Page 45 - Academic Press Encyclopedia of Physical Science and Technology 3rd Organic Chemistry

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Encyclopedia of Physical Science and Technology EN001F-21 May 7, 2001 13:44

484 Alkaloids

TABLE III Basic Stages of the Hofmann Degradation of Alkaloids
N-Methylation product First degradation product Second degradation product Third degradation product
of an alkaloid Repetition Repetition
−−−−−−−−→ −−−−−−−−→
β α H 5 C 6
H 5 C 6 CH 3
CH CH 2 N CH 3 CH CH 2 N(CH 3 ) 3
CH 3 H 2 O
H
Result: one bond between
OH N atom and C skeleton
β β β
H 2 C CH 2 HC CH 2 HC CH
H 2 O
H 2 C CH 2 H 2 C CH 2 H 2 C CH 2
N(CH 3 ) 3
N OH N H 2 O Result: two bonds between
H 3 C CH 3 H 3 C CH 3 N atom and C skeleton

β β β
H H H
C CH 3 C C CH 3 β
H 2 C CH 2 H 2 C H 2 C H CH 2 H 2 C
N N C CH 3
H 2 C H 2 C
CH 2 CH 2 H 2 O N CH 2 H 2 O
CH 3
C C N(CH 3 ) 3
β OH β CH 2
H H H 2 O
Result: three bonds between
N atom and C skeleton

five-membered ring contains two nitrogen atoms, as in HOOC CH 3
the amino acid histidine. N H

H
HO H
N CH 3
CH 3
H N
N H
H 3 CO N N
H ( )-Lysergic acid
CH 3 H 3 C O
Harmaline ( )-Triabunnine
HO H N
The peptide ergot alkaloids consist of one molecule of R
lysergic acid and a peptide unit. Typical examples are er- 1 CH O O
gotamine and ergocornine, both isolated from Claviceps R N
HN 2
purpurea. O R
CH 3
In a similar variation of alkaloids with a five-membered O N
H
ring, the nitrogen atom is part of a six-membered ring. Ex-
amples are coniine, piperine, sedridine (Sedum acre), β-
skytanthine (Skytanthus acutus), pelletierine, and actini-
dine. Nicotine consists of both a five- and a six-membered N
ring, each containing a nitrogen atom. H
Through fusion of a benzene to a six-membered ring 2
( )-Ergotamine, R = R′ = H; R = CH 2 C 6 H 5
2
with one nitrogen atom, two ring systems can be formed: ( )-Ergocornine, R = R′ = CH 3 ; R = CH(CH 3 ) 2