Measuring the Hamiltonian of dipolar coupled spin systems is usually a difficult task due to the high complexity of their spectra. Currently, molecules with unknown geometrical structure and low symmetry are extremely...Measuring the Hamiltonian of dipolar coupled spin systems is usually a difficult task due to the high complexity of their spectra. Currently, molecules with unknown geometrical structure and low symmetry are extremely tedious or impossible to analyze by sheer spectral fitting. We present a novel method that addresses the problem of spectral analysis and report experimental results of extracting, by spectral fitting, the parameters of an oriented 6-spin system with very low symmetry in structure, without using apriori knowledge or assumptions on the molecular geometry or order parameters. The advantages of our method are achieved with the use of a new spectral analysis algorithm non-assigned frequency optimization of NMR spectra （NAFONS） and by the use of simplified spectra obtained by transition selective pulses. This new method goes beyond the limit of spectral analysis for dipolar coupled spin systems and is helpful for related fields, such as quantum computation and molecular structure analysis.展开更多
Skipped polyol is a common motif in numerous biologically significant polyketides and has been the focus of the development of novel synthetic methods and strategies. In this work, we devised a highly diastereoselecti...Skipped polyol is a common motif in numerous biologically significant polyketides and has been the focus of the development of novel synthetic methods and strategies. In this work, we devised a highly diastereoselective approach to access skipped triol(anti,syn-isomer) from a chiral α-allenic alcohol which was derived from kinetic resolution in our previous studies. An iodolactonization and subsequent radical deiodonation efficiently introduced the hydroxyl group at C3 in a highly diastereoselective manner and exemplified in enantioselective total synthesis of (+)-yashabushitriol.展开更多
Asymmetric hydrogenation of α-keto Weinreb amides has been realized with [Ru（（S）-Sunphos）（benzene）C1]C1 as the catalyst and CeC13·7H20 as the additive. A series of enantiopure -hydroxy Weinreb amides （up ...Asymmetric hydrogenation of α-keto Weinreb amides has been realized with [Ru（（S）-Sunphos）（benzene）C1]C1 as the catalyst and CeC13·7H20 as the additive. A series of enantiopure -hydroxy Weinreb amides （up to 97% ee） have been obtained. Cata- lytic amount of CeC13·7H20 is essential for the high reactivity and enantioselectivity and the ratio of CeC13·7H20 to [Ru（（S）-Sunphos）（benzene）C1]C1 plays an important role in the hydrogenation reaction.展开更多
文摘Measuring the Hamiltonian of dipolar coupled spin systems is usually a difficult task due to the high complexity of their spectra. Currently, molecules with unknown geometrical structure and low symmetry are extremely tedious or impossible to analyze by sheer spectral fitting. We present a novel method that addresses the problem of spectral analysis and report experimental results of extracting, by spectral fitting, the parameters of an oriented 6-spin system with very low symmetry in structure, without using apriori knowledge or assumptions on the molecular geometry or order parameters. The advantages of our method are achieved with the use of a new spectral analysis algorithm non-assigned frequency optimization of NMR spectra （NAFONS） and by the use of simplified spectra obtained by transition selective pulses. This new method goes beyond the limit of spectral analysis for dipolar coupled spin systems and is helpful for related fields, such as quantum computation and molecular structure analysis.
基金This work was supported by the National Natural Science Foundation of China (21472186)the Shanghai Science and Technology Commission (15JC1400400)+1 种基金partially supported by the Ministry of Science and Technology (2011CB710800)Calvine Lai thanks the internship from ENSCL to conduct the summer research (June–August of 2013) in the Hong laboratory
文摘Skipped polyol is a common motif in numerous biologically significant polyketides and has been the focus of the development of novel synthetic methods and strategies. In this work, we devised a highly diastereoselective approach to access skipped triol(anti,syn-isomer) from a chiral α-allenic alcohol which was derived from kinetic resolution in our previous studies. An iodolactonization and subsequent radical deiodonation efficiently introduced the hydroxyl group at C3 in a highly diastereoselective manner and exemplified in enantioselective total synthesis of (+)-yashabushitriol.
文摘Asymmetric hydrogenation of α-keto Weinreb amides has been realized with [Ru（（S）-Sunphos）（benzene）C1]C1 as the catalyst and CeC13·7H20 as the additive. A series of enantiopure -hydroxy Weinreb amides （up to 97% ee） have been obtained. Cata- lytic amount of CeC13·7H20 is essential for the high reactivity and enantioselectivity and the ratio of CeC13·7H20 to [Ru（（S）-Sunphos）（benzene）C1]C1 plays an important role in the hydrogenation reaction.
