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2-Hydroxypropanoic Acid

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Fumihiko Yoshizaki – One of the best experts on this subject based on the ideXlab platform.

D. Palma-ramírez – One of the best experts on this subject based on the ideXlab platform.

  • PLA degradation pathway obtained from direct polycondensation of 2-Hydroxypropanoic Acid using different chain extenders
    Journal of Materials Science, 2018
    Co-Authors: C. A. Ramírez-herrera, A. I. Flores-vela, A.m. Torres-huerta, Miguel A. Domínguez-crespo, D. Palma-ramírez

    This work is focused on the structural, thermal and mechanical studies of direct polycondensation of poly (lactic Acid) (PLA) modified with three different chain extenders (1,3-phenylene-bis-2-oxazoline, PBO; pyromellitic dianhydride, PMDA; and 1,1′-carbonyl bis caprolactam, CBC). Three concentrations of PBO, PMDA and CBC chain extenders (0.2, 0.5 and 1 wt%) were added during three stages (S): monomer dehydration (80 °C, S1), oligomer polycondensation (130 °C, S2) and melt polycondensation (160 °C, S3). FTIR, Raman and 1H-NMR spectroscopies revealed the presence of signals produced by interactions between OH and C=O end groups of PLA and reactive functional groups of chain extenders. It was found that the interaction with the PMDA chain extender decreased the PLA crystallinity. Furthermore, data from thermal analysis revealed that the interaction between PLA and chain extenders increased the chain mobility, which represented a decrease in its Tg. Enhanced mechanical properties, hardness, elastic modulus and indentation creep were observed with the addition of chain extenders, improving the performance with the addition of 1 wt% of PBO at S3, 1 wt% of PMDA at either S2 or S3 and 0.25 wt% of CBC at either S2 or S3. Additionally to the synthesis, the degradation was mainly influenced by the interaction more than by any specific stage of chain extender addition. Finally, the thermal and structural characterizations revealed that the PLA-PBO, PLA-PMDA and PLA-CBC systems were more resistant than PLA to UV light and humidity during the accelerated weathering test.

Toshihiro Murata – One of the best experts on this subject based on the ideXlab platform.

  • Diastereomers of lithospermic Acid and lithospermic Acid B from Monarda fistulosa and Lithospermum erythrorhizon.
    Fitoterapia, 2013
    Co-Authors: Toshihiro Murata, Kanae Oyama, Minami Fujiyama, Bunmei Oobayashi, Kaoru Umehara, Toshio Miyase, Fumihiko Yoshizaki

    Monardic Acids A (1) and B (2), which are (7R,8R) diastereomers of lithospermic Acid (LA) and lithospermic Acid B, respectively, were isolated from Monarda fistulosa. A (7S,8R) isomer (3) of LA was also isolated from this plant, and a (7R,8S) isomer (7) of LA was obtained from Lithospermum erythrorhizon. The absolute configuration of 1 was confirmed by analysis of its hydrolysates, 7-epiblechnic Acid and 2R-3-(3,4-dihydroxyphenyl)-2-Hydroxypropanoic Acid. The configuration in the dihydrobenzofuran moieties of 2, 3, and 7 was extrapolated by using the phenylglycine methyl ester method and a Cotton effect at approximately 250-260 nm in their electronic circular dichroism spectra. Diastereomers (1-3 and 7) displayed moderate hyaluronidase inhibitory and histamine release inhibitory activities.

Marcelo I Guzman – One of the best experts on this subject based on the ideXlab platform.

  • negative production of acetoin in the photochemistry of aqueous pyruvic Acid
    Proceedings of the National Academy of Sciences of the United States of America, 2013
    Co-Authors: Alexis J Eugene, Marcelo I Guzman

    Recently, Griffith et al. reported that acetoin is a major product of the photolysis of aqueous pyruvic Acid (PA), and proposed that its mechanism of formation involves the thermal decarboxylation of α-acetolactic Acid (AL) intermediate (1). This finding is in contrast with a previous study by Guzman et al., based on experiments performed under similar conditions, which reported the formation of two major products: 2,3-dimethyl tartaric Acid ( A ) and 2-(3-oxobutan-2-yloxy)-2-Hydroxypropanoic Acid ( B ) (2⇓–4). Both A and B result after triplet radical pairs are formed via long-range (proton-coupled) electron transfer between carbonyl groups (5). Product B can thermally decompose into acetoin, but its carbonyl chromophore absorbs at λmax ∼ 285 nm vs. 276 nm for acetoin (2). In fact, Guzman et al. had shown … [↵][1]1To whom correspondence should be addressed. E-mail: marcelo.guzman{at}uky.edu. [1]: #xref-corresp-1-1

Jacek Gregorowicz – One of the best experts on this subject based on the ideXlab platform.