200 research outputs found

    An Improved Power Saving Mechanism for MAC Protocol in Ad Hoc Networks

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    Facile Guanidine Formation under Mild Acidic Condition

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    An efficient method for converting isothioureas into guanidines was developed. The use of amine salts of bis(trifluoromethanesulfonyl)imide as a nitrogen source was found to induce an efficient conversion under weak acidic condition at 50 °C. The conversion was applicable to the various amines and carbamate-protected thioureas, and various carbamate-protected cyclic guanidines were obtained in high yields. In particular, ammonium bis(trifluoromethanesulfonyl)imide salt is a useful N1 source with which to construct mono-protected cyclic guanidines

    Total synthesis of palau’amine

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    Palau’amine has received a great deal of attention in the past two decades as an attractive synthetic target by virtue of its intriguing molecular architecture and significant immunosuppressive activity. Here we report the total synthesis of palau’amine characterized by the construction of an ABDE tetracyclic ring core including a trans-bicylo[3.3.0]octane skeleton at a middle stage of total synthesis. The ABDE tetracyclic ring core is constructed by a cascade reaction of a cleavage of the N–N bond, including simultaneous formation of imine, the addition of amide anion to the resulting imine (D-ring formation) and the condensation of pyrrole with methyl ester (B-ring formation) in a single step. The synthetic palau’amine is confirmed to exhibit excellent immunosuppressive activity. The present synthetic route has the potential to help elucidate a pharmacophore as well as the mechanistic details of immunosuppressive activity

    Synthesis of 13a-methylphenanthroindolizidines using radical cascade cyclization: synthetic studies toward (±)-hypoestestatin 1

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    金沢大学大学院自然科学研究科生理活性物質科学A radical cascade involving 6-endo cyclization of aryl radicals generated from N-acryloyl-N-(1-methylethenyl)-9-bromophenanthren-10-ylmethylamines, followed by 5-endo-trig cyclization of the resulting α-amidoyl radicals afforded phenanthroindolizidines bearing a methyl substituent at the angular C13a position. 2,3,6-Trimethoxy derivative was synthesized by using this method, but its spectral data were not in accord with those of literature values reported for hypoestestatin 1. Further synthetic study toward hypoestestatin 1 is demonstrated. © 2007 Elsevier Ltd. All rights reserved

    Quelles compétences pour les bibliothèques de recherche ?

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    The one-step preparation of 1-nitrobicyclo[3.1.0]­hexane and bicycloisoxazoline-<i>N</i>-oxide was readily achieved from conjugate adducts of nitro alkenes and allylmalonates by treatment with Ag<sub>2</sub>O and iodine under basic conditions. We observed that when a primary alkyl group was present at the β-position of the nitro group, bicyclo[3.1.0]­hexane was preferentially formed, whereas if a secondary alkyl group occupied that position, isoxazoline-<i>N</i>-oxide was predominantly produced. High <i>cis</i>-selectivity was observed for the formation of cyclopentane units for both reactions. An iodomethyl adduct, considered an intermediate of the cyclization, was isolated, and its conversion to isoxazoline-<i>N</i>-oxide was successfully achieved. The isoxazoline-<i>N</i>-oxide underwent 1,3-dipolar cycloaddition with alkenes to yield tricycloheterocyclic compounds, which were readily converted to spirolactam in good yield by reductive cleavage of N–O bonds using Raney-Ni. On the other hand, 1,3-dipolar cycloaddition of the isoxazoline-<i>N</i>-oxide to terminal alkynes yielded tricyclic aziridines stereoselectively

    Efficient construction of the hexacyclic ring core of palau'amine : the pKa concept for proceeding with unfavorable equilibrium reactions

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    Palau'amine has received a great deal of attention as an attractive synthetic target due to its intriguing molecular architecture and significant immunosuppressive activity, and we achieved its total synthesis in 2015. However, the synthesized palau'amine has not been readily applicable to the mechanistic study of immunosuppressive activity, because it requires 45 longest linear steps from a commercially available compound. Here, we report the short-step construction of the ABCDEF hexacyclic ring core of palau'amine. The construction of the CDE tricyclic ring core in a single step is achieved by our pKa concept for proceeding with unfavorable equilibrium reactions, and a palau'amine analog without the aminomethyl and chloride groups is synthesized in 20 longest linear steps from the same starting material. The palau'amine analog is confirmed to retain the immunosuppressive activity. The present synthetic approach for a palau'amine analog has the potential for use in the development of palau'amine probes for mechanistic elucidation

    An efficient procedure for preparation of 2-monoalkyl or 2-monoaryl-3-ethoxycyclobutanones

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    金沢大学医薬保健研究域薬学系Optimized reaction conditions for the preparation of various 2-monosubstituted 3-ethoxycyclobutanones are described. 2-Monoalkyl 3-ethoxycyclobutanones were efficiently prepared by the reaction of the corresponding carboxylic acid chlorides and an excess amount of ethyl vinyl ether in the presence of diisopropylethylamine at 90 °C in a sealed tube. 2-Monoaryl 3-ethoxycyclobutanones were prepared by using 2,6-lutidine as a base in the above-mentioned procedure. © 2010 Published by Elsevier Ltd. All rights reserved

    A practical synthesis of enantiopure N-carbobenzyloxy-N′-phthaloyl-cis-1,2-cyclohexanediamine by asymmetric reductive amination and the Curtius rearrangement

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    金沢大学大学院自然科学研究科生理活性物質科学金沢大学薬学部Enantiomerically pure N-carbobenzyloxy-N′-phthaloyl-cis-1,2-cyclohexanediamine was synthesized by the asymmetric reduction of a β-enamino ester formed from benzyl 2-oxocyclohexanecarboxylate and (R)-phenylethylamine, followed by hydrogenolysis, phthaloylation, and the Curtius rearrangement. © 2007

    Spondylolysis with pedicle fracture

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    We describe successful surgical treatment in a case of L5 unilateral spondylolysis with contralateral pedicle stress fracture that was not resolved by conservative treatment in a high-performing college baseball player. The 20-year-old man presented with left low back pain that stopped his sports activities. Over the previous year, he had experienced a couple of episodes of pain that subsided with cessation of sports but reappeared after a return to sports. Computed tomography and magnetic resonance imaging revealed a right terminal stage pars fracture and a left pedicle stress fracture at L5. The pain originated from the left pedicle fracture, with no pain from the right unilateral spondylolysis. Given that conservative treatment for 1 year had not been effective, we decided on surgical treatment. Bilateral pedicle screws and the smiley face rod method were applied, and both fractures subsequently healed. In the 2 years since the surgery, the patient has returned to sports and has the potential to become a professional player
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