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Catalyst‐Enabled Site‐Divergent Stereoselective Michael Reactions: Overriding Intrinsic Reactivity of Enynyl Carbonyl Acceptors 下载免费PDF全文
Dr. Daisuke Uraguchi Ryo Shibazaki Naoya Tanaka Kohei Yamada Dr. Ken Yoshioka Prof. Dr. Takashi Ooi 《Angewandte Chemie (International ed. in English)》2018,57(17):4732-4736
A site‐divergent stereoselective Michael reaction system is developed based on the identification of two distinct catalysts. Cinchonidine‐derived thiourea catalyzes the 1,4‐addition of prochiral azlactone enolates to enynyl N‐acyl pyrazoles in a highly diastereo‐ and enantioselective manner to give stereochemically defined alkynes, while P‐spiro chiral triaminoiminophosphorane catalytically controls the stereoselective 1,6‐addition and the consecutive γ‐protonation of the vinylogous enolate intermediate to afford Z,E‐configured conjugated dienes. This 1,6‐adduct serves as a valuable precursor for the synthesis of a 2‐amino‐2‐deoxy sugar. 相似文献
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Bjrn Kusebauch Benjamin Busch Kirstin Scherlach Martin Roth Christian Hertweck 《Angewandte Chemie (International ed. in English)》2009,48(27):4869-4869
The fungus Rhizopus microsporus …? ; shown in the micrograph on the cover picture, harbors the endosymbiotic bacteria Burkholderia rhizoxinica that produces the antimitotic polyketide macrolide rhizoxin (see structure). In their Communication on page 5001 ff. , C. Hertweck and co‐workers show that the enzyme rhizoxin polyketide synthase is uniquely capable of introducing a β branch (highlighted by the magnifying glass) by a Michael‐type addition of a malonyl unit to an acryloyl intermediate.
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Zhipeng Yu Xiaohua Liu Dr. Lin Zhou Lili Lin Dr. Xiaoming Feng Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(28):5195-5198
Two activations are better than one : The chiral bifunctional guanidine 1 , which features an amino amide backbone, catalyzes the asymmetric Michael addition of a range of substrates and gives products with excellent stereoselectivities. The method also allows the efficient synthesis of optically pure β‐amino acid esters. Both the guanidine group and the NH proton of the amide were important for the dual activation.
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