Discovery of new A- and B-type laxaphycins with synergistic anticancer activity

Two new cyclic lipopeptides termed laxaphycins B4 (1) and A2 (2) were discovered from a collection of the marine cyanobacterium Hormothamnion enteromorphoides, along with the known compound laxaphycin A. The planar structures were solved based on a combined interpretation of 1D and 2D NMR data and mass spectral data. The absolute configurations of the subunits were determined by chiral LC-MS analysis of the hydrolysates, advanced Marfey’s analysis and 1D and 2D ROESY experiments. Consistent with similar findings on other laxaphycin A- and B-type peptides, laxaphycin B4 (1) showed antiproliferative effects against human colon cancer HCT116 cells with IC₅₀ of 1.7?µM, while laxaphycins A and A2 (2) exhibited weak activities. The two major compounds isolated from the sample, laxaphycins A and B4, were shown to act synergistically to inhibit the growth of HCT116 colorectal cancer cells.     

Some analogs of luteinizing hormone releasing hormone (LH-RH) having intense ovulation-inducing activity

Five new analogs of luteinizing hormone releasing hormone (LH-RH), des-Gly¹⁰-[Ala⁶]-LH-RH-ethylamide, des-Gly¹⁰-[D-Ala⁶]-LH-RH-ethylamide, des-Gly¹⁰-[α-aminoisobutyric acid⁶]-LH-RH-ethylamide, des-Gly¹⁰-[Phe⁵, D-Ala⁶]-LH-RH-ethylamide and des-Gly¹⁰-[Ile⁵, D-Ala⁶]-LH-RH-ethylamide were synthesized and evaluated for the ovulation-inducing activity in the rat, and it was found that the analogs, des-Gly¹⁰-[D-Ala⁶]-LH-RH-ethylamide and des-Gly¹⁰-[Phe⁵, D-Ala⁶]-LH-RH-ethylamide, were 50 times or more active than the original molecule.     

Impaired negative cooperativity of the semisynthetic analogues human [LeuB24]- and [LeuB25]-insulins

Several semisynthetic analogues of human insulin were prepared by enzyme-assisted coupling of synthetic octapeptides to the C-terminal of porcine desoctapeptide insulin. We report the receptor-binding and biological properties of [Leu^B24]- and [Leu^B25]-insulins, one of which has the same sequence as a “mutant” insulin recently found in a diabetic patient (Tager, H. et al.(1979) Nature $\text{28}$:121–125). [Leu^B24]- and [Leu^B25]-insulins had, respectively, 8–12% and 0.9–1.1% of the binding affinity of human insulin, and 11% and 2.7% of its potency in stimulating lipogenesis in isolated rat fat cells. Neither one was an antagonist of the biological effects of native insulin. While the ability of [Leu^B24]-insulin to induce negative cooperativity was clearly impaired, that of [Leu^B25]-insulin was almost abolished. [Leu^B25]-insulin was also a potent antagonist of the negative cooperativity induced by native insulin.     

Acylated des-(Ala1-Gly2)-somatostatin analogs: prolonged inhibition of growth hormone secretion

The following eight analogs of somatostatin were synthesized by solid phase: des-[Ala¹-Gly²]-somatostatin (I); des-[Ala¹-Gly²]-H₂somatostatin (II); $\text{N}$-acetyl-Cys³-somatostatin (III); $\text{N}$-acetyl-Cys³-H₂somatostatin (IV); $\text{N}$-pyvalyl-Cys³-H₂somatostatin (V); $\text{N}$-acrylyl-Cys³-H₂somatostatin (VI); $\text{N}$-benzoyl-Cys³-H₂somatostatin (VII); $\text{N}$-hexanoyl-Cys³-H₂somatostatin (VIII). Deletion of the N-terminal dipeptide Ala¹-Gly² is compatible with high biological activity. A single s.c. injection of these analogs as a microsuspension in saline inhibits for 24–72 hours (depending on the compound) the secretion of growth hormone normally stimulated in rats by pentobarbital.     

