Indoline system

The nitrogen atom of the indole or indoline system of these alkaloids and their parent heterocycles is designated Na and the second nitrogen atom is referred to as Nb. 

The indoline UV-spectrum of caracurine II is virtually unchanged in the presence of 1 N hydrochloric acid and corresponds to the presence of two indoline systems in the C38H38N4O2 molecule. Mass-spectrometric... 

The first, and hitherto only, synthesis of lysergic acid was effected by the research group of Kornfeld et al. (50, 26). In this particular synthesis a X-acyl-2,3-dihydroindole derivative was used as starting material, thus allowing the formation of rings C and D by classical methods. Dehydrogenation of the 2,3-dihydroindole system to the indole system was only effected in the last stage so that the formation of the benz[c,d]-indoline system was prevented. 

The indole alkaloids so far discussed all have a tetrahydro-/ -carboline system. The main fragments of these alkaloids contain the indole part of the molecules. This situation is changed in alkaloids which have a larger ring C or an indoline system, permitting the production of fragments characteristic of both the indole and piperidine moieties. 

An interesting [4-F2] cycloaddition approach to various indoline systems has been devised, as illustrated by the preparation of the tricyclic molecule 158 (Equation 48). The inclusion of 2,6-di-/-butyl-4-methylphenol (BHT) in the reaction mixture gave somewhat improved yields <2005JA5776>. 

Studies on asymmetric annulation of the precursor 203 resulted in development of reaction conditions for the construction of the fused indoline system 204 (Equation 64). Similar cyclization of a substrate containing a longer chain gave a corresponding indoline fused to a six-membered ring <2002TA1351>. 

Mild nitration of vobtusine results in exclusive attack on the indoline system at position 5 (as shown by the u.v. spectrum) with the formation of nitrovobtusine (257). °... 

Aniline derivatives have been used to synthesize the indoline system. A large variety of indoline alkaloid substructures are available in a very efficient way. Enamine derivatives such as 39 bearing electron withdrawing substituents on the olefinic double bond were transformed in high yields (Scheme 7). Two syn/anti isomers 41 and 42 were isolated. The isomeric ratio of the final products was influenced by a photostationary equilibrium between the substrates 39 and 40. The reaction was applied to the synthesis of a variety of derivatives of the alkaloid aspidospermidine." In this context, the cyclization products 43 were transformed into the polycyclic indole derivatives 44,45, and 46. Polycyclic indolone compounds 48 have been successfully produced by cyclization of enaminone derivatives 47 carrying a quinoline substituentIn these cases and contrary to the examples 41,42, and 43, the products 48 resulted from an oxidation of the cyclization product (also compare the formation of 30 in Scheme 5). 

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