Scalable Synthesis of the Desoxy-biphenomycin B Core
摘要:
We describe the evolution of a kilogram-scale synthesis of the protected cyclic tripeptide desoxy-biphenomycin B, based on an early discovery route. The retrosynthetic concept included a macrolactamization strategy to build the core ring system of biphenomycin B in combination with a double catalytic asymmetric hydrogenation protocol for the construction of the ansa-tripeptide precursor. Eventually, the kilogram process comprised a 16-step sequence with an overall yield for the longest linear sequence of 19.5%.
The total synthesis of the cyclopeptide biphenomycin B (1b), a compound exhibiting a potent antibacterial activity against Gram-positive bacteria, is described. The non-proteinogenic amino acid (S,S)-diisotyrosine (2) was prepared by enantioselective hydrogenation of the corresponding didehydroamino acids. The 15-membered ansa ring was obtained in 85% yield within 5 minutes by ring closure of the appropriate linear pentafluorophenyl ester in the two phase system chloroform-aqueous sodium hydrogen carbonate without dilution.
The total synthesis of biphenomycin A is described. Two of the five stereogenic centres were formed by enantioselective hydrogenation of the corresponding didehydroamino acids using the rhodium-DIPAMP catalyst and the two stereogenic centres of the α-amino-β-hydroxy unit were created by enantioselective hydrogenation using the ruthenium-BINAP catalyst or via a stereoselective aldol condensation, respectively. The biphenyl structural element was constructed by a palladium(0)-catalyzed coupling reaction. The 15-membered ansa ring was closed in 85 % yield by use of the appropriate, linear pentafluorophenyl ester in the two phase system chloroform/aqueous sodium hydrogen carbonate.
本文描述了联苯霉素 A 的全合成过程。五个立体中心中的两个是通过使用铑-DIPAMP 催化剂对相应的双脱氢氨基酸进行对映选择性氢化形成的,δ-氨基-δ-羟基单元的两个立体中心分别是通过使用钌-BINAP 催化剂进行对映选择性氢化或通过立体选择性醛醇缩合形成的。联苯结构单元是通过钯(0)催化的偶联反应生成的。在氯仿/水性碳酸氢钠两相体系中,使用适当的线性五氟苯基酯封闭 15 元的安萨环,收率为 85%。
Biphenomycin B, a highly potent antibiotic against Gram-negative, β-lactam-resistant bacteria, which was previously isolated from culture filtrates of Streptomyces griseorubiginosusNO. 43708, has now been synthesised.