Development of diversified methods for chemical modification of the 5,6-double bond of uracil derivatives depending on active methylene compounds.

The reaction of 5-halogenouracil and uridine derivatives 1 and 7 with active methylene compounds under basic conditions produced diverse and selective C-C bond formation products by virtue of the nature of the carbanions. Three different types of reactions such as the regioselective C-C bond formation at the 5- and 6-positions of uracil and uridine derivatives (products 2, 5, 8, 17, 20 and 21), and the formation of fused heterocycle derivatives 2,4-diazabicyclo[4.1.0]heptane (15) and 2,4-diazabicyclo-[4.1.0]nonane (16) via dual C-C bond formations at both the 5- and 6-positions were due to the different active methylene compounds used as reagents.

DJ-1-binding compounds prevent oxidative stress-induced cell death and movement defect in Parkinson's disease model rats.

Parkinson's disease (PD) is caused by neuronal cell death. Although a precursor of dopamine and inhibitors of dopamine degradation have been used for PD therapy, cell death progresses during treatment. DJ-1, a causative gene product of a familial form of PD, PARK7, plays roles in transcriptional regulation and anti-oxidative stress, and loss of its function is thought to result in the onset of PD. Superfluous oxidation of cysteine at amino acid 106 (C106) of DJ-1 renders DJ-1 inactive, and such oxidized DJ-1 has been observed in patients with the sporadic form of PD. In this study, we isolated compounds that bind to the region at C106 by a virtual screening. These compounds prevented oxidative stress-induced death of SH-SY5Y cells, embryonic stem cell-derived dopaminergic cells and primary neuronal cells of the ventral mesencephalon, but not that of DJ-1-knockdown cells of SH-SY5Y and NIH3T3 cells, indicating that the effect of the compounds is specific to DJ-1. These compounds inhibited production of reactive oxygen species and restored activities of mitochondrial complex I and tyrosine hydroxylase that had been compromised by oxidative stress. These compounds prevented dopaminergic cell death in the substantia nigra and restored movement abnormality in 6-hydroxyldopamine-injected PD model rats. One mechanism of action of these compounds is prevention of superfluous oxidation of DJ-1, and the compounds passed through the blood-brain barrier in vitro. Taken together, the results indicate that these compounds should become fundamental drugs for PD therapy.

Pd/C-catalyzed deoxygenation of phenol derivatives using Mg metal and MeOH in the presence of NH(4)OAc.

A Pd/C-catalyzed deoxygenation method of phenolic hydroxyl groups via aryl triflates or mesylates using Mg metal in MeOH at room temperature was developed. The addition of NH4OAc dramatically affects the reactivity and reaction rate. This method is particularly attractive to provide an environmentally benign and widely applicable removal method of phenolic alcohols under quite mild reaction conditions.

Facile and efficient postsynthetic tritium labeling method catalyzed by Pd/C in HTO.

[reaction: see text] We have developed a facile and efficient tritium labeling method using a Pd/C-HTO-H2 system. This method can provide multitritium-labeled compounds in highly diluted HTO under T2 gas-free conditions, and is environmentally benign since purification by silica gel column chromatography is not necessary, which causes a large quantity of radioactive waste such as silica gel and eluent.

Reductive and catalytic monoalkylation of primary amines using nitriles as an alkylating reagent.

[reaction: see text] A selective and catalytic mono-N-alkylation method of both aromatic and aliphatic amines using nitriles as an alkylating agent with Pd/C or Rh/C as a catalyst is described. This method is particularly attractive to provide an environmentally benign and applicable alkylation method of amines without using toxic and corrosive alkylating agents such as alkyl halides and carbonyl compounds.

Complete replacement of H2 by D2 via Pd/C-catalyzed H/D exchange reaction.

[reaction: see text] A general and in situ D2 gas generation method using 10% Pd/C-catalyzed H2-D2 exchange reaction in a H2-D2O system has been developed. H2 gas sealed in a reaction flask was efficiently converted into nearly pure D2 gas, which can be used for the reductive deuteration of substrates possessing reducible functionalities within the molecule.

Efficient C-H/C-D exchange reaction on the alkyl side chain of aromatic compounds using heterogeneous Pd/C in D2O.

[reaction: see text] An efficient and extensive deuterium incorporation using heterogeneous Pd/C-D(2)O-H(2) system into many different types of unactivated C-H bond positions was developed. The present method provides a deuterium gas-free, totally catalytic, and post-synthetic deuterium labeling method in D(2)O media.

