Six-Membered, Heterocycles with One Heteroatom

As we mentioned in Section 1.2, pyridine has an additional lone pair of electrons at the nitrogen atom after it contributes a pair of two electrons to make up the 6 7t-electrons for aromaticity. These lone pair electrons are responsible for much of pyridine s unique physical and chemical properties. 

One prominent example is AstraZeneca s H /K -ATPase inhibitor, pyridine-containing omeprazole (Prilosec) and its enantiomerically pure follow-up esomeprazole (Nexium). 

They are both pro-drugs and their MOA is through the omeprazole cycle, initiated by pyridine s lone pair of electrons. In fact, pyridine s lone pair of electrons could be viewed as the engine that propels the omeprazole cycle. The pyridinium sulfydryl intermediate is the actual inhibitory species. 

There are quinoline-containing drugs from both nature and synthesis. Natural product drugs may be exemplified by quinine, an anti-malarial drug used for three centuries. Syndetic quinoline-containing drugs are 

The most important example of this category is pyridine (azabenzene),.  

Problem 20.17 Write the structural formulas and give the names of the isomeric methylpyridines. There are three isomers. 

Problem 20.18 (a) Account for the aromaticity of pyridine, a planar structure with 120° bond angles. (f ) Is pyridine basic Explain, (c) Explain why piperidine (azacyclohexane) is more basic than pyridine, (d) Write the equation for the reaction of pyridine with HCl. 

The less s character in the orbital holding the unshared pair of electrons, the more basic the site. 

Problem 20.19 Explain why pyridine (a) undergoes electrophilic substitution at the position, and (b) is less reactive than benzene. 

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Chemistry of furazanes fused with six-membered heterocycles with one heteroatom 99UK154. 

Fig. 3.9 Six-membered heterocycles with one heteroatom obtained by solid-phase chemistry.

DIMEDONE-ANNULATED SIX-MEMBERED HETEROCYCLES WITH ONE HETEROATOM... 

Properties of ILs 439 4.2.1 Synthesis of Six-Membered Heterocycles with One Heteroatom 459... 

According to WHO fact sheet, CVD is the main cause of death globally more people die aimually from CVD than from any other cause. An estimated 17.3 million people died from CVD in 2008, representing 30% of all global deaths. Of these deaths, an estimated 7.3 million were due to coronary heart disease and 6.2 million were due to stroke. The number of people who die from CVD, mainly from heart disease and stroke, will increase to reach 23.3 million by 2030. CVDs are projected to remain the single leading cause of death [87]. On the other hand, 1,4-dihydropyridines (1,4-DHPs) are an important class of six-membered heterocycle with one heteroatom. This medicinally important... 

The microwave-induced synthesis of other medicinally important six-membered heterocycles with one heteroatom was also reported (Table 3, Fig. 14). 

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