Synthesis, Insecticidal Evaluation, and 3D-QASR of Novel Anthranilic Diamide Derivatives Containing N-Arylpyrrole as Potential Ryanodine Receptor Activators.

To cope with the global food shortage and insect pest, there is an urgent need to discover new pesticides with novel modes of actions. Ryanodine receptor (RyR) insecticides showed great promise in integrated pest management. Herein, we report the synthesis of novel anthranilic diamide derivatives incorporating pyrrole moieties targeting at insect RyRs. The structures were confirmed by 1H NMR, 13C NMR, 19F NMR, and high-resolution mass spectrometry. The preliminary bioassay results indicated that most of the title compounds showed good to excellent insecticidal activities against the oriental armyworm (Mythimna separata) and diamondback moth (Plutella xylostella). For the oriental armyworm, Ij displayed the same level of larvicidal activity as the positive control chlorantraniliprole, with an LC50 value of 0.21 mg/L. For the diamondback moth, In, Io, Ip, and Iq exhibited higher insecticidal activities than chlorantraniliprole. In particular, In had 50% larvicidal activity at 0.00001 mg/L. The calcium imaging technique was applied to study the effect of Ij, In, and Ip on the intracellular calcium ion concentration ([Ca2+]i) in central neurons isolated from the oriental armyworm. The results indicated that the tested compounds, such as chlorantraniliprole, could activate the insect RyRs. Furthermore, comparative molecular field analysis and density functional theory calculations were carried out to study the structure-activity relationship.

Synthesis, insecticidal evaluation and mode of action of novel anthranilic diamide derivatives containing sulfur moiety as potential ryanodine receptor activators.

Anthranilic diamide insecticide could control lepidopteran pests by selectively binding and activating insect ryanodine receptors (RyRs), and the unique mode of action is different from other conventional insecticides. In order to discover new anthranilic diamide insecticide as ryanodine receptors activators, a series of 11 novel anthranilic diamides derivatives (Ia-k) were synthesized and confirmed by melting point, 1H NMR, 13C NMR and elemental analyses. The preliminary bioactivity revealed that most title compounds showed moderate to remarkable activities against oriental armyworm (Mythimna separata) and diamondback moth (Plutella xylostella). Especially, compounds Ia and If, which exhibited 100% larvicidal activity against oriental armyworm at 1.0 mg L-1, and comparable to that of chlorantraniliprole (100% at 1 mg L-1). If displayed 60% insecticidal activity against diamondback moth at 0.01 mg L-1, better than chlorantraniliprole (45% at 0.01 mg L-1). The preliminary structure activity relationships were discussed. In addition, the calcium imaging experiment indicated that the insect ryanodine receptor is the potential target of If.

Synthesis, pharmacological evaluation and molecular docking of pyranopyrazole-linked 1,4-dihydropyridines as potent positive inotropes.

1,4-Dihydropyridines are well-known calcium channel blockers, but variations in the substituents attached to the ring have resulted in their role reversal making them calcium channel activators in some cases. We describe the microwave-assisted eco-friendly approach for the synthesis of pyranopyrazole-1,4-dihydropyridines, a new class of 1,4-DHPs, under solvent-free conditions in good yield, and screen them for various in silico, in vitro and in vivo activities. The in vivo experimentation results show that the compounds possess positive inotropic effect, and the docking results validate their good binding with calcium channels. Compounds 7c, 7g and 7i appear to be the most effective positive inotropes, even at low doses, and bind with the calcium channels even more strongly than Bay K 8644, a well-known calcium channel activator. The chronotropic effect for the new compounds was also studied. The target and off-target affinity profiling supported the in vivo results and revealed that the hybridized pyranopyrazole dihydropyridine scaffold has delivered new moderate hits, to be optimized, for the cytochrome P450 3A4 enzymes, opening avenues for combined pharmacological activity through standard structural modification.

Novel Anthranilic Diamide Scaffolds Containing N-Substituted Phenylpyrazole as Potential Ryanodine Receptor Activators.

