综合创新型实验:乙胺嘧啶合成的设计与教学实践

乙胺嘧啶(商品名:达拉匹林)是一种抗寄生虫药物,改进了合成方法,并设计转化为创新型综合教学实验。从对氯苯乙腈出发,使用丙酸乙酯为酰化试剂,在叔丁醇钾作用下得到烯醇前体。在三甲基氧鎓四氟硼酸盐(Me3O·BF4,Meerwein盐)和碱作用下进行选择性甲基化反应得到烯醇甲醚后,与胍在碱性条件下环化得到最终产物达拉匹林,并通过红外光谱、核磁共振对其结构进行表征。改进后的实验方法具有重现性好、毒性低、操作方便、实验微型化等优点。实验过程中不仅提升了学生的实验技能和科研思维,更提高了学生的创新能力和绿色环保意识。     

硫的发展与应用

硫是一种非金属元素，属于氧族元素（ⅥA族）。硫的发现和使用具有悠久的历史，现代化学中含硫生命分子、含硫药物、含硫材料、精细化学品等都十分普遍。从硫元素的发展历史出发，逐步介绍硫化学在人类生活中的重要用途。重点介绍当代硫化学在生命功能、药物作用、食品和有机光电材料中的重要用途，尤其是生活中常见的含硫药物、含硫食品和含硫材料的主要成分以及它们独特性质的化学本源。     

A planning strategy for diversity-oriented synthesis

In contrast to target-oriented synthesis (TOS) and medicinal or combinatorial chemistry, which aim to access precise or dense regions of chemistry space, diversity-oriented synthesis (DOS) populates chemical space broadly with small-molecules having diverse structures. The goals of DOS include the development of pathways leading to the efficient (three- to five-step) synthesis of collections of small molecules having skeletal and stereochemical diversity with defined coordinates in chemical space. Ideally, these pathways also yield compounds having the potential to attach appendages site- and stereoselectively to a variety of attachment sites during a post-screening, maturation stage. The diverse skeletons and stereochemistries ensure that the appendages can be positioned in multiple orientations about the surface of the molecules. TOS as well as medicinal and combinatorial chemistries have been advanced by the development of retrosynthetic analysis. Although the distinct goals of DOS do not permit the application of retrosynthetic concepts and thinking, these foundations are being built on, by using parallel logic, to develop a complementary procedure known as forward-synthetic analysis. This analysis facilitates synthetic planning, communication, and teaching in this evolving discipline.     

The development of an 18-locus Y-STR system for forensic casework

The aim of the present work was to improve the discriminatory potential, and hence the probative value, of Y-STR-based testing by extending the set of Y chromosome STR loci available for forensic casework. In accordance with the requirements of a Y chromosome multiplex analytical system developed specifically for forensic casework use, we have sought to maximize the number of loci able to be co-amplified, ensure appropriate assay sensitivity (1–2 ng of input genomic DNA), balance inter-locus signals and minimize confounding female DNA artifacts. Two Y chromosome STR systems, multiplex I (MPI) and multiplex II (MPII), have been developed which permit the robust co-amplification of 18 Y-STRs. The loci include DYS19, DYS385(a) and (b), DYS388, DYS389I and II, DYS390, DYS391, DYS392, DYS393, DYS425, DYS434, DYS437, DYS438, DYS439, Y-GATA-C4, Y-GATA-A7.1 (DYS460) and Y-GATA-H4. The two multiplex systems are robust over a wide range of primer, magnesium, and DNA polymerase concentrations and perform well under a variety of cycling conditions. Complete male haplotypes can be obtained with as little as 100–250 pg of template DNA. Although a limited number of female DNA artifacts are observed in mixed stains in which the male DNA comprises 1/100 of the total, the male profile is easily discernible. Slightly modified versions of MPI and MPII demonstrate a significant reduction in female artifacts. Thus, it may not be necessary to employ a differential extraction strategy to obtain a male haplotype (or haplotypes in the case of multiple male donors) in cases of sexual assault. The potential utility of MPI and MPII for forensic casework is exemplified by their ability to dissect out the male haplotype in post-coital vaginal swabs and to determine the number of male donors in mixed semen stains.This study has emphasized the need for novel Y-STR multiplexes developed for forensic use to undergo a series of validation exercises that go beyond simply optimizing the PCR reaction conditions. Specifically, stringent performance checks on their efficacy need to be carried out using casework-type specimens in order to determine potential confounding effects from female DNA.     

A highly efficient synthesis of antiobestic ligand GW501516 for the peroxisome proliferator-activated receptor δ through in situ protection of the phenol group by reaction with a Grignard reagent

A new synthesis of an agonist for the peroxisome proliferator-activated receptor δ (PPARδ) GW501516 as a potential antiobesity drug is described. The synthetic route involves the in situ protection of the phenol group with a Grignard reagent and a regio-controlled one-pot reaction for the formation of a sulfide bond as the key step. Starting from commercially available 4-iodo-2-methylphenol, this approach affords GW501516 with an overall yield of 87%.     

