Design, synthesis, apoptotic, and antiproliferative effects of 5-chloro-3- (2-methoxyvinyl)-indole-2-carboxamides and pyrido[3,4-b]indol-1-ones as potent EGFRWT/EGFRT790M inhibitors.

A new series of indole-2-carboxamides 5a-g, 6a-f and pyrido[3,4-b]indol-1-ones 7a and 7b have been developed as new antiproliferative agents that target both wild and mutant type EGFR. The antiproliferative effect of the new compounds was studied. 5c, 5d, 5f, 5 g, 6e, and 6f have the highest antiproliferative activity with GI50 values ranging from 29 nM to 47 nM in comparison to the reference erlotinib (GI50 = 33 nM). Compounds 5d, 5f, and 5 g inhibited EGFRWT with IC50 values ranging from 68 to 85 nM while the GI50 of erlotinib is 80 nM. Moreover, compounds 5f and 5 g had the most potent inhibitory activity against EGFRT790M with IC50 values of 9.5 ± 2 and 11.9 ± 3 nM, respectively, being equivalent to the reference osimertinib (IC50 = 8 ± 2 nM). Compounds 5f and 5 g demonstrated excellent caspase-3 protein overexpression levels of 560.2 ± 5.0 and 542.5 ± 5.0 pg/mL, respectively, being more active than the reference staurosporine (503.2 ± 4.0 pg/mL). they also increase the level of caspase 8, and Bax while decreasing the levels of anti-apoptotic Bcl2 protein. Computational docking studies supported the enzyme inhibition results and provided favourable dual binding modes for both compounds 5f and 5 g within EGFRWT and EGFRT790M active sites. Finally, in silico ADME/pharmacokinetic studies predict good safety and pharmacokinetic profile of the most active compounds.

Discovery of novel oxazole-based macrocycles as anti-coronaviral agents targeting SARS-CoV-2 main protease.

We have discovered a family of synthetic oxazole-based macrocycles to be active against SARS-CoV-2. The synthesis, pharmacological properties, and docking studies of the compounds are reported in this study. The structure of the new macrocycles was confirmed by NMR spectroscopy and mass spectrometry. Compounds 13, 14, and 15a-c were evaluated for their anti-SARS-CoV-2 activity on SARS-COV-2 (NRC-03-nhCoV) virus in Vero-E6 cells. Isopropyl triester 13 and triacid 14 demonstrated superior inhibitory activities against SARS-CoV-2 compared to carboxamides 15a-c. MTT cytotoxicity assays showed that the CC50 (50% cytotoxicity concentration) of 13, 14, and 15a-c ranged from 159.1 to 741.8 µM and their safety indices ranged from 2.50 to 39.1. Study of the viral inhibition via different mechanisms of action (viral adsorption, replication, or virucidal property) showed that 14 had mild virucidal (60%) and inhibitory effects on virus adsorption (66%) at 20 µM concentrations. Compound 13 displayed several inhibitory effects at three levels, but the potency of its action is primarily virucidal. The inhibitory activity of compounds 13, 14, and 15a-c against the enzyme SARS-CoV-2 Mpro was evaluated. Isopropyl triester 13 had a significant inhibition activity against SARS-CoV-2 Mpro with an IC50 of 2.58 µM. Large substituents on the macrocyclic template significantly reduced the inhibitory effects of the compounds. Study of the docking of the compounds in the SARS CoV-2-Mpro active site showed that the most potent macrocycles 13 and 14 exhibited the best fit and highest affinity for the active site binding pocket. Taken together, the present study shows that the new macrocyclic compounds constitute a new family of SARS CoV-2-Mpro inhibitors that are worth being further optimized and developed.

Thio-Claisen rearrangement used in preparing anti-ß-functionalized γ,δ-unsaturated amino acids: scope and limitations.

Multifunctionalized amino acids, especially amino acids with unsaturation, are important, demanding building blocks in peptide chemistry. Here we present a summary of our most recent study using the thio-Claisen rearrangement for the synthesis of anti-ß-functionalized γ,δ-unsaturated amino acids. Investigations on scope, limitations, chemoselectivities and stereoselectivities regarding an FeBr(3)-catalyzed allylation strategy and a thio-enolate dianion formation strategy for asymmetric thio-Claisen rearrangement are documented. An explanation of the chirality crossover observed between the Eschenmoser-Claisen rearrangement and the thio-Claisen rearrangement is proposed. Novel optically active N(α)-protected amino acids with biologically interesting functional groups were prepared for the first time.

