4-(Dimethylamino)pyridine N-Oxide-Catalyzed Macrolactamization Using 2-Methyl-6-nitrobenzoic Anhydride in the Synthesis of the Depsipeptidic Analogue of FE399

Abstract

A depsipeptidic analogue of FE399 was efficiently synthesized mainly through macrolactamization using 2-methyl-6nitrobenzoic anhydride (MNBA), and a detailed investigation of the desired 16-membered macrolactam core of FE399 was performed. It was determined that the combination of MNBA and a catalytic amount of 4-(dimethylamino)pyridine N-oxide exhibits much higher activity than that of conventionally used coupling reagents such as hexafluorophosphate azabenzotriazole tetramethyl uronium and benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate.

DMAPO/Boc2O‐Mediated One‐Pot Direct N1‐Acylation of Indazole with Carboxylic Acids: A Practical Synthesis of N1‐Functionalized Alkyl Indazoles

“…This direct transformation of indazole also proceeded smoothly with naphthalene-containing carboxylic acids to provide the corresponding N1-acyl indazoles in good yields (25 and 26). Furthermore, various heteroaromatic carboxylic acids, such as furans, pyridines, pyrazine and quinoline, were found to be excellent substrates, and the corresponding N1-acyl indazoles (27)(28)(29)(30)(31)(32) were obtained in satisfactory yields.…”

“…[30] Furthermore, Shiina and coworkers developed an efficient protocol for macrolactamization and reported that DMAPO was the best catalyst for the process. [31] Ishihara and coworkers reported boronic acidÀ DMAPO cooperative catalysis for dehydrative condensation between carboxylic acids and amines. [32] In this context, we originally focused on the development of one-pot direct N-acylation of less nucleophilic N-heterocycles with carboxylic acids.…”

“…For example, Shiina and coworkers discovered in 2008 that DMAPO is an effective catalyst for amide bond formation reactions [30] . Furthermore, Shiina and coworkers developed an efficient protocol for macrolactamization and reported that DMAPO was the best catalyst for the process [31] . Ishihara and coworkers reported boronic acid−DMAPO cooperative catalysis for dehydrative condensation between carboxylic acids and amines [32] …”

Stereoselective Synthesis of Volicitin and 9-D 1-Volicitin

“…The synthesis of volicitin ( 1 ) is shown in Scheme 4 . The Wittig reaction of phosphonium salt 3 with aldehyde 4 , 11 derived from nonane-1,9-diol ( 15 ) by a two-step reaction via 16 , proceeded smoothly to give disilyl ether 17 . 12 Deprotection of 17 with PPTS afforded alcohol 18 in a 71% yield from phosphonium salt 3 .…”