Alkaloids Flashcards
low molecular weight nitrogen containing compounds found mainly in plants, but also to a
lesser extent in microorganisms and animals; over 27,000 different alkaloid structures have been
characterized, with 21,000 from plants.
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one or more nitrogen atoms, typically as primary, secondary, or tertiary amines, and this
usually places basicity on the alkaloid, facilitating isolation and purification, since water-soluble salts can be
formed in the presence of mineral acids.
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The biological activity of many alkaloids is
often dependent on the
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Pyrrolidine
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Simple pyrrolidine-containing alkaloid structures are illustrated by
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hygrine
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cuscohygrine
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The pyrrolidine ring system is formed initially as a
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Δ1-pyrrolinium cation.
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oxidative deamination of N-methylputrescine
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diamine oxidase
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The N-methyl-1-pyrrolinium cation is then generated via
…. formation.
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The extra carbon atoms required for hygrine formation are derived from acetate via
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the enolate anion from acetyl-CoA acts as nucleophile towards the ….
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Mannich-like reaction,
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Claisen condensation
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thioester group
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and most of the natural tropane alkaloids lack this particular carbon atom, which can be lost by
suitable hydrolysis/decarboxylation reactions.
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The bicyclic structure of the tropane skeleton in cocaine is achieved by a repeat
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the ester of tropine with (S)-tropic acid, which is derived from l-phenylalanine via
phenyl-lactic acid.
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The pathway is the same as for hyoscyamine, but must proceed through the S-enantiomer of the N-
methylpyrrolidineacetoacetyl-CoA.
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subsequently obtained from the
methoxycarbonyltropinone by stereospecific reduction of the carbonyl.
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Reduction of the carbonyl occurs from the opposite face to that noted with the
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diester of ecgonine,
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arising from phenylalanine via cinnamic acid
and benzoyl-CoA.
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found in Erythroxylum coca (coca) and is used medicinally as a local anesthetic
, and as an illicit drug for its euphoric properties.
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They began their synthesis
from cycloheptanone and,
in 23 steps, completed the
synthesis of (±)-cocaine.
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The key step is a
…… followed by an
intramolecular
transannular SN2 to form
the tropane skeleton (
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mixed with lime, thus liberating the principal alkaloid cocaine as the free base, and the
combination is then chewed
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are extracted from crushed leaf using alkali (lime) and petrol. The petrol extract is
then re-extracted with aqueous acid,
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he coca alkaloids are often diluted with
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Cocaine Derivatives
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Cocaine Derivatives
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Procaine
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Benzocaine
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Tetracaine
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Lidocaine
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Lidocaine
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ALKALOIDS DERIVED FROM TYROSINE
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dependent decarboxylation of l-tyrosine gives the simple phenylethylamine derivative
tyramine
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phenylethylamine
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tyramine
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tyramine
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which on di-N-methylation yields hordenine, a germination inhibitory alkaloid from barley
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relatively non-specific and can catalyse
decarboxylation of other aromatic amino acids, e.g. tryptophan and histidine.
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Pre-eminent amongst the simple phenylethylamine derivatives are the
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catecholamines
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These
compounds are synthesized by sucessive β-hydroxylation and N-methylation reactions on
dopamine.
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Aromatic hydroxylation and O-methylation reactions in the cactus Lophophora williamsii (Cactaceae
) convert dopamine into
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mescaline
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alkaloid with psychoactive and hallucinogenic properties.
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also found in other species of cactus, e.g. Trichocereus pachanoi, a substantially
larger columnar plant that can grow up to 20 feet tall and found mainly in the Andes.
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anhalamine, anhalonidine, and anhalonine.
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ALKALOIDS DERIVED FROM • Catecholamines: TYROSINE
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can act on both vascular α1 and cardiac β1 receptors, but also has its own receptors in
several other structures.
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but needs
to be administered with a DOPA-decarboxylase inhibitor, to prevent rapid decarboxylation in the
bloodstream.
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Parkinson’s disease, there is a deficiency of dopamine due to neural degeneration
Parkinson’s disease, there is a deficiency of dopamine due to neural degeneration
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cardiac stimulants in cases of cardiogenic shock. These
agents act on β1 receptors.
