Bases simple isoquinoline

New, simple isoquinoline alkaloids isolated and assigned structures during the period under review include thalactamine (I), thalifoline (N-methyl derivative of 2 R = Me, R = H), and noroxyhydrastinine (2 RR = CH2), from Thalic-trum minus, and bases of general structure (3) listed in Table 1 have been identified in Peyote. ... 

Eleven bases have been isolated from Anhalonium lewinii, three phenethylamines mescaline, V-methylmescaline, and V-acetylmescaline (see /8-Phenethylamines Vol. Ill, chap. 22) and eight simple isoquinolines anhalamine, anhalidine, anhalinine, anhalonidine, pellotine, 0-methyl-d-... 

Obviously, under these conditions, it will be quite possible to find bases of the same type in plants of widely separated botanical families or even in products of animal metabolism. The individual cactus alkaloids will be found, therefore, under the headings /8-Phenethylamines (see Vol. Ill, chap. 22) and Simple Isoquinoline Alkaloids (see Vol. IV, chap. 26), where are also included all other natural bases of similar structure but different origin. 

Phenylethylamines and simple isoquinolines are found scattered among ca. 40 families and in over half of these one or other or both types of compound are not accompanied by any more complex alkaloids. The families in which they occur are distributed throu out the plant kingdom. They are especially common in the Cactaceae and Chenopodiaceae (Caryophyllales), Fabaceae (Fabales), and Rutaceae (Rutales), families that belong to orders fairly close to those in which the more complex isoquinoline bases are mainly concentrated (Dahlgren 1980). 

Isoquinoline Reissert compounds of type 12 could be easily converted to the corresponding 1-cyanoisoquinolines (13) by simple base treatment (4,5) (Scheme 3). This transformation also takes place with high yields when type 12 compounds are oxidized with molecular oxygen in a two-phase system in the presence of phase-transfer catalysts (12-14). It should be mentioned that similar oxidation of dihydro Reissert compounds of type 14 afforded the corresponding dihydroisocarbostyril derivatives (15) (12-14). Base treatment of isoquinoline Reissert eompounds followed by intramolecular rearrangement, due to the absence of a proper intermolecular reaction partner, results in 1-acylisoquinoline derivatives (18) (3). 

Only one example of an attachment of heteroarenes by addition/elimination strategy has been devised [77, 111]. Although arenes are more or less resistant toward addition, heteroaromatic systems such as isoquinolines 118 are prone to addition of nucleophiles. Subsequent reaction with addition of electrophiles furnishes the so-called Reissert compounds 120. These are stable compounds which can, for example, be alkylated. In solid-phase synthesis the electrophile chosen was a polymer-based acid chloride. Detachment can be achieved by simple addition of hydroxide ions (Scheme 6.1.30). 

The Pomeranz-Fritsch synthesis [Eqs. (1) and (2)]1 is the only isoquinoline synthesis involving a simple two-step sequence from common starting materials. Furthermore, it is one of the few methods which can be used to prepare isoquinolines substituted in the 7- and 8-positions. The first step, Schiff base formation [Eq. (1)], takes place readily, but the ring closure [Eq. (2)] is difficult. The yields vary markedly with the concentration of H2S04 and are generally low. Frequently the reaction fails completely. Most of the work described in this chapter was undertaken to circumvent these problems and to realize the potential promise of the synthesis. 

Some routes have been described which involve the formation of two C-C bonds in the same pot to produce quinolines and isoquinolines. For the production of 2-arylquinolines a Schiff base is reacted with an enol ether in presence of ytterbium(III) triflate. 2-Chloro-3-formylquinolines result from a practically simple process... 

Another study on leaves from 40 Nicotiana species should be mentioned which provides details on the occurrence of further congeners in addition to the main alkaloids (Sarychev and Sherstyanykh 1985). Accordingly, 2,3 -dipyridyl could be detected in 29, nicotyrine in 19, and A -methylanabasine in 10 species. This study also comprised information on the occurrence of simple bases like pyridine, 3-acetylpyridine, 3-cyanopyridine, a-picoline, 6-picoline, quinoline, and isoquinoline. However, since these simple bases are typical pyrolytic degradation products of nomicotine and myosmine, respectively (Balasubrahmanyam and Quin 1962), it can be assumed that they may also have been artefacts in the study mentioned above. 

---