Molecular modeling of cytochrome P450 3A4

The three-dimensional structure of human cytochrome P450 3A4 was modeled based on crystallographic coordinates of four bacterial P450s: P450 BM-3, P450cam, P450terp, and P450eryF. The P450 3A4 sequence was aligned to those of the known proteins using a structure-based alignment of P450 BM-3, P450cam, P450terp, and P450eryF. The coordinates of the model were then calculated using a consensus strategy, and the final structure was optimized in the presence of water. The P450 3A4 model resembles P450 BM-3 the most, but the B helix is similar to that of P450eryF, which leads to an enlarged active site when compared with P450 BM-3, P450cam, and P450terp. The 3A4 residues equivalent to known substrate contact residues of the bacterial proteins and key residues of rat P450 2B1 are located in the active site or the substrate access channel. Docking of progesterone into the P450 3A4 model demonstrated that the substrate bound in a 6-orientation can interact with a number of active site residues, such as 114, 119, 301, 304, 305, 309, 370, 373, and 479, through hydrophobic interactions. The active site of the enzyme can also accommodate erythromycin, which, in addition to the residues listed for progesterone, also contacts residues 101, 104, 105, 214, 215, 217, 218, 374, and 478. The majority of 3A4 residues which interact with progesterone and/or erythromycin possess their equivalents in key residues of P450 2B enzymes, except for residues 297, 480 and 482, which do not contact either substrate in P450 3A4. The results from docking of progesterone and erythromycin into the enzyme model make it possible to pinpoint residues which may be important for 3A4 function and to target them for site-directed mutagenesis.     

Hydrolysis of new phthalimide-derived esters catalyzed by immobilized lipase

The last step of the production of four phthalimide-derived acids, designed to act as antiasthma drugs, was performed by enzymatic hydrolysis of the respective methyl or ethyl esters. The esters 4-ethyl-[2-(1,3-dioxo-1,3-dihydro-2-isoindoylyl)]-phenoxyacetic methyl ester (PHT-MET), 4-ethyl-[2-(1,3-dioxo-1,3-dihydro-2-isoindoylyl)]-phenoxyacetic ethyl ester, 4-(1,3-dioxo-1,3-dihydro-2-isoindoylyl)-phenoxyacetic ethyl ester, and 2-(1,3-dioxo-1, 3-dihydro-2-isoindoylyl)-phenoxyacetic ethyl ester were hydrolyzed by immobilized lipase. The enzymatic reaction could be used only to produce the desired 4-substituted compounds. The best result that was found to hydrolysis of PHT-MET, and, therefore, that ester was selected for optimization experiments in a three-phase system. Reactions were performed with solid biocatalyst (Lipozyme® RM IM), organic solvent phase (ethyl acetate), and aqueous phase (saturated Na₂CO₃ solution). To optimize the reaction conditions, an experimental design optimization procedure was used. The variables studied were the amount of enzyme, the temperature, and the volume of the aqueous solution. Time course experiments were then performed for different initial enzyme concentrations (0.5, 0.9, and 1.4 U_H/mL of solvent). The optimized reaction conditions found were 20 mg of Lipozyme (0.9 U_H/mL_solvent) and 5.0 mL of Na₂CO_3(sat) at 40°C for 6 h.     

A very large diversity space of synthetically accessible compounds for use with drug design programs

We have constructed a very large virtual diversity space containing more than 10¹³ chemical compounds. The diversity space is built from about 400 combinatorial libraries, which have been expanded by choosing sizeable collections of suitable R-groups that can be attached to each link point of their scaffolds. These R-group collections have been created by selecting reagents that have drug-like properties from catalogs of available chemicals. As members of known combinatorial libraries, the compounds in the diversity space are in general synthetically accessible and useful as potential drug leads. Hence, the diversity space can be used as a vast source of compounds by a de novo drug design program. For example, we have used such a program to generate inhibitors of HIV integrase enzyme that exhibited activity in the micromolar range.     

A genetic algorithm for the automated generation of small organic molecules: Drug design using an evolutionary algorithm

Rational drug design involves finding solutions to large combinatorial problems for which an exhaustive search is impractical. Genetic algorithms provide a novel tool for the investigation of such problems. These are a class of algorithms that mimic some of the major characteristics of Darwinian evolution. LEA has been designed in order to conceive novel small organic molecules which satisfy quantitative structure-activity relationship based rules (fitness). The fitness consists of a sum of constraints that are range properties. The algorithm takes an initial set of fragments and iteratively improves them by means of crossover and mutation operators that are related to those involved in Darwinian evolution. The basis of the algorithm, its implementation and parameterization, are described together with an application in de novo molecular design of new retinoids. The results may be promising for chemical synthesis and show that this tool may find extensive applications in de novo drug design projects.