Docking study and biological evaluation of pyrrolidine-based iminosugars as pharmacological chaperones for Gaucher disease.

We report on the synthesis and biological evaluation of a series of α-1-C-alkylated 1,4-dideoxy-1,4-imino-d-arabinitol (DAB) derivatives as pharmacological chaperones for Gaucher disease. The parent compound, DAB, did not show inhibition of human ß-glucocerebrosidase but showed moderate intestinal α-glucosidase inhibition; in contrast, extension of α-1-C-alkyl chain length gave a series of highly potent and selective inhibitors of the ß-glucocerebrosidase. Our design of α-1-C-tridecyl-DAB (5j) produced a potent inhibitor of the ß-glucocerebrosidase, with IC50 value of 0.77 µM. A molecular docking study revealed that the α-1-C-tridecyl group has a favorable interaction with the hydrophobic pocket and the sugar analogue part (DAB) interacted with essential hydrogen bonds formed to Asp127, Glu235 and Glu340. Furthermore, α-1-C-tridecyl-DAB (5j) displayed enhancement of activity at an effective concentration 10-times lower than isofagomine. α-1-C-Tridecyl-DAB therefore provides the first example of a pyrrolidine iminosugar as a new class of promising pharmacological chaperones with the potential for treatment of Gaucher disease.

A mouse model of peripheral postischemic dysesthesia: involvement of reperfusion-induced oxidative stress and TRPA1 channel.

Peripheral postischemic dysesthesia was examined behaviorally in mice and we investigated the underlying molecular mechanism with a focus on oxidative stress. Hind-paw ischemia was induced by tight compression of the ankle with a rubber band, and reperfusion was achieved by cutting the rubber tourniquet. We found that reperfusion after ischemia markedly provoked licking of the reperfused hind paw, which was significantly inhibited by systemic administration of the antioxidant N-acetyl-l-cysteine and the transient receptor potential (TRP) A1 channel blocker HC-030031 [2-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purin-7-yl)-N-(4-isopropylphenyl)acetamide]. Postischemic licking was also significantly inhibited by an intraplantar injection of another antioxidant, phenyl-N-tert-butylnitrone. The TRPV1 channel blocker BCTC [N-(4-tert-butylphenyl)-4-(3-chloropyridin-2-yl)tetrahydropyrazine-1(2H)-carboxamide] did not inhibit postischemic licking. An intraplantar injection of hydrogen peroxide elicited hind-paw licking, which was inhibited by N-acetyl-l-cysteine, phenyl-N-tert-butylnitrone, and HC-030031. Postischemic licking was not affected by chemical depletion of sensory C-fibers, but it was inhibited by morphine, which has been shown to inhibit the C- and Aδ-fiber-evoked responses of dorsal horn neurons. Interestingly, postischemic licking was not inhibited by gabapentin and pregabalin, which have been shown to inhibit the C-fiber- but not Aδ-fiber-evoked response. The present results suggest that ischemia-reperfusion induces oxidative stress, which activates TRPA1 channels to provoke postischemic licking. It has been suggested that this behavior is mediated by myelinated (probably Aδ-type) afferent fibers. Oxidative stress and TRPA1 channels may be potential targets to treat peripheral ischemia-associated dysesthesia.

Synthesis and biological evaluation of α-1-C-4'-arylbutyl-L-arabinoiminofuranoses, a new class of α-glucosidase inhibitors.

A series of α-1-C-4'-arylbutyl-L-arabinoiminofuranoses 3 with functional groups attached to the phenyl ring, which are potential α-glycosidase inhibitors, was designed and synthesized by using a Negishi cross-coupling reaction as the key reaction. Arylbutyl derivatives 3a-e showed potent inhibitory activities against intestinal maltase. Among them, difluorophenylbutyl derivative 3e showed good inhibition activities against intestinal isomaltase and sucrase as compared to those of 1 and commercial drugs.

Asymmetric synthesis of 2,5-disubstituted 3-hydroxypyrrolidines based on stereodivergent intramolecular iridium-catalyzed allylic aminations.

