高橋 孝志

The glycosidation of a polymer-supported glycosyl donor, N-phenyltrifluoroacetimidate, with various glycosyl acceptors is reported. The application of the polymer-supported N-phenyltrifluoroacetimidate is demonstrated in the synthesis of vancomycin derivatives. 2-O-[2-(azidomethyl)benzoyl]glycosyl imidate was attached to a polymer support at the 6-position by a phenylsulfonate linked with a C13 alkyl spacer. Solid-phase glycosidation with a vancomycin aglycon, selective deprotection of the 2-(azidomethyl)benzoyl group, and glycosylation of the resulting 2-hydroxy group with a vancosamine unit were performed. Nucleophilic cleavage from the polymer support with acetate, chloride, azido, and thioacetate ions provided vancomycin derivatives in pure form after simple purification. The semisynthesis of vancomycin was achieved by deprotection of the acetate derivative.

Methotrexate ( MTX) is the anticancer and antirheumatoid drug that is believed to block nucleotide synthesis and cell cycle by inhibiting dihydrofolate reductase activity. We have developed novel affinity matrices, termed SG beads, that are easy to manipulate and are compatible with surface functionalization. Using the matrices, here we present evidence that deoxycytidine kinase ( dCK), an enzyme that acts in the salvage pathway of nucleotide biosynthesis, is another target of MTX. MTX modulates dCK activity differentially depending on substrate concentrations. 1-beta-D-Arabinofuranosylcytosine ( ara-C), a chemotherapy agent often used in combination with MTX, is a nucleoside analog whose incorporation into chromosome requires prior phosphorylation by dCK. We show that, remarkably, MTX enhances incorporation and cytotoxicity of ara-C through regulation of dCK activity in Burkitt's lymphoma cells. Thus, this study provides new insight into the mechanisms underlying MTX actions and demonstrates the usefulness of the SG beads.

Methotrexate ( MTX) is the anticancer and antirheumatoid drug that is believed to block nucleotide synthesis and cell cycle by inhibiting dihydrofolate reductase activity. We have developed novel affinity matrices, termed SG beads, that are easy to manipulate and are compatible with surface functionalization. Using the matrices, here we present evidence that deoxycytidine kinase ( dCK), an enzyme that acts in the salvage pathway of nucleotide biosynthesis, is another target of MTX. MTX modulates dCK activity differentially depending on substrate concentrations. 1-beta-D-Arabinofuranosylcytosine ( ara-C), a chemotherapy agent often used in combination with MTX, is a nucleoside analog whose incorporation into chromosome requires prior phosphorylation by dCK. We show that, remarkably, MTX enhances incorporation and cytotoxicity of ara-C through regulation of dCK activity in Burkitt's lymphoma cells. Thus, this study provides new insight into the mechanisms underlying MTX actions and demonstrates the usefulness of the SG beads.

An efficient solution-phase synthesis of rac-15-deoxy-Delta(12,14)-PGJ(2) (15dPGJ(2)) derivatives that contain variable alpha and omega chains based on a polymer-assisted strategy and their neurite-outgrowth-promoting activity are described. The strategy for the synthesis of PGJ(2) derivatives involves the use of a vinyl iodide bearing cyclopentenone as a key intermediate, which undergoes Suzuki-Miyaura coupling and subsequent Lewis acid catalyzed aldol condensation for incorporation of the omega and alpha chains, respectively. For easy access to the PGJ(2) derivatives, a polymer-supported catalyst and scavengers were adapted for use in these four diverse steps, in which workup and purification can be performed by simple filtration of the solid-supported reagents. By using this methodology, we succeeded in the synthesis of 16 PGJ(2) derivatives with four alkyl boranes and four aldehydes. The neurite-outgrowth promoting activity of the 16 synthetic compounds in PC12 cells revealed that the side-chains play a major role in modulating their biological activity. The carboxylic acid on the a chain improved the biological activity, although it was not absolutely required. Furthermore, a PGJ(2) derivative with a phenyl moiety on the omega chain was found to exhibit an activity comparable to that of natural 15dPGJ(2).

