Sparteine is a class 1a

antiarrhythmic agent Antiarrhythmic agents, also known as cardiac dysrhythmia medications, are a group of pharmaceuticals that are used to suppress abnormally fast rhythms ( tachycardias), such as atrial fibrillation, supraventricular tachycardia and ventricular tac ...

; a sodium channel blocker. It is an

alkaloid Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar s ...

and can be extracted from

scotch broom ''Cytisus scoparius'' (syn. ''Sarothamnus scoparius''), the common broom or Scotch broom, is a deciduous leguminous shrub native to western and central Europe. In Britain and Ireland, the standard name is broom; this name is also used for other ...

. It is the predominant alkaloid in '' Lupinus mutabilis'', and is thought to

chelate Chelation is a type of bonding of ions and molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central metal atom. These ligands are ...

the bivalent cations

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...

and

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...

. It is not FDA approved for human use as an antiarrhythmic agent, and it is not included in the Vaughan Williams classification of antiarrhythmic drugs. It is also used as a

chiral Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from i ...

ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electro ...

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...

, especially in syntheses involving

organolithium reagent In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom ...

Biosynthesis

Sparteine is a lupin

containing a tetracyclic bis-quinolizidine ring system derived from three C₅ chains of

lysine Lysine (symbol Lys or K) is an α-amino acid that is a precursor to many proteins. It contains an α-amino group (which is in the protonated form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −CO ...

, or more specifically, L-lysine. The first intermediate in the biosynthesis is

cadaverine Cadaverine is an organic compound with the formula (CH2)5(NH2)2. Classified as diamine, it is a colorless liquid with an unpleasant odor. It is present in small quantities in living organisms but is often associated with the putrefaction of anim ...

, the decarboxylation product of lysine catalyzed by the enzyme lysine decarboxylase (LDC). Three units of cadaverine are used to form the quinolizidine skeleton. The mechanism of formation has been studied enzymatically, as well as with tracer experiments, but the exact route of synthesis still remains unclear. Tracer studies using ¹³C-¹⁵N-doubly labeled cadaverine have shown three units of cadaverine are incorporated into sparteine and two of the C-N bonds from two of the cadaverine units remain intact. The observations have also been confirmed using ²H NMR labeling experiments. Enzymatic evidence then showed that the three molecules of cadaverine are transformed to the quinolizidine ring via enzyme bound intermediates, without the generation of any free intermediates. Originally, it was thought that conversion of cadaverine to the corresponding aldehyde, 5-aminopentanal, was catalyzed by the enzyme diamine oxidase. The aldehyde then spontaneously converts to the corresponding Schiff base, Δ¹-piperideine. Coupling of two molecules occurs between the two tautomers of Δ¹-piperideine in an aldol-type reaction. The imine is then hydrolyzed to the corresponding aldehyde/amine. The primary amine is then oxidized to an aldehyde followed by formation of the imine to yield the quinolizidine ring.

Via 17-oxosparteine synthase

More recent enzymatic evidence has indicated the presence of 17-oxosparteine synthase (OS), a transaminase enzyme. The deaminated cadaverine is not released from the enzyme, thus is can be assumed that the enzyme catalyzes the formation of the quinolizidine skeleton in a channeled fashion . 7-oxosparteine requires four units of pyruvate as the NH₂ acceptors and produces four molecules of alanine. Both lysine decarboxylase and the quinolizidine skeleton-forming enzyme are localized in chloroplasts.

References

External links

* {{Antiarrhythmic agents Antiarrhythmic agents Quinolizidine alkaloids Sodium channel blockers

Biosynthesis

Via 17-oxosparteine synthase

See also

References

External links