethylene-, 1β-hydroxy-5'-kaprolaktamo- and 4β-hydroxy-4α,14α-epoxy-13(15)-ene-dihydroquinopimaric acid derivatives have also shown activity against replication of HCV nucleic acid and low toxicity.

Synthesis and anticancer activity of quinopimaric and maleopimaric acids’ derivatives

A series of quinopimaric and maleopimaric acids’ derivatives modified in the E-ring, at the carbonyl- and carboxyl-groups were synthesized and their in vitro cytotoxic activity was evaluated at the National Cancer Institute, USA. Methyl esters of dihydroquinopimaric, 1a,4a-dehydroquinopimaric, 2,3-epoxyquinopimaric, 1-ethylenketal-dihydroquinopimaric, 1-ethylenketal-4-hydroxyiminodihydroquinopimaric acids displayed an activity on renal cancer, leukemia, colon cancer and breast cancer cell lines in concentration 10(−5) M. Methyl 1,4-dihydroxyiminodihydroquinopimarate showed both a potent and broad spectrum of cytotoxic activity against NSC lung cancer, colon cancer, breast cancer, renal cancer and leukemia and revealed in vivo antineoplastic activity towards mouse solid transplantable mammary carcinoma Ca755 and colon adenocarcinoma AKATOL. The information about antineoplastic activity of the studied quinopimaric and maleopimaric acids’ derivatives will be used for hit to lead optimization in these chemical series.

An Efficient Oxyfunctionalization of Quinopimaric Acid Derivatives with Ozone

An access to oxyfunctionalized quinopimaric acid derivatives is reported. The ozonolysis of methyl dihydroquinopimarate occurs through 1,2-cycloaddition of ozone to the bridging double bond followed by intermolecular rearrangements and formation of nontrivial 4β-hydroxy-4α,14α-epoxy-13(15)-ene derivative 2. The oxidation of methyl furfurilydene dihydroquinopimarate with ozone led to anhydride 5 and unexpected carboxymethyl substituted cyclopentane lactone 6. The structure of compound 6 was confirmed by X-Ray analysis of its methyl ester.