Quinoline, structure

The Friedlander reaction is the acid- or base-catalyzed condensation of an ortho-acylaniline with an enolizable aldehyde or ketone. Henichart and coworkers have described microwave-assisted Friedlander reactions for the synthesis of indoli-zino[l,2-b]quinolincs, which constitute the heterocyclic core of camptothecin-type antitumor agents (Scheme 6.238) [421], The process involved the condensation of ortho-aminobenzaldehydcs (or imines) with tetrahydroindolizinediones to form the quinoline structures. Employing 1.25 equivalents of the aldehyde or imine component in acetic acid as solvent provided the desired target compounds in 57-91% yield within 15 min. These transformations were carried out under open-vessel conditions at the reflux temperature of the acetic acid solvent. 

The use of quinolines [7] were examined with the addition of fuel oil as co-collector. According to the data provided (Table 22.5), quinolines are effective pyrochlore flotation collectors. The number of carbons in the quinoline structure determines the grade and recovery of pyrochlore. 

Another interesting alkaloid is tubocurarine chloride (14), with a bisbenzyliso-quinoline structure. It is the active principle of tubocurare, an arrow poison used by Indians in South America and medicinally used as a muscle relaxant. However, the source, the leaves of the tropical rainwood liane Chondodenron tomento-sum, is not easily accessible and the compound exhibits unwanted side-effects. Investigations showed that the basic structure can be replaced by an appropriate steroid skeleton with two nitrogen substituents at the right distance (see next section). 

The 1,2-dihydroquinoline and quinoline structural units, ubiquitous in natural products, were synthesized utihzing... 

A mechanism for the transformation of the benzodiazepine to the quinoline structure, which accounts for all data obtained from both cyclopenase- and acid- or base-catalyzed reactions, has been proposed by White and Dimsdale (79) (Fig. 8). The conversion is induced by attack of an electron acceptor (e.g., H" ) at the epoxide oxygen or by attack of an electron donor (e.g., OH ) on the N-1 atom. Bond formation between C-10 and C-5a of cyclopenin is facilitated by the close approach of these two atoms in the boat conformation. Therefore, the formation of a tricyclic intermediate appears likely, although a compound of this type has not been isolated so far. Another mechanism that would explain the enzymatic and acid-catalyzed conversions was proposed by Luckner and Never (42). 

Mercapto-2-substituted quinolines, structure and properties of chelates 90MI37. 

On the basis of and NMR spectral data, McLaughlin s group (66) has confirmed that (+)-psychotrine (3), newly isolated from the sap of P. speciosus (Jacq.) K. Schum. (Rubiaceae), has the genuine 3,4-dihydroiso-quinoline structure (the endocyclic double bond structure) as in the case (1,102) of O-methylpsychotrine (4). The same conclusion had already been reached by Fujii s group (S5) as a result of their NMR study of 3. 

The alkaloids of the cinchona bark are natural products containing a quinoline structure [111]. Examples are the diastereoisomeric pairs quinine/quinidine and cinchonidine/cinchonine 108 and 109 in which a 4-methylquinoline unit is bonded to a vinyl-substituted quinuclidine system (1-azabi-cyclo[2.2.2]octane). Camptothecin 110, a highly toxic polycyclic quinoline alkaloid, was isolated from the stem wood of the Chinese tree Camphoteca acuminata (Nyssaceae). 

The degree of toxicity in the 8-amino quinoline structural analogues appears to be directly associated with the degree of substitution at the terminal amino function. Using the said criterion pamaquine, having a tertiary amino moiety, happens to be more toxic than primaquine, having a... 

From Ouyang, J., Chu, C.W., Sievers, D., and Yang, Y., Appl conjugated quinoline structure and... 

The approach of Wang et al. [78] uses the redox-sensitive nature of quinoline structures that form dihydro quinolines in the presence of mild reducing agents and cyclize after treatment with TEAR Another special linker type is the class of allylic linkers because they can be cleaved by Pd-catalysis via allyl transfer to give carboxylic acids [79]. 

Renewed examination by TLC and electrophoresis of calebassinine, another curare alkaloid, but also known to be present in S. solimoesana (Table 1.4), has now revealed that it consists of two components, the major one calebassinine 1 together with a small proportion of calebassinine 2. X-ray crystal analysis of calebassinine 1 (436) has shown it to possess the quinoline structure 46a. The suggestion has been made that it could arise through a number of oxidative transformations from 2,16-dihydroakuammicine (47) a variant on the route originally proposed has been outlined (437). Isolation of the alkaloid from S. solimoesana (325) would thus imply the occurrence of an akuammicine derivative in the plant, which has not yet been demonstrated. 

---