Isomers dextrorotatory

The synthesis of dextromethorphan is an outgrowth of early efforts to synthesize the morphine skeleton. /V-Methy1morphinan(40) was synthesized in 1946 (58,59). The 3-hydroxyl and the 3-methoxy analogues were prepared by the same method. Whereas the natural alkaloids of opium are optically active, ie, only one optical isomer can be isolated, synthetic routes to the morphine skeleton provide racemic mixtures, ie, both optical isomers, which can be separated, tested, and compared pharmacologically. In the case of 3-methoxy-/V-methylmorphinan, the levorotatory isomer levorphanol [77-07-6] (levorphan) was found to possess both analgesic and antitussive activity whereas the dextrorotatory isomer, dextromethorphan (39), possessed only antitussive activity. Dextromethorphan, unlike most narcotics, does not depress ciUary activity, secretion of respiratory tract fluid, or respiration. 

Although the D-form of glyceraldehyde was arbitrarily chosen as the dextrorotatory isomer without any knowledge of its absolute configuration, the choice was a fortuitous one. In 1951, with the aid of modern analytical methods, the D-configuration of the dextrorotatory isomer was unambiguously established. 

Levorotatory isomers of these drugs are much more powerful adrenoblockers than dextrorotatory isomers however, all of these drugs are made and used as racemic mixtures. 

Quinidine is an alkaloid obtained from various species of Cinchona or its hybrids, from Remijia pedunculata, or from quinine. Quinidine is the dextrorotatory isomer of quinine. 

Exercise 5-5 The work of the German chemist Wislicenus on hydroxypropanoic acids was influential in the development of van t Hoff s ideas on stereoisomerism. By 1869, Wislicenus had established that there are three isomeric hydroxypropanoic acids, let us call them A, B, and C, of partial structure CzH4(OH)(C02H). Isomer A was isolated from sour milk and Isomer B from a meat extract. Both A and B had the same physical properties, except for optical rotation, wherein A was levorotatory and B was dextrorotatory. Isomer C was not optically active and had considerably different physical and chemical properties from A or B. Work out structures A, B, and C in as much detail as you can from the information given. 

The dextrorotatory isomer of 3-methoxy-A-methylmorphinan, a synthetic morphine derivative (Roinilar hydrobromide , Tusilan ) is employed exclusively as an antitussive agent. Its levorotary isomer (in the form of the 3-hydroxy tartrate) is described next. These compounds differ from morphine chemically in lacking the -O- bridge between carbons 4 and 5, the OH group at C6, and... 

Does this mean that (/ >butan-2-ol is the dextrorotatory isomer because it is named (.R), and (S)-butan-2-ol is levorotatory because it is named (5) Not at all The rotation of a compound, (+) or (-), is something that we measure in the polarimeter, depending on how the molecule interacts with light. The (R) and (S) nomenclature is our own artificial way of describing how the atoms are arranged in space. 

Calcium Pantothenate occurs as a slightly hygroscopic, white powder. It is the calcium salt of the dextrorotatory isomer of pantothenic acid. It is stable in air. One gram dissolves in about 3 mL of water. It is soluble in glycerin, but is practically insoluble in alcohol, in chloroform, and in ether. 

Note The physiological activity of Racemic Calcium Pantothenate is approximately one-half that of the dextrorotatory isomer. 

Dexpanthenol occurs as a clear, viscous, somewhat hygroscopic liquid. It is the dextrorotatory isomer of the alcohol... 

Dar, D.E., and Zinder, O. 1998. Catecholamine secretion from bovine adrenal chromaffin cells induced by the dextrorotatory isomer of anatoxin-a. Gen Pharmacol 31, 737-740. 

Quinidine, the dextrorotatory-isomer of quinine, has antimalarial activity, but is used mainly as a cardiac antiarrhythmic (see p. 500). 

Dexamfetamine, the dextrorotatory isomer of amfetamine, is about twice as active in humans as the laevo isomer and is the main prescribed amfetamine. It is rapidly absorbed and its duration of action varies among individuals most people with narcolepsy find twice daily dosing optimal to maintain alertness during the day. 

Dexbrompheniramine is the dextrorotatory isomer of the first-generation antihistamine brompheniramine. 

Dextromethorphan is the dextrorotatory isomer of the synthetic opioid levorphanol and is thought to act as a central nervous system antitussive (1). It binds to CNS sigma opioid binding sites and increases 5-HT concentrations by inhibiting uptake and by enhancing the release of 5-HT. It is also an antagonist at NMD A receptors. 

Dexfenfluramine, the dextrorotatory isomer, was previously widely marketed as an appetite suppressant in the management of obesity. It appears to be a pure serotonin receptor agonist without the dopaminergic and sympathetic activity of the racemic mixture. 

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