Intramolecular iridium-catalyzed allylic aminations of homochiral (E)-6-N-nosylaminohept-2-en-1-yl methyl carbonates were investigated. The relative position of the 2,5-substituents of the resulting pyrrolidines was found to be controlled by using both enantiomers (4 and 5) of the appropriate chiral ligand, demonstrating a simple and highly stereodivergent synthetic protocol. Selected trans- and cis-2,5-disubstituted 3-hydroxypyrrolidines (2a and 18a) were converted to (+)-bulgecinine (6) and (+)-preussin (7), respectively.

Gabapentin inhibits bortezomib-induced mechanical allodynia through supraspinal action in mice.

Bortezomib, an inhibitor of proteasome holoenzyme, is used to treat relapsed and refractory multiple myeloma. Peripheral neuropathy is a treatment-limiting adverse effect of bortezomib and is very difficult to control. In this study, we examined the efficacy of gabapentin in inhibiting bortezomib-induced peripheral neuropathy. Single intravenous injections of bortezomib (0.03 - 0.3 mg/kg) dose-dependently induced mechanical allodynia with a peak effect 12 days after injection. Bortezomib (0.3 mg/kg) also caused mechanical hyperalgesia, but neither affected thermal nociception nor induced cold allodynia. Bortezomib increased the response of the saphenous nerve to weak punctate stimulation but not response to cool stimulation of the skin. When administered 12 days after bortezomib injection, oral and intracisternal gabapentin markedly inhibited mechanical allodynia. Intrathecal, but not intraplantar, gabapentin had a tendency to reduce mechanical allodynia. The antiallodynic activity of orally administered gabapentin was suppressed by noradrenaline, but not serotonin, depletion in the spinal cord. Bortezomib did not affect the expression levels of the calcium channel α2δ-1 subunit, a high-affinity binding site of gabapentin, in the plantar skin, spinal cord, medulla oblongata, and pons. These results suggest that gabapentin inhibits bortezomib-induced mechanical allodynia, most likely through the activation of the descending noradrenergic system.

Achieving a cure for anastomotic leakage following laparoscopic low anterior resection for rectal cancer using an endoscopic closure device, a MANTIS clip.

Anastomotic leakage (AL) following low anterior resection (LAR) for rectal cancer is a major complication. While most reports focus on the closure of AL using over-the-scope clip (OTSC), few reports are available on the use of through-the-scope clip (TTSC). This is because TTSC is not typically designed for full-thickness closure, unlike OTSC. However, a MANTIS clip, categorized as TTSC, is indicated for full-thickness closure. A 73-year-old man diagnosed with AL 7 days postoperatively following laparoscopic LAR underwent laparoscopic drainage and ileostomy the next day. Although the drainage led to the shrinkage of the fistula, it persisted even after 2 months. Consequently, the fistula orifice was closed using a MANTIS clip under colonoscopy and radiography. Two days later, the patient was discharged. The drain was withdrawn cautiously to prevent residual fistula and removed completely on day 29. This report highlights our experience in using a MANTIS clip for AL following LAR.

A facile synthesis of fully protected meso-diaminopimelic acid (DAP) and its application to the preparation of lipophilic N-acyl iE-DAP.

Synthesis of beneficial protected meso-DAP 9 by cross metathesis of the Garner aldehyde-derived vinyl glycine 1b with protected allyl glycine 2 in the presence of Grubbs second-generation catalyst was performed. Preparation of lipophilic N-acyl iE-DAP as potent agonists of NOD 1-mediated immune response from 9 is described.

Recent advances in cyclonucleosides: C-cyclonucleosides and spore photoproducts in damaged DNA.

