依赖于螺缩醛形成的动力学和热力学控制,描述了altohyrtin A /海绵抑素1的C16-C28 CD-螺缩醛亚基的立体控制合成。动力学控制方法导致所希望的螺缩醛异构体稍微偏爱(60∶40)。通过热力学方法,可以通过酸促进的平衡,C23差向异构体的色谱分离以及不希望的异构体重新达到平衡条件,从而容易地获得所需的螺缩醛。这种可扩展的合成序列提供了数克的,因此能够成功完成altohyrtin A /海绵体抑素1的总合成,如本系列文章的第4部分所报道。
依赖于螺缩醛形成的动力学和热力学控制,描述了altohyrtin A /海绵抑素1的C16-C28 CD-螺缩醛亚基的立体控制合成。动力学控制方法导致所希望的螺缩醛异构体稍微偏爱(60∶40)。通过热力学方法,可以通过酸促进的平衡,C23差向异构体的色谱分离以及不希望的异构体重新达到平衡条件,从而容易地获得所需的螺缩醛。这种可扩展的合成序列提供了数克的,因此能够成功完成altohyrtin A /海绵体抑素1的总合成,如本系列文章的第4部分所报道。
Being selective: The catalyticallylation of α,β‐unsaturated aldehydes with allyltrichlorosilane in the presence of chiral 3,3′‐unsymmetrically substituted bis(tetrahydroisoquinoline) N,N‐dioxides was explored. The allylation of various aldehydes proceeded under mild reaction conditions (−78 °C) with high yields and enantioselectivity (see scheme). This allylation was applied in the synthesis of (
Tetrahydroisoquinoline-Based N-Oxides as Chiral Organocatalysts for the Asymmetric Allylation of Aldehydes
作者:Tricia Naicker、Per I. Arvidsson、Hendrik G. Kruger、Glenn E. M. Maguire、Thavendran Govender
DOI:10.1002/ejoc.201100923
日期:2011.12
The short synthesis of a series of novel chiral N-oxideorganocatalysts and their evaluation in the asymmetricallylation reaction of aromatic and α-β-unsaturated aldehydes with allyltrichlorosilane is reported. These readily modifiable organocatalysts are the first of their kind based on the tetrahydroisoquinoline framework. The chiral homoallyl products were obtained with good chemical efficiency
A highly stereoselective synthesis of (+)-cryptocarya diacetate is achieved through our recently developed strategy for the construction of 1,3-diols via Prins cyclisation. The route relies mainly on the reductive cleavage of allylic ethers, ozonolysis and Wittig olefination along with Prins cyclisation.
Studies towards the total synthesis of the marine-derived immunosuppressant discodermolide; asymmetric synthesis of a C<sub>1</sub>–C<sub>8</sub>δ-lactone subunit
作者:Ian Paterson、Stephen P. Wren
DOI:10.1039/c39930001790
日期:——
The stereoselective, boron-mediated, aldol/reduction sequence, 4+5â8â9, allows an efficient asymmetric synthesis of the δ-lactone-containina. C1âC8 subunit 2 of discodermolide 1.
Oxyanion Orientation in Anionic Oxy-Cope Rearrangements
作者:Eun Lee、Yong Rok Lee、Bongjin Moon、Ohyun Kwon、Mi Seong Shim、Jae Sook Yun
DOI:10.1021/jo00085a037
日期:1994.3
Efficiency of chirality transfer in anionic oxy-Cope rearrangement depends solely on the orientational preference of the oxyanionic bond in the substrates with a single carbinol carbon chiral center. In chairlike transition-state conformations for the rearrangement of simplest substrates like anions generated from (E)-1-phenyl-1,5-hexadien-3-ol and (E)-1,5-heptadien-4-ol, the oxyanionic bond is more prone to adopt the pseudoaxial orientation. On the other hand, anions generated from (E)-2-methyl-1,5-heptadien-4-ol, (E)-5-tert-butyl-1-phenyl-1,5-hexadien-3-ol, and 4-(2'-methyl-1'-cyclohexenyl)-1-buten-3-ol undergo rearrangement via chairlike transition states in which the pseudoequatorial oxyanionic bond is favored. It can thus be surmized that there is a slight stereoelectronic preference for the pseudoaxial oxyanionic bond in the chairlike transition states for the rearrangement of substrates without steric constraints. Substitution at C5 of the basic 1,5-hexadien-3-ol framework of substrates, however, leads to 1,3-diaxial steric interaction in the chairlike transition states with pseudoaxial oxyanionic bond, and pseudoequatorial disposition of oxyanionic bond becomes more favorable.