Development of fluorine-substituted NH_(2)-biphenyl-diarylpyrimidines as highly potent non-nucleoside reverse transcriptase inhibitors:Boosting the safety and metabolic stability

Our recent studies for nonnucleoside reverse transcriptase inhibitors identified a highly potent compound JK-4b against WT HIV-1(EC_(50)=1.0 nmol/L),but the poor metabolic stability in human liver microsomes(t_(1/2)=14.6 min)and insufficient selectivity(SI=2059)with high cytotoxicity(CC_(50)=2.08μmol/L)remained major issues associated with JK-4b.The present efforts were devoted to the introduction of fluorine into the biphenyl ring of JK-4b,leading to the discovery of a novel series of fluorine-substituted NH_(2)-biphenyl-diarylpyrimidines with noticeable inhibitory activity toward WT HIV-1 strain(EC_(50)=1.8–349 nmol/L).The best compound 5t in this collection(EC_(50)=1.8 nmol/L,CC_(50)=117μmol/L)was 32-fold in selectivity(SI=66,443)compared to JK-4b and showed remarkable potency toward clinically multiple mutant strains,such as L100I,K103N,E138K,and Y181C.The metabolic stability of 5t was also significantly improved(t_(1/2)=74.52 min),approximately 5-fold higher than JK-4b in human liver microsomes(t_(1/2)=14.6 min).Also,5t possessed good stability in both human and monkey plasma.No significant in vitro inhibition effect toward CYP enzyme and hERG was observed.The single-dose acute toxicity test did not induce mice death or obvious pathological damage.These findings pave the way for further development of 5t as a drug candidate.

Linker optimization of HEPT derivatives as potent non-nucleoside HIV-1 reverse transcriptase inhibitors: From S=O to CHOR

A novel series of CHOR-HEPT non-nucleoside HIV-1 reverse transcriptase inhibitors were developed by means of structure-based design strategy based on compound 6 reported previously by our group. Most of these compounds showed moderate to good activity toward wild-type HIV-1 strain with EC50values in the range of 0.18–51.88 μmol/L and SI values in the range of 4–907. The compound 14aj with a CHOH linker and compound 13i with a CHOTMS linker in this series exhibited improved anti-HIV-1 activity(EC50= 0.18 μmol/L, and 0.20 μmol/L) with higher selectivity(SI = 907, and 665) as comparison with the lead compound 6(EC50= 0.59 μmol/L, SI = 9). These two compounds 14aj and 13i were more sensitive than 6 toward clinically relevant mutant L100I, K103N and E138K viruses, which were further evaluated for their activity against wild-type reverse transcriptase and displayed a good correlation with the cell-based activity. Preliminary molecular modeling investigations provided insight for further structural optimization of HEPT.

Asymmetric synthesis of syn-aryl-(2S,3R)-2-chloro-3-hydroxy esters via an engineered ketoreductase-catalyzed dynamic reductive kinetic resolution

We report here a generic,green synthesis of 17 valuable syn-aryl-(2S,3R)-2–chloro-3–hydroxy esters(syn-(2S,3R)-1)in 73%-99%isolated yields along with 6.1:1–83:1 dr and 31%~>99%ee,through dynamic reductive kinetic resolution of racemic arylα–chloroβ-keto esters(2)catalyzed by an engineered ketoreductase which was obtained via ep PCR-based directed evolution.The hectogram scale synthesis of syn-(2S,3R)-1b at a substrate concentration of 120 g/L showcased the application potential of the biocatalytic method developed presently.

Intramolecularly lactam stapled oxyntomodulin analogues inhibit cancer cell proliferation in vitro

As a glucagon(GCG) receptor(GCGR) and glucagon-like peptide 1(GLP-1) receptor(GLP-1R) dual agonist, oxyntomodulin(OXM) has been attracting scientific attentions due to its efficacies of suppressing appetite, increasing energy expenditure, and inducing body weight loss in obese humans. Based on the scaffold of native OXM, specific helix-favoring amino acids substitutions and the consequent salt bridge formations were believed to offer enhanced and balanced GCGR/GLP-1R activations through increasing α-helical conformation. Novel OXM analogues are obtained by intramolecular lactam stapling of positions[Glu16 & Lys20] or [Lys17 & Glu21] to further strengthen conformationally constrained stabilization. Even though the lactam staple does not provide additional dual GCGR/GLP-1R activations in vitro, the stapled OXM analogues are firstly reported to have higher or lower anti-PANC-1 cell proliferation activity, meanwhile which has no obvious inhibitory effect on the proliferation of He La cells. Therefore, it is speculated that the stapled analogues may have the potential to inhibit the proliferation of specific cancer cell types.Among the stapled peptides as well as their precursors, analogue 6 has the most prominent anti-PANC-1 proliferation activity with the IC50value of 115.1 μmol/L. Its mechanism of actions including effective signal pathways should be worth further investigations in future.

