Design,synthesis, and biological evaluation of biotin-labeled (−)-ternatin,a potent fat-accumulation inhibitor against 3T3-L1 adipocytes

The design, synthesis, and biological activity of biotin-labeled (?)-ternatin are reported. Chemical modification, that is, biotinylation, was conducted using Click chemistry at the 6-position (NMe-d-ProGly moiety), which was a plausible location selected on the basis of our SAR studies. The compound displayed sufficient fat-accumulation inhibitory effect against 3T3-L1 adipocytes for further bio-organic studies.     

Synthesis,biological activity and receptor-based 3-D QSAR study of 3'-N-substituted-3'-N-debenzoylpaclitaxel analogues

3'-N-Substituted-3'-N-debenzoylpaclitaxel analogues were synthesized and investigated for their 3-D QSAR by using comparative molecular field analysis (CoMFA). The CoMFA model obtained from receptor(microtubule)-paclitaxel binding structure displays an excellent predictive power to forecast the biological activity of new 3'-N-substituted-3'-N-debenzoylpaclitaxel analogues as well as the ability to explain the activity of the known paclitaxel analogues. The cross-validated r(2)(cv) values of the selected models are 0.835 and 0.616 for A549 and SK-OV-3, respectively, and the non-cross-validated r(2)(ncv) values of them are 0.992 and 0.974.     

Design and synthesis of 3'-ureidoadenosine-5'-uronamides: effects of the 3'-ureido group on binding to the A3 adenosine receptor

On the basis of high binding affinity at the A(3) adenosine receptor of 3'-aminoadenosine derivatives with hydrogen bonding donor ability, novel 3'-ureidoadenosine analogues were synthesized from 1,2:5,6-di-O-isopropylidene-d-glucose in order to lead to stronger hydrogen bonding than the corresponding 3'-aminoadenosine derivatives. However, the synthesized 3'-ureidoadenosine analogues were totally devoid of binding affinity, because 3'-urea moiety caused steric and electrostatic repulsions at the binding site of the A(3) adenosine receptor, leading to conformational distortion.     

Inhibition of influenza virus A RNA-polymerase activity by various 3'-amino-3'-deoxy- and 3'-azido-3'-deoxyribonucleoside-5'-triphosphates

The effects of 3'-amino-3'-deoxy- and 3'-azido-3'-deoxyribonucleoside-5'-triphosphates on the RNA synthesis catalyzed by influenza virus A RNA polymerase were studied. All nucleotide analogues tested decreased the RNA synthesis twofold at the inhibitor: substrate ratio about 1:5 (in moles). The hypothetic mechanism of inhibitors action based on the incorporation of inhibitors into the 3'-termini of the RNA chains and subsequent blocking of the RNA chains elongation is proposed. The nucleotide analogues under investigation were several times more effective as compared with the ribavirine 5'-triphosphate, a well-known inhibitor of influenza A virus reproduction.     

Synthesis of 3'-ureidoadenosine analogues and their binding affinity to the A3 adenosine receptor

Novel 3'-ureidoadenosine analogues were synthesized from 1,2:5, 6-di-O-isopropylidene-D-glucose in order to lead to stronger hydrogen bonding at the A3 adenosine receptor than the corresponding 3'-aminoadenosine derivatives. However, all synthesized 3'-ureidoadenosine analogues have lost their binding affinities to the all subtypes of adenosine receptors, indicating that bulky 3'-urea moiety led to conformational distortion.     

Synthesis of 3-(3-hydroxyphenyl)pyrrolidine dopamine D3 receptor ligands with extended functionality for probing the secondary binding pocket

A series of 3-(3-hydroxyphenyl)pyrrolidine analogues which incorporate N-alkyl groups and N-butylamide-linked benzamide functionality have been synthesized and their in vitro binding affinities at human dopamine receptors have been evaluated. Our ligand design strategy was to take the 3-(3-hydroxyphenyl)pyrrolidine scaffold and extend functionality from the orthosteric binding site to the secondary binding pocket for enhancing affinity and selectivity for the D₃ receptor. The N-alkyl analogues constitute a homologous series from N-pentyl to N-decyl to probe the length/bulk tolerance of the secondary binding pocket of the D₃ receptor. Enantiomeric 3-(3-hydroxyphenyl)pyrrolidine analogues were also prepared in order to test the chirality preference of the orthosteric binding site for this scaffold. Benzamide analogues were prepared to enhance affinity and/or selectivity based upon the results of the homologous series.     

