作者:Yuki Iwaki、Hiroyuki Akita
DOI:10.1248/cpb.55.1610
日期:——
A convergent synthesis of cystothiazoles C 1 and D 3 was achieved based on Julia coupling between the functionalized aldehyde 5b, corresponding to left half of the final molecule, and aryl sulfone 6 or 7, bearing a bithiazole moiety, corresponding to right half. Methylation of 1 and 3 gave cystothiazole A 2 and melithiazol B 4, respectively. The overall yield (5 steps from (2R,3S)-3-methylpent-4-yne-1,2-diol 10; 57%) of 5b via the present route was improved in comparison to that of the previously reported functionalized aldehyde 5a (7 steps from 10; 13%). By applying the modified Julia coupling method, selectivity (6E/6Z=20 : 1—26 : 1) toward the (6E)-form of the coupled products (15 or 19) against the corresponding (6Z)-form was improved in comparison to the Wittig method (6E/6Z=4 : 1—6.9 : 1).
通过茱莉亚偶联,最终分子左半部分的官能化醛 5b 与右半部分的芳基砜 6 或 7(含有双噻唑分子)实现了环噻唑 C 1 和 D 3 的聚合合成。将 1 和 3 甲基化后,分别得到胱噻唑 A 2 和三甲基噻唑 B 4。与之前报道的官能化醛 5a(从 10 开始,分 7 步制备;13%)相比,通过本方法制备 5b 的总收率(从 (2R,3S)-3-甲基戊-4-炔-1,2-二醇 10 开始,分 5 步制备;57%)有所提高。通过应用改进的 Julia 偶联法,与 Wittig 法(6E/6Z=4 : 1-6.9 : 1)相比,提高了偶联产物(15 或 19)的 (6E) 形式对相应 (6Z) 形式的选择性(6E/6Z=20 : 1-26 : 1)。