Synthesis and Configurational Assignment of the Amino Alcohol in the Eastern Fragment of the GE2270 Antibiotics by Regio- and Stereoselective Addition of 2-Metalated 4-Bromothiazoles to α-Chiral Electrophiles
作者:Oscar Delgado、Golo Heckmann、H. Martin Müller、Thorsten Bach
DOI:10.1021/jo060462g
日期:2006.6.1
S)-4-bromothiazolyl β-amino alcohol 29 was prepared from O-TBS protected (S)-ethyl mandelate in four steps and 33% overall yield. The bithiazole moiety in the desired products 2 and 3 was finally established by the regioselective Negishi coupling of 2,4-dibromothiazole (5) and the 4-zincated, N-Boc protected thiazole derivatives of the diastereomeric 4-bromothiazolyl β-amino alcohols 6 and 29.
已经开发了噻唑肽GE2270 A(1)的东部片段的合成。合成方法依赖于通过金属化和亲核加成(在C2处)或钯介导的交叉偶联(在C2或C4处)对2,4-二溴噻唑(5)的区域选择性功能化。通过将2金属化的4-溴噻唑(4)与对映体纯的扁桃酸衍生物偶联,可以确定N端立体中心的立体化学。无论是赤(2)和苏式(3)可配置的氨基醇用根据所使用的亲电子的高非对映选择性制备。更具体地说,苏里奥由O- TBS保护的(R)-扁桃腈合成62-构型的(S,R)-4-溴噻唑基β-氨基醇6,产率为62%。从N -PMB保护的(R,S)-对映异构体20获自O -TBS保护的(S)-扁桃醛,产率为67%。所述赤-构型(S,S)-4- bromothiazolylβ氨基醇29从制备ø -TBS保护(小号在四个步骤和33%的总收率) -乙基扁桃酸盐。所需产物2和通过2,4-二溴噻唑(5)与非对映体4-溴噻唑基β-氨基醇6和29的4-锌,N