Rh(III)-Catalyzed Diastereo- and Enantioselective Regiodivergent (Hetero)Arylamidation of (Homo)Allylic Sulfides.

A rhodium-catalyzed 3-component conjunctive diastereo- and regioselective arylamidation of (homo)allylic sulfides, organon boronic acids, and dioxazolones is reported. These reactions deliver the 1,2-insertion and 2,1-insertion arylamidation products, respectively, for allylic sulfides and homoallylic sulfides. The enantioselective arylamidation of terminal and internal allylic sulfides is achieved, furnishing various 1,3-N,S compounds featuring one or two contiguous stereocenters in high yields and with high diastereo- and enantioselectivities. Mechanistic studies suggest a change in the turnover-limiting and selectivity-determining steps induced by the native and easily removable sulfide group.

Synthesis of γ-Thiapyrones by Diels-Alder/Retro-Diels-Alder Reaction of α-Pyrones with 5-H-1,2,3-Thiadiazoles.

The efficient synthesis of γ-thiapyrones by a base-mediated Diels-Alder/retro-Diels-Alder reaction of α-pyrones with 5-H-1,2,3-thiadiazoles is reported herein. Thioketenes in situ generated from thiadiazoles as electron-poor dienophile and electron-rich 4-hydroxy-2-pyrones as dienes are conjunctively transformed into a series of γ-thiapyrones with broad functional group compatibility in good to excellent yields (35 examples, 67% average yield).

Species diversity of freshwater shrimp in Henan Province, China, based on morphological characters and COI mitochondrial gene.

Freshwater shrimp are a rich species group, with a long and problematic taxonomic history attributed to their wide distribution and similar morphological characteristics. Shrimp diversity and species identification are important cornerstones for fisheries management. However, identification based on morphological characteristics is a difficult task for a nonspecialist. Abundant freshwater shrimp species are distributed in the waters of Henan Province, but investigations of freshwater shrimp are limited in this region, especially concerning molecular features. Here, we combined morphology and DNA barcodes to reveal the species diversity of freshwater shrimp in Henan province. A total of 1,200 freshwater shrimp samples were collected from 46 sampling sites, and 222 samples were chosen for further microscopic examination and molecular delimitation. We used tree-based methods (NJ, ML, and bPTP) and distance-based methods (estimation of the paired genetic distances and ABGD) to delimit species. The results showed that there were nine morphospecies based on morphological characteristics; all could effectively be defined by molecular methods, among which bPTP and ABGD defined 13 and 8 MOTUs, respectively. The estimation of the paired genetic distances of K2P and the p-distances had similar results. Mean K2P distances and p-distances within species were both equal to 1.2%. The maximum intraspecific genetic distances of all species were less than 2%, with the exception of Palaemon modestus and M. maculatum. Various analyses have shown that P. modestus and M. maculatum have a large genetic differentiation, which may indicate the existence of cryptic species. By contrast, DNA barcoding could unambiguously discriminate 13 species and detect cryptic diversity. Our results demonstrate the high efficiency of DNA barcoding to delimit freshwater shrimp diversity and detect the presence of cryptic species.

Application of DNA barcoding in fish identification of supermarkets in Henan province, China: More and longer COI gene sequences were obtained by designing new primers.

In recent years, DNA barcode technology has been widely used in food identification, especially in the identification of fish. In China, there are few studies on the authenticity of fish products in Henan province of China. In this study, 179 fish samples were collected from supermarkets in Zhengzhou city and Xinxiang city in Henan province, China. COI gene sequences were obtained with PCR technology by designing specific primers and universal primers. COI gene sequences of all samples were obtained to identify species, which is used to investigate species substitution and mislabeling of the fish sold in the two regional markets. The molecular identification results showed that 28.49% (51/179) fish samples were not consistent with the labels. Substitution of high-price fish by low-price fish was prevalent. For example, halibut (Pleuronectiformes) and cod (Gadus) are replaced by striped catfish (Pangasianodon hypophthalmus), and some merchants label bighead carp (Hypophthalmichthys nobilis) as cod (Gadus), there are also accidental labeling errors (such as labels for greenfin horse-faced filefish (Thamnaconus septentrionalis) have been identified as grass carp (Ctenopharyngodon idella) and Wuchang bream (Megalobrama amblycephala) etc. Most of the samples labeled correctly are the fish of low economic value and the fresh fish. This study shows that almost all the commercial fish can be identified by COI DNA barcoding by newly designed primers. Finally, this study also gives a reference of real species of fish fillet in Henan province in China.