Substitution at the 8-position of 3'-deoxy-cyclic ADP-carbocyclic-ribose, a highly potent Ca2+-mobilizing agent, provides partial agonists

We previously showed that 3'-deoxy-cyclic ADP-carbocyclic-ribose (3'-deoxy-cADPcR, 4) is a stable and highly potent analogue of cyclic ADP-ribose (cADPR, 1), a Ca(2+)-mobilizing second messenger. From these results, we designed and synthesized other 3'-modified analogues of cADPcR having a substituent at the 8-position and found that this modification at the 8-position made them partial agonists. Among these compounds, 8-NH(2)-3'-deoxy-cADPcR (10) was identified as a potent partial agonist with an EC(50) value of 17 nM.     

1,5-Benzodiazepines as CCK-B antagonists. Effect of halogen substitution at the benzo-fused ring on potency and selectivity

Some 1,5-benzodiazepines substituted with halogen atoms in the benzo-fused ring were synthesized and evaluated as CCK antagonists at both CCK-A and CCK-B receptors. Details of the binding of these agents to both receptors are reported and discussed briefly.     

Nucleosides and Nucleotides. 192. Toward the Total Synthesis of Cyclic ADP-Carbocyclic-Ribose. Formation of the Intramolecular Pyrophosphate Linkage by a Conformation-Restriction Strategy in a Syn-form Using a Halogen Substitution at the 8-Position of the Adenine Ring

Abstract

The synthesis of cyclic ADP-carbocyclic-ribose (2), as a stable mimic for cyclic ADP-ribose, was investigated. Construction of the 18-membered backbone structure was successfully achieved by condensation of the two phosphate groups of 19, possibly due to restriction of the conformation of the substrate in a syn-form using an 8-chloro substituent at the adenine moiety. SN2 reactions between an optically active carbocyclic unit 8, which was constructed by a previously developed method, and 8-bromo-N ⁶-trichloroacetyl-2′,3′-O-isopropylideneadenosine 9c gave N-1-carbocyclic derivative, which was deprotected to give 5′,5′-diol derivatives 18. When 18 was treated with POCl₃ in PO(OEt)₃, the bromo group at the 8-position was replaced to give N-1-carbocyclic-8-chloroadenosine 5′,5′-diphosphate derivative 19 in 43% yield. Treatment of 19 with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride gave the desired intramolecular condensation product 20 in 10% yield. This is the first chemical construction of the 18-membered backbone structure containing an intramolecular pyrophosphate linkage of a cADPR-related compound with an adenine base.     

Nucleophilic substitution at the anomeric position of 1,2-O-isopropylidenefuranose derivatives. A novel stereoselective synthesis of cyclic phosphates analogous to cAMP

1,2-O-Isopropylidenefuranose derivatives were treated with various nucleophiles in the presence of either BF(3).OEt(2) or trimethylsilyl trifluoromethanesulfonate (TMSOTf) leading to substitution products in a regio- and stereoselective manner. In particular, nucleophilic substitution of 1,2-O-isopropylidenefuranose derivatives when treated with allyltrimethylsilane was controlled by steric and electronic factors (similar to Woerpel's stereoelectronic model). On the other hand, when 1,2-O-isopropylidenefuranose derivatives were treated with trimethylsilane, in the presence of bis-O-trimethylsilyl-5-iodouracil or bis-O-trimethylsilyl-thymidine, substitution products were generated in high regio- and stereoselectivities via an unusual nucleophilic substitution with opening of the furanose ring. Based on these results, a stereoselective method for the synthesis of neutral cyclic phosphates analogous to cAMP was developed.     

An efficient synthesis of nucleotides via the phosphoramidite method using a triflic acid salt of an imidazole-related compound as a promoter.

N-Phenylimidazolium triflate and N-methylbenzimidazolium triflate, new imidazole-related compound/triflic acid-complex type of promoters in the phosphoramidite method, has been developed. These reagents are, particularly, useful for internucleotide-bond formation with lowly reactive reactants and have allowed an efficient, high-yield synthesis of oligodeoxyribonucleotides both in a solution phase and on a solid supports.     

Studies on intramolecular hydrogen bonding between the pyridine nitrogen and the amide hydrogen of the peptide: synthesis and conformational analysis of tripeptides containing novel amino acids with a pyridine ring.

For the first time tripeptides, Z-AA(1)-Xaa-AA(3)-OMe (AA(1) and AA(3) = Gly or Aib, Xaa = 2Pmg and 2Pyg) were prepared containing alpha-methyl-alpha-(2-pyridyl)glycine (2Pmg) and alpha-(2-pyridyl)glycine (2Pyg) by solid-phase Ugi reaction. These results clearly indicate that for the preparation of tripeptides containing an amino acid with a pyridine ring, the solid-phase Ugi reaction is very useful.NMR analysis clarified that 2Pmg-containing tripeptides adopt a unique conformation with an intramolecular hydrogen bond between 2Pmg-NH and the pyridine nitrogen. However, in the case of Z-Gly-2Pyg-Gly-OMe, the intramolecular hydrogen bonding between 2Pyg-NH and the pyridine nitrogen was not observed, whereas Z-Aib-2Pyg-Aib-OMe adopts a unique conformation with an intramolecular hydrogen bond between 2Pyg-NH and a pyridine nitrogen. Conformational analysis of the tripeptides, Z-AA(1)-Xaa-AA(3)-OMe (AA(1), AA(3) = Gly or Aib, Xaa = alpha,alpha-di(2-pyridyl)glycine (2Dpy), alpha-phenyl-alpha-(2-pyridyl)glycine (2Ppg), 2Pmg and 2Pyg), clarified that when an alpha,alpha-disubstituted glycine with a 2-pyridyl group at an alpha-carbon atom is introduced into any peptide, an intramolecular hydrogen bond between a pyridine nitrogen and an amide proton is formed and conformational mobility of the peptide backbone is restricted.     

