Highly potent cell differentiation-inducing analogues of 1alpha,25-dihydroxyvitamin D3: synthesis and biological activity of 2-methyl-1,25-dihydroxyvitamin D3 with side-chain modifications

Eight 2-methyl substituted analogues of 20-epi-22R-methyl-1alpha,25-dihydroxyvitamin D3 (5) and 20-epi-24,26,27-trihomo-22-oxa-1alpha,25-dihydroxyvitamin D3 (6: KH-1060) were convergently synthesized. Preparation of the CD-ring portions with modified side chains of 5 and 6, followed by palladium-catalyzed cross-coupling with the A-ring enyne synthons (20a-d), (3S,4S,5R)-, (3S,4R,5R)-, (3S,4S,5S)- and (3R,4R,5S)-3,5-bis[(tert-butyldimethylsilyl)oxy]-4-methyloct-1-en-7-yne, afforded two sets of four A-ring stereoisomers of 20-epi-2,22-dimethyl-1,25-dihydroxyvitamin D3 (7a-d) and 20-epi-24,26,27-trihomo-2-methyl-22-oxa-1,25-dihydroxyvitamin D3 (8a-d). The biological profiles of the hybrid analogues were assessed in terms of affinity for vitamin D receptor (VDR) and HL-60 cell differentiation-inducing activity in comparison with the natural hormone. The combined modifications of the A-ring at the 2-position and the side chain yielded analogues with high potency.     

Synthesis and activity of pyrimidinylpropenamide antibiotics: the alkyl analogues of sparsomycin

Facile syntheses of sparsomycin (3) and its four analogues (4-7) based on diastereoselective oxidation of sulfide, sulfenylation, and coupling of 6-methyluracylacryllic acid with monooxodithioacetal amine, are described. Studies on the biological activity of morphological reversion on src(ts)-NRK cells were also carried out.     

Synthesis and cardiovascular activity of metoprolol analogues

The synthesis of four novel analogues of metoprolol, a well-known beta1-blocker used to reduce arterial blood pressure, is described. The preparation of (2S,2'S)-7, (2R,2'S)-7, (2R,2'R)-8, and (2S,2'R)-8 was based on the reaction of racemic 2-[4-(2'-methoxyethyl)-phenoxymethyl]-oxirane (4) with (R)- or (S)-2-amino-1-butanol. Salient characteristics of analogues 7 and 8 relative to metoprolol are the incorporation of an additional stereogenic center, as well as a methyl group and a hydroxyl function on the nitrogen-containing chain. These novel derivatives present significant hypotensive and bradycardiac activity, although no blocking action toward beta1 and beta2 adrenergic receptor.     

alpha-Glucosidase inhibitory constituents from stem bark of Terminalia superba (Combretaceae)

The CH(2)Cl(2)/CH(3)OH (1/1) extract of the dried stem bark of Terminalia superba afforded two compounds, (7S,8R,7'R,8'S)-4'-hydroxy-4-methoxy-7,7'-epoxylignan and meso-(rel 7S,8R,7'R,8'S)-4,4'-dimethoxy-7,7'-epoxylignan along with 11 known compounds. The structures of the compounds were established by analysing the spectroscopic data and also comparing it with the data of previously known analogues. All the isolated compounds were evaluated for their glycosidase inhibition activities. Gallic acid and methyl gallate showed significant alpha-glucosidase inhibition activity.     

14-membered cyclic opioids related to dermorphin and their partially retro-inverso modified analogues. I. Synthesis and biological activity.

As a continuation of our program to study structure-activity relationships of opiate peptides, we report the syntheses and biological activities of a series of 14-membered cyclic dermorphin analogues closely related to enkephalin analogue Tyr-c[D-A2bu-Gly-Phe-Leu] incorporating a phenylalanine at the third position in place of glycine. In addition to two parent dermorphin analogues Tyr-c[D-A2bu-Phe-Phe-(L and D)-Leu], four stereoisomeric retro-inverso modified analogues Tyr-c[D-A2bu-Phe-gPhe-(S and R)-mLeu] with a reversed amide bond between residues four and five, and Tyr-c[D-Glu-Phe-gPhe-(L and D)-rLeu] with two reversed amide bonds between residues four and five, and between residue five and the side chain of residue two have been synthesized. The results from the guinea pig ileum (GPI) and mouse vas deferens (MVD) assays show that all analogues are superactive at either one or both opiate receptors and in general display higher activities as compared to the corresponding enkephalin analogues with a glycine at the third position. Results from the in vitro biological assays and conformational analysis using 1H-NMR spectroscopy (adjoining paper) will provide useful information to understand the role of the Phe3 aromatic side chain in dermorphin, and that of the Phe4 aromatic side chain in enkephalin, on opiate activity since these cyclic dermorphin analogues contain two Phe residues at both the third and fourth positions.     