Radioligands for Probing Opioid Receptors

Abstract

The three endogenous opioid precursors of almost 30000 Da are pro-opiocortin, proenkephalin and prodynorphin. Pro-opiocortin contains β-endorphin, melanotropins and ACTH. Proenkephalin yields one [Leu⁵] enkephalin, three [Met⁵] enkephalins, one [Met⁵] enkephalyl-Arg-Arg-Val-NH₂ (metorphamide or adrenorphin), one [Met⁵] enkephalyl-Arg-Gly-Leu and one [Met⁵] enkephalyl-Arg-Phe. [Leu⁵] enkephalin is common to all fragments of prodynorphin; its carboxyl extension by Arg-Lys leads to α- and β-neo-endorphin and its carboxyl extension by Arg-Arg gives two dynorphins A and B of 17 and 13 amino acids, respectively. Another endogenous peptide is dynorphin A (1-8). The three main opioid binding sites are μ, δ and ?. Their analysis has been facilitated by the synthesis of analogues of peptides and non-peptide compounds, which have selective agonist or antagonist action at only one site. The various physiological roles of the three types of the opiate receptor have so far not been sufficiently investigated.     

Design,synthesis, and biological evaluation of radioiodinated benzo[d]imidazole-quinoline derivatives for platelet-derived growth factor receptor β (PDGFRβ) imaging

Several malignant tumors and fibrotic diseases are associated with PDGFRβ overexpression and excessive signaling, making this receptor attractive for molecular targeting and imaging approaches. A series of benzo[d]imidazole-quinoline derivatives were designed and synthesized to develop radioiodinated compounds as PDGFRβ-specific imaging probes. The structure activity relationship (SAR) evaluation of the designed compounds was performed. Among them, 2-[5-(2-methoxyethoxy)-1H-benzo[d]imidazol-1-yl]-8-(piperazin-1-yl)quinoline (5a) and 4-{2-[5-(2-methoxyethoxy)-1H-benzo[d]imidazol-1-yl]quinolin-8-yl}morpholine (5d) exhibited a relatively high PDGFRβ-TK inhibitory potency, whereas iodinated 5a derivative 5-iodo-2-[5-(2-methoxyethoxy)-1H-benzo[d]imidazol-1-yl]-8-(piperazin-1-yl)quinoline (8) exhibited a superior inhibitory potency as PDGFRβ inhibitor than iodinated 5d derivative 4-{5-iodo-2-[5-(2-methoxyethoxy)-1H-benzo[d]imidazol-1-yl]quinolin-8-yl}morpholine (11). Furthermore, [¹²⁵I]8 and [¹²⁵I]11 were synthesized and evaluated for PDGFRβ radioligand ability, both in vitro and in vivo. Cellular uptake experiments showed that [¹²⁵I]8 had a higher uptake in BxPC3-luc cells as PDGFRβ-positive cells than [¹²⁵I]11. Incubation of [¹²⁵I]8 after pretreatment of PDGFRβ ligands significantly reduced the uptake of [¹²⁵I]8. In biodistribution experiments using tumor-bearing mice, [¹²⁵I]8 accumulation in the tumor 1?h postinjection was higher than that of the benzo[d]imidazol-quinoline derivative [¹²⁵I]IIQP, used in our previous research. These results indicate that [¹²⁵I]8 could be a promising PDGFRβ imaging agent. Although its clinical application requires further structural modifications, the results obtained in this research may be useful for the development of PDGFRβ-specific radioligands.     

