methyl-3-hydroxy-5-phenylpentanoate and (6E)-ethyl 5-hydroxy-3-oxo-7-phenylhept-6-enoate is described in high enantiomeric excess and good yields. The effect of different lipases in different solvents has been screened using different acylating agents. This protocol has been extended for the preparation of enantiomerically pure biologically important kavalactones.
Efficient Enantioselective Hetero-Diels−Alder Reaction of Brassard's Diene with Aliphatic Aldehydes: A One-Step Synthesis of (<i>R</i>)-(+)-Kavain and (<i>S</i>)-(+)-Dihydrokavain
An efficient catalytic asymmetrichetero-Diels-Alderreaction of Brassard'sdiene with aliphatic aldehydes was reported. The catalyst, which was generated from (R)-BINOL, Ti(i-PrO)4, and 4-picolyl chloride hydrochloride, promoted the reaction smoothly to afford the corresponding alpha,beta-unsaturated delta-lactone derivatives in moderate-to-good yields (46-79%) with high enantioselectivities (up to
Copper(I)‐Catalyzed Asymmetric Conjugate 1,6‐, 1,8‐, and 1,10‐Borylation
作者:Chang‐Yun Shi、Jungmin Eun、Timothy R. Newhouse、Liang Yin
DOI:10.1002/anie.202016081
日期:2021.4.19
Catalytic asymmetric remote conjugate borylation is challenging as the control of regioselectivity is not trivial, the electrophilicity of remote sites is extenuated, and the remote asymmetric induction away from the carbonyl group is difficult. Herein, catalytic asymmetric conjugate 1,6‐, 1,8‐ and 1,10‐borylation was developed with excellent regioselectivity, which delivered α‐chiral boronates in moderate
Heterogeneous enantioselective hydrogenation of 2-pyrones over cinchona-modified palladium
作者:Wolf-Rüdiger Huck、Tamas Mallat、Alfons Baiker
DOI:10.1039/b108944g
日期:2002.1.24
Asymmetric hydrogenation of 4-alkoxy and 4-methyl derivatives of 2-pyrones to the corresponding dihydro- or tetrahydropyrones over cinchona-modified Pd/TiO2 is fast under ambient conditions and affords good yields and high ee. cis-Tetrahydropyrones are obtained with 98–99% de. The ee can be further increased by kinetic resolution.
不对称 氢化在环境条件下,在金鸡纳改性的Pd / TiO 2上2-吡喃酮的4-烷氧基和4-甲基衍生物转化为相应的二氢-或四氢吡喃酮是快速的并且提供了良好的产率和高ee。顺式-四氢吡喃酮的de含量为98-99%。ee可以通过动力学拆分进一步提高。
Asymmetric synthesis of (<i>S</i>)-dihydrokavain from <scp>l</scp>-malic acid
Abstract A practical and efficient asymmetricsynthesis of (S)-dihydrokavain from known ethyl (S)-2-hydroxy-4-phenylbutanoate which is, in turn, readily available from l-malic acid as a cheap chiral pool material is described using regioselective ring-opening of the 1,2-cyclic sulfate with lithium-3,3,3-triethoxypropiolate and subsequent HgO/H2SO4-mediated lactonization as the key steps. Its opposite