Evaluation of the amino acid binding site of Mycobacterium tuberculosis glutamine synthetase for drug discovery

A combination of a literature survey, structure-based virtual screening and synthesis of a small library was performed to identify hits to the potential antimycobacterial drug target, glutamine synthetase. The best inhibitor identified from the literature survey was (2S,5R)-2,6-diamino-5-hydroxyhexanoic acid (4, IC(50) of 610+/-15microM). In the virtual screening 46,400 compounds were docked and subjected to a pharmacophore search. Of these compounds, 29 were purchased and tested in a biological assay, allowing three novel inhibitors containing an aromatic scaffold to be identified. Based on one of the hits from the virtual screening a small library of 15 analogues was synthesized producing four compounds that inhibited glutamine synthetase.     

Synthesis of new class dipeptide analogues with improved permeability and antithrombotic activity

3-(S)-1,2,3,4-Tetrahydro-beta-carboline-3-carboxylic acid isolated from A. Chinese G. Don was found to possess moderate anti-aggregation activity, but with poor bioavailability. To improve its pharmacological property, we designed and synthesized a series of novel dipeptide analogues by incorporating tetrahydro-beta-carboline-3-carboxylic acid skeleton as an amino acid surrogate (*Trp). It turned out these dipeptide analogues exhibited good membrane permeability based on in vitro Caco-2 cell monolayers permeability assay. As a result, the overall biological properties of these molecules were significantly improved depending on the nature of the amino acid residues introduced onto the 3-position of the tetrahydro-beta-carboline moiety. It was very interesting to notice that these dipeptide analogues (5b,c,h,i,n,o,p,q) displayed a remarkable dual antiaggregatory activity in both of ADP- and PAF-induced platelet aggregation assay, and their aggregation response was significantly higher than that of aspirin (p<0.01). In addition, these dipeptide analogues were observed for the dose-dependent antithrombotic effect using in vivo rat arterial thrombosis model. The potency of antithrombotic activity of 5h,i,n,p was significantly higher than that of aspirin (n=12, p<0.01) at equal dose (5 micromol/kg).     

Design, syntheses, and antitumor activity of novel chromone and aurone derivatives

A series of new chromone analogues bearing heterocyclic thioether moiety and aurone analogues bearing cyclic tertiary amine moiety were designed and synthesized under microwave irradiation. The synthetic protocol was found to present many advantages, such as higher yields, shorter reaction time (10-20 min), mild condition, and readily isolation of the products. The synthesized compounds were assayed for their antitumor activity against four kinds of human solid tumor cell lines including HCCLM-7, Hep-2, MDA-MB-435S, and SW-480. Two compounds, (Z)-2-((4-benzyl-piperazin-1-yl)methylene)benzofuran-3(2H)-one 5e and (Z)-2-((4-(bis(4-fluorophenyl)methyl)piperazin-1-yl)methylene)benzofuran-3(2H)-one 5f, were identified as the most promising candidates with the IC(50) values in the range of 4.1-13.1 microM. Further cell cycle studies revealed that compounds 5e and 5f arrest the cell cycle in G(0)/G(1) phase and displayed apoptosis-inducing effect on Hep-2 cells.     

Design and synthesis of potent vitamin D receptor antagonists with A-ring modifications: remarkable effects of 2alpha-methyl introduction on antagonistic activity

Novel A-ring analogues of the vitamin D receptor (VDR) antagonist (3a), ZK-159222, and its 24-epimer (3b) were convergently synthesized. Preparation of the CD-ring portions with the side chains of 3a,b, followed by palladium-catalyzed cross-coupling with the A-ring enyne precursors (15a,b), (3S,4S,5R)- and (3S,4S,5S)-bis[(tert-butyldimethylsilyl)oxy]-4-methyloct-1-en-7-yne, afforded the 2alpha-methyl-introduced analogues (4a,b) and their 3-epimers (5a,b). The biological profiles of the hybrid analogues were assessed in terms of affinity for VDR, and antagonistic activity to inhibit HL-60 cell differentiation induced by the natural hormone, 1alpha,25-dihydroxyvitamin D(3). The analogue 4a showed an approximately fivefold higher antagonistic activity compared with 3a. The 2alpha-methyl introduction into 3a increased the receptor affinity, thereby enhancing VDR antagonism. This approach to design potent antagonists based on hybridization of structural motifs in the A-ring and in the side chain may prove to be valuable.     