Cyclonucleosides which are fixed in a specific conformation around the glycosyl bond by a carbon and heteroatom chain constitute a unique category of nucleoside derivatives. Because they are structural analogs, cyclonucleosides and oligodeoxynucleotides containing them would be useful tools for investigating the biological functions and conformations of DNA, RNA as well as their steric interactions with proteins. C-Cyclonucleosides bridged by a carbon chain between the base and sugar moieties are the most attractive from the synthetic points of view as well as for use as biological tools. In this review, recent progress of the synthesis of C-cyclonucleosides is surveyed. Among the C-cyclonucleosides, 5',8-C-cyclodeoxyadenosine is one of the well-known derivatives of which the first practical synthesis was reported over 30 years ago. Recently, 5',8-C-cyclodeoxyadenosine has attracted considerable interest as a biomarker, since its formation in oxidatively-damaged DNA is considered to be related to various diseases and aging. Another important analogue of cyclonucleosides is a unique thymidine phosphate dimer, a so-called spore photoproduct, which has been found in photo-damaged DNA. Recent advances in the synthesis, mechanism-studies, and stereochemical preference of repairing enzymes related to 5',8-C-cyclodeoxyadenosine and spore photoproducts are also reviewed.

Synthesis of 5-thiodidehydropyranylcytosine derivatives as potential anti-HIV agents.

As a part of our ongoing efforts to identify new anti-HIV agents, a 5'-thiopyrano-nucleoside derivative 4, designed based on 4'-thioD4C 1 and cyclohexenylnucleoside 3, was synthesized. The dihydrothiopyran skeleton of 4 was constructed by the ring closing metathesis of 21 which was synthesized from but-2-yne-1,4-diol. After converting the protecting group from MOM to TBS followed by oxidation, a Pummerer-type thioglycosylation reaction of 24 with persilylated uracil gave the desired 5-thiodihydrothiopyranyluracils 25 and 26 as a mixture of anomers. The conversion of 25 to a cytosine derivative and subsequent deprotection gave a 5-thiodidehydropyranosylcytosine derivative 4 in good yield. The anti-HIV activity of 4 was also evaluated.

The synthesis and biological evaluation of 1-C-alkyl-L-arabinoiminofuranoses, a novel class of α-glucosidase inhibitors.

The asymmetric synthesis of 1-C-alkyl-l-arabinoiminofuranoses 1 was achieved by asymmetric allylic alkylation (AAA), ring closing metathesis (RCM), and Negishi cross coupling as key reactions. Some of the prepared compounds showed potent inhibitory activities towards intestinal maltase, with IC(50) values comparable to those of commercial drugs such as acarbose, voglibose, and miglitol, which are used in the treatment of type 2 diabetes. Among them, the inhibitory activity (IC(50)=0.032µM) towards intestinal sucrase of 1c was quite strong compared to the above commercial drugs.

Docking and SAR studies of D- and L-isofagomine isomers as human ß-glucocerebrosidase inhibitors.

We report the structure-activity relationship of a series of D-, and L-isofagomine and fagomine isomers as glycosidase inhibitors. Our study revealed that a positive charge at the anomeric position of d-isofagomines enhanced the potency toward ß-glycosidases, while the epimerization at the C3 OH group drastically reduced their inhibitory potency by over three orders of magnitude. Furthermore, d-3,4-di-epi-isofagomine abolished their inhibition activities against all enzymes. L-Isofagomine was also a fairly potent inhibitor of human ß-glucocerebrosidase, with an IC50 value of 8.7 µM. A molecular docking study revealed that the positions and orientations of the piperidine ring of D-3-epi-isofagomine in the binding site was similar to that of D-isofagomine, while D-3-epi-isofagomine missed the hydrogen bond interactions between Asp127 and the 3-OH group and between Trp179 and the 3-OH group. Furthermore, the top 10 docking models ranked by IFDscore suggested that D-3,4-di-epi-isofagomine can not bind to ß-glucocerebrosidase at a stable interaction mode. These results provide an insight into the structural requirements of isofagomine isomers for developing a new type of pharmacological chaperone for Gaucher disease.

Design and synthesis of isonucleosides constructed on a 2-oxa-6-thiabicyclo[3.2.0]heptane scaffold.