To discover potent insecticides targeting ryanodine receptors (RyRs), a series of novel anthranilic diamides analogues (12a-12u) containing N-substituted phenylpyrazole were designed and synthesized. These compounds were characterized by (1)H NMR, (13)C NMR, and HRMS, and the structure of compound 12u was confirmed by X-ray diffraction. Their insecticidal activities indicated that these compounds displayed moderate to excellent activities. In particular, 12i showed 100 and 37% larvicidal activities against oriental armyworm (Mythimna separata) at 0.25 and 0.05 mg L(-1), equivalent to that of chlorantraniliprole (100%, 0.25 mg L(-1); and 33%, 0.05 mg L(-1)). The activity of 12i against diamondback moth (Plutella xylostella) was 95% at 0.05 mg L(-1), whereas the control was 100% at 0.05 mg L(-1). The calcium-imaging technique experiment results showed that the effects of 12i on the intracellular calcium ion concentration ([Ca(2+)]i) in neurons were concentration-dependent. After the central neurons of Helicoverpa armigera were dyed by loading with fluo-5N and treated with 12i, the free calcium released in endoplasmic reticulum indicated the target of compound 12i is RyRs or IP3Rs. The activation of RyRs by natural ryanodine completely blocked the calcium release induced by 12i, which indicated that RyRs in the central neurons of H. armigera third-instar larvae is the possible target of compound 12i.

Lessons learned from a novel calcium-channel protagonist and person.

A long time ago (circa 1976), David C. Triggle was Chair of the Department of Biochemical Pharmacology at S.U.N.Y. Buffalo where he led the faculty and staff in the education and mentoring of countless pharmacy and graduate students who passed through the hallowed halls of the University. Trained as a chemist, David spent his days synthesizing new and improved calcium channel blockers in a cramped, makeshift organic chemistry lab while a lab full of aspiring pharmacologists measured their effects on contractile responses of various smooth muscle preparations. I was a graduate student fortunate enough to land in David's laboratory, and thanks to him, I successfully navigated out with a Ph.D. in hand. That being said, his influence was less through his role as thesis advisor and more by the example he set in his simple, everyday life in Buffalo, N.Y: his love for - and dedication to - his family, his concern for the environment and his health, his perseverance in that tiny organic chemistry closet, his command of the English language, his unbridled honesty and cynicism, and his quiet pursuit of excellence. This article chronicles student life during that particular time period and provides a glimpse into David's unique personality and lifestyle that made him a role model to me and others. Interwoven is my own circuitous career path both before and after leaving S.U.N.Y. Buffalo that culminated in a productive career at the opposite end of the drug development process from where it all started in pharmacology.

Structure-activity relationship studies on acremomannolipin A, the potent calcium signal modulator with a novel glycolipid structure 3: role of the length of alditol side chain.

Five homologs of a novel glycolipid acremomannolipin A (1a), the potential Ca(2+) signal modulator isolated from Acremonium strictum, bearing alditols of different length (1g-1k) were synthesized by a stereoselective ß-mannosylation of appropriately protected mannosyl sulfoxide (2) with five alditols (1g: C2, 1h: C3, 1i: C4, 1j: C5 and 1k: C7 units), and their potential in modulating Ca(2+) signaling were evaluated. Homologs with alditols of more than 4 carbons (1i, 1j and 1k) were equally or more potent than the parent compound (1a) regardless of the length of the alditol chain. Whereas activities of two homologs with shorter chains (1g and 1h) decreased to a considerable extent. The results indicated that the length of the alditol side chain was a crucial determinant for the potent calcium signal modulating activity.

Chiral dicarboxamide scaffolds containing a sulfiliminyl moiety as potential ryanodine receptor activators.