Structural and biological effects of a beta2- or beta3-amino acid insertion in a peptide.

Molecular mechanics calculations on conformers of Ac-HGly-NHMe, Ac-beta2-HAla-NHMe and Ac-beta3-HAla-NHMe indicate that low-energy conformations of the beta-amino acids backbone, corresponding to gauche rotamers around the Calpha-Cbeta bond, may overlap canonical backbone conformers observed for alpha-amino acids. Therefore, Substance P (SP) was used as a model peptide to analyse the structural and biological consequences of the substitution of Phe7 and Phe8 by (R)-beta2-HPhe and of Gly9 by HGly (R)-beta2-HAla or (S)-beta3-HAla. [(R)-beta2-HAla9]SP has pharmacological potency similar to that of SP while [HGly9]SP and [(S)-beta3-HAla9]SP show a 30- to 50-fold decrease in biological activities. The three analogues modified at position 9 are more resistant to degradation by angiotensin converting enzyme than SP and [Ala9]SP. NMR analysis of these SP analogues suggest that a beta-amino acid insertion in position 9 does not affect the overall backbone conformation. Altogether these data suggest that [HGly9]SP, [(S)-beta3-HAla9]SP and [(R)-beta2-HAla9]SP could adopt backbone conformations similar to that of SP, [Ala9]SP and [Pro9]SP. In contrast, incorporation of beta2-HPhe in position 7 and 8 of SP led to peptides that are almost devoid of biological activity. Thus, a beta-amino acid could replace an alpha-amino acid within the sequence of a bioactive peptide provided that the additional methylene group does not cause steric hindrance and does not confine orientations of the side chain to regions of space different from those permitted in the alpha-amino acid.     

Synthesis and contractile activity of new pseudopeptido and thioaromatic analogues of leukotriene D4.

Seven new pseudopeptido and thioaromatic leukotriene analogues were synthesized and their agonist-antagonist and binding activities investigated. The synthesis led to the pleasing observation that the analogue in which the cysteinyl-glycine moiety was replaced by a 6-mercapto-3-(E)-hexenoic acid, not only exhibited potent affinity (guinea-pig lung parenchyma, IC50: 5 x 10(-9) M) but also showed 30% of the LTD4 agonist activity (guinea-pig ileum, ED 50: 2.7 x 10(-9)) giving very important key information on LTD4 geometry to the receptor. This compound was the first stable new pseudopeptido-leukotriene with such agonist activity and should contribute to the understanding of the metabolism of leukotriene D4. In addition, inversion of chirality at C5 and C6 carbon atoms of the leukotriene chain or replacement of the cysteinyl-glycine moiety by a thioaromatic acid led to new weak antagonists of the LTD4.     

Synthesis and structure-activity relationships of TEI-9647 derivatives as Vitamin D3 antagonists

The Vitamin D(3) lactone analogues, (23S)- and (23R)-25-dehydro-1alpha-hydroxyvitamin D(3)-26,23-lactone (TEI-9647 and TEI-9648) are antagonists of the 1alpha,25-dihydroxyvitamin D(3) (1alpha,25-(OH)(2)D(3)) nuclear receptor (VDR)-mediated differentiation of human leukemia (HL-60) cells. In order to clarify the structure-Vitamin D antagonistic activity relationship, we paid attention to the unique lactone moiety of TEI-9647 and TEI-9648: alpha-exo-methylene-gamma-lactone structure. We synthesized the exo-methylene-modified analogues (methylene saturated, endo-methylene, methylene-deleted, methyl-substituted, dimethyl-substituted, methylene-replaced with dimethyl and cyclopropane) and oxygen-modified analogues (oxygen atom replaced with nitrogen and carbon atom) by convergent method using palladium-catalyzed coupling reaction or direct modification of VD(3) skeleton. The antagonistic activity in HL-60 cell differentiation evaluating system of these analogues revealed that any exo-methylene-modified analogues and nitrogen analogue did not have the antagonistic activity, on the other hand carbon analogue did show. The results suggest that "alpha-exo-methylene carbonyl" structure of VD(3) side-chain is crucial for antagonistic activity. The structure is integral building block of many natural products which have interesting biological and it is thought that Michael-type addition of alpha-exo-methylene carbonyl structure with protein nucleophiles such as cysteine would play an important role for the activities. According to this theory, Michael-type reaction of TEI-9647 and TEI-9648 with cysteine residue in protein related to VDR/VDRE-mediated genomic actions such as VDR would be essential step of the antagonistic action.     