An efficient solution-phase synthesis of rac-15-deoxy-Delta(12,14)-PGJ(2) (15dPGJ(2)) derivatives that contain variable alpha and omega chains based on a polymer-assisted strategy and their neurite-outgrowth-promoting activity are described. The strategy for the synthesis of PGJ(2) derivatives involves the use of a vinyl iodide bearing cyclopentenone as a key intermediate, which undergoes Suzuki-Miyaura coupling and subsequent Lewis acid catalyzed aldol condensation for incorporation of the omega and alpha chains, respectively. For easy access to the PGJ(2) derivatives, a polymer-supported catalyst and scavengers were adapted for use in these four diverse steps, in which workup and purification can be performed by simple filtration of the solid-supported reagents. By using this methodology, we succeeded in the synthesis of 16 PGJ(2) derivatives with four alkyl boranes and four aldehydes. The neurite-outgrowth promoting activity of the 16 synthetic compounds in PC12 cells revealed that the side-chains play a major role in modulating their biological activity. The carboxylic acid on the a chain improved the biological activity, although it was not absolutely required. Furthermore, a PGJ(2) derivative with a phenyl moiety on the omega chain was found to exhibit an activity comparable to that of natural 15dPGJ(2).

Methotrexate ( MTX) is the anticancer and antirheumatoid drug that is believed to block nucleotide synthesis and cell cycle by inhibiting dihydrofolate reductase activity. We have developed novel affinity matrices, termed SG beads, that are easy to manipulate and are compatible with surface functionalization. Using the matrices, here we present evidence that deoxycytidine kinase ( dCK), an enzyme that acts in the salvage pathway of nucleotide biosynthesis, is another target of MTX. MTX modulates dCK activity differentially depending on substrate concentrations. 1-beta-D-Arabinofuranosylcytosine ( ara-C), a chemotherapy agent often used in combination with MTX, is a nucleoside analog whose incorporation into chromosome requires prior phosphorylation by dCK. We show that, remarkably, MTX enhances incorporation and cytotoxicity of ara-C through regulation of dCK activity in Burkitt's lymphoma cells. Thus, this study provides new insight into the mechanisms underlying MTX actions and demonstrates the usefulness of the SG beads.

The synthesis of (+/-)-epigallocatechin gallate by direct cyclization to the cis-3-acyloxy-2-arylbenzopyranee is described. alpha-Acyloxylketones, possessing a 2-hydroxylphenyl group at the beta-position, underwent intramolecular reductive etherification to give cis-3-acyloxy-2-arylbenzopyran due to neighboring group participation of the acyloxyl group at the a-position. Using this method, we accomplished the stereoselective synthesis of (+/-)-epigallocatechin gallate.

Fungal beauveriolide III (BeauIII, 1b), a cyclodepsipeptide inhibiting acyl-CoA:cholesterol acyltransferase (ACAT) and showing antiatherogenic activity in mouse models, consists of L-Phe, L-Ala, D-allo-Ile, and 3-hydroxy-4-methyloctanoic acid (HMA) moieties, but the stereochemistry of the HMA part has not until now been fully defined. To determine it, four HMA stereoisomers were synthesized and labeled with (S)-(+)-2-(anthracene-2,3-dicarboximido)-1-propyl trifluoromethane sulfonate (AP-OTf), a chiral fluorescent reagent. The derivatives were separated by HPLC and compared with the natural HMA derivative, which was thereby identified as (3S,4S)HMA in BeauIII. Furthermore, the four beauveriolide III isomers ((3S,4S)BeauIII (23a), (3R,4R)BeauIII (23b), (3R,4S)BeauIII (23c), and (3S,4R)BeauIII (23d)) were synthesized, and it was shown that all the spectral data for 23a were identical with those for natural 1b. Isomers 23a and 23d showed potent inhibitory activity of lipid droplet accumulation in macrophages, while the other two isomers caused weak inhibition. Thus, the 3S configuration of BeauIII is important for this activity. Furthermore, 23a and 23d showed rather specific inhibition against the ACAT1 isozyme.

A 36-step synthesis was carried out in automated synthesizers to provide a synthetic key intermediate of taxol. A key step involved a microwave-assisted alkylation reaction to construct the ABC ring system from an AC precursor. Subsequent formation of the D ring afforded baccatin III, a well-known precursor of taxol.