To search for new environmentally benign insecticides with high activity, low toxicity, and low residue, novel chiral configurations introduced into dicarboxamide scaffolds containing N-cyano sulfiliminyl moieties were first studied. Four series of phthalamides with sulfur-containing side chains were designed, synthesized, and evaluated against oriental armyworm (Pseudaletia separata Walker) and diamondback moth (Plutella xylostella (L.)) for their insecticidal activities. All structures were characterized by (1)H NMR, (13)C NMR, and HRMS (or elemental analysis), and their configurations were confirmed by optical polarimetry. The biological assessment indicated that some title compounds exhibited significant insecticidal activities. For oriental armyworm, these stereoisomers exerted different impacts on biological activity following the sequence (Sc, Ss) ≥ (Sc, Rs) ≫ (Rc, Ss) > (Rc, Rs), and carbon chirality influenced the activities more strongly than sulfur. Compounds Ia and IIa reached as high an activity as commercial flubendiamide, with LC50 values of 0.0504 and 0.0699 mg L(-1), respectively, lower than that of flubendiamide (0.1230 mg L(-1)). For diamondback moth, the sequence of activity was (Sc, Ss) > (Sc, Rs), and the sulfur chirality influenced the activities more greatly than carbon. Compound IIe exhibited even higher activity than flubendiamide, whereas Ie and Ic,d reached the activity of the latter. The results indicated that the improvement of insecticidal activity probably required a coordination of both carbon and sulfur chirality. Comparative molecular field analysis calculation indicated that stereoisomers with Sc configurations containing strong electron-withdrawing groups such as as CN are important in maintaining the high activity. The chiral scaffolds containing the N-cyano sulfiliminyl moiety are also essential for high larvicidal activity. Some title compounds could be considered as potential candidates for ryanodine receptor activators.

Nicotinic acid adenine dinucleotide phosphate analogues containing substituted nicotinic acid: effect of modification on Ca(2+) release.

Analogues of nicotinic acid adenine dinucleotide phosphate (NAADP) with substitution at either the 4- or the 5-position position of the nicotinic acid moiety have been synthesized from NADP enzymatically using Aplysia californica ADP-ribosyl cyclase or mammalian NAD glycohydrolase. Substitution at the 4-position of the nicotinic acid resulted in the loss of agonist potency for release of Ca(2+)-ions from sea urchin egg homogenates and in potency for competition ligand binding assays using [(32)P]NAADP. In contrast, several 5-substituted NAADP derivatives showed high potency for binding and full agonist activity for Ca(2+) release. 5-Azido-NAADP was shown to release calcium from sea urchin egg homogenates at low concentration and to compete with [(32)P]NAADP in a competition ligand binding assay with an IC(50) of 18 nM, indicating that this compound might be a potential photoprobe useful for specific labeling and identification of the NAADP receptor.

Synthesis and docking studies of new 1,4-dihydropyridines containing 4-(5)-Chloro-2-ethyl-5-(4)-imidazolyl substituent as novel calcium channel agonist.

1,4-Dihydropyridines have been recognized as calcium channel agonist. Three new analogues of Bay K8644 in which the ortho trifluromethyl phenyl group at position 4 is replaced by the 4-(5)-Chloro-2-ethyl-5-(4)-imidazolyl substituent, were designed and synthesized as calcium channel agonist. For this propose, the structures of designed compounds were drawn by HYPERCHEM program. Conformations of the compounds were optimized through semi-empirical method followed by PM3 calculation. Then the crystalin stucture of L-type calcium channel was obtained from the Protein Data Bank (PDB) server. Docking calculations were carried out using Auto-Dock.4 program. The good interaction of our 1,4-DHP derivatives showed that they can be as possible calcium channel agonist agents. Finally compounds were synthesized according to a modified Hantzsch condensation procedure.

Cationic reduction of bastadin-4 to bastadin-5. Preparation of 5-[2h]-bastadin-5 by site-specific isotopic labeling.

A chemoselective conversion of bastadin-4 to the important Ca2+ channel modulator bastadin-5 (1a) has been achieved using cationic hydrogenation (Et3SiH, TFA, 60%). Specifically deuterated bastadin-5 (1b, >95 at. %) was prepared following this method and the simplified 1H NMR H-5/H2-6 spin system of 1b exploited to study temperature-dependent macrocyclic ring dynamics.