Synthesis and anti-HIV evaluation of 3'-triazolo nucleosides

A series of hitherto unknown 3'-α-[1,2,3]-substituted triazolo-2',3'-dideoxypyrimidine nucleoside analogues of the anti-HIV 3'-azido-3'-deoxythymidine (AZT) were synthesized through catalyzed alkyne-azide 1,3-dipolar cycloaddition (Huisgen reaction). Those 3'-[1,2,3]-triazolo analogues bearing an azido alkyl chain were evaluated for their anti-HIV activity against HIV-1 in primary human lymphocytes as well as for their cytotoxicity in different cells. None of them inhibit HIV replication (EC(50) > 20 μM); two of them were converted to their triphosphate form to evaluate their HIV-RT inhibition.     

In silico and in vitro characterization of anti-amyloidogenic activity of vitamin K3 analogues for Alzheimer's disease

Background

Aggregation of amyloid-beta (Aβ) has been proposed as the main cause of Alzheimer's disease (AD). Vitamin K deficiency has been linked to the pathogenesis of AD. Therefore, 15 synthesized vitamin K3 (VK3) analogues were studied for their anti-amyloidogenic activity.

Methods

Biological and spectroscopic assays were used to characterize the effect of VK3 analogues on amyloidogenic properties of Aβ, such as aggregation, free radical formation, and cell viability. Molecular dynamics simulation was used to calculate the binding affinity and mode of VK3 analogue binding to Aβ.

Results

Both numerical and experimental results showed that several VK3 analogues, including VK3-6, VK3-8, VK3-9, VK3-10, and VK3-224 could effectively inhibit Aβ aggregation and conformational conversion. The calculated inhibition constants were in the μM range for VK3-10, VK3-6, and VK3-9 which was similar to the IC₅₀ of curcumin. Cell viability assays indicated that VK3-9 could effectively reduce free radicals and had a protective effect on cytotoxicity induced by Aβ.

Conclusions

The results clearly demonstrated that VK3 analogues could effectively inhibit Aβ aggregation and protect cells against Aβ induced toxicity. Modified VK3 analogues can possibly be developed as effective anti-amyloidogenic drugs for the treatment of AD.

General significance

VK3 analogues effectively inhibit Aβ aggregation and are highly potent as anti-amyloidogenic drugs for therapeutic treatment of AD.     

Modelling of substrate binding to 3-phosphoglycerate kinase with analogues of 3-phosphoglycerate

Two short analogues of 3-phosphoglycerate, -OOC-CHOH-CH2-O-PO32-, phosphonolactate, (-OOC-CHOH-CH2-PO32-) and arsonolactate (-OOC-CHOH-CH2-AsO32-) have been tested with 3-phosphoglycerate kinase. None of these served as substrate for the kinase reaction, unlike the previously studied [Orr, G. A. & Knowles, J. R. (1974) Biochem. J. 141, 721-723] analogues -OOC-CHOH-CH2-CH2-PO32- and -OOC-CHOH-CH2-CH2-AsO32-, which are isosteric with 3-phosphoglycerate. Thus, a decrease in the substrate size and the accompanying stereochemical changes cannot be tolerated by the catalytic mechanism. Instead, both analogues acted as relatively poor competitive inhibitors with respect to both 3-phosphoglycerate and MgATP. AT pH 8.5 and 20 degrees C, the inhibitory constants (Ki) of phosphonolactate and arsnolactate against both substrates are 17 +/- 5 mM and 30 +/- 7 mM, respectively. Surprisingly, however, both analogues proved to be more effective than either 3-phosphoglycerate or its isosteric analogues in protecting the enzyme against modification of its fast-reacting thiols. This comparison suggests that the shorter analogues bind differently, and that the catalytic mechanism demands a precise fitting of the -CH2-O-PO32- segment of the substrate.     

3-chloro-1, 3, 5-pregnatriene derivatives with glucocorticoid activity

Novel synthetic glucocorticoid analogues were tested for receptor binding and glucocorticoid activity. They were of unusual structure, insofar as they had a 3-chloro rather than a 3-oxo function. 3-Chloro analogues of fluorinated glucocorticoids formed extremely stable complexes with the rat liver glucocorticoid receptor. 3-Chloro derivative of fluocinolone acetonide also had $\text{in vivo}$ glucocorticoid activity. It induced tyrosine aminotransferase in the liver and repressed thymidine kinase in the thymus very effectively. It is concluded that 3-chloro analogues may retain glucocorticoid activity as well as the ability to bind to the glucocorticoid receptor protein.     

