A concise synthesis of WIN 64821 (1), eurocristatine (2), 15,15’-bis-epi-eurocristatine (3), ditryptophenaline (4), ditryptoleucine A (6), WIN 64745 (7), cristatumin C (8), asperdimin (9), naseseazine A (10), and naseseazine B (11) is detailed based on a unique bioinspired dimerization reaction of tryptophan derivatives in aqueous acidic solution and one-pot procedure for construction of diketopiperazine rings. Total yields of these alkaloid syntheses were from 10% up to 27%. In addition, 1’-(2-phenylethylene)-ditryptophenaline (5) was synthesized using three one-pot operations. The studies detailed herein provided synthesized natural products for inhibitory activities of ubiquitin-specific protease 7 (USP7) and foam cell formation in macrophages.
In our continuing study of the reactivity and synthetic application of indolylborate as a versatile synthetic intermediate, we found that the use of indolylborate in palladium-catalyzed cross-coupling reaction is highly effective for the synthesis of indole derivatives. The present account deals with the results concerning a novel approach to indole alkaloids based on the use of the palladium-catalyzed cross-coupling. Dimeric indole alkaloid, yuechuke, was synthesized through the palladium-catalyzed carbonylative cross-coupling reaction. Pyridocarbazole alkaloids (ellipticine, olivacine, and their related alkaloids), and indolophenanthridine alkaloid (calothrixins A and B) were obtained by the use of cyclization/cross-coupling domino reaction. In addition, (CuOTf)2·toluene complex was demonstrated to catalyze 6π-electrocyclization of hexatrienes, leading to pyrido [4,3-b] carbazoles.
1-Methyl-3,5-dinitropyridone serves as an excellent substrate for the nucleophilic-type three-component ring transformation (TCRT). The reaction of dinitropyridone with aromatic ketones in the presence of ammonium acetate afforded 2-arylated 5-nitropyridines. In the TCRTs using cycloalkanones and α,β-unsaturated ketones, nitrated cycloalka[b]pyridines and alkenyl/alkynylpyridines were obtained, respectively. This protocol was also applicable to reactive aldehydes, which affords 3-substituted 5-nitropyridines. On the other hand, aliphatic ketones having two kinds of α-protons underwent a different type ring transformation leading to 2,6-disubstituted 4-nitroanilines. It was possible to use a combination of amine and acetic acid, by which N,N,2,6-tetrasubstituted nitroanilines were synthesized. This TCRT will be an efficient method for the synthesis of compounds possessing both an electron-donating and electron-withdrawing groups, which are useful for developing new functional materials.
Nucleic acids bridged between 2’- and 4’-positions are attracting much attention because the oligonucleotides bearing these derivatives generally increase in the binding affinity with single-stranded RNA and have an increased resistance against nuclease. It is found that their properties are greatly affected by size and composition of the bridge. In particular, introduction of heteroatom into the bridge unit is considered to give an influence on network of surrounding water molecules in formation of nucleic acid complex. Therefore, it would be meaningful to investigate and understand the properties of various 2’,4’-bridged nucleic acids. Under such a background, this account focuses on 2’,4’-bridged nucleic acids containing multiple heteroatoms in the bridge structures, with five-, six- and seven-membered bridges, have recently been reported by us, and the synthesis, duplex-forming ability with single-stranded nucleic acid and nuclease resistance of their modified oligonucleotides are mainly described.
Phthalocyanines and subphthalocyanines have been considerably researched in both academia and industry for the development of advanced materials such as photosensitizers for organic solar cells, anti-cancer agents for photodynamic therapy, electrochromic devices and among others. For the last decade, we have been interested in phthalocyanines having fluorine(s) at their peripheral positions, due to their specific properties induced by fluorine atoms; in particular, trifluoroethoxy-coated phthalocyanines. This review introduces the synthesis and application of trifluoroethoxy peri- substituted phthalocyanines and subphthalocyanines reported by our research group. The utilities and advantages induced by trifluoroethoxy group onto phthalocyanines and subphthalocyanines are discussed comparing to the well-studied analogues of non-substituted or tert-butyl substituted ones.
Jiadifenolide is a seco-prezizaane-type sesquiterpenoid isolated from the pericarps of the Chinese plant Illicium jiadifengpi in 2009. Jiadifenolide has shown potent activities in promoting neurite outgrowth. The structural features of jiadifenolide are pentacyclic ring system and seven contiguous stereocenters. In this review, total syntheses of jiadifenolide reported by four groups are described.