Synthesis of glucopyranoside-based ligands for D-myo-inositol 1,4,5-trisphosphate receptors.

Adenophostins A and B are naturally occurring glyconucleotides that interact potently with receptors for D-myo-inositol 1,4,5-trisphosphate, an important second messenger molecule in most cell types. Here we describe the design and synthesis of glucopyranoside-based analogues of adenophostin A lacking the adenine component. The key synthetic strategy involves glycosylation of selectively protected alcohols, derived from methyl beta-D-ribofuranoside or 1,4-anhydroerythritol, using glycosyl donors synthesised from 2,6-di-O-benzyl-D-glucopyranose derivatives. Further elaboration and deprotection of the coupled products gave two trisphosphate analogues; methyl 3-O-alpha-D-glucopyranosyl-beta-D-ribofuranoside 2,3',4'-trisphosphate ("ribophostin") and (3'S,4'R)-3'-hydroxytetrahydrofuran-4'-yl alpha-D-glucopyranoside 3,4,3'-trisphosphosphate ("furanophostin"). The route to furanophostin was further modified to give (3'S,4'R)-3'-hydroxytetrahydrofuran-4'-yl alpha-D-glucopyranoside 3'-phosphate 3,4-bisphosphorothioate, the first phosphorothioate-containing adenophostin analogue.

Syntheses, calcium channel agonist-antagonist modulation activities, nitric oxide release, and voltage-clamp studies of 2-nitrooxyethyl 1,4-dihydro- 2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)pyridine-5-carboxylate enantiomers.

The novel (-)-(S)-2 and (+)-(R)-3 enantiomers of 2-nitrooxyethyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)pyridine-5-carboxylate were synthesized for evaluation as calcium channel modulators. Determination of their in vitro calcium-channel-modulating activities using guinea pig left atria (GPLA) and ileum longitudinal smooth muscle (GPILSM) showed that the (-)-(S)-2 enantiomer acted as a dual cardioselective calcium channel agonist (GPLA)/smooth muscle selective calcium channel antagonist (GPILSM). In contrast, the (+)-(R)-3 enantiomer exhibited calcium channel antagonist activity on both GPLA and GPILSM. The 2-nitrooxyethyl racemate is a nitric oxide (.NO) donor that released 2.7% .NO, relative to the reference drug glyceryl trinitrate (5.3% .NO release/ONO(2) moiety), in the presence of N-acetylcysteamine. Whole-cell voltage-clamp studies using isolated guinea pig ventricular myocytes indicated that both enantiomers inhibit calcium current but that the (-)-(S)-2 enantiomer is a weaker antagonist than the (+)-(R)-3 enantiomer. These results indicate that replacement of the methyl ester substituent of (-)-(S)-methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)pyridine-5-carboxylate [(-)-(S)-1] by the 2-nitrooxyethyl ester .NO donor substituent present in (-)-(S)-2 provides a useful drug design concept to abolish the contraindicated calcium channel agonist effect of (-)-(S)-1 on vascular smooth muscle. The novel (-)-(S)-2 enantiomer is a useful lead compound for drug discovery targeted toward the treatment of congestive heart failure, and it provides a useful probe to study the structure-function relationships of calcium channels.

D-myo-inositol-1,4,5-trisphosphate and adenophostin mimics: importance of the spatial orientation of a phosphate group on the biological activity.

Three different routes for the synthesis of heterocyclic analogues of the second messenger D-myo-inositol-1,4,5-trisphosphate (InsP(3)) and the natural adenophostins, starting from allyl D-xyloside are described. The two diastereoisomers at C-2 of new compounds, which we named xylophostins, were obtained. The preliminary biological studies shows that the presence of the adenine residue has a beneficial effect on the affinity for the receptor. The low potency of one of the two diastereoisomeric compounds shows that the configuration of the carbon bearing the non-vicinal phosphate group is an important requirement for a high affinity to the receptor. These results provide evidence for the existence of a binding pocket for the adenine ring nearby the InsP(3) binding site. The consequence of these stabilizing interactions should be to place the phosphate group in a suitable position to perfectly mimic InsP(3) in the more active diastereoisomer. Obviously, in the other diastereoisomer, the phosphate cannot accommodate the same orientation, thus explaining the low affinity. The existence of such a binding pocket for adenine is in line with the high potency of adenophostins.