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found in plants, e.g. Corydalis spp. (Papaveraceae), but can also be detected in the urine
of humans
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product from dopamine and acetaldehyde formed via a Pictet–Spengler reaction.
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are elaborated from (R)-reticuline.
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change in configuration is known to be achieved by an oxidation–reduction process through the intermediate 1,2-
dehydroreticulinium cation.
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S)-reticuline, a pivotal intermediate to
other alkaloids, is attained by ….
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only the phenylethylamine fragment of the
tetrahydroisoquinoline ring system is formed via DOPA,
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hydroxyphenylacetaldehyde
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benzylisoquinoline alkaloid found in opium,
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from N-nor-reticuline by
successive O-methylations and oxidation in the heterocyclic ring.
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the principal opium alkaloids, are derived by this type of
coupling, though the subsequent reduction of one aromatic ring.
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is the precursor of these morphinan alkaloids
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tetrahydroisoquinoline
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dienone salutaridine,
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The coupling enzyme salutaridine synthase is a
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P-450-dependent monooxygenase.
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Only the original ……. can be restored to aromaticity, since the
tetrahydroisoquinoline fragment is coupled para to the phenol function, a position which is already
substituted
.
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Ring closure to form the ether linkage in thebaine would be the result of nucleophilic attack
of the phenol group onto the dienol system and subsequent displacement of the hydroxyl.
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conversion of thebaine into codine and morphine, involves a process which modifies the
oxidation state of the diene ring, …… two O-methyl groups.
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which gives …… and then codeine by non-
enzymic keto–enol tautomerism and NADPH-dependent reduction.
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……. of the phenol ether codeine to the phenol morphine
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The enzymic demethylations of both the enol ether (in thebaine) and the phenol ether (in codeine)
involve ……… followed by loss of the methyl groups as ………
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withdrawal symptoms, including agitation, severe abdominal cramps,
diarrhoea, nausea, and vomiting, which may last for 10–14 days unless a further dose of morphine
is taken. This leads to physical dependence which is difficult to overcome, so that the major current
use of morphine is thus in the relief of terminal pain.
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withdrawal symptoms, including agitation, severe abdominal cramps,
diarrhoea, nausea, and vomiting, which may last for 10–14 days unless a further dose of morphine
is taken. This leads to physical dependence which is difficult to overcome, so that the major current
use of morphine is thus in the relief of terminal pain.
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dependent on partial demethylation in the liver to produce morphine, so it produces
morphine-like analgesic effects,
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structurally from morphine/codeine mainly by its possession of a conjugated diene ring system. It is almost
devoid of analgesic activity, but may be used as a morphine antagonist. Its main value is as substrate for the semi-synthesis of
other drugs.
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benzylisoquinoline alkaloid, and is structurally very different from the morphine, codeine, thebaine
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phthalideisoquinoline alkaloids and
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but no analgesic or narcotic
action.
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effective and reliable antitussive, can be obtained by alkylation with N-(chloroethyl)morpholine.
• Dihydrocodeine is a reduced form of codeine with similar analgesic properties.
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…… is a reduced form of codeine with similar analgesic properties.
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the double bond of morphine has been reduced, and in addition the 6-hydroxyl has been oxidized to a
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hydromorphone
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diacetate of morphine; i
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used for terminal care, e.g.
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common and extremely important precursor of
alkaloids, l-phenylalanine is less frequently utilized;
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Phenylalanine-derived Alkaloids
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the main alkaloid in species of Ephedra (Ephedraceae) and a valuable nasal
decongestant and bronchial dilator.
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major constituent of the leaves of khat (Catha edulis; Celastraceae),
chewed in African and Arab countries as a stimulant. Its traditional use alleviates hunger and fatigue
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major constituent of the leaves of khat (Catha edulis; Celastraceae),
chewed in African and Arab countries as a stimulant. Its traditional use alleviates hunger and fatigue
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Prolonged usage can lead to hypertension, insomnia, or even mania.
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caffeine
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theobromine
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theophylline
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PURINE ALKALOIDS
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important as a drug compound because of its muscle relaxant properties,
utilized in the relief of bronchial asthma.
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major constituent of cocoa and related chocolate products, it acts as a diuretic
and smooth muscle relaxant.
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Theobromine
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