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Enantioselective Synthesis of All‐Carbon Quaternary Stereogenic Centers via Copper‐Catalyzed Asymmetric Allylic Alkylation of (Z)‐Allyl Bromides with Organolithium Reagents 下载免费PDF全文
Dr. Martín Fañanás‐Mastral Dr. Romina Vitale Dr. Manuel Pérez Prof. Dr. Ben L. Feringa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(11):4209-4212
A copper/phosphoramidite catalyzed asymmetric allylic alkylation of Z trisubstituted allyl bromides with organolithium reagents is reported. The reaction affords all‐carbon quaternary stereogenic centers in high yields and very good regio‐ and enantioselectivity. This systematic study illustrates the crucial role of the olefin geometry of the allyl substrate on the outcome of the reaction and provides a viable alternative to access these important structural motifs. 相似文献
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Yoshihiro Hayakawa Reiko NagataAkiyoshi Hirata Mamoru HyodoRie Kawai 《Tetrahedron》2003,59(34):6465-6471
This paper describes a new method for synthesizing biologically important cyclic bis(3′→5′)diguanylic acid (cGpGp) in a higher yield than that of the existing synthetic method. In the new synthesis, the following two means, in place of those used in the existing synthesis are employed as main strategies to cause the increase in product yield. One of these distinctive strategies in the new synthesis is that the phosphoramidite method is used for the preparation of a key synthetic intermediate of a linear guanylyl(3′→5′)guanylic acid derivative. This method allowed higher-yield formation of the intermediate than that by the triester method used in the existing synthesis. The second distinctive strategy used in the new synthesis is that allyloxycarbonyl and allyl groups are used for the protection of two guanine bases and two internucleotide bonds, respectively. These four allylic protectors can be removed all at once by the organopalladium-catalyzed reaction under neutral conditions. Thus, deprotection of the protected cGpGp precursor was achieved in the present synthesis in a shorter step and under milder conditions than the deprotection achieved in the existing synthesis, which uses diphenylacetyl and o-chlorophenyl groups as protectors for two guanine bases and two internucleotide bonds, respectively, whose full removal requires two different procedures including rather harsh basic treatment. As a result, technical loss and decomposition of the target product in the new synthesis is remarkably reduced. 相似文献
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Vera I MaslennikovaRoman V Merkulov Maria V DyagilevaLarisa K Vasyanina Konstantin A LyssenkoMikhail Yu Antipin Dirk WeberIngmar Bauer Wolf D Habicher 《Tetrahedron》2003,59(10):1753-1761
It was found that the cyclophosphorylation of polyphenols by diamidoarylphosphites proceeds via the rupture of only one P-N bond and one P-O bond, the second P-N bond remaining intact. It is supposed that the unusual lack of reactivity of the P-N bond is due to the spatial arrangement of the amido group with respect to the reaction site in phosphorylated intermediates 5. 相似文献
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Shui-Bing Chen Yan-Mei Li Shi-Zhong Luo Gang Zhao Bo Tan Yu-Fen Zhao 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):277-291
Abstract O-phosphorylated peptide and amino acid are important in living system. In this paper, Dialkyl-N,N-dialkyl phosphoramidites (DDPA) 3 were synthesized using two methods. The reaction of DDPA with the hydroxyl group of the corresponding amino acids in the presence of tetrazole, followed by oxidation, gave O-phosphoryl amino acid methyl esters in a good yield. A systematical study of the reactivity of DDPA was presented too. 相似文献
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Hongying Tang Xiamin Cheng Zhongbiao Zhang 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):8-15
Abstract Two novel chiral thiophosphoramides and two chiral phosphoramidites were synthesized starting from (S)-α-phenylethylamine and (R)-(+) or (S)-(?)-1,1′-Bi-2-naphthol (BINOL), respectively, and their application in combination with Lewis acid as cocatalysts in asymmetric Morita–Baylis–Hillman (MBH) reaction was investigated. Dramatic rate acceleration (the corresponding adducts were obtained in fair to excellent chemical yield within 15 min–5 h) was observed in these chiral phosphorus reagents/Lewis acid cocatalyzed MBH reaction between 4-nitrobenzaldehyde and activated alkenes, and in one case, moderate enantioselectivity was achieved (the corresponding adduct's ee value is 44%). 相似文献
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Cationic Ir/Me‐BIPAM‐Catalyzed Asymmetric Intramolecular Direct Hydroarylation of α‐Ketoamides 下载免费PDF全文
Tomohiko Shirai Prof. Dr. Hajime Ito Prof. Dr. Yasunori Yamamoto 《Angewandte Chemie (International ed. in English)》2014,53(10):2658-2661
Asymmetric intramolecular direct hydroarylation of α‐ketoamides gives various types of optically active 3‐substituted 3‐hydroxy‐2‐oxindoles in high yields with complete regioselectivity and high enantioselectivities (84–98 % ee). This is realized by the use of the cationic iridium complex [Ir(cod)2](BArF4) and the chiral O‐linked bidentate phosphoramidite (R,R)‐Me‐BIPAM. 相似文献
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Zehong Liang Dr. Petja Rosenqvist Ella Pajuniemi Dr. Mikko Ora Dr. Petri Heinonen Prof. Pasi Virta Prof. Mikko Oivanen 《European journal of organic chemistry》2023,26(36):e202300614
5'-O-(2-isopropoxyprop-2-yl) (IIP)-protection was introduced to 5’-OH function of nucleosides in high yields by an acid-catalysed transacetalization with 2,2-diisopropoxypropane. The applicability of this temporal 5’-O-protecting group was demonstrated in the liquid phase oligonucleotide synthesis (LPOS) using the corresponding phosphoramidite building blocks (dA, dG, dC and dT) and a tetrapodal precipitative soluble support. Standard protecting groups were used on nucleobases. Tetrazole as an activator, followed by oxidation using m-chloroperbenzoic acid, was used for the coupling. The IIP was shown to be a capable choice to the 5’-O protection in solution phase synthesis. It could be readily removed with formic acid (t1/2<10 s in 6 % HCOOH in dichloromethane/methanol (2/1) at RT), resulting in volatile byproducts (acetone and isopropanol). 相似文献