Quality loss of two gadiform fish species (blue whiting, Micromesistius poutassou; hake, Merluccius merluccius) during frozen storage (-30 and -10 7C; up to 12 months) was studied. For this, hydrolytic (formation of free fatty acids, FFA) and oxidative (conjugated dienes, peroxide and interaction compound formation) lipid damage were analysed. For both species, individual fishes captured in two different trials (May and November) were considered. Increasing (p ,0.05) lipid hydrolysis and oxidation (peroxide and interaction compound formation) were observed for all kinds of samples throughout the frozen storage. Interaction compound detection by fluorescence analysis showed the best correlation values with storage time. Some higher (p ,0.05) hydrolysis development could be observed in hake captured in May than in its counterpart from the November trial, while frozen blue whiting did not provide definite differences for FFA formation between both trials. Concerning peroxide formation, higher (p ,0.05) values were obtained for individual blue whiting and hake captured in November when compared to their corresponding May fish for both frozen storage conditions. Interaction compound formation was also found to be higher (p ,0.05) for November hake fish than for its counterpart captured in May, while blue whiting did not provide definite differences between trials.
Optically pure carboxylic acid segments, which are common key intermediates for the synthesis of naturally occurring bicyclic depsipeptide histone deacetylase inhibitors, have been produced efficiently. The method features the chromatographic separation of two diastereomers, which were formed by direct amide condensation of racemic (3RS,4E)-3-hydroxy-7-mercaptohept-4-enoic acid (rac-Hmh) with chiral amino acids. This approach offers a reliable and practical method for producing optically pure carboxylic acid segments, which can facilitate easier access to important anticancer agents derived from them.
The naturally occurring bicyclic depsipeptide histone deacetylase inhibitors thailandepsins D–F were efficiently synthesized for the first time in 49–61% overall yield over five steps, starting from known amine and carboxylic acid segments. The synthesis includes the condensation of the two known starting materials to directly assemble the corresponding seco-acids, which are the key precursors for macrolactonization. The seco-acids are then macrolactonized using the Shiina method to construct the requisite 15-member macrocycles.
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