Min Xu

Bio: Min Xu is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topic(s): Panax notoginseng & Glacier. The author has an hindex of 25, co-authored 122 publication(s) receiving 1832 citation(s). Previous affiliations of Min Xu include Nanjing Normal University & Griffith University.

Highly Enantioselective Construction of a Quaternary Carbon Center of Dihydroquinazoline by Asymmetric Mannich Reaction and Chiral Recognition

Abstract: The highly enantioselective construction of a quaternary carbon center of dihydroquinazoline by an asymmetric Mannich reaction and chiral recognition are described The key transformation was to establish the chiral trifluoromethyl quaternary carbon center by a diamine-Bronsted acid-catalyzed enantioselective and regioselective Mannich reaction of a methyl ketone and 4-trifluoromethyldihydroquinazoline An unusual phenomenon of self-discrimination of enantiomers in hydrogen-bonded dimers was observed A valuable intermediate was transformed into the enantiopure HIV reverse transcriptase inhibitor DPC 083 (>999 ee) simply by reduction of the carbonyl group and elimination of the hydroxy group in hexamethylphosphoric tramide (HMPA)

Puerins A and B, two new 8-C substituted flavan-3-ols from Pu-er tea.

Abstract: Pu-er tea is a special treated fermented tea produced from crude green tea, which is prepared from the leaves of Camellia sinensis var. assamica. It is a traditional beverage having been used in China, particularly the southern areas, for a long time. Chemical investigation led to the identification of two new 8-C substituted flavan-3-ols, puerins A (1) and B (2), and two known cinchonain-type phenols, epicatechin-[7,8-bc]-4 alpha-(4-hydroxyphenyl)-dihydro-2(3"-pyranone (3) and cinchonain lb (4), together with other seven known phenolic compounds, 2,2',6,6'-tetrahydroxydiphenyl (5), (-)-epicatechin-8C-beta-D-glucopyranoside (6), (-)-epicatechin (EC) (7), (-)-epigallocatechin (EGC) (8), (+/-)-gallocatechin (GC) (9), gallic acid (10), and myricetin (11), in addition to caffeine (12). Their structures were determined by spectroscopic methods. The compounds 1-5, which might be formed in the postfermentative process of Pu-er tea, were isolated from tea and theaceous plants for the first time.

The processing of Panax notoginseng and the transformation of its saponin components

Abstract: Notoginseng, the root of Panax notoginseng (Burk.) F. H. Chen (Araliaceae), a famous traditional Chinese medicine, has been used in both raw and processed forms due to their different therapeutic functions. In this study, HPLC analyses on saponin composition of processed notoginseng were conducted, which revealed that, during the steaming process, the five main saponin constituents (ginsenosides Rg(1), Rb-1, Rd, and Re, and notoginsenoside R-1) in raw notoginseng decreased gradually and some other new saponins were formed. Among these, eight newly converted ginsenosides were identified,as 20(S)-Rh-1, 20(R)Rh-1, Rk(3), Rh-4, 20(S)-Rg(3), 20(R)-Rg(3), Rk(1) and Rg(5). Different processing methods, including steaming and baking, were studied, along with the correlative dynamic curves of the transformation of saponins. The results indicated that the moisture content and temperature were the determinant effecting factors in the preparing process, and water content was necessary and high temperature was helpful for saponin transformation. (C) 2011 Elsevier Ltd. All rights reserved.

Design, synthesis, and biological evaluation of deuterated C-aryl glycoside as a potent and long-acting renal sodium-dependent glucose cotransporter 2 inhibitor for the treatment of type 2 diabetes.

Abstract: SGLT2 inhibitors deuterated at sites susceptible to oxidative metabolism were found to have a slightly longer tmax and half-life (t1/2), dose-dependent increase in urinary glucose excretion (UGE) in rats, and slightly superior effects on UGE in dogs while retaining similar in vitro inhibitory activities against hSGLT2. In particular, deuterated compound 41 has the potential to be a robust long-acting antidiabetic agent.

Successive copper(I)-catalyzed cross-couplings in one pot: A novel and efficient starting point for synthesis of carbapenems

Abstract: An efficient approach for synthesizing a series of 2-sulfide carbapenems has been developed using two successive Cu(I)-catalyzed cross-couplings in a single pot. The method involves highly selective intramolecular coupling of lactam and dihaloalkene using 2,2'-bipyridine as a ligand, followed by intermolecular C-S formation in the presence of another ligand (1,10-phenanthroline, PPh3) and mercaptan.

Marine natural products.

Abstract: This review covers the literature published in 2014 for marine natural products (MNPs), with 1116 citations (753 for the period January to December 2014) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1378 in 456 papers for 2014), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Dietary phenolics: chemistry, bioavailability and effects on health.

Abstract: There is much epidemiological evidence that diets rich in fruit and vegetables can reduce the incidence of non-communicable diseases such as cardiovascular diseases, diabetes, cancer and stroke. These protective effects are attributed, in part, to phenolic secondary metabolites. This review summarizes the chemistry, biosynthesis and occurrence of the compounds involved, namely the C6-C3-C6 flavonoids-anthocyanins, dihydrochalcones, flavan-3-ols, flavanones, flavones, flavonols and isoflavones. It also includes tannins, phenolic acids, hydroxycinnamates and stilbenes and the transformation of plant phenols associated with food processing (for example, production of black tea, roasted coffee and matured wines), these latter often being the major dietary sources. Events that occur following ingestion are discussed, in particular, the deglycosylation, glucuronidation, sulfation and methylation steps that occur at various points during passage through the wall of the small intestine into the circulatory system and subsequent transport to the liver in the portal vein.We also summarise the fate of compounds that are not absorbed in the small intestine, but which pass into the large intestine where they are degraded by the colonic microflora to phenolic acids, which can be absorbed into the circulatory system and subjected to phase II metabolism prior to excretion. Initially, the protective effect of dietary phenolics was thought to be due to their antioxidant properties which resulted in a lowering of the levels of free radicals within the body.However, there is now emerging evidence that themetabolites of dietary phenolics,which appear in the circulatory systemin nmol/L to low mmol/L concentrations, exertmodulatory effects in cells through selective actions on different components of the intracellular signalling cascades vital for cellular functions such as growth, proliferation and apoptosis. In addition, the intracellular concentrations required to affect cell signalling pathways are considerably lower than those required to impact on antioxidant capacity. The mechanisms underlying these processes are discussed.

Different glacier status with atmospheric circulations in Tibetan Plateau and surroundings

Abstract: Glacial melting in the Tibetan Plateau affects the water resources of millions of people. This study finds that—partly owing to changes in atmospheric circulations and precipitation patterns—the most intensive glacier shrinkage is in the Himalayan region, whereas glacial retreat in the Pamir Plateau region is less apparent.