Positioning of mRNA 3' of the a site bound codon on the human 80S ribosome

Short mRNA analogues carrying a UUU triplet at the 5'-termini and a perfluorophenylazide group at either the N7 atom of the guanosine or the C5 atom of the uridine 3' of the triplet were applied to study positioning of mRNA 3' of the A site codon. Complexes of 80S ribosomes with the mRNA analogues were obtained in the presence of tRNAPhe that directed UUU codon to the P site and consequently provided placement of the nucleotide with cross-linker in positions +9 or +12 with respect to the first nucleotide of the P site bound codon. Both types mRNA analogues cross-linked to the 18S rRNA and 40S proteins under mild UV-irradiation. Cross-linking patterns in the complexes where modified nucleotides of the mRNA analogues were in position +7 were analyzed for comparison (cross-linking to the 18S rRNA in such complexes has been studied previously). The efficiency of cross-linking to the ribosomal components depended on the nature of the modified nucleotide in the mRNA analogue and its position on the ribosome, extent of cross-linking to the 18S rRNA being decreased drastically when the modified nucleotide was moved from position +7 to position +12. The nucleotides of 18S rRNA cross-linked to mRNA analogues were determined. Modified nucleotides in positions +9 and +12 cross-linked to the invariant dinucleotide A1824/A1825 and to variable A1823 in the 3'-minidomain of 18S rRNA as well as to protein S15. The same ribosomal components have been found earlier to cross-link to modified mRNA nucleotides in positions from +4 to +7. Besides, all mRNA analogues cross-linked to the invariant nucleotide c1698 in the 3'-minidomain and to and the conserved region 605-620 closing helix 18 in the 5'-domain.     

Chemoenzymatic synthesis and biological evaluation of C-3 carbamate analogues of 1alpha,25-dihydroxyvitamin D3

The synthesis of new analogues of 1alpha,25-dihydroxyvitamin D3 containing a carbamate function at the A-ring fragment has been described using the cross-coupling approach. The carbamate group was selectively introduced at the C-3 position by regioselective enzymatic alkoxycarbonylation of A-ring enyne 3 and subsequent treatment with ammonia, amines, amino alcohols, and amino acids. Biological studies to evaluate the potency of all five of these carbamate analogues were performed and demonstrated very low binding affinity for the vitamin D receptor compared with 1alpha,25-dihydroxyvitamin D3. Moreover, all the carbamate analogues were less active than 1alpha,25-dihydroxyvitamin D3 in inhibiting cell proliferation or stimulating cell differentiation. Of all the five analogues, the 3-O-carbamoyl-1alpha,25-(OH)2-D3 analogue 10a was the most potent one in vitro. However, all investigated carbamate analogues demonstrated lower calcemic effects in vivo than the parent compound.     

Synthesis and biological evaluation of C-3'NH/C-10 and C-2/C-10 modified paclitaxel analogues

Concurrent modifications on the C-3'NH/C-10, and C-2/C-10 positions on paclitaxel were carried out as a way of investigating possible synergistic effects. The biological activities of these analogues were evaluated in both a microtubule assembly assay and human ovarian cancer (A2780) and prostate cancer (PC3) cytotoxicity assay. In some cases the doubly modified analogues were more active than would have been predicted based on the activity of the singly modified analogues, indicating probable synergistic effects.     

Importance of aliphatic side-chain structure at positions 2 and 3 of the insulin A chain in insulin-receptor interactions.