Synthesis and biological properties of (Leu-6)-LH-RH and (D-Leu-6,desGly-NH210)-LH-RH ethylamide

[Leu⁶,desGly-NH₂¹⁰]-LH-RH ethylamide and [Leu⁶]-LH-RH, two analogs of LH-RH, were prepared by the solid phase method. LH- and FSH-releasing activity of these peptides was assayed against LH-RH by subcutaneous administration in immature male rats. When the integrated levels of LH and FSH over a 6 hr period after the injection were used as parameter of the LH- and FSH-releasing activities, the [Leu⁶]-LH-RH showed LH-releasing activity of 9 times and FSH-releasing activity of 5 times greater than that of LH-RH. [Leu⁶,desGly-NH₂¹⁰]-LH-RH ethylamide showed LH- and FSH-releasing activities of 53.6 and 14.5 times greater, respectively, than that of LH-RH.     

Synthesis and evaluation of new endomorphin analogues modified at the Pro2 residue

Six new endomorphin analogues, incorporating constrained amino acids in place of native proline have been synthesized. Residues of (S)-azetidine-2-carboxylic acid (Aze), 3,4-dehydro-(S)-proline (Δ³Pro), azetidine-3-carboxylic acid (3Aze) and dehydro-alanine (ΔAla) have been used to prepare [Δ³Pro²]EM-2 (1), [Aze²]EM-1 (2), [Aze²]EM-2 (3), [3Aze²]EM-1 (4), [3Aze²]EM-2 (5) and [ΔAla²]EM-2 (6). Binding assays and functional bioactivities for μ- and δ-receptors are reported. The highest affinity, bioactivity and selectivity are shown by peptides 2 and 3 containing the Aze residue.     

N-substituted 8-aminopentacyclo[5.4.0.02,6.03,10.05,9]undecanes as σ receptor ligands with potential neuroprotective effects

Several libraries of similarly N-substituted 8-aminopentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecanes (9), N-methyl-8-aminopentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecanes (14), and N-methyl-11-aminopentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecan-8-ones (13) were synthesised and screened against a panel of CNS targets in order to develop structure–affinity relationships for cage-modified trishomocubane σ receptor ligands based on the N-substituted 4-azahexacyclo[5.4.1.0^2,6.0^3,10.0^5,9.0^8,11]dodecan-3-ol (8) scaffold. In general, compared to the corresponding 4-azahexacyclo[5.4.1.0^2,6.0^3,10.0^5,9.0^8,11]dodecan-3-ols, compounds of type 9 were potent σ receptor ligands with low levels of subtype selectivity, while the corresponding N-methyl-8-aminopentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecanes showed reduced affinity but greater selectivity for σ₂ receptors. The N-methyl-11-aminopentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecan-8-ones demonstrated the poorest σ receptor affinities, suggesting that 4-azahexacyclo[5.4.1.0^2,6.0^3,10.0^5,9.0^8,11]dodecan-3-ols interact with σ receptors in the bridged hemiaminal form rather than as the non-transannular, aminoketone tautomers. Several compounds of type 8, 9, and 14 were assessed for their ability to inhibit nitric oxide release in vitro, and demonstrated comparable or greater efficacy than 4-phenyl-1-(4-phenylbutyl)piperidine (PPBP), an established neuroprotective σ ligand with NOS inhibitory activity.     