Intracellular Ca(2+)-mobilizing adenine nucleotides. Synthesis and biological activity of cyclic ADP-carbocyclic-ribose and C-glycosidic analog of adenophostin A.

We designed novel Ca(2+)-mobilizing purine nucleotides, cyclic ADP-carbocyclicribose 4, and its inosine congener 5, and C-glycosidic adenophostin A 6. In the synthesis of cADPR analogs, the intramolecular condensation to form the pyrophosphate linkage should be the key step. We developed an efficient method for forming such an intramolecular pyrophosphate linkage by the activation of the phenylthiophosphate group with I2 or AgNO3. Using this method, we achieved to synthesize the target compounds 4 and 5. The synthesis of C-glycosidic analog 6 of adenophostin A was achieved using a temporary silicon-tethered radical coupling reaction for constructing (3'alpha, 1" alpha)-C-glycosidic structure as the key step.

Synthesis and biological evaluation of phosphonate analogues of 1alpha,25-dihydroxyvitamin D3.

A new series of phosphonate side chain analogues of 1alpha,25-dihydroxyvitamin D3 (1) have been synthesized. Antiproliferative activities of theses analogues (8a,b and 9a,b) using human keratinocyte cell shows that analogues which have natural A-ring show higher activity than unnatural A-ring series and almost equally active to 1alpha,25-Dihydroxyvitamin D3 (1) at 1 microM level.

The design of (-)-(S)-2-nitrooxyethyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl) pyridine-5-carboxylate: a cardioselective positive inotropic derivative of Bay K 8644.

The title compound, (-)-(S)-9, is a novel cardioselective calcium channel modulator that exhibits a calcium channel agonist effect on heart, a weak calcium channel antagonist effect on smooth muscle, and releases nitric oxide in vitro. (-)-(S)-9 is a useful lead-compound for the design of positive inotropic agents to treat congestive heart failure, and to study the structure-function relationship of calcium channel modulation.

Synthesis and voltage-clamp studies of methyl 1,4-dihydro-2, 6-dimethyl-5-nitro-4-(benzofurazanyl)pyridine-3-carboxylate racemates and enantiomers and of their benzofuroxanyl analogues.

Racemic methyl 1,4-dihydro-2, 6-dimethyl-5-nitro-4-(benzofurazanyl)pyridine-3-carboxylates (+/-)-10 and (+/-)-11 and their benzofuroxanyl analogues (+/-)-12 and (+/-)-13 were prepared using a modified Hantzsch reaction that involved the condensation of nitroacetone with methyl 3-aminocrotonate and the appropriate aldehydes. The racemic mixtures were resolved into the corresponding enantiomers. Whole-cell voltage-clamp studies on L-type Ca2+ channels expressed in a rat insulinoma cell line (RINm5F) showed that all the dextrorotatory antipodes were effective agonists of L-type Ca2+ currents, while the levorotatory ones were weak Ca2+ entry blockers. The (+)-enantiomer of benzofurazan-5'-yl derivative 11 demonstrated unusual activity in that, in addition to producing a potentiation of L-type currents, it interfered with the voltage-dependent gating of L-type channels by producing a net delay of their activation at low voltages. This compound represents an interesting tool to probe L-type Ca2+ channel structure and function.

Synthesis, rotamer orientation, and calcium channel modulation activities of alkyl and 2-phenethyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(3- or 6-substituted-2-pyridyl)-5-pyridinecarboxylates.

