硅胶催化的选择性去除N-Boc保护基

发现了在回流的甲苯中, 以硅胶为催化剂, 多种N-Boc保护的伯胺、仲胺、氨基酸的氨基都可以迅速脱除Boc. 该方法具有条件温和、操作简便、反应时间短和产率高等优点. 同时, 其它常用的保护基Cbz和Fmoc等在同样的条件下不受影响.     

Highly Selective Preparation of 3-and 6-Modified Mannose/Altrose Derivatives

Introduction Asacoretrisaccharide,the3,6branchedtriman nosaccharideunit(Manα16Man31αMan)iswidely expressedonalotofglycoproteins.Itexistsinallas paragines linkedoligosaccharides(N glycans)andthe majorConAbindingepitopeonoligosaccharide type carbohydrate[…     

Design and Synthesis of Some Novel Oxiconazole‐Like Carboacyclic Nucleoside Analogues,as Potential Chemotherapeutic Agents

The syntheses of some novel carboacyclic nucleosides, 17a – 17o , containing oxiconazole‐like scaffolds, are described (Schemes 1–3). In this series of carboacyclic nucleosides, pyrimidine as well as purine and other imidazole derivatives were employed as an imidazole successor in oxiconazole. These compounds could be prepared in good yields by using two different strategies (Schemes 1 and 2). Due to Scheme 1, the N‐coupling of nucleobases with 2‐bromoacetophenones was attained for 18a – 18e , and their subsequent oximation affording 19a – 19e and finally O‐alkylation with diverse alkylating sources resulted in the products 17a – 17g, 17n , and 17o . In Scheme 2, use of 2‐bromoacetophenone oximes 20 , followed by N‐coupling of nucleobases, provided 19f – 19j whose final O‐alkylation produced 17h – 17m (Scheme 2). For the rational interpretation of the dominant formation of (E)‐oxime ethers rather than (Z)‐oxime isomers, PM3 semiempirical quantum‐mechanic calculations were discussed and the calculations indicated a lower heat of formation for (E)‐isomers.     

含有二糖结构的核苷类似物的合成

利用Ferrier重排反应合成了两个系列的连有核音的2,3-不饱和糖苷(其中核耷包括尿苷、腺苷、肌苷等).这些新化合物的结构通过NMR和MS(HRFAB)得到证实.     

Syntheses of Nucleoside Derivatives Containing Fmoc- or Trityl-protected Amino Acids

Facile direct esterification reactions between 2‘, 3‘-O-isopropylidene-nucleosides and Fmoc- or trityl-protected amino acids via N, N-dicyclohexyl-carbodiimide(DCC) mediated condensation are described. These reactions offer a mild and convenient method to synthesize aminoacylated nucleoside derivatives.     

A New Method for Selective Deprotection of Anomeric N,O-Dimethylhydroxylamine Promoted by TMSCl

TMSCl was shown to be an efficient reagent for selective deprotection of the anomeric position protected as N,O-dimethylhydroxylamine glycoside. This deprotection condition was proved to be compatible with a number of protecting groups, such as the TBDPS, acetyl, benzyl, benzylidene, and benzoyl groups.     

NaOAc-Mediated Selective Deprotection of Aromatic Acetates and Its Application in the Synthesis of Natural Products

We have developed an efficient method to deacetylate the aromatic acetates using NaOAc in excellent yields and demonstrated the application of the procedure in the synthesis of natural products.     

溴代1,4,5,8-萘四甲酸酐的选择性合成

在常压下, 以溴化钠和发烟硫酸(含质量分数为40%的SO₃)为溴化试剂, 通过控制反应温度、 反应时间和溴化钠的投料比选择性地合成了2-溴-1,4,5,8-萘四甲酸酐和2,6-二溴-1,4,5,8-萘四甲酸酐. 本研究提供了一种合成溴代1,4,5,8-萘四甲酸酐衍生物的新方法.     

