共查询到20条相似文献,搜索用时 15 毫秒
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Kirill Nikitin Kamalraj V. Rajendran Helge Müller‐Bunz Declan G. Gilheany 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(7):1937-1940
Synthetic routes that provide facile access to either enantiomeric form of a target compound are particularly valuable. The crystallization‐free dual resolution of phosphine oxides that gives highly enantioenriched materials (up to 94 % ee) in excellent yields is reported. Both enantiomeric oxides have been prepared from a single intermediate, (RP)‐alkoxyphosphonium chloride, which is formed in the course of a selective dynamic kinetic resolution using a single enantiomer of menthol as the chiral auxiliary. The origin of the dual stereoselectivity lies in bifurcation of the reaction pathway of this intermediate, which works as a stereochemical railroad switch. Under controlled conditions, Arbuzov‐type collapse of this intermediate proceeds through C O bond fission with retention of the configuration at the phosphorus center. Conversely, alkaline hydrolysis of the P O bond leads to the opposite SP enantiomer. 相似文献
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Fei Jiang Ke‐Wei Chen Ping Wu Yu‐Chen Zhang Yinchun Jiao Feng Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(42):15248-15254
A new strategy for enantioselective synthesis of axially chiral naphthyl‐indoles has been established through catalytic asymmetric addition reactions of racemic naphthyl‐indoles with bulky electrophiles. Under chiral phosphoric acid catalysis, azodicarboxylates and o‐hydroxybenzyl alcohols served as bulky but reactive electrophiles that were attacked by C2‐unsubstituted naphthyl‐indoles, which underwent a dynamic kinetic resolution to afford two series of axially chiral naphthyl‐indoles in good yields (up to 98 %) and high enantioselectivities (up to 98:2 er). 相似文献
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Monika Dudek Ewa Machalska Tomasz Oleszkiewicz Ewa Grzebelus Rafal Baranski Piotr Szczeniak Jacek Mlynarski Grzegorz Zajac Agnieszka Kaczor Malgorzata Baranska 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(25):8471-8476
Carotenoid microcrystals, extracted from cells of carrot roots and consisting of 95 % of achiral β‐carotene, exhibit a very intense chiroptical (ECD and ROA) signal. The preferential chirality of crystalline aggregates that consist mostly of achiral building blocks is a newly observed phenomenon in nature, and may be related to asymmetric information transfer from the chiral seeds (small amount of α‐carotene or lutein) present in carrot cells. To confirm this hypothesis, we synthesized several model aggregates from various achiral and chiral carotenoids. Because of the sergeant‐and‐soldier behavior, a small number of chiral sergeants (α‐carotene or astaxanthin) force the achiral soldier molecules (β‐ or 11,11′‐[D2]‐β‐carotene) to jointly form supramolecular assemblies of induced chirality. The chiral amplification observed in these model systems confirmed that chiral microcrystals appearing in nature might consist predominantly of achiral building blocks and their supramolecular chirality might result from the co‐crystallization of chiral and achiral analogues. 相似文献