High yield protection of alcohols, including tertiary and base sensitive alcohols, as benzhydryl ethers by heating with diphenyldiazomethane in the absence of any other reagent

A protecting group that can be introduced efficiently without the need for any acid or base catalysis and which is not prone to acid or base catalysed migration is a significant advantage for many syntheses. Benzhydryl [diphenylmethyl] ethers of sugar lactones are formed in high yield under neutral conditions when the corresponding alcohol is heated with diphenyldiazomethane in an inert solvent such as acetonitrile or toluene; this allows the easy protection of base sensitive and highly hindered tertiary alcohols in the absence of any other reagents.     

Convenient method for the preparation of carbamates, carbonates, and thiocarbonates

A convenient, rapid, and efficient method for the preparation of carbamates from amines with 1-alkoxycarbonyl-3-nitro-1,2,4-triazole transfer reagents is reported. Reactions of newly synthesized stable crystalline reagents with alkyl amines were completed in a few minutes without any additional base, and highly pure carbamates were obtained without chromatographic purification. These highly active reagents are also useful for the selective protection of nucleobases and preparation of carbonates and thiocarbonates.     

Betti Base as an Efficient Ligand for Copper-Catalyzed Ullmann Coupling of Phenol with Aryl Halides

A simple, general, and highly efficient Betti base ligand has been developed for copper-catalyzed Ullmann coupling of phenol with aryl halides without the protection of an inert atmosphere. The reaction proceeds smoothly in the presence of K₂CO₃ as the base and dimethylsulfoxide as the solvent. The catalyst was reused several times with no evident loss of catalytic activity and is environmentally friendly.     

钯催化氟磺酸酚酯Suzuki反应合成三联苯类化合物

发展了一个高效、简便合成三联苯类化合物的方法。以氯化钯为催化剂,碳酸钾与三乙胺为碱,无需加入任何配体,在乙醇水溶液中催化氟磺酸联苯酚酯与芳基硼酸的Suzuki反应,可高效合成含有多种官能团的三联苯类化合物。该方法操作简便,无需氮气保护;且芳基硼酸自偶联副产物少,有利于产品的分离。为三联苯类化合物的合成提供了一条简便而高效的途径。     

Expeditious synthesis of C2- or N4-aryl-1,4-benzothiazin-3-one via orthogonal Pd-catalyzed C-arylation and Cu-catalyzed N-arylation

Direct, chemo-specific arylation at C-2 or N-4 of 1,4-benzothiazin-3-one with aryl halides, based on Pd or Cu catalyst system, respectively, provided easy entry to arylated derivatives, a class of molecules not easily accessible via existing methods. Under Pd-catalysis conditions with LiHMDS as the base, N-arylation of 1,4-benzothiazin-3-one was inhibited leading to Cα-arylation of a secondary amide without the need for protection and de-protection of more acidic amido NH.     

Versatile procedure for asymmetric and orthogonal protection of symmetric polyamines and its advantages for solid phase synthesis

To date, many polyamine syntheses are carried out on solid phase to allow the generation of biologically active polyamine conjugates and libraries of natural product analogs. The synthesis of compounds and libraries, which derive from a symmetric polyamine building block such as spermine requires asymmetric and orthogonal protection of the symmetric polyamine. For this purpose we have established a novel Aloc- and Nosyl-protection group strategy, which displays several advantages. Solution phase synthesis and an easy workup reveals high yield of the asymmetrically and orthogonally protected polyamine. Asymmetric protection prevents cross-linking of the resin, and sequential deprotection can occur on highly acid and base labile resins without cleavage of the linker. Finally, it tolerates the elongation and modification of the symmetric polyamine backbone with several functional groups by conventional Fukuyama-alkylation. The suitability of this protection group strategy was shown by the first solid phase synthesis of the philanthotoxin-analog HO359b.     

A new strategy for the synthesis of oligodeoxynucleotides directed towards perfect O-selective internucleotidic bond formation without base protection

Deoxyadenosine and deoxycytidine have nucleophilic amino groups so that the undesired N-phosphitylation of these amino groups occurred in the previous phosphoramidite methods without base protection. We report that the N-phosphitylation could be considerably suppressed in our new HOBt-mediated coupling strategy via phosphite intermediates as reactive species. Thus, 99.7-99.9% O-selective internucleotidic bond formation was achieved.     

Synthesis of non-hydrolyzable substrate analogs for Asp-tRNA/Glu-tRNA amidotransferase

Non-hydrolyzable substrate analogs for tRNA-dependent amidotransferase, 2′- or 3′-aspartyl or -glutamyl adenosine, were synthesized from adenosine without protection of the adenine base. The hydroxyl groups of adenosine were selectively protected, followed by a series of oxidation/reductions to alter the stereochemistry. DFT calculations revealed the driving forces for the ketone hydrate formation at C-2′, but not the C-3′ carbon during the oxidation step. Subsequently, triflation and azide replacement yielded azidoadenosines, which were coupled to protected amino acids after deprotection and reduction. After global deprotection, the target substrate analogs were obtained in 2–14% overall yields from adenosine.     

