3347-90-8Relevant articles and documents
Fredga,Tenow,Billstroem
, p. 5 (1943)
Polycyclic guanidine-containing compounds from the mediterranean sponge Crambe crambe: The structure of 13,14,15-isocrambescidin 800 and the absolute stereochemistry of the pentacyclic guanidine moieties of the crambescidins
Jares-Erijman,Ingrum,Carney,Rinehart,Sakai
, p. 4805 - 4808 (1993)
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Highly Enantioselective O-H Bond Insertion Reaction of α-Alkyl- A nd α-Alkenyl-α-diazoacetates with Water
Li, You,Zhao, Yu-Tao,Zhou, Ting,Chen, Meng-Qing,Li, Yi-Pan,Huang, Ming-Yao,Xu, Zhen-Chuang,Zhu, Shou-Fei,Zhou, Qi-Lin
supporting information, p. 10557 - 10566 (2020/07/27)
Catalytic asymmetric reactions in which water is a substrate are rare. Enantioselective transition-metal-catalyzed insertion of carbenes into the O-H bond of water can be used to incorporate water into the stereogenic center, but the reported chiral catalysts give good results only when α-aryl-α-diazoesters are used as the carbene precursors. Herein we report the first highly enantioselective O-H bond insertion reactions between water and α-alkyl- A nd α-alkenyl-α-diazoesters as carbene precursors, with catalysis by a combination of achiral dirhodium complexes and chiral phosphoric acids or chiral phosphoramides. Participation of the phosphoric acids or phosphoramides in the carbene transfer reaction markedly suppressed competing side reactions, such as β-H migration, carbene dimerization, and olefin isomerization, and thus ensured good yields of the desired products. Fine-tuning of the ester moiety facilitated enantiocontrol of the proton transfer reactions of the enol intermediates and resulted in excellent enantioselectivity. This protocol represents an efficient new method for preparation of multifunctionalized chiral α-alkyl and α-alkenyl hydroxyl esters, which readily undergo various transformations and can thus be used for the synthesis of bioactive compounds. Mechanistic studies revealed that the phosphoric acids and phosphoramides promoted highly enantioselective [1,2]- A nd [1,3]-proton transfer reactions of the enol intermediates. Maximization of molecular orbital overlap in the transition states of the proton transfer reactions was the original driving force to involve the proton shuttle catalysts in this process.
Method for Improving Optical Purity of 2-Hydroxycarboxylic Acid or Derivative Thereof
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Paragraph 0082; 0083, (2016/04/20)
To provide a method for improving optical purity of an optically active 2-hydroxycarboxylic acid or a derivative thereof, which is useful as a raw material in the manufacture of medicines, agrochemicais, and industrial products. The method of the invention for improving purity of a hydroxycarboxylic acid of the following formula (1a) or (1b) or a derivative thereof includes the steps of reacting the hydroxycarboxylic acid of the following formula (1a) or (1b) with at least one optically inactive base selected from the group consisting of an alkali metal, alkoxide and a secondary amine in the presence of a solvent and, subsequently, performing recrystallization, to thereby form a hydroxycarboxylic acid salt of the following formula (IIIa) or (IIIb): wherein R1 represents a C1-8 alkyl group, and R2 represents an alkali metal or a secondary amine.