Enantioselective synthesis of anti-beta-substituted gamma,delta-unsaturated amino acids: a highly selective asymmetric thio-Claisen rearrangement.

A novel synthesis of optically active anti-beta-substituted gamma,delta-unsaturated amino acids via a thio-Claisen rearrangement has been achieved. A 2,5-diphenylpyrrolidine was used as a C2-symmetric chiral auxiliary to control the stereochemistry, giving good yields and excellent diastereoselectivities and enantioselectivities.

A derivative of the melanocortin receptor antagonist SHU9119 (PG932) increases food intake when administered peripherally.

Melanocortin receptors are considered promising candidates for the treatment of behavioral and metabolic disorders ranging from obesity to anorexia and cachexia. These experiments examined the response of mice to peripheral injections of two compounds. PG932 is a derivative of SHU9119 which is non-selective antagonist of melanocortin-3 and melanocortin-4 receptors (Mc3r and Mc4r). PG946 is a derivative of a hybrid of alpha- and beta-MSH, and is a moderately selective Mc3r antagonist. SHU9119 increases food intake when administered intracerebroventricularly but is without effect when injected into the periphery. In contrast, PG932 was found to be highly effective at stimulating food intake when administered peripherally by intraperitoneal injection. The orexigenic effect of PG932 required functional Mc4r, suggesting that inhibition of this receptor is involved in the stimulation of food intake. PG946 did not significantly affect on feeding behavior. PG932 is thus a useful new compound for studies examining the regulation of appetite and energy balance, and may also prove useful for the treatment of cachectic conditions.

Synthesis of a novel benzyl-octahydropyrazino[1,2-a]pyrimidin-6-one derivative as a convenient internal bicyclic peptidomimetic.

A substituted hydropyrazino[1,2-a]pyrimidin-6-one derivative was synthesized stereoselectively via the intramolecular N-acyliminium ion cyclization between an amide nitrogen and an N(α)-acetal derived from Cbz-protected aminopropyl-phenylalaninamide in very good yields. The formation of a single diastereomer is due to the low energy chairlike conformation of its bicyclic structure. This methodology provides a convenient tool to build internal bicyclic peptidomimetics.

Asymmetric Eschenmoser-Claisen rearrangement for anti-beta-substituted gamma,delta-unsaturated amino acids.

Optically active anti-beta-substituted gamma,delta-unsaturated amino acids are important synthetic building blocks in organic synthesis and for peptidomimetics. A novel asymmetric Eschenmoser-Claisen rearrangement with use of a C2-symmetric chiral auxiliary was developed to generate this type of amino acid. Excellent diastereoselectivities and high enantioselectivities (87-93% ee) were obtained after the chiral auxiliary was removed via iodolactonization/zinc reduction.

Design, synthesis, and biological evaluation of new cyclic melanotropin peptide analogues selective for the human melanocortin-4 receptor.

Intensive efforts have been made to develop potent and selective ligands for certain human melanocortin receptors as possible treatments for obesity and sexual dysfunction due to the role of these receptors in feeding behavior, energy homeostasis, sexual function, etc. A number of novel alpha-MSH analogues were designed and synthesized primarily on the basis of our previous MTII NMR structure. In these peptide analogues, a disulfide or lactam bridge between residues at positions 5 and 8 was used as a conformational constraint to enhance the beta-turn spanning His6 and D-Phe7, while the pharmacophore group in Arg8 was mimicked via Nalpha-alkylation of residues 8 or 9 with the guanidinylbutyl group. Biological assays for binding affinities and adenylate cyclase activities for the hMC1R, hMC3R, hMC4R, and hMC5R showed that three analogues have good binding affinity for the hMC4R (0.7-4.1 nM), but have no binding affinity up to 10 microM at the other three melanocortin receptors. Interestingly, the three hMC4R selective analogues display only 50% binding efficiency, suggesting there is allosteric modulation of the melanocortin-4 receptor. These analogues were found to act as antagonists of the hMC4R. This result represents a discovery of very selective peptide-based antagonists for the hMC4R. The high selectivity may be due to the strong conformational constraint via ring contraction as compared to MTII, and the rigid conformation preferred by these new ligands allows them to recognize only the hMC4R, but not to activate the second messenger. The MTII NMR structure-based design thus not only examined the structural model of melanocortin ligands, but also yielded new biologically unique alpha-MSH analogues.

Synthesis of Anti-beta-substituted gamma,delta-unsaturated amino acids via Eschenmoser-Claisen rearrangement.