A novel method for the design and synthesis of an isonucleoside containing a 2-oxa-6-thiobicyclo[3.2.0]heptane skeleton is described. 2,2-Dimethyl-1,3-dioxan-5-one 13 was converted into a dioxabicyclohexane derivative in six steps. After cleavage of the epoxide group with a thiol (thiophenol or PMB mercaptan), the resulting product was subjected to the Mitsunobu reaction in the presence of a nucleobase. The reaction proceeded via the migration of the thiosulfide groups and gave the desired isonucleoside derivatives. In the case of a phenyl sulfide derivative, radical desulfurization followed by deprotection gave 4'-substituted 2',3'-dideoxyisonucleosides. A PMB sulfide derivative, on the other hand, was converted into the corresponding dimesylate, which was then treated with mercury acetate and trifluoroacetic acid to remove the PMB group. The resulting thiol derivative was treated with DBU to give the desired isonucleoside constructed on a 2-oxa-6-thiobicyclo[3.2.0]heptane scaffold after deprotection. The optimized conformer of the isonucleoside was calculated using DFT at the B3LYP/6-31G** level and was compared with that of lamivudine using model compounds.

Acceleration effect of an allylic hydroxy group on ring-closing enyne metathesis of terminal alkynes: scope, application, and mechanistic insights.

An interesting acceleration effect of an allylic hydroxy group on ring-closing enyne metathesis has been found. Ring-closing enyne metathesis of terminal alkynes possessing an allylic hydroxy group proceeded smoothly without the ethylene atmosphere generally necessary to promote the reaction. The synthesis of (+)-isofagomine with the aid of this efficient reaction has been demonstrated. Mechanistic studies of the acceleration effect were also carried out. Results of NMR studies suggested that the reaction proceeded via an "ene-then-yne" pathway. Kinetic studies indicated switching of the rate-determining step as a consequence of the presence of an allylic hydroxy group. These results suggest acceleration of the reentry step of Ru-carbene species by the allylic hydroxy group.

Nociceptin-receptor deficiency prevents postherpetic pain without effects on acute herpetic pain in mice.

Using nociceptin-receptor-deficient mice, we studied the participation of nociceptin in herpetic and postherpetic allodynia in mice. Although nociceptin-receptor deficiency did not affect the development of skin lesions and herpetic allodynia, it prevented postherpetic allodynia. Messenger ribonucleic acid (mRNA) of pronociceptin increased in the dorsal horn of lumbar enlargement on day 6, but not on day 40, after inoculation. No changes were observed in the mRNA of the nociceptin receptor. Inhibition of herpetic allodynia by repeated oral administration of gabapentin (100 mg/kg) alleviated the overexpression of mRNA of pronociceptin, as well as the severity of postherpetic allodynia. These results suggest that the spinal nociceptin system is involved in the transitional process from herpetic allodynia to postherpetic allodynia.

Synthesis of all stereoisomers of 3-hydroxypipecolic acid and 3-hydroxy-4,5-dehydropipecolic acid and their evaluation as glycosidase inhibitors.

A highly practicable synthesis of both enantiomers of 3-hydroxypipecolic acid derivatives 1, 2, 3, 4 is described. Screening of these molecules for glycosidase inhibition has been examined. Compound 3 was shown to be a potent inhibitor of beta-N-acetylglucosaminidase as well as Escherichia coli beta-glucuronidase.

Synthesis of both enantiomers of hydroxypipecolic acid derivatives equivalent to 5-azapyranuronic acids and evaluation of their inhibitory activities against glycosidases.

We have synthesized 3-hydroxy- and 3,4,5-trihydroxypipecolic acid derivatives corresponding to 5-aza derivatives of uronic acids and evaluated their inhibitory activities against various glycosidases including beta-glucuronidase. Compounds 4 and 5 were chosen as common intermediates for the synthesis of 3,4,5-trihydroxypipecolic acids and 3-hydroxypipecolic acids as well as for 3-hydroxybaikiain, a unique natural product isolated from a toxic mushroom. Cross aldol reaction of N-Boc-allylglycine derivative with acrolein followed by the ring-closing metathesis gave 4 and 5 as a mixture of diastereomers which could be separated by silica gel column chromatography. By employing lipase-catalyzed kinetic resolution, the synthesis of both L- and D-isomers of 3,4,5-trihydroxy- and 3-hydroxypipecolic acids was achieved. None of the compounds tested showed inhibitory activity against alpha- and beta-glucosidases. On the other hand, L-23 and L-29 were found to have potent inhibitory activity against beta-glucuronidase. In addition, it is interesting that some uronic-type azasugar derivatives showed moderate inhibitory activities against beta-N-acetylglucosaminidase.