Selective phosphate protection: a novel synthesis of double-labeled oligonucleotides

[structure: see text] A novel, selective labeling of oligonucleotides with two different reporter groups is described. The oligonucleotide is synthesized using a stable 2-(4-methoxybenzamido)ethyl protection for a selected internucleosidic thiophosphate (PS) and a labile 2-(N-isopropyl-4-methoxybenzamido)ethyl for the 3'-terminal PS and internucleosidic phosphates. The latter group and the base protection are removed, and the 3'-terminal PS is labeled. The former protection is then cleaved by a prolonged ammonolysis, and the second reporter is introduced at the internucleosidic PS.     

拉帕替尼新中间体的合成

通过使用市售的5-溴糠醛与2-甲磺酰基乙胺进行亲和加成得到席夫碱,该席夫碱通过还原氢化、氨基保护和与硼酸酯反应,得到一种拉帕替尼的新中间体5-((苄基(2-(甲基磺酰基)乙基)氨基)甲基)呋喃-2-基硼酸,四步反应总收率为66.32%。     

Synthesis and biological activity of sulfur-containing aryl-aldehyde Schiff bases

A series of chemically modified aryl-aldehyde Schiff bases has been synthesized and tested for their antioxidant activity and radiation protection. We observed that disulfide-containing aryl-aldehyde Schiff base 6c exhibited potent free radical scavenging, antioxidation, and radioprotection activities.     

New Advances in Protection Against Solar Ultraviolet Radiation in Textiles for Summer Clothing

Clothing is considered one of the most important tools for photoprotection against harmful solar ultraviolet radiation (UVR). The standard for sun‐protective clothing is based on erythema despite other biological effects of UVR on the skin. We analyzed the potential protection against UVR in fabrics destined for summer clothing based on several action spectra. We examined 50 garments classified by type of fabric composition, structure of the fiber yarn and color. The ultraviolet protection factor was calculated based on fabric ultraviolet transmittance corrected for erythema according to the EU standard E‐13758 as well as the UVA transmittance of fabrics. UVR protection was also analyzed in base of different action spectra as for previtamin D3, nonmelanoma skin cancer, photoimmunosuppression and photoaging. Most knitted fabrics used for sports T‐shirts offered excellent ratings for ultraviolet protection while normal shirts showed very low ratings, particularly against photoaging. The cover is the most influential variable in fabric photoprotection, having an exponential relationship with the UPF. The relation between cover and UVA protection was linearly negative. Information about ultraviolet protection in textiles used for summer clothing should be included in labeling as some types of fabrics, especially those used for shirts, offer very low UVR protection.     

Synthesis of Pt/C Electrocatalysts Under Protection of Glucose and Their Improved Methanol Electrooxidation Activity

Carbon supported Pt(Pt/C) electrocatalysts were prepared with glucose as protection agent and NaBH₄ as reductant. The Pt nanoparticles deposited on carbon support presented reduced size and well dispersity attributed to the protection effect of glucose. Glucose absorbed on the particle surface was readily removed by water washing without leading to agglomeration of the Pt nanoparticles. The as-prepared Pt/C electrocatalysts showed improved mass activity for methanol electrooxidation compared to the catalyst prepared without glucose protection. The improved performance is attributed to the larger electrochemical active surface area thus increased active sites on the Pt/C elctrocatalysts prepared under the protection of glucose.     

Solid-phase Synthesis of a Novel Kind of Hydroxylated Heterocyclic Ketene Aminals

An efficient solid-phase synthesis method for novel heterocyclic ketene aminals containing a hydroxyl group has been developed. The loading of the substrate on the resin through the hydroxyl group and the protection of the amine by the Schiff base were the key steps in the synthesis.     

不锈钢表面Schiff碱自组装分子膜的制备及性能

以乙二胺和乙酰丙酮为原料,在盐酸催化下合成了新的Schiff 碱化合物,其收率为73.2%。 采用红外光谱和核磁共振谱对化合物的结构进行了表征。 并将其自组装在不锈钢基体表面,利用极化曲线、电化学阻抗谱和自腐蚀电位 时间曲线进行电化学分析。 结果表明,在1 mol/L HCl中,不锈钢表面自组装分子膜能快速有效的抑制异相电子的转移,促进不锈钢表面发生钝化,减少了不锈钢基体的腐蚀。 总结了Schiff碱自组装分子膜对金属防护的效用和价值。     

The application of 2-(4-chlorophenyl)-sulfonylethoxycarbonyl (CPSEC) group in the synthesis of a DNA segment using the phosphotriester approach

The new base labile CPSEC group has been successfully employed for the protection of the 5′-hydroxyl function to synthesize a “universal Stop codon” DNA sequence: ^5′d(TCAATCAATCA)^3′.     