Anti-beta-substituted gamma,delta-unsaturated amino acids have been synthesized via a novel design of the Eschenmoser-Claisen rearrangement. The rearrangement gives good isolated yields and excellent diastereoselectivity due to (Z)-N,O-ketene acetal formation and the pseudochairlike conformations of the reaction intermediates. Upon reductive hydrolysis, important novel amino acids and amino alcohols were synthesized for the first time via this methodology.

[N-({(R)-2-[(N-Benzylprolyl)amino]phenyl}-phenylmethylene)-2(S)-(pent-4-enyl)-glycinato]nickel(II).

The title compound, [Ni(C(32)H(33)N(3)O(3))], crystallized as a minor product during the purification of its 2(R)-pent-4-enyl diastereomer. Mixtures of the title compound and its enantiomer self-resolve.

Parallel synthesis and biological evaluation of different sizes of bicyclo[2,3]-Leu-enkephalin analogues.

Parallel synthesis of peptides and peptidomimetics has been an important approach to search for biologically active ligands. A novel systematic synthesis of different size bicyclic dipeptide mimetics was developed on solid-phase supports. By taking advantage of the enantioselective synthesis of omega-unsaturated amino acids and their N-methylated derivatives, the hemiaminal problem was prevented in the pathway to thiazolidine formation. The bicyclic dipeptide was generated on the solid-phase support in three steps by an unconventional method. By inserting this bicyclic scaffold into the synthesis of a larger bioactive peptide, 11 different sizes of bicyclo[2,3]-Leu-enkephalin analogues were synthesized in a fast and efficient way. Modeling studies show that a reversed turn structure at positions 2-3 was favored when an L- and L-bicyclic scaffold was used, and that an extended conformation at the N-terminal was favored when a D- and L-bicyclic scaffold was inserted. Binding affinities and bioassay studies show ligands with micromolar binding affinities and antagonist bioactivities for the [6,5]- and [7,5]-bicyclo-Leu-enkephalin analogues.

Novel design of bicyclic beta-turn dipeptides on solid-phase supports and synthesis of [3.3.0]-Bicyclo([2,3])-leu-enkephalin analogues.

[structure: see text] External bicyclic beta-turn dipeptide mimetics provide an excellent design approach that can offer a rich chiral ensemble of structures with different backbone conformations. We report herein a novel design of a convergent combinatorial synthetic methodology, which is illustrated by the solid-phase synthesis of a series of [3.3.0]-bicyclo([2,3])-Leu-enkephalin analogues. The reactions were optimized and the epimeric configurations were determined by 2D NMR spectroscopy. Biological assays show that these analogues have more potent delta binding affinity and bioactivity for delta vs micro opioid receptor, which may be related to the different conformations preferred by these analogues in our modeling studies.

Solution structures of cyclic melanocortin agonists and antagonists by NMR.

The melanocortin receptors are involved in many physiological functions, including pigmentation, sexual function, feeding behavior, and energy homeostasis, making them potential targets for drugs to treat obesity, sexual dysfunction, etc. Understanding the conformational basis of the receptor-ligand interactions is crucial to the design of potent and selective ligands for these receptors. The solution structures of the cyclic melanocortin agonists, partial agonist, and antagonists MTII, VJH085, SHU9119, MK5, and MK9 were determined by two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy at pH 4.5 and 25 degrees C in water (90% H(2)O/10% D(2)O). The overall backbone structures of these cyclic alpha-melanocyte-stimulating hormone (alpha-MSH) analogues around the message sequence (His(6)-D-Phe(7)/D-Nal(2')(7)-Arg(8)-Trp(9)) were similar and reasonably well defined. beta-Turns spanning His(6) and D-Phe(7)/D-Nal(2')(7) were identified in all analogues, and an amphiphilic molecular surface was obtained for the message sequence residues in most structures within the NMR ensembles. The beta-turn, which most closely resembles a type II beta-turn, leads to stacking between the aromatic rings of His(6) and D-Phe(7) in MTII and VJH085. However, no aromatic stacking between His(6) and D-Nal(2')(7) was found in structures of the D-Nal(2')(7)-containing analogues. The difference in the side-chain dispositions of His(6) and D-Nal(2')(7) may be responsible for the reduced potency or antagonist activity of the D-Nal(2')(7)-containing analogues. In addition, our results suggest that the side-chain orientations may also modulate the receptor selectivity. The information found in this study will be useful for the further design of ligands for melanocortin receptors.