Synthesis of oxazolidinone phospholipid analogue as a new inhibitor of phospholipase A2

(S)- and (R)-3-dodecanoyl-4-phosphatidylcholinohydroxymethyl-2-oxazolidinone (1), which are cyclic analogues of the amide phospholipid 7, were synthesized. The inhibitory activities of these analogues toward phospholipase A₂ were compared with that of the amide analogue 7.     

Effects of backbone structures and stereospecificities of lipid A-subunit analogues on their biological activities

Among chemically synthesized analogues corresponding to the nonreducing sugar part of lipid A, we have found an analogue (GLA-27) which exhibits Limulus, mitogenic, polyclonal B cell activation (PBA), interferon-inducing, and tumor necrosis factor (TNF)-inducing activities but not pyrogenic activity. The structure of GLA-27 comprises 4-O-phosphono-D-glucosamine with tetradecanoyl and 3-tetradecanoyloxytetradecanoyl (C14-O-(C14] groups as the 3-O- and 2-N-acyl substituents, respectively. Derivatives of GLA-27 with different backbone structures, such as the 1-deoxy, 3-epimeric, 3-amino, and 1-deoxy-3-epimeric derivatives of glucosamine, were chemically synthesized, and their mediator-inducing activities such as interferon- and TNF-inducing activities were investigated in comparison with their B cell activation activities including mitogenic and PBA activities. Among these derivatives, a derivative with a 1-deoxyglucosamine backbone (GLA-40) exhibited stronger B cell activation activities than those of GLA-27 while the mediator-inducing activities of GLA-40 were weaker than those of GLA-27. In addition to these derivatives, stereoisomers of GLA-27 which possess the (R) and (S) forms of C14-O-(C14) as the 2-N-acyl substituent were also synthesized and their biological activities compared. The (S) isomer exhibited much stronger mediator-inducing activities than the (R) isomer. On the other hand, B cell activation activities of the (R) isomer were strong and those of the (S) isomer weak. These results clearly demonstrate that mediator-inducing activities and B cell activation activities can be selectively expressed by modifying the structures of lipid A analogues.     

Synthesis and Activity of Pyrimidinylpropenamide Antibiotics: The Alkyl Analogues of Sparsomycin

Facile syntheses of sparsomycin (3) and its four analogues (4-7) based on diastereoselective oxidation of sulfide, sulfenylation, and coupling of 6-methyluracylacryllic acid with monooxodithioacetal amine, are described. Studies on the biological activity of morphological reversion on src ^ts-NRK cells were also carried out.     

Effect of natural and structurally modified bile acids on cholesterol metabolizing enzymes in rat liver microsomes. II

The effect of ursodeoxycholic acid analogues bearing modifications at the side-chain moiety of the molecule was tested on cholesterol 7 alpha-hydroxylase and HMG-CoA reductase in rat liver microsomes. The compounds included 23 R,S mixture and the single isomers 23R and 23S of 23 methylursodeoxycholic acid (23-methyl UDCA), the isomeric mixture (cis + trans) of 3 alpha,7 beta-dihydroxy-20,22-methylen-5 beta-cholan-23-oic acid (norcypro-UDCA) and the corresponding single isomers. Each steroid was added to liver microsomes as the sodium salt, at concentrations ranging from 25 to 200 microM. Isomers 23R and 23S of 23-methyl-UDCA inhibited cholesterol 7 alpha-hydroxylase in a concentration-dependent manner. The inhibitory capacity was similar for the two isomers. The extent of inhibition of the analogues was greater than that of the parent compound UDCA. Shortening of the side-chain in norcypro-UDCA resulted in a partial loss of the inhibitory effect, as compared to cypro-UDCA (3 alpha,7 beta-dihydroxy-22,23-methylen-5 beta-cholan-24-oic acid). None of these bile acid derivatives affected the activity of the enzyme HMG-CoA reductase.     

Type I beta-turn conformation is important for biological activity of the melanocyte-stimulating hormone analogues.