Synthesis and evaluation of 2-substituted 8-hydroxyadenines as potent interferon inducers with improved oral bioavailabilities.

In order to create novel compounds which possess potent interferon (IFN) inducing activities with excellent oral bioavailabilities, a series of 8-hydroxyadenines, which have various alkoxy or alkylthio moieties at the adenine C(2)-position, were synthesized and evaluated. The introduction of hydrophobic groups was not considered to be effective for potentiating the IFN-inducing activity, but several compounds having hydrophilic groups were effective. Among the compounds tested, compound 13f induced IFN from the dosage of 0.03 mg/kg, which was approximately 100-fold more potent than that of Imiquimod, and showed an excellent oral bioavailability (F=40%) which was 10-fold improved over 5, a lead compound (F=4%).

Modification of the sugar moiety in uridine via 2',3'-epoxyuridine derivatives.

The reaction of 5'-O-mesyl-2',3'-epoxyuridine or 5'-Oiodo-2',3'-epoxyuridine with a nucleophile gave 2'- and 3'-adducts as a mixture while the use of 4',5'-didehydro-5'-deoxy-2',3'-epoxyuridine as a substrate gave 4',5'-didehydro-5'-deoxy 3'-substituted derivatives as a main product. The slow N3 rearrangement reaction of the 3'-N3 adduct of 4',5'-didehydro-5'-deoxy-2',3'-epoxyuridine to the 5'-N3 adduct was observed in DMSO-d6.

Synthesis and structure-activity relationships of 2-amino-8-hydroxyadenines as orally active interferon inducing agents.

Recently, we have reported the 8-hydroxyadenine derivatives (2-4) as a novel class of interferon (IFN) inducing agents. In the present study, a series of 8-hydroxyadenines, which possess various amino moieties at the adenine C(2)-position, were synthesized and evaluated for their ability to induce endogenous IFN in comparison to the known active agent, Imiquimod. Among the compounds prepared, compound 9o possessing a 2-methoxyethylamino group at C(2)-position of adenine was found to exhibit potent IFN inducing activity in vivo. Compound 9o induced IFN from the dosage of 0.1 mg/kg, which was 30-fold potent than that of Imiquimod, and showed a good oral bioavailability (F=81%).

Synthesis of pyrimidine derivatives possessing an antioxidative property and their inhibitory effects on picryl chloride-induced contact hypersensitivity reaction.

We conducted a preliminary structure-activity relationship (SAR) study of some barbituric acid and uracil derivatives against the picryl chloride-induced contact hypersensitivity reaction. The introduction of an antioxidative moiety to the side chain of the C(6)-position of uracil was effective against this model. The introduction of dimethoxyphenol (8b) or dimethylphenol (8c) instead of di-t-butylphenol (8a) as an antioxidative moiety gave diminished activities, so, the reactive oxygen would contribute to the inflammation of this model, and an antioxidative activity was required for exhibiting the inhibitory activity. The inhibitory activity was significantly affected by the substituent at the N(1)-phenyl moiety.

Palladium-catalyzed H-D exchange into nucleic acids in deuterium oxide.

We have developed an efficient and extensive deuterium incorporation method using a heterogeneous Pd/C-D2O-H2 system into the base moiety of nucleic acids. The results presented here provide a deuterium gas-free, totally catalytic and post-synthetic deuterium labeling method in D2O media.

Efficient synthesis of 2,9-disubstituted 8-hydroxyadenine derivatives.

An efficient and general method for the synthesis of 2,9-disubstituted 8-hydroxyadenines, which are expected to have various biological activities, was realized. 5-Amino-4-cyano-2-hydroxyimidazoles(1) were prepared from aminomalononitrile and isocyanates as key intermediates. The condensation of 1a with amidines, imidates, guanidine, urea and thioureas afforded 8-hydroxyadenines (2-6) possessing various substituents at the 2-position. Furthermore, selective alkylation of 2-amino- and 2-hydroxyadenines (4 and 6) successively proceeded to give the corresponding 2-alkylamino- and 2-alkoxyadenines (5 and 7), respectively. 2-Alkylthioadenines (15) were prepared by an analogous reaction of 1a with benzoyl isothiocyanate and subsequent S-alkylation. The imidazoles 1 are most useful intermediates for the synthesis of 8-hydroxyadenine derivatives.