Fungal beauveriolide III (BeauIII, 1b), a cyclodepsipeptide inhibiting acyl-CoA:cholesterol acyltransferase (ACAT) and showing antiatherogenic activity in mouse models, consists of L-Phe, L-Ala, D-allo-Ile, and 3-hydroxy-4-methyloctanoic acid (HMA) moieties, but the stereochemistry of the HMA part has not until now been fully defined. To determine it, four HMA stereoisomers were synthesized and labeled with (S)-(+)-2-(anthracene-2,3-dicarboximido)-1-propyl trifluoromethane sulfonate (AP-OTf), a chiral fluorescent reagent. The derivatives were separated by HPLC and compared with the natural HMA derivative, which was thereby identified as (3S,4S)HMA in BeauIII. Furthermore, the four beauveriolide III isomers ((3S,4S)BeauIII (23a), (3R,4R)BeauIII (23b), (3R,4S)BeauIII (23c), and (3S,4R)BeauIII (23d)) were synthesized, and it was shown that all the spectral data for 23a were identical with those for natural 1b. Isomers 23a and 23d showed potent inhibitory activity of lipid droplet accumulation in macrophages, while the other two isomers caused weak inhibition. Thus, the 3S configuration of BeauIII is important for this activity. Furthermore, 23a and 23d showed rather specific inhibition against the ACAT1 isozyme.

A 36-step synthesis was carried out in automated synthesizers to provide a synthetic key intermediate of taxol. A key step involved a microwave-assisted alkylation reaction to construct the ABC ring system from an AC precursor. Subsequent formation of the D ring afforded baccatin III, a well-known precursor of taxol.

A 36-step synthesis was carried out in automated synthesizers to provide a synthetic key intermediate of taxol. A key step involved a microwave-assisted alkylation reaction to construct the ABC ring system from an AC precursor. Subsequent formation of the D ring afforded baccatin III, a well-known precursor of taxol.

We have achieved a total synthesis of telomestatin, and its absolute configuration was determined to be (R). Coupling of cysteine-containing trisoxazole amine and serine-containing trisoxazole carboxylic acid, followed by macrocyclization, provided a 24-membered diamide. The seventh oxazole ring was formed by a Shin's procedure via dehydroamide. Cyclodehydration of a modified (R)-cysteine-(S-Bu-t) moiety using Kelly's method (PPh3(O)-Tf2O) with anisole furnished (R)-telomestatin, whose CD spectrum was in good agreement with that of the natural product.

We have achieved a total synthesis of telomestatin, and its absolute configuration was determined to be (R). Coupling of cysteine-containing trisoxazole amine and serine-containing trisoxazole carboxylic acid, followed by macrocyclization, provided a 24-membered diamide. The seventh oxazole ring was formed by a Shin's procedure via dehydroamide. Cyclodehydration of a modified (R)-cysteine-(S-Bu-t) moiety using Kelly's method (PPh3(O)-Tf2O) with anisole furnished (R)-telomestatin, whose CD spectrum was in good agreement with that of the natural product.

A 24-member combinatorial library based on the structure of aeruginosin 298-A (1a) was synthesized utilizing solid-phase, and their inhibitory activity against trypsin was evaluated. Among the library, we found that D-Hpla-D-Leu-L-Choi-Agma (1h) is 300 times more potent than the parent natural product 1a.

A 24-member combinatorial library based on the structure of aeruginosin 298-A (1a) was synthesized utilizing solid-phase, and their inhibitory activity against trypsin was evaluated. Among the library, we found that D-Hpla-D-Leu-L-Choi-Agma (1h) is 300 times more potent than the parent natural product 1a.

Although the idea of homogeneous electrochemical immunoassay using antibody and an electroactive modified antigen as a probe looks to be very useful for high-throughput drug screening, there have been few reports. One reason for this is the difficulty experienced making an electroactive probe, because the introduction of electroactive compounds to antigens often interferes with the antigen-antibody interaction. To apply a homogeneous electrochemical assay to drug screening, we have designed new probes referring to the information of immobilization on beads which could identify the drug receptor. FK506 (also called Tacrolimus), immunosuppressive agent is modified with ferrocene derivatives as an electron mediator between glucose oxidase and an electrode. at a non-obstructing part. One of the probes still indicated the electrochemical activity as a mediator and had the specific binding capability for FKBP12 (FK506 binding protein). The current decrease in response to the additional FKBP 12, detected with constant voltage amperometry using the probe, was observed within 5 min. Then, free FK506 as a leader drug, rapamycin and cyclosporine A as unknown drugs were used as a model for drug screening. Since the order of response currents at the same concentration of each drug reflected their binding constants, it was shown that binding capacity of an unknown drug candidate could be estimated by comparison of response currents between the leader drug and the unknown drug candidate. Thus, this glucose oxidase assisted homogeneous electrochemical drug-receptor binding assay has been proved to be a useful tool for drug screening. (c) 2005 Elsevier B.V. All rights reserved.