Synthesis and cytokinin activity of N-acylaminodeazapurines

Three 7-acylaminoimidazo[4,5-b]pyridines, namely 7-pentanoylaminoimidazo[4,5-b]pyridine (1), 7-benzoylaminoimidazo[4,5-b]pyridine(2), and 7-(2-furoylamino)imidazo[4,5-b]pyridine(3), six 4-acylaminoimidazo[4,5-c]pyridines, namely 4-propionylaminoimidazo[4,5-c]pyridine(4), 4-butyryl-aminoimidazo[4,5-c]pyridine(5), 4-pentanoylaminoimidazo[4,5-c]pyridine(6) 4-hexanoylaminoimidazo[4,5-c]pyridine(7),4-benzoylaminoimidazo[4,5-c]pyridine(8), and 4-(2-furoylamino)imidazo[4,5-c]-pyridine(9), and seven 7-acylaminoimidazo[4,5-c]pyridines, namely 7-propionylaminoimidazo[4,5-c]-pyridine(10), 7-butyrylaminoimidazo[4,5-c]pyridine(11), 7-pentanoylaminoimidazo[4,5-c]pyridine(12), 7-hexanoylaminoimidazo[4,5-c]pyridine(13), 7-benzoylaminoimidazo[4,5-c]pyridine(14), 7-phenylacetylaminoimidazo[4,5-c]pyridine(15), and 7-(2-furoylamino)imidazo[4,5-c]pyridine(16) were synthesized and tested for their cytokinin activity with the tobacco callus bioassay. 2 showed a cytokinin activity at 1 × 10⁻⁸ M and gave a callus yield about 72% of that produced by kinetin at 1 × 10⁻⁶ M. 1, 3 and 8 showed the optimum growth responses in the range of 10⁻⁷−10⁻⁶ M. 4, 5, 7, 9–16 were slightly active. These results support previous reports that a nitrogen atom at the 3-position in the purine ring plays an important role in conferring high cytokinin activity.     

Synthesis of novel indenoquinoxaline derivatives as potent α-glucosidase inhibitors

A series of new N-(11H-Indeno[1,2-b]quinoxalin-11-ylidene)benzohydrazide derivatives (3a–3p) were synthesized and evaluated for their α-glucosidase inhibitory activity. The synthesized compounds 3d, 3f, 3g, 3k, 3n, 3p and 4 showed significant α-glucosidase inhibitory activity as compared to acrabose, a standard drug used to treat type II diabetes. Structures of the synthesized compounds were determined by using FT-IR, ¹H NMR, ¹³C NMR, mass spectrometry and elemental analysis techniques.     

Effect of the carboxyl-terminal of endokinins on SP-induced pain-related behavior

The preprotachykinin C gene encodes four endokinins, A, B, C, and D. Endokinins A and B and substance P (SP) are typical tachykinin peptides since their carboxyl-terminal regions share an F-F-G-L-M-amide, while endokinins C and D share an F-Q-G-L-L-amide. It is demonstrated that pretreatment with a peptide consisting of a common sequence between endokinins C and D (EKC/D) attenuates the induction of scratching behavior and thermal hyperalgesia by intrathecal administration of SP or EKA/B (the carboxyl-terminal dacapeptide common in endokinins A and B), suggesting that leucine at the carboxyl-terminal of EKC/D may have a crucial role in eliciting these effects. When the effect of [Leu¹¹]-SP and [Leu¹⁰]-EKA/B on SP-induced pain-related behavior was examined, the induction of pain-related behavior was markedly attenuated by pretreatment with these peptides. This indicates that leucine at the carboxyl-terminal of these peptides plays a crucial role in eliciting this antagonistic effect.     

Synthesis and antitumor activity of substituted triazolo[4,3-a]pyrimidin-6-sulfonamide with an incorporated thiazolidinone moiety

Chlorosulfonation of 3-methyl[1,2,4]triazolo[4,3-a]pyrimidine with chlorosulfonic acid in the presence of thionyl chloride was studied. When triazolo[4,3-a]pyrimidines are used as substrates, the substitution occurs at C-6. Also the reactivity of the hydrazides (7) towards aldehydes, thioglycolic acid and amines were studies. The newly prepared compounds 10a,d and 11a,d demonstrated inhibitory effects on the growth of a wide range of cancer cell lines generally at 10^?5 M level and in some cases at 10^?7 M concentrations.     

