Bioanalytical applications of isothermal nucleic acid amplification techniques

The most popular in vitro nucleic acid amplification techniques like polymerase chain reaction (PCR) including real-time PCR are costly and require thermocycling, rendering them unsuitable for uses at point-of-care. Highly efficient in vitro nucleic acid amplification techniques using simple, portable and low-cost instruments are crucial in disease diagnosis, mutation detection and biodefense. Toward this goal, isothermal amplification techniques that represent a group of attractive in vitro nucleic acid amplification techniques for bioanalysis have been developed. Unlike PCR where polymerases are easily deactivated by thermally labile constituents in a sample, some of the isothermal nucleic acid amplification techniques, such as helicase-dependent amplification and nucleic acid sequence-based amplification, enable the detection of bioanalytes with much simplified protocols and with minimal sample preparations since the entire amplification processes are performed isothermally. This review focuses on the isothermal nucleic acid amplification techniques and their applications in bioanalytical chemistry. Starting off from their amplification mechanisms and significant properties, the adoption of isothermal amplification techniques in bioanalytical chemistry and their future perspectives are discussed. Representative examples illustrating the performance and advantages of each isothermal amplification technique are discussed along with some discussion on the advantages and disadvantages of each technique.     

Antioxidative Cassane Diterpenoids from the Seeds of Caesalpinia minax

Five new cassane diterpenoids, caesalmins I–M ( 1 – 5 ), and 23 known analogs were isolated from the seeds of Caesalpinia minax. Their structures were elucidated by spectroscopic methods and comparison with reported data. The antioxidant properties of 1 – 28 were determined by the method of oxygen radical absorbance capacity of fluorescein (ORAC‐FL), and 14 compounds exhibited good antioxidant activities with ORAC‐FL values of 2.24–4.89 Trolox equivalents. The structure? activity relationship of the active compounds was also discussed.     

Facile Synthesis of the Pentasaccharide Repeating Unit of the Exopolysaccharide from Cryptococcus neoformans Serotype D

β‐D ‐GlcpA‐(1→2)‐[β‐D ‐Xylp‐(1→2)‐α‐D ‐Manp‐(1→3)]‐α‐D ‐Manp‐(1→3)‐α‐D ‐Manp, the repeating unit of the exopolysaccharide from Cryptococcus neoformans serotype D, was synthesized as its 4‐methoxyphenyl glycoside. The approach presented here also provides a route to the synthesis of more complex repeating units of glucuconoxylomannan (GXM) of C. neoformans serotypes A–C.     

Highly Diastereo‐ and Enantioselective Michael Addition of Nitroalkanes to 2‐Enoyl‐Pyridine N‐Oxides Catalyzed by Scandium(III)/Copper(II) Complexes

A C₂‐symmetric Schiff‐base ligand, derived from tridentate‐Schiff‐base, was developed and successfully applied to the asymmetric Michael addition of nitroalkanes to 2‐enoyl‐pyridine N‐oxides. With this newly catalytic system, an unprecedented diastereoselectivity was obtained in the asymmetric Michael addition of nitroalkanes to 2‐enoyl‐pyridine N‐oxides. In addition, a switch in enantioselectivity was achieved by using this newly catalytic system and our previous catalyst. After a facile reduction, the optically active adduct was converted to a biologically active dihydro‐2H‐pyrrol 4 a . Furthermore, a connection of two tridentate‐Schiff‐base subunits proved to be an effective strategy in ligand design.     

Reversal Circularly Polarized Luminescence of AIE‐Active Chiral Binaphthyl Molecules from Solution to Aggregation

Four aggregation‐induced emission (AIE)‐active chiral binaphthyl‐based molecules, (R/S)‐ 1 and (R/S)‐ 2 , were designed and synthesized. Interestingly, all of them can exhibit reversal circularly polarized luminescence (CPL) signals from solution to aggregation, which could be attributed to the different dihedral angle of binaphthyl units from cis‐conformation in pure THF solution to trans‐conformation in THF/water mixtures.     

Cyclotetrabenzoin: Facile Synthesis of a Shape‐Persistent Molecular Square and Its Assembly into Hydrogen‐Bonded Nanotubes

Cyanide‐catalyzed benzoin condensation of terephthaldehyde produces a cyclic tetramer, which we propose to name cyclotetrabenzoin. Cyclotetrabenzoin is a square‐shaped macrocycle ornamented with four α‐hydroxyketone functionalities pointing away from the central cavity, the dimensions of which are 6.9×6.9 Å. In the solid state, these functional groups extensively hydrogen bond, resulting in a microporous three‐dimensional organic framework with one‐dimensional nanotube channels. This material exhibits permanent—albeit low‐porosity, with a Langmuir surface area of 52 m² g^?1. Cyclotetrabenzoin’s easy and inexpensive synthesis and purification may inspire the creation of other shape‐persistent macrocycles and porous molecular crystals by benzoin condensation.     

A novel synthesis route to furo[3,2-a]carbazole

In this paper,we report a novel approach to the heteroaryl-condensed nuclei of natural furo[3,2-a]carbazole alkaloids.Our synthetic studies use N-phthaloyl tryptophan methyl ester as starting material and zinc ion mediated transamination reaction as the key step.This work also implicated a novel strategy to assemble other [a]-fused carbazoles.     

5-甲氧基-2-[(E)-(6-甲基吡啶-2-亚氨基)甲基]苯酚的合成与表征

研究了以2-羟基-4-甲氧基苯甲醛和2-氨基-6-甲基吡啶为原料合成新型席夫碱化合物5-甲氧基-2-[(E)-(6-甲基吡啶-2-亚氨基)甲基]苯酚的方法。当2-羟基-4-甲氧基苯甲醛与2-氨基-6-甲基吡啶摩尔比为1∶1.6,反应时间为6 h,反应温度为75℃时,反应产率最高。采用元素分析、UV-Vis、IR、1H NMR、X-射线单晶衍射等方法进行结构表征。该化合物为单斜晶系,空间群P21/c,a=1.1886(3)nm,b=0.65948(16)nm,c=1.6897(4)nm,β=108.505(3)°,V=1.2560(5)nm3,Dc=1.281 g·cm-3,Z=4,F(000)=512,μ=0.087 mm-1,R1=0.0477,wR2=0.1342。通过π···π堆积和分子内氢键O2-H2···N1、C8-H8A···N2形成较稳定的晶体结构,并具有蓝色荧光。