Synthesis and structure-activity relationships of 2-substituted-8-hydroxyadenine derivatives as orally available interferon inducers without emetic side effects.

Recently we reported the adenine derivatives (2-4) as new interferon (IFN) inducers. In the present study, we conducted a detailed structure and activity relationship study of 4 and its related derivatives on IFN inducing activity. From this study, we found that compound 4 exhibited the most potent IFN inducing activity in vitro with a minimum effective concentration of 0.01 microM, and 4 also showed strong IFN-inducing activity at doses of more than 0.3mg/kg by oral administration in mice. This potency was 10-fold stronger than that of Imiquimod. Moreover, 4 did not cause emesis in ferrets even at doses as high as 10mg/kg, whereas, 80% of animals were emetic when orally administered with the same dose of Imiquimod. These results indicate that compound 4 is superior to Imiquimod with respect to efficacy and safety.

Synthesis and biological evaluation of 2,8-disubstituted 9-benzyladenines: discovery of 8-mercaptoadenines as potent interferon-inducers.

Recently, we have identified 9-benzyl-8-hydroxyadenines bearing an appropriate substituent (a butoxy, propylthio or butylamino group) at the 2-position as potent interferon (IFN)-inducers. Herein we report the design, synthesis, and IFN-inducing activity of 8-substituted 9-benzyladenines possessing such an appropriate substituent at the 2-position. Introduction of the appropriate substituent into the 2-position of the adenine nucleus gave rise to expression of the activity even in 9-benzyladenines bearing no hydroxyl group at the 8-position. An amino group at the 6-position and a hydroxyl or thiol group carrying an acidic proton at the 8-position are required to express excellent IFN-inducing activity. 9-Benzyl-2-butoxy-8-mercaptoadenine (9) indicated the most potent activity with MEC of 0.001 microM.

Synthesis of 6-substituted 9-benzyl-8-hydroxypurines with potential interferon-inducing activity.

Various 6-substituted 9-benzyl-8-hydroxypurines were synthesized in order to investigate the structure-activity relationship at the 6-position of 9-benzyl-8-hydroxyadenine (1), which is a lead compound for the screening of interferon (IFN)-inducing activity. 6-Unsubstituted, mercapto-, methylthio- and hydroxy-9-benzyl-8-hydroxypurines (2-5) were prepared from 5-amino-1-benzyl-4-cyano-2-hydroxyimidazole (9). Synthesis of a 6-methoxy analog (6) was conducted from 5-amino-4-benzylamino-6-chloropyrimidine (13). 6-Alkylamino and acylaminopurines (7 and 8) were also prepared by alkylation and acylation of 1, respectively. Since these compounds (2-8) indicated no activity, it was found that a free amino group of 1 is required for the expression of IFN-inducing activity.

A remarkable solvent effect toward the Pd/C-catalyzed cleavage of silyl ethers.

Selective hydrogenation conditions of olefin, benzyl ether and acetylene functionalities in the presence of TBDMS or TES ether have been developed.

Pd/C-catalyzed chemoselective hydrogenation in the presence of a phenolic MPM protective group using pyridine as a catalyst poison.

Employment of a Pd/C-pyridine combination as a catalyst is a very useful method for the selective removal (hydrogenolysis) of phenolic O-benzyl, N-Cbz and benzyl ester protective groups and for the selective hydrogenation of nitro and olefin functions of phenol derivatives protected with the MPM group. These discriminatory results are apparently attributable to the effect of pyridine. The MPM group could be extensively applied to chemoselective hydrogenation as a protective group for phenolic hydroxyl functions.

Discovery of 8-hydroxyadenines as a novel type of interferon inducer.

9-Benzyl-8-hydroxyadenine (6) was found to possess interferon-inducing activity in vitro as a lead compound. Although replacement of the 9-benzyl group of 6 did not improve the activity, the introduction of a substituent such as alkyl, alkylthio, alkylamino, and alkoxy groups into the 2-position of the adenine ring resulted in a remarkable increase in the activity. The 2-alkylthio (30-32), 2-butylamino (41), and 2-butoxy (47) analogues indicated the highest activities by oral administration to mice.

A novel C-C bond formation at the 5-position of uridine derivatives.

We have developed a novel C-C bond formation at the 5-position of uridine derivatives using intramolecular base-catalyzed Baylis-Hillman type reaction.