Determination of the cellular location of cyclic nucleotide binding sites using 8-azidoadenosine-3', 5'-monophosphate, a photoaffinity probe.

A photoaffinity analog of cyclic AMP, 8-azidoadenosine-3′,5′-monophosphate (8-N₃cAMP), and a linear gradient sodium dodecyl sulfate-polyacrylamide gel system have been used to photolabel and separate possible cyclic AMP binding sites in whole cells of the sarcoma 37 line. At least four sites within the whole sarcoma 37 cell bind [³²P]8-N₃cAMP such that they are saturated at 1.0 μm concentration. These four binding moieties appear to have measurably different affinities for 8-N₃cAMP and the number of total sites labeled per cell differs with each binding moiety. Cell fractionation allows separation of some of the photolabeled sites and gives an indication as to the geographical location of these binding sites within the whole cell. Enrichment by cell fractionation allows additional photolabeled sites to be observed.     

Combined pituitary stimulation test using LHRH, TRH and insulin in subjects with short stature: evaluation of the response of pituitary tropins at 8 a.m. and at 8 p.m]

The effect of a combined test (insulin, TRH, LHRH) on plasma levels of GH, LH, FSH, PRL and Cortisol was studied in 5 subjects with short stature. Two test were performed at 8 a.m. and at 8 p.m. In all subjects the GH, FSH, LH, TSH, PRL and Cortisol levels showed no relevant response during the two tests.     

Experiments towards the synthesis of the ergot alkaloids and related structures. Part 8. The total synthesis of 4-methyl-2,3,4,4a,5,6-hexahydrobenzo[f]quinoline-2-carbonitrile hydrochloride hemihydrate,an immediate precursor of the despyrrole analogues of lysergic acid and its amides

Exposure of the N-methoxycarbonyl-bicyclic-keto-acid 5 (improved preparation) to the Barnick beta-keto-acid synthesis yielded an aqueous solution of the sodium salts of the beta-keto-acids 26 and 27 which on heating at 60-65 degrees C furnished the N-methoxycarbonyl-tricyclic-ketone 9 (55%) plus the hydroxy-ketone 28 which on acid treatment raised the yield of 9 to 68%. Reduction (NaBH4) of 9 yielded the alcohol 32 (94%) which was treated with thionyl chloride followed by copper (I) cyanide and sodium iodide in acetonitrile to give the tricyclic-N-methoxycarbonyl nitrile 35 whose relative configuration was obtained by X-ray analysis. Attempts to remove the N-methoxycarbonyl group from 35 were unsuccessful. Conversion of the alcohol 32 to its methoxypropyl ether 41 followed by reaction with ethereal MeLi-LiBr yielded the amino-alcohol 39 (75%) converted to the N-formyl-tricyclic alcohol 42 with formic-acetic anhydride (70%). The alcohol 42 was then converted into the N-formyl nitrile 44 via the chloride 43 as employed in the earlier synthesis of the nitrile 35. Removal of the N-formyl group from the nitrile 44 was achieved by refluxing methanolic hydrochloric acid to give the required amino-nitrile hydrochloride 46 (91%) whose structure was confirmed by X-ray analysis. Reaction of the free base with methyl iodide in ethyl acetate in the presence of calcium carbonate furnished the N-methyl base 48 isolated as its hydrochloride, hemihydrate 49 (59%). The overall yield of 49 via this eleven-step synthesis was 3.4%.     

A new strategy for the preparation of peptide-targeted technetium and rhenium radiopharmaceuticals. The automated solid-phase synthesis, characterization, labeling, and screening of a peptide-ligand library targeted at the formyl peptide receptor

A new solid-phase synthetic methodology was developed that enables libraries of peptide-based Tc(I)/Re(I) radiopharmaceuticals to be prepared using a conventional automated peptide synthesizer. Through the use of a tridentate ligand derived from N-alpha-Fmoc-l-lysine, which we refer to as a single amino acid chelate (SAAC), a series of 12 novel bioconjugates [R-NH(CO)ZLF(SAAC)G, R = ethyl, isopropyl, n-propyl, tert-butyl, n-butyl, benzyl; Z = Met, Nle] that are designed to target the formyl peptide receptor (FPR) were prepared. Construction of the library was carried out in a multiwell format on an Advanced ChemTech 348 peptide synthesizer where multi-milligram quantities of each peptide were isolated in high purity without HPLC purification. After characterization, the library components were screened for their affinity for the FPR receptor using flow cytometry where the K(d) values were found to be in the low micromolar range (0.5-3.0 microM). Compound 5j was subsequently labeled with (99m)Tc(I) and the product isolated in high radiochemical yield using a simple Sep-Pak purification procedure. The retention time of the labeled compound matched that of the fully characterized Re-analogue which was prepared through the use of the same solid-phase synthesis methodology that was used to construct the library. The work reported here is a rare example of a method by which libraries of peptide-ligand conjugates and their rhenium complexes can be prepared.