Visible-light-driven intramolecular xanthylation of remote unactivated C(sp^(3))-H bonds

Visible light-mediated site-specific C(sp^(3))-H xanthylation of amides has been accomplished using N-xanthylamides.The N-centered radicals generated by light initiation of N-xanthylamide substrates undergo 1,5-hydrogen atom transfer to form benzylic or alkyl radical intermediates under metal-and catalyst-free conditions.This method exhibits a broad substrate scope,high functional group tolerance,and high regioselectivity.Furthermore,this strategy provides straightforward access to a range of derivatives through the subsequent elaboration of the xanthate group.

Development of non-nucleoside reverse transcriptase inhibitors(NNRTIs):our past twenty years

Human immunodeficiency virus(HIV)is the primary infectious agent of acquired immunodeficiency syndrome(AIDS),and non-nucleoside reverse transcriptase inhibitors(NNRTIs)are the cornerstone of HIV treatment.In the last 20 years,our medicinal chemistry group has made great strides in developing several distinct novel NNRTIs,including 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine(HEPT),thio-dihydro-alkoxy-benzyl-oxopyrimidine(S-DABO),diaryltriazine(DATA),diarylpyrimidine(DAPY)analogues,and their hybrid derivatives.Application of integrated modern medicinal strategies,including structure-based drug design,fragment-based optimization,scaffold/fragment hopping,molecular/fragment hybridization,and bioisosterism,led to the development of several highly potent analogues for further evaluations.In this paper,we review the development of NNRTIs in the last two decades using the above optimization strategies,including their structure-activity relationships,molecular modeling,and their binding modes with HIV-1 reverse transcriptase(RT).Future directions and perspectives on the design and associated challenges are also discussed.

Improving the positional adaptability:structurebased design of biphenyl-substituted diaryltriazines as novel non-nucleoside HIV-1 reverse transcriptase inhibitors

In order to improve the positional adaptability of our previously reported naphthyl diaryltriazines(NP-DATAs),synthesis of a series of novel biphenyl-substituted diaryltriazines(BP-DATAs)with a flexible side chain attached at the C-6 position is presented.These compounds exhibited excellent potency against wild-type(WT)HIV-1 with EC50 values ranging from 2.6 to 39 nmol/L and most of them showed low nanomolar anti-viral potency against a panel of HIV-1 mutant strains.Compounds 5 j and 6 k had the best activity against WT,single and double HIV-1 mutants and reverse transcriptase(RT)enzyme comparable to two reference drugs(EFV and ETR)and our lead compound NP-DATA(1).Molecular modeling disclosed that the side chain at the C-6 position of DATAs occupied the entrance channel of the HIV-1 reverse transcriptase non-nucleoside binding pocket(NNIBP)attributing to the improved activity.The preliminary structure-activity relationship and PK profiles were also discussed.

Structure-based linker optimization of 6-(2-cyclohexyl-1-alkyl)-2-(2-oxo-2-phenylethylsulfanyl)pyrimidin-4(3H)-ones as potent non-nucleoside HIV-1 reverse transcriptase inhibitors

In continuation of our efforts toward the discovery of potent HIV-1 NNRTIs with diverse structures,a series of novel S-DACO analogues of 6-(2-cyclohexyl-1-allkyl)-2-(2-oxo-2-phenyl-ethylsulfanyl)pyrimidin-4(3 H)-ones were designed,synthesized and evaluated for their antiviral activities in MT-4 cells.Most of these new compounds showed moderate to good activities against wild type HIV-1 with IC_(50) values ranging from 7.55μmol/L to 0.018μmol/L.Among them,compound 5 c was identified as the most promising inhibitor against HIV-1 replication with an IC_(50)=0.018μmol/L,CC_(50)=194μmol/L,and SI=12791,which was much more potent than the reference drugs NVP and DLV and comparable to AZT and EFV.In addition,5 c also exhibited improved activity against double mutant HIV-1 strain RES056 compared to that of the reference drugs NVP/DLV and DB02.The preliminary structure-activity relationship(SAR)and molecular modeling studies were also discussed,which provides some useful indications for guiding the further rational design of new S-DACO analogues.

Targeting human MutT homolog 1(MTH1) for cancer eradication:current progress and perspectives

Since accelerated metabolism produces much higher levels of reactive oxygen species(ROS)in cancer cells compared to ROS levels found in normal cells,human MutT homolog 1(MTH1),which sanitizes oxidized nucleotide pools,was recently demonstrated to be crucial for the survival of cancer cells,but not required for the proliferation of normal cells.Therefore,dozens of MTH1 inhibitors have been developed with the aim of suppressing cancer growth by accumulating oxidative damage in cancer cells.While several inhibitors were indeed confirmed to be effective,some inhibitors failed to kill cancer cells,complicating MTH1 as a viable target for cancer eradication.In this review,we summarize the current status of developing MTH1 inhibitors as drug candidates,classify the MTH1 inhibitors based on their structures,and offer our perspectives toward the therapeutic potential against cancer through the targeting of MTH1.

