Tetrahydropyridine ring

Autoxidation of an impurity of meperidine (XII) leads to the aroma-tization product (XIII) (57) (Fig. 10). Some time ago, this was the major feature in an important criminal case, because this impurity, found in a drug manufactured illicitly, produced a severe parkinsonian syndrome in men. The tetrahydropyridine ring, not uncommon in pharmaceuticals, easily gives aromatization. In fact, the allylic methylene group adjacent to the nitrogen atom is activated and two dihydropyridine molecules formed by this oxidation may disproportionate to the finally aromatized product and to the starting material (57). 

X-ray study of 39 (R = Br) showed the presence of an axial methyl group in a half-chair tetrahydropyridine ring (73T2571).The structure of the perchlorate salt of 19 was determined by means of X-ray investigations (91MI12). The solid-state structures of (45)-derivatives of 4-phenyl-l-oxoperhydropyrido[2,l-c][l,4]oxazine-9-carboxylates 40-42 (95TL1657 ... 

In the reaction of 3,5-dimethyl-2,6-diphenylpiperid-4-one oxime (10) with acetylene and RbOH-DMSO, migration of the 3a-Me group to the anionic nitrogen atom occurred, leading to 5,7-dimethyl-4,6-diphenyl-4,5,6,7-tetrahydropyrrolo[3,2-c]pyridine (11) (04CHE326). The formation of the N-anion caused aromatization of the tetrahydropyridine ring. Tetrahydropyrrolo[l,2-c]pyrimidine 12 resulted from the decomposition of the intermediate 3H-pyrrole in a retro-Mannich reaction (Scheme 3). 

Tetrahydropyridine ring (ICgQ value 250 pM) Initial hits... 

The first example of aromatization of a tetrahydropyridine ring by hydroperoxide is the dehydrogenation of 1,2,3,4-tetrahydroisoquinoline to the isoquinoline with H2O2 or TBHP in the presence of ebselen <2003PJC1579>. 

Further application of the bioisosterism strategy replaced the tetrahydropyridine ring of arecoline with tetrahydropyrimidine (139a-e) (177). 

The tetrahydropyridine ring was fused with a 3-alkoxyisoxazole moiety in a series of compounds (161a-g) (174). Both (161a) and... 

In the case of the Ng-phenylsulfonyl derivative 403, synthesized by Sund-berg etal. 267), attempts to move the double bond in the tetrahydropyridine ring into the 20,21-position failed instead, disproportionation of the tetrahydropyridine ring supervened. 

A synthesis of 181, a venom alkaloid of Solenopsis [454], was reported in which the tetrahydropyridine ring was formed in an intramolecular amine addition to an alkyne, catalyzed by a gold (III) salt [455],... 

In the second phase, the final three C-14 conformers (11, 12, 22) in both series were analyzed concerning the helicity of the dihydropyran and tetrahydropyridine rings (N or P). In ring conformers, in which the dihedral angle of bond C-14-C-15 has a negative value ( -52°) with bond C-19-C-20 (positive conformation of the dihydropyran ring in SI 2, S22... 

The benzoylation of anatabine does not open the tetrahydropyridine ring with addition of water (Lipp-Widmann reaction) and this eliminates the possibility of the double bond being in an a, /8-position to the N-atom. One of these two positions is already eliminated by the fact that the alkaloid is optically active and furthermore, since the nitrogen is secondary the double bond cannot be next to it. Hence the double bond can occupy one or the other of the two positions as in formulas CLXXXV and CLXXXVI. A choice between these two formulas is made possible by... 

Incorporation of the alkylamine side-chain of trsrptamine into a tetrahydropyridine ring increases 5-HT,b receptor affinity hy more than 3 decades (Table 3). In contrast to the tryptamines, the 5-position of the indole nucleus of the... 

Incorporation of the alkylamine side-chain of 5-MeO-T into a 4-substituted tetrahydropyridine ring results in RU 24969, a non-selective 5-HT ligand [2, 18,... 

Four bisindole alkaloids, leucoridines A—D (146-149), were isolated from the stem bark of Leuconotis griffithii (Apocynaceae)." Leucoridine A (146) was composed of two tubifoHne (150)-like units having a spiro center at C-16, an enamine double bond, and a tetrahydropyridine ring consisting of the atoms C-16, C-22, N-1 C-2, C-16 and C-22 The relative... 

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