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分子内環化反応を利用した非天然アミノ酸及びプロリン誘導体の効率的合成法に関する研究
Get PDF九州工業大学博士学位論文 学位記番号:工博甲第401号 学位授与年月日:平成27年9月25日1. Introduction||2. Instrumentation||3. Intramolecular cyclization of epoxy amino acids produced from allylglycines to prepare four stereoisomers of 4-hydroxyproline derivatives||4. Chemoenzymatic synthesis of 5-hydroxy pipecolic acid via Jacobsen's hydrolytic kinetic resolution of epoxy amino acids||5 Regioselective cyclization and facile separation of 5-hydroxypipecolic acid||6. General ConclusionCyclic amino acids (imino acids) were synthesized from intramolecular cyclization of amino
acids functionalized with side chain epoxides; The allyl glycine and homo allyl glycine
derivatives were obtained from the diethyl 2-aminomalonate derivatives, in a series of
reaction which finally gave a racemic mixture of allyl glycine/homo allyl glycine. These
racemic mixture were well resolved and separated by one of these commercially available
enzymes, L-acylase, ?-chymotrypsin and subtilisin Carlsberg. The epoxides were obtained by
epoxidation of the side chain of enatiomerically pure 2-amino-4-pentenoic acid and its higher homologue 2-amino-5-hexenoic acid (homo allyl glycine). The epoxides were then
intramolecularly cyclized to form 4-hydroxyproline from epoxide of allyl glycine or
5-hydroxypipecolic acid from epoxide of homo allyl glycine.
The enatiomers of allyl glycine were separated by effective resolution aided by
subtilisin Carlsberg or L-acylase. The enatiomerically pure allyl glycine derivatives with
(Boc) protection were epoxidized with m-CPBA which generated the inseparable
diastereomeric epoxide. Upon removal of the Boc protection generated highly nucleophilic
amine which attacked the side-chain epoxide intramolecularly at the C5 carbon generating 4-
hydroxyproline derivatives. Due to presence of 2 chiral centers formed during the
epoxidation trans- and cis- isomers of 4-hydroxyprolines are formed. Fortunately the cisisomer was transformed to a lactone with the removal of alcohol. The cis-conformation of the hydroxyl and ester was necessary for the intramolecular reaction; the trans- isomer remained as such without lactone formation. Due to the selective intramolecular lactonization of the cis- isomer into an hydrophobic lactone, the separation of the lactone from the hydrophilic trans- isomer was facile and easy. Similarly starting from the D- isomers two diastereomers 6 of 4-hydroxyproline were synthesized.
Similarly racemic mixture of 2-amino-5-hexenoic acid were synthesized from diethyl
malonate derivatives. This racemic mixture of 2-amino-5-hexenoic acid was separated by
resolution aided by L-acylase or ?-chymotrypsin. The separated enatiomerically pure amino
acids with tert-butoxycarbonyl (Boc) protection were oxidized with excess amount of 3-
chloroperbenzoic acid (m-CPBA). The oxidation by m-CPBA generates two inseparable
diastereomeric epoxides which are formed due to new chiral center at C5 carbon. One of the
diastereomeric epoxide in the inseparable mixture was selectively converted to a dihydroxyl
compound catalyzed by Jacobsen's hydrolytic kinetic resolution (HKR) which was easily
separated from the remaining diastereomeric epoxide. The epoxide was converted to a vicinal
halohydrin, with bromide attacking on terminal C6 carbon. Upon (Boc) deprotection of the
halohydrin, the free amine attacked the C6 carbon, generating 5-hydroxypipecolic acid which
was isolated in good yield after protection of the amine with (Boc) group. In a similar manner the dihydroxyl component which was converted to an halohydrin by efficient regioselective mono-tosylation with catalytic (Bu2SnO) followed tosyl replacment by iodine substitution.
The halohydrin was used to synthesize 5-hydroxypipecolic acid derivative by Boc removal
with acid treatment, intramolecular cyclization, N- reprotection and isolation. The same
sequence was repeated for D- isomers.
Finally racemic mixture of 2-amino-5-hexenoic acid were prepared by the same
sequence described above. This racemates were subjected to subtilisin carlsberg based
resolution, which gave chiraly pure 2-amino-5-hexenoic acid. The alkene side chain of the
fully protected amino acids were oxidized with m-CPBA, which gave the diastereomers,
which were not separable. On treating the epoxide with acid led to the removal of N-Boc
group and formation of the free amine. This amine was allowed to attack the epoxide, by
treating the amine with base, which led to the neutralization of the acid. The amine
7 regioselective attacked the C6 carbon to generate the 5-hydroxypipecolic acid derivatives.
The amine was again reprotected with Boc2O to generate the fully protected 5-hydroxy
pipecolic acid derivatives Due to the diastereomeric nature of the starting material, two
product were formed (cis-) and (trans)-5-hydroxypipecolic acid. But in our reaction
conditions the cis- isomer due to the close proximity of the hydroxyl and ester group
underwent in-situ lactonization to form the hydrophobic lactone. The lactone was easily
isolated from the trans- ester. Similarly starting from the L- isomer two isomers of 5-
hydroxypipecolic acid were obtained
Effective Synthesis of Non-natural Cyclic Amino Acids and Proline Derivatives by Intramolecular Cyclization.
No full text九州工業大学博士学位論文（要旨） 学位記番号：工博甲第401号 学位授与年月日：平成27年9月25
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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