Total control: The antibiotic BE‐43472B with a unique bisanthraquinone structure has been synthesized in a completely stereocontrolled manner. The key steps are 1) a pinacolrearrangement to install the angular naphthyl group, 2) a diastereoselective methylation of a lactol derivative, and 3) the late‐stage installation of the labile hydroxy group through an epoxide.
A variety of highly functionalized polycyclic isoxazoles are prepared by a two-step protocol: (1) 1,3-dipolar cycloaddition of o,oâ²-disubstituted benzonitrile oxides to para-quinone mono-acetals, then (2) dehydrogenation. The cycloaddition proceeds in a regioselective manner, favouring the formation of the 4-acyl cycloadducts, which are suitable intermediates for the synthesis of semi-aromatized polycyclic targets derived from polyketide type-II biosynthesis.
我们采用两步法制备了多种高度官能化的多环异噁唑:(1) o,oâ²-二取代苯腈氧化物与对苯醌单乙醛的 1,3-二极环化反应,然后 (2) 脱氢反应。该环化反应以区域选择性的方式进行,有利于形成 4-酰基环化产物,这些环化产物是合成来自多酮 II 型生物合成的半芳香化多环目标物的合适中间体。
Molecular Sieve (MS 4A) Promoted Cyclocondensation of Hindered, Aromatic Nitrile Oxides and Cyclic Diketones under Mild Conditions
作者:Keisuke Suzuki、Tomoo Matsuura、Jeffrey W. Bode、Yoshifumi Hachisu
DOI:10.1055/s-2003-41436
日期:——
Molecular sieves (MS 4A) serve as efficient promoters for the cyclocondensation of stable, hindered nitrile oxides and a variety of cyclic diketones to afford fused isoxazoles in good yield. The operational simplicity and remarkably mild reaction conditions compliment our amine-promoted cyclocondensation conditions and demonstrate broad substrate scope.
Structural incongruities of coleophomone natural products: insights by total synthesis of a semi-synthetic derivative
作者:Jeffrey W Bode、Keisuke Suzuki
DOI:10.1016/s0040-4039(03)00615-4
日期:2003.4
unexpected structural incongruity between coleophomones 1 and the reported structure of recently isolated natural product 2 was confirmed by totalsynthesis of key semi-synthetic derivative 3 and its positional isomer 4. In addition, possible mechanisms for the interconversion of expected structure 22 to observed compound 2 are postulated, some of which may have an important role in the biosynthetic origin