A group of racemic alkyl and 2-phenethyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(3- or 6-substituted-2-pyridyl)-5-pyridinecarboxylates (13a-q) was prepared using a modified Hantzsch reaction that involved the condensation of a 3- or 6-substituted-2-pyridinecarboxaldehyde (7a-j) with an alkyl or 2-phenethyl 3-aminocrotonate (11a-d) and nitroacetone (12). Nuclear Overhauser (NOE) studies indicated there is a significant rotamer fraction in solution where the pyridyl nitrogen is oriented above the 1,4-dihydropyridine ring, irrespective of whether a substituent is located at the 3- or 6-position. A potential H-bonding interaction between the pyridyl nitrogen free electron pair and the suitably positioned 1,4-dihydropyridine NH moiety may stablize this rotamer orientation. In vitro calcium channel antagonist and agonist activities were determined using guinea pig ileum longitudinal smooth muscle (GPILSM) and guinea pig left atrium (GPLA) assays, respectively. Compounds having an i-Pr ester substituent acted as dual cardioselective calcium channel agonists (GPLA)/smooth muscle-selective calcium channel antagonists (GPILSM), except for the C-4 3-nitro-2-pyridyl compound which exhibited an antagonist effect on both GPLA and GPILSM. In contrast, the compounds with a phenethyl ester group, which exhibited antagonist activity (IC50 = 10(-5)-10(-7) M range) on GPILSM, were devoid of cardiac agonist activity on GPLA. Structure-activity relationships showing the effect of a substituent (Me, CF3, Cl, NO2, Ph) at the 3- or 6-position of a C-4 2-pyridyl moiety and a variety of ester substituents (Me, Et, i-Pr, PhCH2CH2-) upon calcium channel modulation are described. Compounds possessing a 3- or 6-substituted-2-pyridyl moiety, in conjuction with an i-Pr ester substituent, are novel 1,4-dihydropyridine calcium channel modulators that offer a new drug design approach directed to the treatment of congestive heart failure and may also be useful as probes to study the structure-function relationships of calcium channels.

Synthesis and calcium channel-modulating effects of alkyl (or cycloalkyl) 1,4-dihydro-2,6-dimethyl-3-nitro-4-pyridyl-5-pyridinecarboxylate racemates and enantiomers.

A group of racemic alkyl (or cycloalkyl) 1,4-dihydro-2,6- dimethyl-3-nitro-4-(2-, 3-, or 4-pyridyl)-5-pyridinecarboxylate isomers (6-14) were prepared using a modified Hantzsch reaction that involved the condensation of nitroacetone with an alkyl (or cycloalkyl) 3-aminocrotonate and 2-, 3-, or 4-pyridinecarboxaldehyde. Determination of their in vitro calcium channel-modulating activities using guinea pig ileum longitudinal smooth muscle (GPILSM) and guinea pig left atrium (GPLA) assays showed that the 2-pyridyl isomers acted as dual cardioselective calcium channel agonists (GPLA)/smooth muscle selective calcium channel antagonists (GPILSM). In contrast, the 3-pyridyl and 4-pyridyl isomers acted as calcium channel agonists on both GPLA and GPILSM. In the C-4 2-pyridyl group of compounds, the size of the C-5 alkyl (or cycloalkyl) ester substituent was a determinant of GPILSM antagonist activity where the relative activity profile was cyclopentyl and cyclohexyl > t-Bu, i-Bu, and Et > MeOCH2CH2 > Me. The point of attachment of the C-4 pyridyl substituent was a determinant of GPLA agonist activity where the potency order was generally 4- and 3-pyridyl > 2-pyridyl. (+)-Cyclohexyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-pyridyl)-5- pyridinecarboxylate [(+)-14a] was a less potent calcium antagonist (IC50 = 5.27 x 10(-6) M) than the (-)-enantiomer (IC50 = 7.48 x 10(-8) M) on GPILSM. In the GPLA assay, (+)-14a exhibited a much more potent agonist effect (EC50 = 8.45 x 10(-6) M) relative to the marginal agonist effect produced by (-)-14a. The C-4 2-pyridyl compounds (enantiomers) constitute a novel type of 1,4-dihydropyridine calcium channel modulator that could provide a new drug design concept directed toward the treatment of congestive heart failure, and for use as probes to study the structure-function relationships of calcium channels.