Palladium-catalyzed base-and solvent-controlled chemoselective allylation of amino acids with allylic carbonates

The utilization of readily available amino acids,which is not only an oxygen nucleophile but also a nitrogen nucleophile,in palladium-catalyzed allylic substitution is realized under mild conditions.The chemoselectivity and multiple allylation are controlled by adjusting the reaction conditions.This represents the first example of this convenient access to valuable N,O-diallylated amino acids.Under the title conditions,a range of amino acids(α-,β-,γ-)and dipeptides can be readily converted in to the corresponding allylic products with excellent yields(67 examples,up to 99%yield)as well as good functional group tolerance.

Fragment-based discovery of sulfur-containing diarylbenzopyrimidines as novel nonnucleoside reverse transcriptase inhibitors

Two series of sulfur-containing diarylbenzopyrimidines are designed by the fragment combination of a thioacetamide with our previous disclosed DABP 3 and further oxidation.The best compound 6 e with a sulfonyl scaffold displayed EC(50)values of 0.0356μmol/L against WT and 0.0228μmol/L against HIV K103 N mutant strain.More pronounced,it had a lower cytotoxicity(CC(50)=99.6μmol/L),higher selectivity index(SIWT=2799,SIK103 N=4375)and better calculated logarithm of the octanol-water partition coefficient(cLogP)than the lead compound 3.Molecular docking and dynamics provided the binding modes of these compounds with reve rse transcriptase,explaining their activity.Collectively,the new compounds could be candidates for anti-HIV drug discovery.

Concise syntheses of 13-methylprotoberberine and 13-methyltetrahydroprotoberberine alkaloids

The concise syntheses of eight 13-methylprotoberberine(13-MePB)and eight enantioenriched 13-methyltetrahydroprotoberberine(13-MeTHPB)alkaloids have been achieved in a tactically modular fashion.This synthetic work features a one-pot metal-free Pictet-Spengler/Friedel-Crafts hydroxyalkylation/dehydration/oxidation sequence and a following highly enantioselective Ir-catalyzed hydrogenation.Given such brevity and modularity,our developed synthetic route would be greatly beneficial to the efficient syntheses of existing natural products and new fully synthetic variants of 13-MePB and 13-MeTHPB family.

Unified total synthesis of eburnamine-vincamine indole alkaloids based on catalytic asymmetric hydrogenation/lactamization cascade

The enantioselective total synthesis of representative members of the eburnamine-vincamine alkaloids(+)-vincamine,(-)-eburnamonine,and(-)-criocerine has been accomplished.The synthesis took advantage of a highly stereoselective Ir-catalyzed hydrogenation/lactamization cascade reaction,which allows for the stereo-selective construction of the C/D rings as well as the installation of the critical cis-C20/C21 relative stereo-chemistry of the eburnamine-vincamine alkaloid skeleton in one pot.

Flow chemistry in the multi-step synthesis of natural products

The total synthesis of natural products is constantly facing many challenges derived from the complexed chemical structures,the lengthy synthetic routes,the time-consuming workup procedures and the large environmental footprint.In the past two decades,performing chemical transformations in continuous flow using various types of microreactors and in-line auxiliary technologies have been demonstrated effectively in respects of enhanced re-action yield and selectivity,excellent reproducibility and easy scale-up,safe proceeding hazardous reaction.And the rapid synthesis of natural products,which has been enabled in continuous flow based upon the significant improvement of overall yield within a short residence time via processing intensification and systematic auto-mation,is essential to furnish sufficient quantity for the bioactivity investigation of structural diversity modifi-cation,structure-activity relationship during drug discovery and the increasing consumption of medical treatment.In this review,the multi-step continuous flow synthesis of natural products is highlighted to provide a comprehensive recognization on the intrinsic merits of flow chemistry for organic chemists to purposefully develop the flow synthetic approaches of natural products in the future.

Benzaldehyde lyase-catalyzed enantioselective C-C bond formation and cleavage:A review

Benzaldehyde lyase(BAL)is an enzyme which was originally found from Pseudomonas fluorescens biovar I.It has long been used in the formation of a C-C bond.BAL can exclusively yield(R)-enantioselective products from the synthesis ofα-hydroxy ketones and has so far been explored as an important enzyme to prepare the corresponding intermediate of pharmaceuticals.Due to its substrate spectrum and stereospecificity,this enzyme extends the synthetic potential for carboligations appreciably.In this review,we highlight the biotransformation applications of BAL in recent years,some of which have achieved intriguing results and provided the theoretical basis for drug development and industrial purpose in the future.