Total synthesis and conformational studies of hapalosin, N-desmethylhapalosin and 8-Deoxyhapalosin1Dedicated with affection and respect to the memory of Professor Sir Derek H. R. Barton in recognition of his distinguished contributions to science and in sincere gratitude for the immense degree of inspiration and encouragement he provided to one of us (J. Zhu).1
作者:Björn Wagner、Gabriel Islas Gonzalez、Marie Elise Tran Hun Dau、Jieping Zhu
DOI:10.1016/s0968-0896(98)00208-9
日期:1999.5
vicinal amino alcohol and latent N-methyl function was established which allowed synthesizing both hapalosin (2) and N-desmethylhapalosin (3) from the same linear precursor 32 in a step-efficient and atom economic way. In contrast to hapalosin (2) and N-desmethyl analogue (3), the amide bond of 8-deoxy hapalosin (4) exists at room temperature (CDCl3) exclusively in s-cis conformation as evidenced by NOE
Hapalosin(2),一种具有MDR逆转活性的12元环状双缩肽,已经使用大内酰胺化作为重要的成环步骤合成了类似物(3)和(4)。三个结构单元:(2S,3R)-3-(叔丁基二甲基甲硅烷氧基)-2-甲基癸酸(13),(S)-2-羟基-3-甲基丁酸苄酯(14)和(4S,3R)分别由Evans的手性酰亚胺(9),L-缬氨酸和LN-Boc苯丙氨酸(17)制备了-4-(苄氧基羰基-甲基氨基)-3-甲氧基甲氧基-5-苯基1-戊酸(28),分别为通过两次使用山口的耦合方法组装在一起。在这项研究过程中发现了利用邻位氨基醇功能的新型和有效的选择性N-甲基化的γ-羟基-β-氨基酯。从而,在催化量的pTsOH存在下,用HCHO处理化合物19,然后还原(NaBH3CN,TFA,CH2Cl2)如此形成的恶唑烷24,得到N-甲基化产物25。此外,恶唑烷起着保护基的双重作用。建立了邻氨基氨基醇和潜在的N-甲基功能,该