Synthesis and biological evaluation of novel pyrazolopyrimidines derivatives as anticancer and anti-5-lipoxygenase agents

A novel series of 6-aryl-3-methyl-1-phenyl-1H-pyrazolo[3,4-d]pyrimidin-4(5H)-ones 3a-h were synthesized in a single step via condensation of carboxamide 2 with some aromatic aldehydes (presence of iodine). Treatment of aminopyrazole 1a with acetic anhydride afforded pyrazolopyrimidines 4 which on treatment with ethyl chloroacetate in refluxing dry DMF furnished a single product identified as ethyl 2-(3,6-dimethyl-4-oxo-1-phenyl-1H-pyrazolo[3,4-d]pyrimidin-5(4H)-yl) acetate 5. On the other hand, esterification of compound 6 with different alcohol, led to the formation of new esters linked pyrazolo[3,4-d]pyrimidinones hybrids 7a-f. The reaction of compound 2 with 3-propargyl bromide gave the compound 8 used as a dipolarophile to access to triazoles (4- and 5-regioisomers (9a-e) and (10a-e), respectively) via the 1,3-dipoar cycloaddition reaction. Finally, condensation reaction of aminopyrazole 1b with α-cyanocinnamonitiles gave the new pyrazolo[1,5-a]pyrimidine-3,6-dicarbonitriles 11a-e. Structures of compounds were established on the basis of ¹H/¹³C NMR and ESI-HRMS. Compounds were screened for their cytotoxic (HCT-116 and MCF-7) and 5-lipoxygenase inhibition activities. The structure-activity relationship (SAR) was discussed.     

Synthesis of carbon-11-labeled CK1 inhibitors as new potential PET radiotracers for imaging of Alzheimer’s disease

The reference standards methyl 3-((2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)carbamoyl)benzoate (5a) and N-(2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)-3-methoxybenzamide (5c), and their corresponding desmethylated precursors 3-((2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)carbamoyl)benzoic acid (6a) and N-(2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)-3-hydroxybenzamide (6b), were synthesized from 5-amino-2,2-difluoro-1,3-benzodioxole and 3-substituted benzoic acids in 5 and 6 steps with 33% and 11%, 30% and 7% overall chemical yield, respectively. Carbon-11-labeled casein kinase 1 (CK1) inhibitors, [¹¹C]methyl 3-((2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)carbamoyl)benzoate ([¹¹C]5a) and N-(2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)-3-[¹¹C]methoxybenzamide ([¹¹C]5c), were prepared from their O-desmethylated precursor 6a or 6b with [¹¹C]CH₃OTf through O-[¹¹C]methylation and isolated by HPLC combined with SPE in 40–45% radiochemical yield, based on [¹¹C]CO₂ and decay corrected to end of bombardment (EOB). The radiochemical purity was >99%, and the molar activity (MA) at EOB was 370–740?GBq/μmol with a total synthesis time of ～40-min from EOB.     

Novel pyrimidine-pyridine hybrids: Synthesis,cyclooxygenase inhibition,anti-inflammatory activity and ulcerogenic liability

Some derivatives containing pyrido[2,3-d:6,5d′]dipyrimidine-4,5-diones (9a-f), tetrahydropyrido[2,3-d]pyrimidine-6-carbonitriles (11a-c) and 6-(4-acetylphenyl)-2-thioxo-2,3,5,6,7,8-hexahydro-1H-pyrimido[4,5-d]pyrimidin-4-one (12) were synthesized from 6-amino-2-thioxo-2,3-dihydro-1H-pyrimidin-4-one (8). The anti-inflammatory effect of these candidates was determined and the ulcer indices were calculated for active compounds. 7-Amino-5-(3,4,5-trimethoxyphenyl)-4-oxo-2-thioxo-1,2,3,4-tetrahydropyrido[2,3-d] pyrimidine-6-carbonitrile (11c) exhibited better edema inhibition than celecoxib. Moreover, compounds 9b, 9d and 11c revealed better COX-2 inhibitory activity in a range (IC₅₀ = 0.25–0.89 µM) than celecoxib (IC₅₀ = 1.11 µM). Regarding ulcerogenic liability, all of the compounds under the study were less ulcerogenic than indomethacin. Molecular docking studies had been carried on active candidates 9d and 11c to explore action mode of these candidates as leads for discovering other anti-inflammatory agents.     