In vitro inhibition of glycogen-degrading enzymes and glycosidases by six-membered sugar mimics and their evaluation in cell cultures.

We investigated in vitro inhibition of mammalian carbohydrate-degrading enzymes by six-membered sugar mimics and their evaluation in cell cultures. 1-Deoxynojirimycin (DNJ) showed no significant inhibition toward glycogen phosphorylase (GP) but was a potent inhibitor of another glycogen-degrading enzyme, amylo-1,6-glucosidase (1,6-GL), with an IC(50) value of 0.16 microM. In primary rat hepatocytes, the inhibition of glycogen breakdown by DNJ reached plateau at 100 microM with 25% inhibition and then remained unchanged. The potent GP inhibitor 1,4-dideoxy-1,4-imino-D-arabinitol (D-AB1) inhibited hepatic glucose production with an IC(50) value of about 9 microM and the inhibition by D-AB1 was further enhanced in the presence of DNJ. DNJ and alpha-homonojirimycin (HNJ) are very potent inhibitors of rat intestinal maltase, with IC(50) values of 0.13 and 0.08 microM, respectively, and also showed a similar strong inhibition toward maltase in Caco-2 cell model system, with IC(50) value of 0.05 and 0.10 microM, respectively. D-Isofagomine (D-IFG) and L-IFG are competitive and noncompetitive inhibitors of human lysosomal beta-glucosidase (beta-GL), respectively, with K(i) values of 8.4 nM and 6.9 microM. D-IFG increased intracellular beta-GL activity by twofold at 10 microM in Gaucher N370S cell line as an 'active-site-specific' chaperone, and surprisingly a noncompetitive inhibitor L-IFG also increased intracellular beta-GL activity by 1.6-fold at 500 microM.

Peripheral gabapentin regulates mosquito allergy-induced itch in mice.

The antipruritic activity of gabapentin, an anticonvulsant, was studied in a mouse model of allergic itch. In mice sensitized by an extract of the salivary glands of the mosquito (ESGM), an intradermal injection of ESGM elicited scratching and increased peripheral nerve firing. Oral or intradermal administration of gabapentin at the ESGM injection site inhibited ESGM-induced scratching and peripheral nerve firing. However, gabapentin did not affect histamine-induced scratching. The distributions of immunoreactivity to the voltage-dependent calcium channel α2δ-1 subunit, a site of gabapentin action, and the histamine H1 receptor differed in the mouse dorsal root ganglia. The α2δ-1 subunit was mainly found in neurons that were 15-20 µm in diameter, whereas the H1 receptor was mainly in 20-30 µm neurons. In addition, α2δ-1 subunit immunoreactivity co-localized with that of transient receptor potential vanilloid 1 (TRPV1). These results suggest that gabapentin regulates allergic itch by acting on the calcium channel α2δ-1 subunit in peripheral TRPV1-positive neurons.

An asymmetric synthesis of all stereoisomers of piclavines A1-4 using an iterative asymmetric dihydroxylation.

The asymmetric synthesis of both enantiomers of piclavines A1, A2, A3, and A4 has been achieved using an iterative asymmetric dihydroxylation with enantiomeric enhancement.

New synthesis of (+/-)-isonucleosides.

[Structure: see text] A novel method for synthesizing isonucleosides, a new class of anti-HIV nucleosides, is described. 2,2-Dimethyl-1,3-dioxan-5-one was converted into a dioxabicyclohexane derivative in six steps. After cleaving the epoxide group with thiophenol, the resulting product was subjected to the Mitsunobu reaction in the presence of a nucleobase to give the desired isonucleoside derivative via migration of the thiophenyl group. Removal of the thiophenyl group under radical conditions followed by deprotection led to the 4'-substituted 2',3'-dideoxyisonucleosides as a racemic mixture.