Synthesis and biological evaluation of bombesin constrained analogues

Analogues of bombesin which incorporate dipeptide or turn mimetics have been synthesized. One of them (compound 11) containing a seven-membered lactam ring revealed a good affinity for GRP/BN receptors on rat pancreatic acini (K(i) value of 1.7 +/- 0.4 nM) and on Swiss 3T3 cells (K(i) value of 1.0 +/- 0.2 nM). On the basis of this observation, antagonists containing the same dipeptide mimic were obtained by modification of the C-terminal part of the bombesin analogues. The most potent constrained compounds (15 and 17) were able to antagonize 1 nM bombesin-stimulated amylase secretion from rat pancreatic acini with high potency (K(i) = 21 +/- 3 and 3.3 +/- 1.0 nM, respectively) and 10(-7) M bombesin-stimulated ?(3)Hthymidine incorporation into Swiss 3T3 cells (K(i) = 7.8 +/- 2. 0 and 0.5 +/- 0.1 nM, respectively).     

Synthesis and biological evaluation of some stilbene-based analogues

The phytoalexin 3,5,4′-trihydroxy-trans-stilbene (resveratrol) has attracted considerable attention from biologists and chemists due to its diverse biological properties. Owing to the biological importance of this compound, we have synthesized new stilbene-based analogues by using substituted benzyl chlorides and substituted aldehydes in a two-step reaction and evaluated their in vitro antioxidant, antibacterial and antifungal potential. Most of the compounds displayed moderate to significant radical scavenging activity. (E)-1-(3,4-difluorophenyl)-2-(4-fluorophenyl)ethene (4c) showed nearer equipotent antibacterial activity against Staphylococcus aureus. (E)-1,2-bis(4-fluorophenyl)ethene (4a), (E)-1-(3-fluorophenyl)-2-(4-fluorophenyl)ethene (4b), (E)-1-(2,4-dichlorophenyl)-2-(3,4-dichlorophenyl)ethene (4f), (E)-1-(2,4-dichlorophenyl)-2-(3-chlorophenyl)ethene (4g), (E)-1-(2,4-dichlorophenyl)-2-(4-fluorophenyl)ethene (4j) (E)-1-(4-fluorophenyl)-2-(3-chlorophenyl)ethene (4l) and (E)-1-(4-chlorophenyl)-2-(4-fluorophenyl)ethene (4n) inhibited the growth of Penicillium chrysogenum.     

Synthesis and biological evaluation of acyclic neplanocin analogues

Acyclic neplanocin analogues were prepared by condensation of adenine or N2-acetylguanine with (E)-1,4-dichlorobut-2-ene and subsequent hydrolysis. The N-9-substituted product 9-[(E)-4-hydroxybut-2-enyl]adenine was obtained when adenine was employed as the starting purine, while N2-acetylguanine yielded both the N-7 and N-9 isomers. Cell-culture studies revealed that only the chloro-substituted intermediate 9-[(E)-4-chlorobut-2-enyl]adenine exhibited significant cytotoxicity against P-388 mouse lymphoid leukemia cells, while the N-9-substituted guanine analogue 9-[(E)-4-hydroxybut-2-enyl]guanine inhibited replication of herpes simplex viruses type 1 and type 2.     

Synthesis and biological evaluation of (-)- and (+)-debromoflustramine B and its analogues as selective butyrylcholinesterase inhibitors

A series of pyrrolidinoindolines have been synthesized as debromoflustramine B (4a) analogues for their evaluation as cholinesterase inhibitors. Structure-activity studies of this series revealed the optimum pharmacophoric elements required for activity and resulted in the discovery of selective butyrylcholinesterase inhibitors with micromolar potency. Biological testing demonstrated that (-)-4a was 7500 times more potent than its enantiomer (+)-4b. The most active inhibitor against BChE in the series was demethyldebromoflustramine B (5a), with an IC50 value of 0.26 microM. X-ray crystallography of 15 and docking studies of selected compounds into human BChE (PDB 1POI) are presented. Molecular modeling studies showed that pi-hydrogen bond, classical hydrogen bond, and cation-pi interactions are critical for optimum potency.     

Synthesis and biological evaluation of bradykinin B(1)/B(2) and selective B(1) receptor antagonists

We recently described a potent bradykinin B(2) receptor agonist (JMV1116) obtained by replacing the D-Tic-Oic dipeptide moiety of HOE140 by a (3S)-amino-5-(carbonylmethyl)-2,3-dihydro-1, 5-benzothiazepin-4(5H)-one (D-BT) moiety. This compound inhibited the specific binding of [(3)H]BK on membranes of CHO cells expressing the human cloned B(2) receptor with nanomolar affinity and contracted both isolated rat uterus and human umbilical vein. These data demonstrated that D-BT could be a good mimic of the Pro-Phe dipeptide. In the present study we characterized B(1) receptor antagonists containing the D-BT moiety. We prepared an analogue of compound JMV1116 deleting the C-terminal arginine residue. The resulting compound (1) had an affinity of 83 nM for the human cloned B(1) receptor. The most remarkable property of 1 is its ability to bind also the B(2) receptor with an affinity of 4.4 nM despite the absence of the C-terminal arginine residue. Modifications at the N-terminal part of 1 associated with the substitution of the thienylalanine residue by alpha-(2-indanyl)glycine resulted in analogues selectively binding to the B(1) receptor with an affinity in the picomolar range.     