Design,synthesis and in vitro anti-tuberculosis activity of benzo[6,7]cyclohepta[1,2-b]pyridine-1,2,3-triazole derivatives

A series of novel benzo[6,7]cyclohepta[1,2-b]pyridine-1,2,3-triazole hybrids (7a–j & 8a–j) have been designed and synthesized in excellent yields by Huisgen’s [3+2] cyclo addition reaction of 3-(azidomethyl)-2-methyl-6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-b]pyridine (5) with various alkynes 6 in presence of copper sulphate and sodium ascorbate and their structures were confirmed by IR, ¹H NMR, ¹³C NMR and HRMS. The newly synthesized compounds 7a–j & 8a–j were evaluated for their in vitro anti-mycobacterial activity against Mycobacterium tuberculosis H37Rv (ATCC 27294). Among the compounds tested, the compounds 7i and 8g displayed most potent activity with MIC value of 1.56?µg/mL with low cytotoxicity.     

High level production of a peptide hormone analogue [Leu13]motilin inE. coli

Summary A peptide hormone analogue [Leu¹³]motilin has been produced in high yield by recombinant DNA techniques. The peptide was expressed from a multicopied [Leu¹³]motilin gene fused to a salmon growth hormone gene fragment. The monomeric [Leu¹³]motilin was obtained by treatment of the fusion protein with cyanogen bromide, carboxypeptidase A and B. [Leu¹³]motilin showed the equivalent biological activity to that of the natural form.     

Synthesis of novel pyrrole and pyrrolo[2,3-d]pyrimidine derivatives bearing sulfonamide moiety for evaluation as anticancer and radiosensitizing agents

Pyrroles and pyrrolo[2,3-d]pyrimidines were reported to act as potent anticancer agents, in this work, a series of novel 2-substituted-3-cyano-4-phenyl-pyrrole 5, 6, 11–18, and 5-phenyl-pyrrolo[2,3-d]pyrimidine derivatives 7–10, 19–24 bearing either sulfathiazole or sulfapyridine were synthesized. The structures of these compounds were confirmed by elemental analysis, IR, ¹H NMR and mass spectral data. All the newly synthesized compounds were evaluated for their in vitro cytotoxicity against liver and breast cancer cell line (HEPG2 and MCF7). Most of the screened compounds showed interesting cytotoxic activities compared with the used reference drug (doxorubicin). The radiosensitizing ability of some of the synthesized compounds was studied and the results showed an increase in the cell killing effect of γ-radiation after combination with the tested compounds.     

Fluorescent cytokinins: Stretched-out analogs of N6-benzyladenine and N6-(Δ2-isopentenyl) adenine

We have synthesized and compared the cytokinin activities in the tobacco bioassay of a series of benzologs of 6-(3-methyl-2-butenylamino)purine (N⁶-(Δ²-isopentenyl)adenine) (1a) and 6-benzylaminopurine (N⁶-benzyl-adenine) (1c). The linear benzo analogs 8-(3-methyl-2-butenylamino)imidazo[4,5-g]quinazoline (2b) and 8-benzyla-minoimidazo[4,5-g]quinazoline (2c) are active, while 9-(3-methyl-2-butenylamino)imidazo[4,5-f]quinazoline (3b) and 6-(3-methyl-2-butenylamino)imidazo[4,5-h]quinazoline (4b) are slightly active and 9-benzylaminoimidazo[4,5-f]-quinazoline (3c) and 6-benzylaminoimidazo[4,5-h]quinazoline (4c) are inactive. Compounds 2b and 2c represent the first examples of active cytokinins containing a tri-heterocyclic moiety. The above series of compounds demonstrates structural factors that affect cytokinin activity. These compounds also have interesting fluorescence properties which could render them useful as probes to study the mechanism of cytokinin action.