In order to define which structure of alpha-melanocyte-stimulating hormone (MSH) analogues plays a critical role for ligand-receptor interaction and selectivity, we analysed receptor-binding and cAMP-generating activity in Chinese hamster ovary cell lines stably transfected with rMC3R and hMC4R, as well as the NMR structures of chemically synthesized alpha-MSH analogues. Compared with [Ahx4]alpha-MSH, the linear MTII designated as alpha-MSH-ND revealed a preference for the MC4R, whereas its IC50 and EC50 values were comparable to those of MTII reported previously. Truncation of Ahx4 and Asp5 of alpha-MSH-ND remarkably decreased the receptor-binding and cAMP-generating activity. Meanwhile, maximum cAMP-generating activity was observed at a higher concentration (10(-5) M) of alpha-MSH-ND(6-10), and MC4R preference was changed into MC3R preference. In contrast, [Gln6]alpha-MSH-ND(6-10) lost its cAMP-generating activity almost completely, even though it bound to both receptors. Whereas the solution conformation of alpha-MSH-ND revealed a stable type I beta-turn structure, [Gln6]alpha-MSH-ND(6-10) revealed a tight gamma-turn composed of Gln6-D-Phe7-Arg8. Replacement of the His6 residue of alpha-MSH-ND by Gln, Asn, Arg or Lys decreased not only the receptor binding, but also the cAMP-generating activity in both the MC3R and the MC4R. The structure of [Gln6]alpha-MSH-ND exhibited a stable type I' beta-turn comprising Asp5, Gln6, D-Phe7 and Arg8. [Lys6]alpha-MSH-ND showed a greatly reduced binding affinity and cAMP-generating activity with the loss of MC4R selectivity. In NMR studies, [Lys6]alpha-MSH-ND also demonstrated a gamma-turn conformation around Lys6-DPhe7-Arg8. From the above results, we conclude that a type I beta-turn conformation comprising the residues Asp5-His6-(D-Phe7)-Arg8 was important for receptor binding and activation, as well as the selectivity of MSH analogues.     

Synthesis and phosphodiesterase inhibitory activity of new sildenafil analogues containing a carboxylic acid group in the 5'-sulfonamide moiety of a phenyl ring

New sildenafil analogues possessing a carboxylic acid group in the 5'-sulfonamide of the phenyl ring, 9a-l, were prepared from the readily available starting compounds 6a-b and cyclic amines 3-5 in a three-step sequence. In the enzyme assays, it has been shown that all the target compounds 9a-l proved to be more potent in inhibiting phosphodiesterase type 5 (PDE5) than sildenafil by 4-38-fold. The effects on the IC(50) values were investigated by varying the alkoxy group (R) of the phenyl ring, the sulfonamide type (X), and the length of the methylene chain linking the carboxylic acid, and the results were discussed in detail. From this study, we have clearly demonstrated that introduction of a carboxylic acid group to the 5'-sulfonamide moiety of the phenyl ring greatly enhanced PDE5 inhibitory activity, probably by mimicking the phosphate group of cGMP. The piperidinyl propionic acid derivative 9i, which showed the highest PDE5 inhibitory activity and comparable to better selectivity over PDE isozymes in comparison with sildenafil, has been selected for more detailed biological investigations.     

Cytotoxic activity of (S)-goniothalamin and analogues against human cancer cells

(R)- and (S)-Goniothalamin (1) and analogues 2-9 were efficiently prepared in high overall yield and enantiomeric purity, and their cytotoxic activities were evaluated against eight human cancer cell lines. A structure-activity relationship study (SAR) allowed us to establish the relevant structural features for the cytotoxic activity of goniothalamin analogues. In addition, we have identified non-natural form of goniothalamin (S)-1 and analogue 5 as the highest and more selective cytotoxic compounds against kidney cancer cell growth (786-0) with IC50 = 4 and 5 nM, respectively, and compound 8 (IC50 = 4 nM) as the more potent against breast cancer cells with resistance phenotype for adryamycin (NCI.ADR).     

Enantioselective effects of optically active alpha-methylbenzyl-s-triazine on the root growth of rice and Echinochloa plants and their herbicidal activity

The chiral requirement on the alpha-methylbenzyl moiety of 2,4-diamino-6-chloro-s-triazine for sufficient inhibition of root growth was similar towards both rice and barnyard millet. With the monoalkylamino series, the most suitable configuration was markedly changed by the substituent on the other amino moiety. However, for the dialkylamino series, the (S)-enantiomer was an active inhibitor. Clear species selectivity between rice and barnyard millet was observed in the series for the (R)-enantiomers, providing high herbicidal activity toward Echinochloa plants and safety toward rice. The enantioselectivity against barnyard millet increased with increasing inhibitory activity of the active enantiomers, following Pfeiffer's rule. R-EtNH (3) controlled the growth of barnyardgrass with leaf-burning (LB) under paddy conditions, and S-EtNH (4) and S-Et2N (20) controlled the growth without LB. The RS-EtNH derivative is an interesting inhibitor controlling the growth of barnyardgrass from the just-germinated stage (by the (R)-enantiomer) to early-middle growth stage (by the (S)-enantiomer).