Synthesis and biological evaluation of 4-arylcoumarin analogues of combretastatins

A series of A-ring polymethoxylated neoflavonoids was prepared by ligand coupling reactions involving either Suzuki or Stille reactions. Cytotoxicity studies indicated a potent activity against a CEM leukemia cell line for the compounds presenting a substitution pattern related to that of combretastatin A-4. The two compounds having a 3'-OH and a 4'-OCH(3) substituents on the 4-phenyl B-ring have no effect on human topoisomerases I and II but potently inhibit, in vitro, microtubule assembly. At the cell level, the active compounds were characterized as proapoptotic agents, but they can also trigger cell death via a nonapoptotic pathway.     

FKBP51 regulation of AKT/protein kinase B phosphorylation

FK506 binding protein 51 (FKBP51, also called FKBP5) belongs to a family of immunophilins, FK506 binding proteins (FKBPs). FKBP family members are targets for drugs such as rapamycin. Although FKBP51 shares characteristics with other FKBPs, it also has unique features, especially the role in its regulation of important signaling pathways such as the AKT kinase/protein kinase B pathway. In this review, we will focus on the function of FKBP51 as a scaffolding protein in the regulation of AKT activation and, in turn, its role in tumorigenesis and response to chemotherapy.     

Synthesis and evaluation of iodinated analogues of diacylglycerols as potential probes for protein kinase C

Analogues of diacylglycerol containing a 3-(3-amino-2,4,6-triiodophenyl)-2-ethylpropanoyl or 3-(3-amino-2,4,6-triiodophenyl)propanoyl group in the 2-position (1a and 1b, respectively) were synthesized and shown to compete with [3H]phorbol dibutyrate [( 3H]PDBu) for binding in a crude rat brain preparation. Phorbol diesters have been shown to bind specifically to protein kinase C and the PDBu receptor has been copurified with protein kinase C activity. The four diastereomers of 1a (1c-f) were synthesized from chiral starting material and studied in the same assay. The affinities for the [3H]PDBu binding site of 1a, 1b, and two isomers of 1a with naturally occurring L configuration were comparable to that of 1-oleoyl-2-acetyl-rac-glycerol (OAG), but the D isomers of 1a were essentially inactive. The chirality of the side chain did not influence the binding affinity. Activation of protein kinase C by 1a, 1c, and 1e demonstrated the same stereochemical requirements, but none were as active as OAG. For the 1,3-isomers 2, 2a, and 2b, the competitive binding studies gave different results. The racemic mixture and the D isomer, 2b, were able to compete for binding, but the L isomer, 2a, did not compete. These studies demonstrate that diacylglycerol binding to and activation of protein kinase C is stereospecific for the glycerol backbone, but not the side chain. Furthermore, the D-1,3-isomer must exist in a conformation such that the acyl and hydroxyl oxygens assume a spatial relationship similar to that in the L-1,2-isomers.     

Synthesis and biological evaluation of meperidine analogues at monoamine transporters

A series of aryl-substituted meperidine analogues was synthesized, and the binding affinities were determined at the DAT, SERT, and NET as well as at mu-opioid receptors. Generally the analogues exhibited increased affinity for the DAT and SERT relative to meperidine but exhibited low binding affinity for the NET. The 2-naphthyl derivative 7f was the most potent ligand at the SERT (K(i) = 0.0072 muM) and was the most selective ligand for the SERT over the DAT (DAT/SERT = 158) and mu-opioid receptors (mu/SERT = 281). The 3,4-dichlorophenyl derivative 7e was the most potent ligand at the DAT (K(i) = 0.125 muM) and was the most selective ligand for the DAT over mu-opioid receptors (mu/DAT = 16.3) but remained slightly more selective for the SERT over the DAT(DAT/SERT = 6.68). Three compounds, the 3,4-dichlorophenyl derivative 7e and the 2-naphthyl analogues 6f and 7f, were identified that were more potent at the DAT than meperidine and that exhibited well-defined biphasic dopamine uptake inhibition similar to meperidine. However, none of the analogues tested produced locomotor effects or substituted for cocaine in drug discrimination studies, suggesting that the mu-opioid effects of these analogues may contribute to the poor efficacy observed in vivo.     

Synthesis and biological evaluation of photoaffinity labeled fusidic acid analogues

Novel photoaffinity labeled fusidic acid analogues were obtained by a synthetic sequence employing a Wittig reaction between a fusidic acid aldehyde and benzyl bromides in the key step. Three commonly used photoreactive groups, benzophenone, trifluoromethyldiazirine, and aryl azide, were used. The photoaffinity labeled fusidic acid analogues demonstrated a potent antibacterial activity (MIC 0.016-4 microg/mL) and therefore represent a potential tool for the elucidation of the interactions between fusidic acid and its receptor EF-G.