Facile Synthesis of Isoquinolines, β‐Carbolines, and 3‐Deazapurines

A metal-free decarboxylative cyclization from natural α-amino acids to construct pyridine derivatives

“…10,11 It is difficult to adopt the previous methods to prepare the pyridines which contain the moiety of natural a-amino acids. On the other hand, decarboxylative coupling reactions, including decarboxylative coupling of aamino acids, have developed remarkably in recent years, 12,[13][14][15][16][17][18]…”

PhI(OAc)2-mediated one-pot oxidative decarboxylation and aromatization of tetrahydro-β-carbolines: synthesis of norharmane, harmane, eudistomin U and eudistomin I

“…It is important to note that previously this transformation has been achieved using DDQ in very low yields. 19c In view of the above findings, this method appeared suitable for the total syntheses of marine β-carboline alkaloids eudistomin U (9) and eudistomin I (12). Eudistomin U (9) was isolated from the marine ascidian Lissoclinum fragile and is reported to possess antimicrobial and anticancer activities with a strong DNA binding ability.…”

“…In the following passages, we disclose a one-pot oxidative decarboxylation and aromatization of tetrahydroβ-carbolines mediated by the hypervalent iodine reagent, iodobenzene diacetate. Additionally, this method has been employed for the synthesis of β-carboline alkaloids such as norharmane (2o), harmane (2p) eudistomin U (9) and eudistomin I (12) in high yields.…”

“…In general, the Pictet-Spengler reaction followed by oxidative decarboxylation and dehydrogenation reactions is the most widely followed method to access β-car-bolines. Oxidative decarboxylation reactions are generally sluggish and are typically carried out at high temperatures using reagents such as K 2 Cr 2 O 7 11 in acetic acid, persulfate in the presence of catalytic silver 12 or copper salts. 13 On the other hand, dehydrogenation of the tetrahydro-β-carboline carboxylate generally requires exposure to a large excess of oxidants like SeO 2 , 14 MnO 2 , 15 sulfur, 3d,16 and palladium on carbon 17 for long periods of time.…”

TCCA; A Mild Reagent for Decarboxylative/Dehydrogenative Aromatization of Tetrahydro-β- carbolines: Utility in the Total Synthesis of Norharmane, Harmane, Eudistomin U, I and N

“…Oxidative decarboxylation of tetrahydro‐ β ‐carboline acids is one among such transformations for the synthesis of aromatized β ‐carbolines. The conventional methods for this transformation involve usage of transition metal reagents like K 2 Cr 2 O 7 or KMnO 4 in acetic acid, copper salts, persulfate in the presence of catalytic silver and also some mild oxidants like iodine and H 2 O 2 . Alternatively, aromatized β‐ carbolines can also be synthesized via dehydrogenation of tetrahydro‐ β‐ carbolines.…”