were introduced, and systematic fluorine, bromine, and phenyl scans for phenylalanine in the P2 position were performed. Moreover, the N-terminal protection was varied. Kinetic investigations were carried out with cathepsin L, S, and K as well as papain. Changes in the backbone structure of the parent N-(tert-butoxycarbonyl)-phenylalanyl-glycine-nitrile (16), such as the introduction of an R-configured
Stereoselective Alkene Isomerization over One Position
作者:Casey R. Larsen、Douglas B. Grotjahn
DOI:10.1021/ja3036477
日期:2012.6.27
Although controlling both the position of the double bond and E:Z selectivity in alkene isomerization is difficult, 1 is a very efficient catalyst for selective mono-isomerization of a variety of multifunctional alkenes to afford >99.5% E-products. Many reactions are complete within 10 min at room temperature. Even sensitive enols and enamides susceptible to further reaction can be generated. Catalyst
carbonylation reactions, analogue coupling via base-metal, nickel catalysis has received less attention because of the easy formation of highly toxic and unreactive Ni(CO)4 species between Ni(0) and CO. To date, the use of inexpensive and widely available carbon monoxide (CO) gas for nickel-catalyzed carbonylation reaction remains challenging, and nickel-catalyzed four-componentcarbonylativereaction has not
过渡金属催化的羰基化是制备羰基化合物最直接的策略之一。然而,与成熟的贵金属催化羰基化反应相比,通过贱金属、镍催化的类似偶联反应较少受到关注,因为在 Ni(0) 和 CO 之间容易形成剧毒和非反应性 Ni(CO)4 物种迄今为止,使用廉价且广泛可用的一氧化碳 (CO) 气体进行镍催化羰基化反应仍然具有挑战性,并且尚未报道镍催化四组分羰基化反应。在这里,我们报告了在一个大气压 (1 atm) 的 CO 气体下,高选择性镍催化的烯烃四组分羰基化,以有效地获得一系列复杂的羰基化合物,包括在药物化学和化学生物学中非常感兴趣的氟化氨基酸和寡肽。该反应依赖于镍催化的一锅级联过程,在烯烃的碳碳双键上组装 CO、芳基硼酸、二氟烷基亲电试剂,为贱金属催化的羰基化级联反应开辟了新途径。
Synthesis of cyclic peptides using a palladium-catalyzed enyne cycloisomerization
In this letter, we report a palladium-catalyzedenynecycloisomerization of linear peptides to generate small cyclic peptides embedded with a conjugated 1,3-diene. The utility of these resulting macrocyclic dienes is demonstrated by carrying out [4+2] cycloadditions with dienophiles to generate constrained cyclic peptides with cyclic linkers.
Tandem Asymmetric Cycloaromatization/ Intramolecular Pictet‐Spengler‐Type Reaction. An Entry to Polycyclic Pyrroles
作者:Daniel Gaviña、Marcos Escolano、Fernando Rabasa‐Alcañiz、Santiago Díaz‐Oltra、María Sánchez‐Roselló、Carlos del Pozo
DOI:10.1002/adsc.202200399
日期:2022.9.6
The asymmetricsynthesis of tetracyclic pyrroles bearing a tetrasubstitutedcarbonstereocenter has been accomplished through a one-pot sequence that comprises a cross metathesis reaction followed by a tandem cycloisomerization/ intramolecular Pictet-Spengler-type reaction. This sequence took place on conveniently functionalized chiral amino acids to render the final products in good overall yields