Synthesis of Cystothiazole E and Formal Syntheses of Cystothiazoles A and C by Pd0-Catalyzed Cross-Coupling Reactions
作者:Thorsten Bach、Stefan Heuser
DOI:10.1002/1521-3765(20021216)8:24<5585::aid-chem5585>3.0.co;2-1
日期:2002.12.16
The synthesis of the naturally occurring bithiazole (+)-cystothiazole E (1e) is described starting from oxazolidinone 2. It proceeded in 10 steps and an overall yield of 37%. The key reaction of the sequence was a Suzuki cross-coupling between bromobithiazole 4 and the (E)-alkenylboronic acid derived from alkyne 18 (94% yield). Prior to the synthesis, more general investigations related to the cross-coupling
从恶唑烷酮2开始描述了天然存在的噻唑(+)-巯基噻唑E(1e)的合成。它以10个步骤进行,总产率为37%。该序列的关键反应是溴联噻唑4与衍生自炔烃18的(E)-烯基硼酸之间的Suzuki交叉偶联(收率94%)。在合成之前,进行了与溴比噻唑4的交叉偶联有关的更广泛的研究。而Heck反应失败了,Suzuki和Stille的交叉偶联反应成功进行了。通过这种方式,可以将源自炔烃11和锡烷12的烯基硼酸转化成相应的烯基联噻唑13(92%)和14(52%)。化合物4和锡烷5的Stille交叉偶联使得能够获得醛21(97%的收率),并为(+)-巯基噻唑E(1e)的替代路线铺平了道路。另外,醛21被转化为醛醇产物22(72%),该醛醇产物22已被用于先前合成的巯基噻唑A(1a)和C(1c)。在这方面,化合物21的制备代表了这些巯基噻唑的正式全合成。