Selective hydrolysis of anti-1,3-diol-acetonides for the differentiation of 1,3-anti and 1,3-syn diols

A mild and general method for the selective cleavage of anti-1,3-acetonides has been developed for the differentiation of 1,3-anti and 1,3-syn diols in long chain polyolic fragments. The diluted acidic conditions applied to these systems are compatible with other common protecting groups such as silyl ethers and benzyloxymethyl ethers.     

Deprotection of t-Butyldimethylsiloxy(TBDMS)Protecting Group

t-Butyldimethylsilyl(TBDMS)ether can be cleaved upon refluxing in acetone/H2O(95: 5)in the presence ora catalytic amount of copper(II)chloride dihydrate(5 mmol %).     

Preparation and Deprotection of Aldehyde Dimethylhydrazones

Aldehydes were conveniently protected as dimethylhydrazones by stirring a mixture of the aldehyde, N,N‐dimethylhydrazine, anhydrous magnesium sulfate, and dichloromethane at room temperature. Azeotropic removal of water, formed during the course of the reaction, was not required because anhydrous magnesium sulfate functions as a water scavenger. Deprotection of aldehyde dimethylhydrazones was accomplished by stirring a mixture of the aldehyde dimethylhydrazone and aqueous glyoxylic acid at room temperature. The reaction time for the preparation and deprotection of aldehyde dimethylhydrazones varied with the structure of the aldehyde.     

Mild, selective deprotection of PMB ethers with triflic acid/1,3-dimethoxybenzene

An efficient method for the cleavage of the p-methoxybenzyl protecting group of several alcohols in the presence of 0.5 equiv of trifluoromethanesulfonic acid and 1,3-dimethoxybenzene in dichloromethane at room temperature is described.     

Deprotection of Acetals from Unsaturated,Unstable Bromoketones

The unstable ketones 1-bromo-3-buten-2-one, 1-bromo-3-butyn-2-one, and 1,3-dibromo-3-buten-2-one can be obtained from the corresponding acetals in high yields by treating the acetals with anhydrous iron (III) chloride suspended on dry silica. A simplified procedure for preparing the reagent is also given.     

An Unusual N-Boc Deprotection of Benzamides under Basic Conditions

For the first time, an unusal cleavage of N‐tert‐butyloxycarbonyl (N‐Boc) protection from N‐Boc‐protected benzamide under basic conditions in excellent yields is reported. The deprotection involves the N‐Boc emigration from the benzamide to form 2‐O‐Boc group followed by O‐Boc deprotection on the phenyl ring.     

Bismuth compounds in organic synthesis. Deprotection of ketoximes using bismuth bromide-bismuth triflate

Ketoximes undergo deprotection in CH₃CN/acetone/H₂O (3:6:1) in the presence of 20-40 mol% BiBr₃/5 mol% Bi(OTf)₃. Bismuth(III) salts are relatively non-toxic, insensitive to air and inexpensive. These features coupled with the use of a relatively non-toxic solvent system make this method an attractive alternative to existing routes for deprotection of ketoximes.     

人工神经网络法预测核苷及核酸碱基的疏水分配系数

用人工神经网络方法预测核苷及核酸碱基一类化合物的ｌｇＰ值,预测精度显著优于ＢｌｇＰ法和ＡｌｇＰ法,根据预测结果讨论了分子内氢健及分子构象柔顺性对这类化合物疏水性的影响。     

Mild Approach to the Deprotection of Troc from Protected Amines Using Mischmetal and TMSCl

The 2,2,2-trichloroethoxycarbonyl (Troc) protecting group was efficiently removed from Troc-protected aliphatic and aromatic amines and also some Troc, Tos- and Troc, Ac-protected amines using activated mischmetal (MM). All reactions were performed by refluxing in dry tetrahydrofuran under an argon atmosphere and gave moderate to excellent yields. Several new compounds were synthesized, and new data about reactivity of Troc group were obtained.