Synthesis of N-α-Fmoc-N-ε-Tetrabutyl Ester-EDTA-L-lysine: An Amino Acid Analog to Prepare Affinity Cleaving Peptides

Synthesis of an amino acid analog. N-α-Fmoc-N-ε-tetrabutyl ester EDTA-L-Lysine, suitable for incorporating a strong metal binding site at any internal sequence position in a peptide is described. To overcome the solubility and purification problems during the synthesis, we prepared esters of N-α-Fmoc-N-ε-Boc-L-Lysine. Since the t- butyl group on the amino acid is acid labile and Fmoc group at α-amino group is base sensitive, protection of N-α-Fmoc-N-ε-Boc-L-Lysine requires an ester that can be prepared and removed under neutral conditions. A scheme for selective protection and deprotection of lysine is reported.     

Measurement of the FMOC loading of protected amine-functionalised polymer beads

This paper presents an HPLC based procedure that has been developed for the determination of the 9-fluorenylmethoxycarbonyl (FMOC) content of protected amine-functionalised polymer beads. FMOC reagents are frequently employed both in the protection of amines and in their determination. The procedure utilises the stoichiometric base cleavage of dibenzofulvene from the protected amine using 1,8-diazabicyclo undec-7-ene. This stearically hindered base prevents the adduct formation that occurs with alternative base systems and measurement performance is enhanced by the incorporation of anthracene into the system as a non-reactive internal standard. HPLC separation of the reaction products permits the measurement of FMOC in the presence of additional chromophores that might otherwise impede direct measurement by UV-vis spectrophotometry. The procedure has been evaluated for the measurement of the FMOC content of protected amine-modified polymer beads employed in combinatorial solid phase synthesis.     

Proton-block strategy for the synthesis of oligodeoxynucleotides without base protection,capping reaction,and P-N bond cleavage reaction

A new N-unprotected phosphoramidite method called the "proton-block" approach was developed for the chemical synthesis of oligodeoxynucleotides based on the hitherto simplest and rational principle of acid-base reactions. This concept involves protection of the nucleobases of deoxycytidine and deoxyadenosine with "protons" to convert them to unreactive protonated bases during condensation by use of promoters having pK(a) values lower than 2.8. This strategy was applied to the synthesis of d[CpT] and d[ApT] to check the side reactions associated with the base residues. In this "proton-block" method, 5-nitrobenzimidazolium triflate (NBT) was found to be the best promoter, and THF was superior to CH(3)CN as the solvent so that the concomitant detritylation due to the inherent acidity of the promoter could be greatly suppressed. Application of this strategy to the solid-phase synthesis gave d[CpT], d[ApT], d[ApA], d[CpC], and d[GpT] as almost single peaks in HPLC analysis. Similarly, d[ApApApT] and d[CpCpCpT] were successfully synthesized without significant side reactions. Finally, d[CpCpCpCpCpCpT] and d[ApApApApApApT] were obtained as the main products. In the case of a longer oligomer, d[CpApGpTpCpApGpTpCpApGpT], a mixed solvent of CH(3)CN-N-methylpyrrolidone (1:1, v/v) was superior to THF so that the desired oligodeoxynucleotide could be isolated in a satisfactory yield. These results suggest that DNA synthesis can be carried out simply by using the protonated bases at the oligomer level not only without base protection but also without the capping reaction and the posttreatment of branched chains with MeOH-benzimidazolium triflate that previously was requisite. It is concluded that most of the reactions and solvent effects involved in this strategy can be explained in terms of simple acid-base reactions. Some problems associated with the previous posttreatment are also discussed with our own results.     

无机原料体系合成TS-1影响因素的研究

以廉价的硅溶胶和三氯化钛分别作为硅源和钛源,四丙基溴化铵(TPABr)为模板剂,二乙胺、正丁胺、氨水等作为碱源,在无机体系中合成了TS-1分子筛。采用XRD,IR,UV-vis,SEM,元素分析和N2吸附/脱附等对合成的分子筛进行了表征。详细考察了碱源、硅钛比N2保护、晶种、模板剂用量、硅源及晶化时间等因素对分子筛合成的影响。结果表明,以无机原料合成的TS-1与用传统有机原料合成的TS-1具有同样的特征。碱度的控制是合成的关键,配胶时需N2保护,加入晶种对合成有明显的导向作用,模板剂最低用量有一临界值,硅溶胶作硅源合成的TS-1晶粒比较大。