查询词典 disubstituted

The synthesis of sterically hindered peptides containing N-alkylated or 〓disubstituted amino acid residues is being a challenge, which results in difficultcondensation using the usual DCC/HOBt or HOBt-derived coupling reagents.

多肽合成的一个主要难题是富含N-烷基化氨基酸或C〓二烷基化氨基酸的肽链的合成，采用BOP或HBTU等常规缩合剂往往不能得到令人满意的结果。

Based on the development of homogeneous gold complex catalyst, the polymer immobilized nano-gold catalyst was also prepared and used for oxidative carbonylation of amines or activation of carbon dioxide to carbamates and disubstituted ureas without addition of any co-catalyst and dehydration agents with greatly enhanced catalytic activity (TOF≈3000mol/mol/h).

同时，纳米金可以催化活化二氧化碳与脂肪族胺反应制备二取代脲，避免了传统上二氧化碳活化所大量使用的脱水剂，是当前文献报道最高效的胺与二氧化碳反应的催化剂体系（TOF≈3000mol/mol/h）。

Novel 2,3-disubstituted indoles as anticancer agent s in total yield of 33%~37% were synthesized from o-iodoaniline and phenylethyne by ten-steps reaction.

以邻碘苯胺和苯乙炔为原料，经10步反应合成了2，3-二取代的新型吲哚抗癌试剂，总收率33%~37%，其结构经1H NMR和MS表征。

This thesis sets up a new method to synthesize stereoselectively ?ra玸--2,5-disubstituted tetrahydrofurans by introducing two alkyl groups in 3-C and 5-C of lactol, flash decomposition and hydrogenation.

本文独创新的合成方法：以-乳醇，即-4，10-二氧杂三环[5.2.1.0~(2，6)]-癸-8-烯-3-醇为原料，在其3-位和5-位先反向引入两个取代基，再经过热分解和催化加氢反应，高立体选择性地合成反式-2，5-二取代四氢呋喃。

The analytical results have shown that p ro ducts mainly consisted of some monosubstituted, disubstituted and a few trisub stituted naphthalenes. Except the low activity of HZSM-5 catalyst, all other z eolite catalysts have higher activity. HY and Hβ catalytic activities were the highest, and their naphthalene conversions attained to 79.12 and 55.79 percent respectively, but their selectivities for 2-isopropylnaphthalene, 2,6-diisopropylnaphthalene(2,6-DIPN) and 2,7-diisopropylnaphthalene ( 2,7-DIPN) were too low. ZM catalysts had good activity and much better selecti vity, especially for ZM4-3, of which its 2,6-DIPN/2,7-DIPN ratio was 2.97. Th er efore, some zeolite catalysts are recommended for shape selective isopropylat ion of coal tar naphthalene.

研究结果表明，煤焦油萘异丙基化产物主要由一取代萘、二取代萘以及少量三取代萘组成；除HZSM-5活性较低以外，其它催化剂均有较高的反应活性，其中HY和Hβ反应活性最高，萘转化率分别达75.15％和55.96％，但β位产物的选择性较差；ZM类催化剂既有一定的活性，又有较高的β选择性，是萘择形异丙基化反应理想的备选催化剂。

The reaction of cyclic b-keto esters with CF3CO2ZnCH2I provides the corresponding ring-expanded products with the advantage of mild condition in moderate to good yields. A simple and efficient procedure has been developed for a variety of 1,3-diketones converted into the corresponding 1,4-diketones and trans-1,2-disubstituted cyclopropanols in high yields. In conclusion, this new type of organozinc reagents has been developed for many useful reaction in organic synthesis.

利用有机锌试剂所具有的双重特性，在新型的Baylis-Hillman反应中，可以直接与炔基酮和醛反应一锅制得多官能团的三取代的顺式烯；在b-酮酯化合物的扩环反应中，取得了重要进展，得到了增加一个碳的扩环产物，&一步法&合成，反应条件温和、环境友好；在1，3-二酮分子中成功地插入1个碳，合成出1，4-二酮和环丙醇，为现代有机合成提供了新的合成方法，具有良好的应用前景。

The facts indicate that apart from the asymmetric induction of chiral diamine backbone,sterically hindered substitute groups on the aromatic rings,and the presence of sp~3-hydridized amino donors and its N,N\'-disubstituted groups in chiral SalanCrX complexes all play important roles in controlling polymer stereochemistry and enantioselectivity.

研究发现除了手性二胺骨架的不对称诱导作用，苯环上的大位阻取代基、N，N\'-二取代基的位阻作用以及N原子上sp~3杂化的供电子效应都对调控聚合物的区域和对映体选择性有很大作用。

The 3,4-disubstituted succinimide substructure-containing natural products andindolizidine alkaloids, tropane alkaloids are widespread in nature. Most of themexhibit important bioactivities.

含有3，4-二取代琥珀酰亚胺结构的天然产物以及吲哚里西啶生物碱、托品烷类生物碱广泛分布于自然界中，它们大多具有重要的生物活性。

Results and discussion Molecular design and synthesis Although a vast number of phthalocyanines have been reported, to our knowledge, these 1,4-disubstituted analogues remain relatively rare.6b,8 Compared with the unsubstituted zinc phthalocyanine, they exhibit a red-shifted Q band at ca.

结果和讨论分子设计和合成虽然数目庞大的酞菁的报告，以我们的知识，这些1，4取代类似物仍然相对 rare.6b ， 8日与unsubstituted锌酞菁，他们表现出了红移Q带

In this dissertation, the efforts were focused on design and synthesis of chiral tmsymmetrical urea, cholic acid and heteroaromatic molecular tweezers and their molecular recognition as well as enantioselective recognition. A series of useful and creative results have been obtained.Three new types of chiral molecular tweezers containing unsymmetrically disubstituted urea unit, four new types of chiral molecular tweezers based on steroid cholic acid and one type of heteroaromatic molecular tweezers involving multiple hydrogen-bonding site have been designed and synthesized.

本文致力于新型手性不对称脲、胆甾和芳杂环类分子钳受体的设计合成及其对阴离子、中性分子和手性分子的识别及对映选择性识别性能研究，取得了一系列具有重要学术意义与应用前景的创新性结果。

In the United States, chronic alcoholism and hepatitis C are the most common ones.

在美国，慢性酒精中毒，肝炎是最常见的。

If you have any questions, you can contact me anytime.

如果有任何问题，你可以随时联系我。