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Biotransformation pathways amines

Bromocriptine is rapidly and completely metabolised in animals and man. The major components of the urinary metabolites have been identified as 2-bromo-lysergic acid and 2-bro-mo-isolysergic acid. Apart from the hydrolytic cleavage of the amine bond and the isomerization at position 8 of the lysergic acid moiety, a third principal biotransformation pathway consists in the oxidative attack of the molecule at the proline fragment of the peptide part, predominantly at position 8, giving rise to the formation of a number of hydroxylated and further oxidized derivatives of bromocriptine, and in addition of conjugated derivatives thereof. [Pg.68]

Metabolites derived by loss of an alkyl or arylalkyl group from ethers [Eq. (4)], thioethers [Eq. (5)], amines [Eq. (6)], and amides [Eq. (7)] represent common biotransformation pathways (R, R" = H, alkyl or aryl). These processes involve oxidation on carbon adjacent to the heteroatom. The intermediates are generally unstable and readily decompose to the corresponding alcohol, thiol, amine, or amide and an aldehyde. Intermediates formed from amides [Eq. (7)] are more stable and may be detected as excreted metabolites. If a secondary carbon atom is adjacent to the heteroatom, then this portion of the molecule is released as a ketone. The heteroatom may also be located in a cyclic structure (e.g., morpholine, piperazine). Two processes have been adopted for amines, namely, N-dealkylation or deamination, that are essentially the same event. In general, which of the two terms applies depends on the... [Pg.312]

In primary aliphatic amines, such as phentermine. chlorphentcrmine (yx-chlotphentcrmine).- and amantadine. N-oxidation appears to be the major biotransformation pathway because a-carbon hydroxylation cannot occur. In hum-ans. chlorphentcrmine is N-hydroxylated extensively. About 30% of a dose of chlorphentermine is found in the urine (48 hours) as Al-hydroxychlorphentermine (free and conjugated) and an additional 18% as other products of N-oxidation (presumably the nitroso and nitro metabolites). In general, /V-hydroxylamines are chemically unstable and susceptible to spontaneous or enzymatic oxidation to the nitro.so and nitro derivatives. For example, the N-hydroxyl-amine metabolite of phentermine undergoes further oxiila-... [Pg.92]

In a related fashion, asymmetric amination of ( )-cinnamic acid yields L-phenylalanine using L-phenylalanine ammonia lyase [EC 4,3,1,5] at a capacity of 10,000 t/year [1274, 1601], A fascinating variant of this biotransformation consists in the use of phenylalanine aminomutase from Taxus chinensis (yew tree), which interconverts ot- to p-phenylalanine in the biochemical route leading to the side chain of taxol [1602], In contrast to the majority of the cofactor-independent C-0 and C-N lyases discussed above, its activity depends on the protein-derived internal cofactor 5-methylene-3,5-dihydroimidazol-4-one (MIO) [1603], Since the reversible a,p-isomerization proceeds via ( )-cinnamic acid as achiral intermediate, the latter can be used as substrate for the amination reaction. Most remarkably, the ratio of a- vs, 3-amino acid produced (which is 1 1 for the natural substrate, R = H) strongly depends on the type and the position of substituents on the aryl moiety While o-substituents favor the formation of a-phenylalanine derivatives, / -substituted substrates predominantly lead to p-amino analogs, A gradual switch between both pathways occurred with m-substituted compounds. With few exceptions, the stereoselectivity remained exceUent (Scheme 2,215) [1604, 1605],... [Pg.241]


See other pages where Biotransformation pathways amines is mentioned: [Pg.146]    [Pg.19]    [Pg.480]    [Pg.128]    [Pg.123]    [Pg.287]    [Pg.238]    [Pg.344]    [Pg.238]    [Pg.53]    [Pg.90]    [Pg.91]    [Pg.205]    [Pg.193]    [Pg.181]    [Pg.121]    [Pg.134]    [Pg.157]    [Pg.328]    [Pg.603]   
See also in sourсe #XX -- [ Pg.312 , Pg.313 ]




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Biotransformation pathways

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