In order to evaluate the cause of the greatly decreased receptor-binding potency of the naturally occurring mutant human insulin Insulin Wakayama ([LeuA3]insulin, 0.2% relative potency), we examined (by the semisynthesis of insulin analogues based on N alpha-PheB1,N epsilon-LysB29-bisacetyl-insulin) the importance of aliphatic side chain structure at positions A2 and A3 (Ile and Val, respectively) in directing the interaction of insulin with its receptor. Analogues bearing glycine, alanine, alpha-amino-n-butyric acid, norvaline, norleucine, valine, isoleucine, allo-isoleucine, threonine, tert-leucine, or leucine at positions A2 or A3 were assayed for their potencies in competing for the binding of 125I-labeled insulin to isolated canine hepatocytes, as were analogues bearing deletions from the A-chain amino terminus or the B-chain carboxyl terminus. Selected analogues were also analyzed by far-UV CD and absorption spectroscopy of Co2+ complexes. Our results identify that (a) Ile and Val serve well at position A2, whereas residues with other side chains (including those with straight chains, alternatively configured beta-branches, or a gamma-branch) exhibit relative receptor-binding potencies in the range 1-5%; (b) greater flexibility is allowed side-chain structure at position A3, with Ile, allo-Ile, alpha-amino-n-butyric acid, and tert-Leu exhibiting relative receptor-binding potencies in the range 11-36%; and (c) simultaneous replacements at positions A2 and A3, and deletions of the COOH-terminal domain of the insulin B chain in related analogues, yield cumulative effects. These findings are discussed with respect to a model for insulin-receptor interactions that involves a structure-orienting role for residue A2, the direct interaction of residue A3 with receptor, and multiple separately defined elements of structure and of conformational adjustment.     

Synthesis of 3′-Amino-3′-deoxyadenosine Derivatives as Potential Drugs for the Treatment of Malaria

Abstract

A series of 3′-substituted 3′-amino-3′-deoxyadenosine analogues were synthesized and subsequently tested against the human malaria parasite Plasmodium falciparum in vitro. Several amongst them displayed pronounced antiplasmodial activities.     

SYNTHESIS OF 3′-UREIDOADENOSINE ANALOGUES AND THEIR BINDING AFFINITY TO THE A3 ADENOSINE RECEPTOR

Novel 3′-ureidoadenosine analogues were synthesized from 1,2:5,6-di-O-isopropylidene-D-glucose in order to lead to stronger hydrogen bonding at the A₃ adenosine receptor than the corresponding 3′-aminoadenosine derivatives. However, all synthesized 3′-ureidoadenosine analogues have lost their binding affinities to the all subtypes of adenosine receptors, indicating that bulky 3′-urea moiety led to conformational distortion.     

Design,synthesis and binding affinity of 3'-fluoro analogues of Cl-IB-MECA as adenosine A3 receptor ligands

Several 3'-fluoro analogues, 1a, 1b, and 1c of selective and potent adenosine A(3) receptor agonist, Cl-IB-MECA were synthesized from D-xylose via highly regioselective opening of lyxo-epoxides, 8a and 8b with fluoride anion. Compared to the high binding affinity of Cl-IB-MECA to the A(3) adenosine receptor, the corresponding 3'-fluoro derivative showed remarkably decreased binding affinity, indicating that 3'-hydroxyl group acts as hydrogen bonding acceptor, not hydrogen bonding donor like fluorine atom in binding to the A(3) adenosine receptor.     

Analogues of arginine vasopressin modified in position 2 and 3 with conformationally constrained dipeptide fragments.

This study describes the synthesis and some pharmacological properties of ten new analogues of arginine vasopressin (AVP) containing a conformationally constrained dipeptide fragment in the N-terminal part of their molecules. Amino acid residues in positions 2 and 3 of AVP and some of its agonistic analogues were replaced with -Phe-Phe and D-Phe-D-Phe, dipeptides having a -CH2-CH2- link bridging two nitrogens. All the new peptides were tested for vasopressor and antidiuretic activities. Four peptides with pA2 values ranging from 5.96 to 7.21 turned out to be weak or moderately potent V1a antagonists. The results supplied new information about the structure-activity relationship of AVP analogues. As some of these were unexpected, they point to the need for caution when extrapolating previously known effects of modifications to analogues having conformationally constrained fragments in their molecules.     

2-Benzyl and 2-phenyl-3-hydroxypropyl pivalates as protein kinase C ligands

A series of 2-benzyl and 2-phenyl-3-hydroxypropyl pivalates designed to incorporate the principal pharmacophores of phorbol esters have been synthesized and tested as PKC-alpha ligands. Among the analogues, 13c exhibited the most potent binding affinity with a Ki = 0.7 microM. The synthesized analogues were subjected to molecular modeling analysis based on two alternative models of the phorbol pharmacophore and a docking study of 13c was carried out.