Although the idea of homogeneous electrochemical immunoassay using antibody and an electroactive modified antigen as a probe looks to be very useful for high-throughput drug screening, there have been few reports. One reason for this is the difficulty experienced making an electroactive probe, because the introduction of electroactive compounds to antigens often interferes with the antigen-antibody interaction. To apply a homogeneous electrochemical assay to drug screening, we have designed new probes referring to the information of immobilization on beads which could identify the drug receptor. FK506 (also called Tacrolimus), immunosuppressive agent is modified with ferrocene derivatives as an electron mediator between glucose oxidase and an electrode. at a non-obstructing part. One of the probes still indicated the electrochemical activity as a mediator and had the specific binding capability for FKBP12 (FK506 binding protein). The current decrease in response to the additional FKBP 12, detected with constant voltage amperometry using the probe, was observed within 5 min. Then, free FK506 as a leader drug, rapamycin and cyclosporine A as unknown drugs were used as a model for drug screening. Since the order of response currents at the same concentration of each drug reflected their binding constants, it was shown that binding capacity of an unknown drug candidate could be estimated by comparison of response currents between the leader drug and the unknown drug candidate. Thus, this glucose oxidase assisted homogeneous electrochemical drug-receptor binding assay has been proved to be a useful tool for drug screening. (c) 2005 Elsevier B.V. All rights reserved.

[GRAPHICS] We have achieved a total synthesis of apratoxin A in which thiazoline formation was accomplished from the moCys containing amide 4 using PPh3(0)/Tf2O. Deprotection of the Troc and allyl ester in 17, coupling with tripeptide 3, and deprotection of the allyl ester and the Fmoc, followed by macrolactamization provided apratoxin A (1).

We achieved the total synthesis of the histone deacetylase inhibitor spiruchostatin A, as the prelude to the preparation of a combinatorial library of its analogues. Two key reactions were an asymmetric acetate aldol reaction using a Zr-enolate and macrolactonization Using the Shiina method. (c) 2005 Published by Elsevier Ltd.

[GRAPHICS] We have achieved a total synthesis of apratoxin A in which thiazoline formation was accomplished from the moCys containing amide 4 using PPh3(0)/Tf2O. Deprotection of the Troc and allyl ester in 17, coupling with tripeptide 3, and deprotection of the allyl ester and the Fmoc, followed by macrolactamization provided apratoxin A (1).

We achieved the total synthesis of the histone deacetylase inhibitor spiruchostatin A, as the prelude to the preparation of a combinatorial library of its analogues. Two key reactions were an asymmetric acetate aldol reaction using a Zr-enolate and macrolactonization Using the Shiina method. (c) 2005 Published by Elsevier Ltd.

A unique two-dimensional (2D) long-range structure has been observed in a low-temperature phase X1 for a banana molecule having bromine atom substituted on the central core using synchrotron radiation (SR) x-ray scattering measurements. The X1 phase is formed from the B2 phase with the Sm CA PA structure upon cooling and then shows multiple reflections around the first layer line, which are interpreted as a peculiar frustrated structure with long-range layer modulation order. Furthermore, the observation of a well-defined (100) reflection with a spacing of 171 means that there is the electron density modulation along the layers. By coupling these reflections, a 2D lattice with a=173 , c=53.4 , and β=81.1° is determined where the a axis is parallel to the original layer of the B2 phase. This unique structure with modulation can be interpreted as an undulated layer structure and suggested to be the result from deformation with polarization splay defects periodically occurring along the layer. The angle, β=81.1°, between a and c axes indicates that the position of splay defects in one layer is staggered from that in the neighboring layer. In other words, the splay defect lines run in a direction tilted by roughly 80° with respect to the a axis. © 2006 The American Physical Society.

Synthesis of beauveriolide III (1b), which is an inhibitor of lipid droplet accumulation in macrophages, was achieved by solid-phase assembly of linear depsipeptide using a 2-chlorotrityl linker followed by solutionphase cyclization. On the basis of this strategy, a combinatorial library of beauveriolide analogues was carried out by radio frequency-encoded combinatorial chemistry. After automated purification using preparative reversed-phase HPLC, the library was tested for inhibitory activity of CE synthesis in macrophages to determine structure-activity relationships of beauveriolides. Among them, we found that diphenyl derivative 7{9,1} is 10 times more potent than 1b.

A unique two-dimensional (2D) long-range structure has been observed in a low-temperature phase X-1 for a banana molecule having bromine atom substituted on the central core using synchrotron radiation (SR) x-ray scattering measurements. The X-1 phase is formed from the B-2 phase with the SmCAPA structure upon cooling and then shows multiple reflections around the first layer line, which are interpreted as a peculiar frustrated structure with long-range layer modulation order. Furthermore, the observation of a well-defined (100) reflection with a spacing of 171 angstrom means that there is the electron density modulation along the layers. By coupling these reflections, a 2D lattice with a=173 angstrom, c=53.4 angstrom, and beta=81.1 degrees is determined where the a axis is parallel to the original layer of the B-2 phase. This unique structure with modulation can be interpreted as an undulated layer structure and suggested to be the result from deformation with polarization splay defects periodically occurring along the layer. The angle, beta=81.1 degrees, between a and c axes indicates that the position of splay defects in one layer is staggered from that in the neighboring layer. In other words, the splay defect lines run in a direction tilted by roughly 80 degrees with respect to the a axis.

Methotrexate (MTX) is the anticancer and antirheumatoid drug that is believed to block nucleotide synthesis and cell cycle by inhibiting dihydrofolate reductase activity. We have developed novel affinity matrices, termed SG beads, that are easy to manipulate and are compatible with surface functionalization. Using the matrices, here we present evidence that deoxycytidine kinase (dCK), an enzyme that acts in the salvage pathway of nucleotide biosynthesis, is another target of MTX. MTX modulates dCK activity differentially depending on substrate concentrations. 1-β-D- Arabinofuranosylcytosine (ara-C), a chemotherapy agent often used in combination with MTX, is a nucleoside analog whose incorporation into chromosome requires prior phosphorylation by dCK. We show that, remarkably, MTX enhances incorporation and cytotoxicity of ara-C through regulation of dCK activity in Burkitt's lymphoma cells. Thus, this study provides new insight into the mechanisms underlying MTX actions and demonstrates the usefulness of the SG beads. Copyright © 2006 The American Society for Pharmacology and Experimental Therapeutics.

Three types of latex nanoparticles carrying naltrindole (NTI) derivatives were synthesized as probes for the affinity isolation of their binding proteins including the δ-opioid receptor. The effect of the attachment of NTI to different positions on the linker was investigated. Only latex nanoparticles in which the NTI derivative was linked through the phenol group were useful for isolating the recombinant δ-opioid receptor solubilized from CHO cell membrane. These latex nanoparticles could be a useful tool for investigations of the pharmacological activity of NTI. © 2005 Elsevier Ltd. All rights reserved.

A unique two-dimensional (2D) long-range structure has been observed in a low-temperature phase X1 for a banana molecule having bromine atom substituted on the central core using synchrotron radiation (SR) x-ray scattering measurements. The X1 phase is formed from the B2 phase with the Sm CA PA structure upon cooling and then shows multiple reflections around the first layer line, which are interpreted as a peculiar frustrated structure with long-range layer modulation order. Furthermore, the observation of a well-defined (100) reflection with a spacing of 171 means that there is the electron density modulation along the layers. By coupling these reflections, a 2D lattice with a=173 , c=53.4 , and β=81.1° is determined where the a axis is parallel to the original layer of the B2 phase. This unique structure with modulation can be interpreted as an undulated layer structure and suggested to be the result from deformation with polarization splay defects periodically occurring along the layer. The angle, β=81.1°, between a and c axes indicates that the position of splay defects in one layer is staggered from that in the neighboring layer. In other words, the splay defect lines run in a direction tilted by roughly 80° with respect to the a axis. © 2006 The American Physical Society.

Three types of latex nanoparticles carrying naltrindole (NTI) derivatives were synthesized as probes for the affinity isolation of their binding proteins including the delta-opioid receptor. The effect of the attachment of NTI to different positions on the linker was investigated. Only latex nanoparticles in which the NTI derivative was linked through the phenol group were useful for isolating the recombinant delta-opioid receptor solubilized from CHO cell membrane. These latex nanoparticles could be a useful tool for investigations of the pharmacological activity of NTI. (c) 2005 Elsevier Ltd. All rights reserved.

An effective approach for the synthesis of oligo-α(2,8) sialosides using N-Troc sialyl donors is described. Glycosylation of N-Troc sialoside with N-Troc sialyl N-phenyltrifluoroimidate and phosphites smoothly proceeded to provide α(2,8) disialosides in good yield and selectivity. © 2006 The Japan Institute of Heterocyclic Chemistry All rights reserved.